OK. So What Is Wrong With This 6" Mak-Cas?
Tony
I recently posted here about the 93mm F16 refractor that I threw together and
put it up against my 6" Orion/Intes Mak-Cas and it seems to me the refractor
easily beat it - on saturn - much sharper, more detail, much more contrast -
cassini was at best gray and poorly defined in the Mak but black and razor
sharp in the refractor and hinting at shading in the outer parts of the ring.
Some people responded and said they would agree to this sort of thing but I
guess the majority said its not possible or I'm a troll or something. (is troll
a polite way of saying "A--Hole". I have had about 20 scopes over the years but
nothing really high end and none cost more than $1000 so I'm not any kind of
expert when it comes to judging scopes but being in this for over 15 years I
think what I see at the eypiece counts for something. The scopes I had in the
past range from several refractors up to 4" all F11 or under, Several
newtonians up to 10" all F8 or under, an ETX90 etc. This homemade 93mm F16
refractor in my opinion beats all those scopes all though I dont have them to
compare side by side. To be fair though the larger newtonians were F4.5 so
probably not a fair comparison anyway on planets.
I bought the 6" Mak-Cas with high expectations of it based on the glowing
reviews on the internet and S&T magazine which basically stated that other than
some minor mechanical annoyances it performed flawlessly, competing with high
end scopes and refractor like images and knows almost no limits on
magnification. I bought it expecting a high end scope and for it to knock my
socks off. $1000 for 6" aperture is somewhat high end in my opinion.
Naturally when I first got it I was treated to 3 straight weeks of clouds. When
I first got to use it the only god target available was the moon. It looked
quite good but nothing spectacular. As time went on, looking at the moon and
planets, I still was never impessed with it. Jupiter rarely showed more than 2
bands with no detail, cassini was difficult in it, stars were not pinpoints. I
attributed this bad performance to either poor seeing or the scope not being
cooled down. As far as the latter I tried everything from leaving it in the
garage all day (which is semi-heated) to actually leaving it hidden and
unattended in the back yard all day. No difference. I soon became bored with
the scope and lost interest in astronomy for the last couple of years until I
came across this 93mm achromat in my drawer and decided to try it.
With all that said where do I go from here. How do I find out if I'm crazy or
the mak has something wrong with it? I hear people doing test reports on scopes
and with one peek it seems they sum up the optics and say its 1/8 wave or
something. What does this mean and how do they know with just a peek. Is there
some kind of test I can do? Anyone near Johnston RI want to come see this for
themselves. I want to add that the Mak has never left my property so it has
not been banged around. If its got something wrong with it, it came that way
from Orion.
Also, I dont want to get off the main issue here or start a big debate, but
since I have never had the pleasure of looking thru an APO, How would a 3 1/2"
F16 refractor compare with a similar aperture APO besides the APO being better
suited for deep sky.
Thanks
Tony
Siegfried Gonzi
> With all that said where do I go from here. How do I find out if I'm crazy or
> the mak has something wrong with it?
Did you ever look whether the collimation is perfect? Or some other
strange things happening with the star-test.
Think:
For your record: My ETX 105 shows clearly more than 2 bands on Jupiter
(occasionaly 6 or the like). My ETX 90 is lined up with my 4" f/10
Fraunhofer achromat from Vixen when considering planets. Additionaly, my
Borg 3" ED apo (no longer mine) performed no better on the planets than
my ETX 90.
But on the other side I think your post smells,...
Normally, there is no competition between a 90mm achromat or apochromat
(whether f/6 or f/10 or f/16 or ...) and a 6" Maksutov. All the retarded
poor souls who will respond differently in the following need
professional help with a priest.
S. Gonzi
Tony
My post smells???????? I am simply asking for advice here. I thought that this
is what this forum is for. Call me stupid if you want for saying a 90mm
outperforms a 6" Mak-Cass but its what I'm seeing with them side by side. I am
trying to find out why.
Saying my post "smells" accomplishes nothing.
Tony
Jon Isaacs
>poor souls who will respond differently in the following need
>professional help with a priest.
>
>
>S. Gonzi
I see no reason to attack others with such statements. In a technical
discussion it is important to stick with the technical issues and avoid
slandering those with differing ideas.
It is actually a sign of a weak argument if someone finds it necessary to stray
from the issues at hand, it amounts to nothing more than name calling and does
not further the discussion.
I hope in the future you avoid making such comments, it would give your words
more credence.
Jon Isaacs
Siegfried Gonzi
> I see no reason to attack others with such statements. In a technical
> discussion it is important to stick with the technical issues and avoid
> slandering those with differing ideas.
>
> It is actually a sign of a weak argument if someone finds it necessary to stray
> from the issues at hand, it amounts to nothing more than name calling and does
> not further the discussion.
>
> I hope in the future you avoid making such comments, it would give your words
> more credence.
I do not deny that the original poster really saw what he described. It
is not a problem that he posts questions and experiences (and I am the
last one who deprives him of posting questions on sci.astro.amateur
because sci.astro.amateur is really unimportant in real life), but I see
a lot of coming posters which will reply with the statement that what he
experienced is common due to some myths. I am not sure whether I got it,
but a "myth" has nothing to do with "differing ideas".
S. Gonzi
Siegfried Gonzi
>>But on the other side I think your post smells,...
>>
>
> My post smells???????? I am simply asking for advice here.
A good advice is the following: take your two scopes and scrutinize the
scene during the daytime. You will be surpised that observing remote
things is not much different from observing planetary details. Write
down magnification and especially exit pupil and report again. I mean
observing during the daytime is not that bad and especially you will
have time at your disposal and you are not forced to keep track of an
otherwise moving object.
Do not forget to let cool down you scope, especially the 6" Maksutov.
I can only assure you this: There is no competition (at planets) between
an otherwise good 90mm apo and a good 6" Maksutov. And when people tell
you different, please cancel this from your mind.
S. Gonzi
Jan Owen
"Siegfried Gonzi" <siegfri...@kfunigraz.ac.at> wrote in message
news:3E300786...@kfunigraz.ac.at...
Snip!
I do not deny that the original poster really saw what he described. It
is not a problem that he posts questions and experiences (and I am the
last one who deprives him of posting questions on sci.astro.amateur
because sci.astro.amateur is really unimportant in real life), but I see
a lot of coming posters which will reply with the statement that what he
experienced is common due to some myths. I am not sure whether I got it,
but a "myth" has nothing to do with "differing ideas".
S. Gonzi
Snip!
**************************************************************************
**************
Snip!
But on the other side I think your post smells,...
Normally, there is no competition between a 90mm achromat or apochromat
(whether f/6 or f/10 or f/16 or ...) and a 6" Maksutov. All the retarded
Bill Meyers
Hello, Jon
Siegfried Gonzi is Shawn Grant, I am told. Is this incorrect?
Bill Meyers
Tony
a fight. Guess I wont be able to get any real good advice or help this time
around. But thanks to those that did offer suggestions thus far. Maybe I should
just sell the Mak in question to the highest bidder.
Tony
John Denver
First, please ignore Shawn Grant. He has serious emotional problems and spends
his time baiting people on this website. He is not typical of the people on this
site.
Second, a 93mm f/16 refracator is about a perfect a telescope as you could
want. If the lens is good, it will show astounding contrast and detail on
planetary objects.
The Mak-Cas scopes are also good, but will never equal the contrast of your
small refractor. If the Mak is not properly collimated, it will not equal the
resolution either. The images in the Mak will be brighter, because of the larger
aperture, but unless it is set up properly it just won't perform to expectation.
In my opinion, these scopes are over-rated anyway. The original reason for
building the Maksutov was not to achieve a superior optical design, it was to
produce a Cassegrain type scope at a lower cost. This is why the optics are
spherical (cheaper to produce than parabaloidal) and why the secondary is just a
silvered spot on the back of the corrector plate. There are improved versions of
the Maks which use a secondary mirror attached to the corrector plate, but they
are expensive. In my opinion, you are better off going with an 8 or 9 inch SCT
than with the 6 or 7-inch Maks.
Just my opinion.
John
DGM Optics
If you feel that the Mak is in excellent collimation, and more than
adequately thermally equalized, then it sounds like you may have just had
bad luck and gotten a poor scope. Is there any chance to address this with
the seller?
But in the mean while, just enjoy the views with the little refractor!
Dan McShane
www.dgmoptics.com
"Tony" <alg...@aol.comnospam> wrote in message
news:20030123102309...@mb-cg.aol.com...
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Davros
> poor souls who will respond differently in the following need
> professional help with a priest.
>
>
> S. Gonzi
Are you really Valery D. posting under a different name?
Or perhaps Shawn Grant's evil twin?
Zane
>Hi
>
>I recently posted here about the 93mm F16 refractor that I threw together and
>put it up against my 6" Orion/Intes Mak-Cas and it seems to me the refractor
>easily beat it - on saturn - much sharper, more detail, much more contrast -
>cassini was at best gray and poorly defined in the Mak but black and razor
>sharp in the refractor and hinting at shading in the outer parts of the ring.
(snip)
Some random thoughts and observations:
A really good 6 inch Mak-Cass should give planetary views very similar to a
near-perfect 4 inch (not far from 93 mm) refractor. The mirror surfaces
and coatings of the M-C need to be very smooth for its contrast to match
the refractor.
If you live in a place where the seeing is not too good, one won't see a
huge difference in planetary views even with a 10 inch Newt. I don't know
where you live, but the extreme weather that a lot of the U.S. has been
having lately could make for some limited seeing and some conditions hard
for mirrored (especially sealed) scopes to ever come to thermal
equilibrium.
Have you compared the scopes without a diagonal in place?
Has the temperature been pretty low in all your tests? Sometimes a
corrector element can bind up at low temperatures and cause degradation of
the image.
Comparing the two scopes at similar powers on some close double stars (not
too dim) at high power might give some insight on whether the M-C is giving
good resolution but lots of scattering from the mirrors or not. (Do you
have a Barlow that you can use to get more power than you currently have?)
Keep in mind that the M-C will have considerably more light in the
diffraction rings than the refractor, so doubles that don't have big
differences in the magnitudes of the two stars are best. If the stars in
the M-C are asymmetric, something is amiss and you should consider sending
it back for checking.
You might compare a bright star or the edge of the moon using the same size
exit pupil (not the same magnification - the M-C will naturally be
brighter) and see how the M-C compares in blackness of the nearby surround.
If it's a whole lot brighter, you may have gotten a bad coating run that's
introducing too much light scatter. (I would expect it to be not as black,
but not an extreme difference.)
Again, the planetary images in a 6 inch M-C shouldn't be a lot better than
a good long focal length 3.7 inch achromat, but should be as good.
If you do any more testing along the lines I mentioned, we'd be interested
in the results.
Zane
Jon Isaacs
> I am not sure whether I got it,
>but a "myth" has nothing to do with "differing ideas".
The problem I am refering to is your following statement:
">All the retarded
>poor souls who will respond differently in the following need
>professional help with a priest."
This has nothing to with the issues at hand and as I pointed out, just weakens
any points you might have.
You certainly have firm ideas but you have not backed them up with analysis
like Brian T. and others have done when looking at the differences between
various obstructed scopes and refractors. Those transfer functions etc really
end up showing real world results.
So please, stay on topic and avoid making personal remarks about the other
posters.
It uncalled for and again, it weaks your creditability.
jon isaacs
Ron B[ee]
>
> A good advice is the following: take your two scopes and scrutinize the
> scene during the daytime. You will be surpised that observing remote
> things is not much different from observing planetary details. Write
> down magnification and especially exit pupil and report again. I mean
> observing during the daytime is not that bad and especially you will
> have time at your disposal and you are not forced to keep track of an
> otherwise moving object.
>
>
Umm, perhaps you meant in the morning. I don't think daytime like
noon and afterward is a good test at all as the heat will make high
magnification impossible (like looking through a mirage). And high
magnification is necessary in order to scrutinize.
Ron B[ee]
Jon Isaacs
A good point. Don't know what diagonal Orion ships with these scopes but one
inexpensive Orion Diagonal I had was badly out of alignment.
Jon Isaacs
Brian Tung
> Siegfried Gonzi is Shawn Grant, I am told. Is this incorrect?
Probably.
Brian Tung <br...@isi.edu>
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt
Tony
somewhere with some good intelligent answers and suggesstions. Thanks to Dan,
John Zane and Jon. So I guess this is in fact somewhat possible to be
happening. My own belief is that you simply cannot beat a refractor with good
optics (long focus or APO) for sharpness and contrast. Why some jumped down my
throat for simply stating what I was seeing at the eyepiece is beyond me. Its
probably due the fact that most of them have never seen or used a refractor
above F9 and are used to the popular cheaply made crop of refractors flooding
the market right now.
On the other hand The 93mm refractor is beating the Mak quite badly - almost
putting it to shame and this should probably not be the case. I am not sure how
to check the collimation on this beast but when I defocus a star image I see
the central obstuction almost perfecty centered within the rest of the white
circle. It looks like it could be just slightly off center but hard to tell.
Comments?
Some of you mentioned temperature and equilibrium and maybe you hit on
something there. I am in the northeast USA (Rhode Island). The temperatures
here have been somewhat cold. I am not a late night person and have been doing
this comparison around 8 to 9 PM when the temperatures have been around 20 deg
F and falling usually to single digits by morning. So possibly the falling
temperatures are in fact affecting the maks optics and the sky conditions but
the refractor could care less. Whilethe mak scope is cooling down some nights I
see some really strange effects like double images of saturn and rotation of
saturn when slightly in and out of focus. Not sure if that means anything. I'll
try to start keeping track of the temperatures vs performance of the mak. Ah
the simplicity of a refractor
I am going to go ahead and properly build this refractor regardless of what the
nay-sayers here have to say. I have access to a machine shop and can and will
do an impeccable job on it. I think it will be more than worth the time and
will result in an even better scope than it is now. (duct tape holding a lens
does not make for good alignment). I enjoy building refractors and have built
others. I would like to make a 4" F6 or so but cant seem to find a source of
such a lens that is reputable.
Again thanks for all your help and any other comments or suggestions you may
have to offer.
Tony
Rod Mollise
>I recently posted here about the 93mm F16 refractor that I threw together and
>put it up against my 6" Orion/Intes
Hi:
Probably Nothing. Did you have the two scopes at the same magnification? Was
the MCT adequately cooled? How was the seeing? At this time of year I'd
especially suspect the latter. In times when the old Jetstream is going
bonkers, the image in a smaller scope can look aesthetically better and
"sharper." If you really try, you'll see more details in the Intes, however.
Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
Goto <http://members.aol.com/RMOLLISE/index.html>
Edward
"John Denver" <spam...@aol.com> wrote in message
news:3E301178...@aol.com...
> Tony,
> In my opinion, these scopes are over-rated anyway. The original reason
for
> building the Maksutov was not to achieve a superior optical design, it was
to
> produce a Cassegrain type scope at a lower cost. This is why the optics
are
> spherical (cheaper to produce than parabaloidal) and why the secondary is
just a
> silvered spot on the back of the corrector plate. There are improved
versions of
> the Maks which use a secondary mirror attached to the corrector plate, but
they
> are expensive. In my opinion, you are better off going with an 8 or 9 inch
SCT
> than with the 6 or 7-inch Maks.
> Just my opinion.
> John
>
>
I think he has an Intes made Orion Argonaut, a rumak design with a seperate
secondary.
Ed
Richard Harding
Big deal...he is still important only in his small mind.
Richard
Edward
"Tony" <alg...@aol.comnospam> wrote in message
> Again thanks for all your help and any other comments or suggestions you
may
> have to offer.
>
> Tony
>
Hi Tony,
Here's a website by a gentleman with the same MCT, there's some good stuff
here:
http://astro.geekjoy.com/scopes/MK67_collmation.html
Ed
andrea tasselli
I have enough experience with scopes and maks especially to know that
something must be deeply wrong if you're experiencing what you've
said. The only two likely reasons are that either the mak is a lemon
(extremely unlikely but might happen) or the mak is badly misaligned
either by its own or because the diagonal is, if you're using one. On
how to collimate a scope you'd better find resources in the net, there
are plenty as well as to evaluate if your scope is a lemon. Mind you,
if the scope is reasonably well collimated and performs poorly even
when left to cool down properly and the seeing is resonably good it
means it's a lemon even if you are not an expert in star testing.
Andrea T.
My Astronomy Pages at:
http://www.geocities.com/andreatax/index.htm
andrea tasselli
> First, please ignore Shawn Grant. He has serious emotional problems and spends
> his time baiting people on this website. He is not typical of the people on this
> site.
> Second, a 93mm f/16 refracator is about a perfect a telescope as you could
> want. If the lens is good, it will show astounding contrast and detail on
> planetary objects.
It will show absolutely nothing that any other resonably well made
scope of the same diameter wouldn't show.
> The Mak-Cas scopes are also good, but will never equal the contrast of your
> small refractor.
Definitely a troll. You know nothing about contrast in scopes. A well
made 6" mak eats away any 4" refractor in *ANY* field you care to
throw it at. And I can prove it.
> In my opinion, these scopes are over-rated anyway. The original reason for
> building the Maksutov was not to achieve a superior optical design, it was to
> produce a Cassegrain type scope at a lower cost. This is why the optics are
> spherical (cheaper to produce than parabaloidal) and why the secondary is just a
> silvered spot on the back of the corrector plate. There are improved versions of
> the Maks which use a secondary mirror attached to the corrector plate, but they
> are expensive. In my opinion, you are better off going with an 8 or 9 inch SCT
> than with the 6 or 7-inch Maks.
Wonder, wonder, that guys got exactly that, a rumak variant of the
maksutov cassegrain. And as contrast goes, a 6" mak is largely
superior to most of the 8" SCTs around.
andrea tasselli
> alg...@aol.comnospam (Tony) wrote:
>
> >Hi
> >
> >I recently posted here about the 93mm F16 refractor that I threw together and
> >put it up against my 6" Orion/Intes Mak-Cas and it seems to me the refractor
> >easily beat it - on saturn - much sharper, more detail, much more contrast -
> >cassini was at best gray and poorly defined in the Mak but black and razor
> >sharp in the refractor and hinting at shading in the outer parts of the ring.
>
> (snip)
>
> Some random thoughts and observations:
>
<snip>
>
> Again, the planetary images in a 6 inch M-C shouldn't be a lot better than
> a good long focal length 3.7 inch achromat, but should be as good.
You obviously have no extended experience with russian maks or you
wouldn't say such a nonsense.
Chuck Scappaticci
through your Mak, are the stars oblong or have little tails (coma) on them?
If so, you scope is very far out of collimation. You should collimate your
scope in any case (just the secondary). Start at about 150x and then move
up to 300x. Make very small adjustments (1/16th of a turn). If you don't
know how, we can point you to some web pages. I had a 5 inch Intes Mak and
it had outstanding optics, so something is either wrong with your scope or
it's way out of collimation ...
--
Thanks,
Chuck
"Tony" <alg...@aol.comnospam> wrote in message
news:20030123071734...@mb-dh.aol.com...
Tony
>maksutov cassegrain
What does rumak variant mean? Since I started all this I'd like to know.
Tony
Zane
>zane...@sansnetcom.com (Zane) wrote in message news:<3e30223d...@nntp.ix.netcom.com>...
>> alg...@aol.comnospam (Tony) wrote:
(snip)
>> Again, the planetary images in a 6 inch M-C shouldn't be a lot better than
>> a good long focal length 3.7 inch achromat, but should be as good.
>
>You obviously have no extended experience with russian maks or you
>wouldn't say such a nonsense.
I have experience with close-to-perfect "maks" and also know their limits
as imposed by Mother Nature.
Zane
Tony
No I dont see the stars having tails except when its still cooling down (which
takes forever). Once cooled down they dont look like pinpoints as in the
refractor.
Thanks
Tony
Tony
that you are trying to trash had some good points. You need to go back to the
textbooks. An unobstructed optical system is clearly superior to an obsructed
one sometimes outperforming a larger one. If you remember the glowing review of
this scope from S&T magazine they compared the 6" Mak Cas to smaller, I REPEAT
SMALLER, refractors. In their opinion the refractors won.
Tony
Zane
BTW, a really fine homemade 6 inch Newtonian will give better planetary
(narrow field) views than any 6 inch Mak-Cass on the market today.
It would be interesting to have some side-by-side contests/bets with people
who think there's some magic about Mak-Cass's if the stakes were high
enough to make it worthwhile.
Not that I have anything against any type of scope.
Zane
Mark
and a 6" Mak-Cass can usually take a full hour to come to equilibrium
completely.
My friend's Intes MN-61 goes through all kinds of wierd looking star
tests until it cools down completely. Sometimes stars would look like a
pac-man from the heat-plume rising off the secondary mirror, and mirror
holder. (it was like "Hey, who took a bite out of that star!?")
If the Star Diagonal Checks out OK, (try viewing without one) and if you
have good collimation at high power, then something else has to be
amiss?
You mention that Stars do not look like Pin-points. What do they look
like at focus? Slightly out of focus? Make sure your star is perfectly
centered in the field of view when checking/adjusting collimation
I assume your not viewing over houses, or other objects that may be
giving off warm air currents, correct? Mark
Siegfried Gonzi
> You certainly have firm ideas but you have not backed them up with analysis
> like Brian T. and others have done when looking at the differences between
> various obstructed scopes and refractors. Those transfer functions etc really
> end up showing real world results.
>
> So please, stay on topic and avoid making personal remarks about the other
> posters.
>
> It uncalled for and again, it weaks your creditability.
I think this is really going off topic: but whether I have creditabilty
in sci.astro.amateur is really not important for me. Look I am a
Freidenker, but the problem actually is that most of the posters in
sci.astro.amateur are engineers and an engineer is hardly ever the guy
who reads book about philosophy.
S. Gonzi
Siegfried Gonzi
> Those transfer functions etc really
> end up showing real world results.
Sorry I surrender, it is useless to discuss with guys who don't get it.
I am in meantime concvinced that 90% of all the amateur astronomers are
a proxy for 100% of all the C/C++ programmers out there.
Sorry, but I have way too weak nerves to stay any longer against such
nonsense. You shouldn't wonder why not more professionals are reading
sci.astro.amateur.
S. Gonzi
Dan Chaffee
>I did not mean to start a war here but I must say to you ANDREA. The poster
>that you are trying to trash had some good points. You need to go back to the
>textbooks. An unobstructed optical system is clearly superior to an obsructed
>one sometimes outperforming a larger one.
The effects of central obstructions are usually blown out of
proportion by amateurs. I have done experiments with a masked
newtonian where the unobstructed 4.2" was still lagging behind the
contrast and detail of Saturn when the same instrument was obstructed
by a 30% diagonal and 4.8" of aperture. That's hardly the difference
being discussed here with 93 and 150 mm unobstructed and obstructed
respectively. The refractor has three other things going for it that
the mak doesn't: lower surface scatter, higher throughput, and less
sensitivity to thermal problems in the tube. But, that is not enough
to overcome a 38% increase in aperture with the obstructed reflector
regarding sharpness and contrast on planets--unless there's a
problem with the optics in the latter.
A good refractor usually does come out ahead of an obstructed
reflector of the same aperture and optical quality on the planets, but
not by very much, and the differences are more along the lines of
aesthetics and personal preferences; with refractors favoring the
blacker backgrounds and stabler images, leaving one with the
impression of being sharper, even if not really showing much more
detail.
How about you putting a paper obstruction of say 20mm in front
of that refractor of yours to simulate 21% secondary and tell us
if it's vastly inferior to unobstructed planetary detail?
Dan Chaffee
Siegfried Gonzi
> The effects of central obstructions are usually blown out of
> proportion by amateurs. I have done experiments with a masked
> newtonian where the unobstructed 4.2" was still lagging behind the
> contrast and detail of Saturn when the same instrument was obstructed
> by a 30% diagonal and 4.8" of aperture. That's hardly the difference
> being discussed here with 93 and 150 mm unobstructed and obstructed
> respectively. The refractor has three other things going for it that
> the mak doesn't: lower surface scatter, higher throughput, and less
> sensitivity to thermal problems in the tube. But, that is not enough
> to overcome a 38% increase in aperture with the obstructed reflector
> regarding sharpness and contrast on planets--unless there's a
> problem with the optics in the latter.
>
> A good refractor usually does come out ahead of an obstructed
> reflector of the same aperture and optical quality on the planets, but
> not by very much, and the differences are more along the lines of
> aesthetics and personal preferences; with refractors favoring the
> blacker backgrounds and stabler images, leaving one with the
> impression of being sharper, even if not really showing much more
> detail.
>
> How about you putting a paper obstruction of say 20mm in front
> of that refractor of yours to simulate 21% secondary and tell us
> if it's vastly inferior to unobstructed planetary detail?
Hi:
Thanks for this reply. I think you nailed it down. Was your Newtonian
self made?
I think there is hope for this newsgroup.
Regards,
Siegfried Gonzi
zgse...@netway.com
Really? That sure doesn't ring any bells with me. (And you would
think it would.) Give us an issue date and some specifics -- which
scopes.
Look, Tony, if you prefer your small refractor to your 6-inch Mak,
then great -- go outside and enjoy the views. No one can or should
tell you to do otherwise. However, if you are inferring from your
experience that in general a small refractor is going to outperform a
substantially larger Mak, then I think you're inferring much too much.
Kind regards,
Gary Seronik
(Remove the "z" for my actual e-mail address.)
Edward
"Dan Chaffee" <dcha...@gvi.net> wrote in message
news:3e30e6d1...@news.planetkc.com...
> How about you putting a paper obstruction of say 20mm in front
> of that refractor of yours to simulate 21% secondary and tell us
> if it's vastly inferior to unobstructed planetary detail?
>
> Dan Chaffee
>
Bingo!
Tony
I am not trying to infer that in general a small refractor is going to
outperform a substantially larger Mak. Thats absurd and we all know aperture
rules no matter what type of scope it is or how much it costs. The key word
there is "substantially larger Mak" and the point of this whole post fom the
beginning is to find out why this seems to be happening in my particular case.
I dont prefer my tiny refractor over a 6" scope or else I would not have spent
$900 for the Mak
Here is a reference to the article in question by S&T
The Magazine "SKY and TELESCOPE" (April, 1999) published an article by Alan
Dyer entitled, "Pair of High- Performance Maksutovs" with the test report on
the scopes Argonaut-150 (MK-67) Maksutov-Cassegrain and the Argonaut-6" (MN61)
Maksutov-Newtonian manufactured by the Russian firm "INTES" (Moscow).
As the test report shows, both versions of Maksutov telescopes have received
the reputation of high-class-image instruments which can rival more expensive
competitive analogues.
In the article, the basic advantages of these telescopes are reflected in
comparison with 4 " and 5" APO refractors for planetary observations.
Tony
Edward
"Tony" <alg...@aol.comnospam> wrote in message
> In the article, the basic advantages of these telescopes are reflected in
> comparison with 4 " and 5" APO refractors for planetary observations.
>
> Tony
>
>
And the rest:
"By comparison, the Argonaut 150-mm Maksutov-Cassegrain provides fine
performance only a notch short of its heavier companion in a much lighter,
more portable package. I feel it makes an excellent general-purpose
telescope that can rival more expensive 4-inch apochromatic refractors."
By Alan Dyer
Adapted from
Sky and Telescope
April 1999
Doesnt sound like it should play second fiddle to a 93mm achromat to me.
Ed
Tony
"Doesnt sound like it should play second fiddle to a 93mm achromat to me."
Since I have never used an expensive 4-inch apochromatic refractor I dont know
for sure but realistically how much difference could you expect between the 4"
APO and a 3.6" F16 achromat (93mm)? Less than 1/2" difference of aperture and
I see no spurious color at all in the F16 (on the moon anyway - have not had
the opportunity to try it yet on tougher targets likeVenus). I mainly ask
because I dont know.
Jon Isaacs
>in sci.astro.amateur is really not important for me.
Well, what is important to me is that people post in a kind and reasonable
manner.
Why even bother posting if you are going to sabotage your effort with a rude
remark about others who may have differing thoughts?
Jon Isaacs
Edward
"Tony" <alg...@aol.comnospam> wrote in message
> Since I have never used an expensive 4-inch apochromatic refractor I dont
know
> for sure but realistically how much difference could you expect between
the 4"
> APO and a 3.6" F16 achromat (93mm)? Less than 1/2" difference of aperture
and
> I see no spurious color at all in the F16 (on the moon anyway - have not
had
> the opportunity to try it yet on tougher targets likeVenus). I mainly ask
> because I dont know.
I dont think the Mak should "blow away" the refractor, but I know the
refractor shouldn't be vastly superior to the Mak if all is as it should be
with that scope. I have an MK67 and the views through it are _really_ very
nice.
Here's a website with some photos taken with this scope:
http://www.geocities.com/andreatax/index.htm
I can add that the planetary images here are quite similar to what I see
visually.
Hope this helps, Ed
Tony
Tony
Jon Isaacs
>I dont think the Mak should "blow away" the refractor, but I know the
>refractor shouldn't be vastly superior to the Mak if all is as it should be
>with that scope. I have an MK67 and the views through it are _really_ very
>nice.
How long do you find it takes your MAK to cool down on a cold winter day?
Maybe you can give Tony some guidelines so he be confident that his scope has
reached thermal equilibrium.
Also, Tony, have you done your comparisons side by side? Variability in seeing
from one day to the next of even over the course of the evening can make big
differences in the quality of the views.
I always remember the best views of the planets I ever got with a given scope,
but it is rare that I see anything close to the super sharp, highly detailed
images that I treasure...
jon isaacs
andrea tasselli
Basically a separate secondary and to you, end user, better field and
lateral color correction.
andrea tasselli
I shall not think so, and I have images to prove that. Even Mother
Nature knows the difference between a 6" and a 4" (or 3.7" for the
matter) and She prefers the former I'm afraid.
andrea tasselli
Their opinion are not facts. And they said that the specimen from
Orion was at least as good for contrast as a good 4" APO. And nowhere
I recall they said the refractor won. In fact it wasn't a comparison
across different type of scopes. I have a deluxe variant of the same
model, which means that it has superior optical quality and better
coatings. After testing against a Tak 5" I put its contrast a tad
lower than that but certainly higher of any other 4" APO. Getting back
to the textbook (how many have you read and understood?) the contrast
transfer function would be equal only in a narrow band of frequencies
(middlle ones). But that assuming the APO is a perfect unobstructed
telescope, something which is not (can I recall spherochromatism for
istance?). You don't need to take my words for world's gold. Go around
and shop for high resolution pictures of anything. My e-mail address
is in the header. Post your findings and I'll post back mine.
Roger Hamlett
"andrea tasselli" <atas...@hotmail.com> wrote in message
news:ba9aa3a9.03012...@posting.google.com...
reason to the persistent 'downgrading' by some people of the real
capabilities of scopes like the Maksutov design, with a small central
obstruction. If you calculate the circle size, containing 75% of the energy
for a perfectly focussed example, the 6" Mak, produces a significantly
smaller circle than the APO. However the redistribution of energy caused by
the central obstruction, makes the effects of any misfocus worse. If (for
instance), you look at examples of a 150mm Mak, with a 20% CO, a 93mm APO,
and a 150mm SCT, with a 34% CO, then at this energy level, the performance
when perfectly focussed, runs Mak, APO, SCT (the Mak produces a radius of
about 0.8 arc second, the APO, about 1 arc second, and the SCT about 1.2 arc
second). At a lower 'critical' level, the SCT does better, while the Mak
stays ahead of the APO, even at the 90% encircled energy level. However if
you misfocus the scope by a tiny amount the degradation is much faster in
the scopes with a central obstruction, to the point where a tiny focal error
of only a fraction of a mm, gives the edge to the APO. Add to this the fact
that many Maksutov designs join with SCT's, in moving the primary mirror to
focus (which amplifies any mechanical focus error by a factor of typically
about 5*), and you have a reason why on many occasions, the APO, will win.
Add an elecrically controlled Crayform focusser to the Mak, and adjust it
very carefully, and the results are well worthwhile.
Best Wishes
Chris1011
instance), you look at examples of a 150mm Mak, with a 20% CO, a 93mm APO, and
a 150mm SCT, with a 34% CO, then at this energy level, the performance
when perfectly focussed, runs Mak, APO, SCT>>
What happens if the Mak has a 36% obstruction, as is the case here?
Roland Christen
Chris1011
address
is in the header. Post your findings and I'll post back mine.>>
How about: http://www.celestialimage.com/page189.html
Tony
Wow! This is getting pretty heavy. This stuff is starting to go over my head.
All this because I said my homemade refractor was beating my prized Mak. I say
prized because I shelled out hard earned bucks for it and had high expectations
of it. Should have bought one from AP. Well Roland - I noticed you have pretty
much stayed out of this one. In my eyes, and probably quite a few others, you
are a legend and could put an end to this mess with just a couple of paragraphs
and I mean that with the utmost respect.
Tony
Roger Hamlett
"Chris1011" <chri...@aol.com> wrote in message
news:20030124160427...@mb-cu.aol.com...
allmost un-noticeable). However this is not the sort of size that is needed
by the standard Mak design. The normal Mak-Cass, has a higher effective
focal ratio, and a smaller CO, at around 20 to 22%. The original Maksutov
designs, often went to even higher focal ratios (f/35), and gave yet smaller
CO's. The Mak Newtonian, gives a lower focal ratio, but normally similar CO.
The Orion Argonaut has a 19.1% CO, and the Intes Micro MN66, a 21% CO.
Best Wishes
Chris1011
by the standard Mak design. The normal Mak-Cass, has a higher effective
focal ratio, and a smaller CO, at around 20 to 22%>>
I think the person in question has an F10 Mak with relatively larger CO around
36%. This is the instrument that is being debated, not a theoretical Mak with
low obstruction.
Roland Christen
zgse...@netway.com
alg...@aol.comnospam (Tony) wrote:
>Hi Gary
>
>I am not trying to infer that in general a small refractor is going to
>outperform a substantially larger Mak. Thats absurd and we all know aperture
>rules no matter what type of scope it is or how much it costs. The key word
>there is "substantially larger Mak" and the point of this whole post fom the
>beginning is to find out why this seems to be happening in my particular case.
My guess is that you're not allowing your Mak anywhere near enough
time to cool down. Depending on conditions, it can take *hours*.
Your scope may be out of collimation too.
>I dont prefer my tiny refractor over a 6" scope or else I would not have spent
>$900 for the Mak
>
>Here is a reference to the article in question by S&T
>
>The Magazine "SKY and TELESCOPE" (April, 1999) published an article by Alan
>Dyer entitled, "Pair of High- Performance Maksutovs"
I'm familiar with that review. I don't see anything in there that
suggests that the 6-inch Mak will be "blown away" by a 93 mm scope, as
your posts report.
I'm not sure that this helps since I'm no longer sure I know what kind
of response you're fishing for. If you want to know if it is normal
for a 93-mm refractor to outperform a 6-inch Maksutov, the answer is
no. If what you observed is accurate, then you can safely conclude
that there is either something wrong with your particular scope or
that you are not using it correctly (I, and others have suggested
possible problem areas). That's it.
Good luck sorting this out.
Regards
Stephen Paul
news:unhY9.1958$6U3....@newsfep4-gui.server.ntli.net...
> However if
> you misfocus the scope by a tiny amount the degradation is much faster in
> the scopes with a central obstruction, to the point where a tiny focal
error
> of only a fraction of a mm, gives the edge to the APO.
I suggested this as well, but the private mail bounced. It is even more
difficult to obtain accurate focus in the SCT/MCT in an environment with
less than optimal seeing, such as is the case here in New England a large
part of the time.
I especially enjoyed your discussion on the Airy disk, and the results of
diffraction by central obstruction (notwithstanding Roland's point that the
particular Mak we are discussing is an F10). These issues are only
exacerbated by the seeing conditions here. We get cells of good seeing. The
trick is to get focused during one of them, and then lock it down and wait
for another. If you change eyepieces a lot, or try to compensate for the
seeing, your going to miss out on those good cells as you constantly chase
focus. Most of my planetary observing is done at roughly 30x per inch.
Unfortunately, I never could get my little 4" Mak focused well beyond 100x,
but I've had my little 80f5 achro up to 125x with better results (although
with chromatic aberration).
I'm getting used to the idea that New England just isn't a very good place
for highly detailed planet observing, and I fear for those who go hog-wild
chasing after larger more detailed views than what is possible. I've
observed a shadow transit of Io, and I've observed the GRS making its way
from the limb. I've seen more than the two equatorial belts, but beyond
that, it's a matter of persistently getting out to try to catch an
exceptional night.
Having said that, I need to go wax the base of my XT10 for a midnight
session with Jupiter.
See ya,
Stephen Paul
Tony
that is it not possible for a smaller aperture to outperform a larger but here
they are saying the opposite. True it does not say anything about a 93mm but
93mm is not much different from 4".
Could be that the scope S&T used was hand picked by Orion for the test and
since Orion advertises with S&T maybe S&T played it up a little. Meaning that
on average these scopes are not quite as good as they say and vary from one to
another.
It seems that whatever you say here someone jumps down your throat. I am making
no claims about anything other than what I have seen at the eyepiece and facts
like the existence of the S&T article.
Tony
Chris1011
time to cool down. Depending on conditions, it can take *hours*.
Your scope may be out of collimation too.>>
It is very easy to tell the difference between collimation errors and optical
errors. Collimation errors cause a star image to be other than round when
slightly defocused. If your stars are round, but mushy, and the seeing is
steady, then you may have an optical correction error. Typical errors include
turned edge, which causes a star to have "hair" or spikes in all directions on
one side of focus. A lot of times these spikes will rotate when the atmosphere
is not quite steady. The other side of focus will be sharp edged. All the
collimation in the world will not fix this.Of course, the scope must be fully
acclimated to the outside temperature when testing.
Roland Christen
Zane
(Comments aimed at the group.)
That's what I was assuming when I made my previous comments. If I was
wrong and the CO _is_ around 20%, I apologize and have to soften my
previous remarks some. The blurring effects of a CO go roughly by the
square of its relative diameter, making the difference between 20% and ,
say, 33% significant.
We (this group) have had this discussion many times before, but one can
easily compute the MTFs of the two scopes and compare them. (I think MTF
is probably the best measure of how Jupiter looks, at least in my
experience. Also, I'm assuming both target and eye response spectral
weighting of the achromat MTF.) If one throws in a little seeing MTF
factor, the two MTF curves are pretty similar for CO's in the 30%+ range,
as the high frequency part of the Mak curve is hit a little harder by the
seeing. Throw in a little non-zero wavefront effect from the extra
surfaces of the two mirrors and they're even closer.
Most other effects one adds to the mix favor the refractor. These
calculations lend credance to the old saw that an obstructed scope gives
_planetary_ performance _roughly_ equal to a near-perfect refractor with
diameter equal to the mirror scope diameter minus the diameter of the CO.
I think Dan Chaffee knows all this and is able to do the math easily, so
I'm a little puzzled by his response unless he is assuming a 20% CO. I
don't know whether Andrea can do the computation or not.
Since some people here don't trust numbers, my observing experiences match
the predictions pretty well, although I admittedly don't run across too
many really good 6 inch mirror instruments these days (only seen one
Russian Mak). The others I've seen have been custom units built for
military use. (A little "dual use" activity after work never hurt anyone.
:-) ) In the olden days, there were a lot more 6 inch Newts around that
were pretty good.
Picking between a really good 6 inch Mak and a really good (short) 4 inch
APO would be a hard call for me, but the simplicity of the refractor is
appealing. (I've owned a couple of good achromats.) Price would probably
make the difference. If the choice were an achromat with a long enough
tube to approach APO performance, I'd go with the Mak every time for ease
of use.
Zane
Ron B[ee]
Wow, that Traveller sure take stunning, jaw dropping pictures, Roland
as I was first shocked last year when I saw M42 taken by the Traveller
on your web site!
Ron B[ee]
DGM Optics
"Stephen Paul" <SPau...@hotmail.com> wrote in message
news:b0sh48$r1j$1...@transfer.stratus.com...
> I'm getting used to the idea that New England just isn't a very good place
> for highly detailed planet observing, and I fear for those who go hog-wild
> chasing after larger more detailed views than what is possible. I've
> observed a shadow transit of Io, and I've observed the GRS making its way
> from the limb. I've seen more than the two equatorial belts, but beyond
> that, it's a matter of persistently getting out to try to catch an
> exceptional night.
>
> Having said that, I need to go wax the base of my XT10 for a midnight
> session with Jupiter.
>
> See ya,
> Stephen Paul
Hi Stephen,
I`m a hop, skip, and jump down Rt.2 from you (Westminster) and couldn`t
agree more, however there are nights when you can get some very fine
plantary detail.
Were you, by chance, out last year the night before Thanksgiving? Right
after a about a half foot snowfall, but the storm departed with sparkling
clear skies and no wind that night. The seeing was about as good as it`s
been around here in a couple years, or more. Saturn was magnificent. The
Cassini division looked as if was drawn on with a fine black felt tip pen.
The Crepe ring was easy but no Encke minima (that`s asking for too much).
The planet itself displayed the obvious dark band around the equator then
varying shades (not really bands, but hinting at them) up to the darkened
pole. And it wasn`t just that the seeing was real good, it was real good for
long spells. Trees to my east didn`t allow me to get a look at Jupiter but
it must have been excellent that night.
I was out the next night hoping for more of the same, but of course, no way!
I think part of problem with the Mak-Cas in question is that with this cold
snap it might not be able to equilize at all with the quickly falling temps
at night. Tony said he`s down in Johnston RI and does his observing earlier
in the evening when temps have been falling like a stone around these parts
so I get the feeling that could be at least part of the issue.
Hope the milky high junk doesn`t spoil your Jupiter look! I got a peek at
Europa transiting around 11:00 pm.
Dan McShane
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Dan Chaffee
<siegfri...@kfunigraz.ac.at> wrote:
> Was your Newtonian
>self made?
No, I made it .....
DC
>
Dan Chaffee
wrote:
Hi Zane,
>That's what I was assuming when I made my previous comments. If I was
>wrong and the CO _is_ around 20%, I apologize and have to soften my
>previous remarks some. The blurring effects of a CO go roughly by the
>square of its relative diameter, making the difference between 20% and ,
>say, 33% significant.
>
>We (this group) have had this discussion many times before, but one can
>easily compute the MTFs of the two scopes and compare them. (I think MTF
>is probably the best measure of how Jupiter looks, at least in my
>experience. Also, I'm assuming both target and eye response spectral
>weighting of the achromat MTF.)
The visually weighted polychromatic MTF for an achromat is not as
near a flat line as one might hope and at f/16 for a 93mm doublet
would correspond to a strehl of between .84 and .9 depending on the
design and specific glasses(asuming normal crowns and flints). Of
course, in green light it can be as high as .99. At any rate, I would
expect such a scope to be very good on planets, even if not quite
the MTF equal of the same sized APO.
> If one throws in a little seeing MTF
>factor, the two MTF curves are pretty similar for CO's in the 30%+ range,
>as the high frequency part of the Mak curve is hit a little harder by the
>seeing. Throw in a little non-zero wavefront effect from the extra
>surfaces of the two mirrors and they're even closer.
>
>Most other effects one adds to the mix favor the refractor. These
>calculations lend credance to the old saw that an obstructed scope gives
>_planetary_ performance _roughly_ equal to a near-perfect refractor with
>diameter equal to the mirror scope diameter minus the diameter of the CO.
>
>I think Dan Chaffee knows all this and is able to do the math easily, so
>I'm a little puzzled by his response unless he is assuming a 20% CO.
I suggested a 21% obstruction as a good place to start testing if one
is convinced of the ravages of central obstructions upon the planetary
image's wavefront, not assuming it was what the Mak was sporting.
However. lets assume the presence of a 33% obstruction in an
instrument with a 38% larger aperture to consider that the
substantially greater ight grasp availible from the larger obstructed
aperture over the smaller unobstructed one will allow a brighter
image at higher magnification. It's my experience that in good seeing,
this factor alone --not to mention the rise in resolving power-
can make it easier to perceive detail on a planet, even in the wake of
what MTF plots tell us is damagingly increased diffraction. I have a
hunch that how well this holds up is a function of an individual's
own eyes.
Dan
andrea tasselli
It doesn't make it, for however good it is is too low in resolution to
compete. Besides, gimme that ST10E, a good mount an H-alfa and I'll
show you as much.
Jon Isaacs
>compete. Besides, gimme that ST10E, a good mount an H-alfa and I'll
>show you as much.
>
>Andrea T.
You forgot to include one thing, an AP scope.
Jon Isaacs
andrea tasselli
The person in question has NOT a f/10 mak but rather a f/12 (with
might turn out to be anything in between f/11 to f/13 depending on
circumstances) 34.5% obstructed mak. Even with such high CO it still
has far more concentrated energy within the first two dark rings
(accounting for nearly the totality of the focused energy) than a 4"
unobstructed scope. That even assuming .985 light transmission by the
unobstructed scope and .786 by the mak. The ratio of the effective
light gathering powers is 1.56 in favour of the mak. If you take my
mak the ratio is 1.74 as it has better coatings. Let's not forget that
a 6" 34.5% obstructed scope has an Airy disk of 1.64" while the 4"
unobstructed one has one of 2.74", that is 70% larger. Yes, scatter
favors the APO but not as much to wipe out all the benefits of the
larger aperture. So just imagine if the scope is only 3.7"!
Tony
airy discs, light transmission etc and its very interesting. I think someone
out there told me I'm and idiot because I only compared the scopes on saturn on
one night (not true). I do have another copmparison of the two. My skys here do
not lend themselves well to deep sky but since the Orion Nebula is so easy I
tried it. No question the Mak shows the nebula brighter and is starting to show
detail in it and it would probably be even better if I viewed a little later in
the evening. However refering to the stars in the trapezium (I dont know their
names) the dimmest of the 4 is noticeably brighter in the 93mm refractor. My
own unproffessional opinion of why is that it is "tighter" in the refractor.
Roland and others mentioned things about collimation. The next clear night here
I will try to check some defocused star images and report here what I see since
I really dont know how to interpret what I see. I do know that if I defocus a
star so its quite large, say 1/2 of the FOV the secondary shadow is centered
but maybe not quite perfectly.
Tony
Tony
someone selling one on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=28181&item=30023933
05&rd=1
Now you can put your money where your mouth is. Bid away.
Be interesting to see what it goes for. If he gets a good price for it will not
tempt me to sell mine. Maybe I have to put a little more effort into using it
properly so I think there's hope for it and if nothing else it is a sharp
looking scope.
Tony
Tony Miller
> Nature knows the difference between a 6" and a 4" (or 3.7" for the
> matter) and She prefers the former I'm afraid.
>
> Andrea T.
>
Not to star another war but I think Mother Nature also sees that big
black contrast robbing "dot" in the center of thet 6" Mak too.
In "MY" limited experience with Takahashi and Zeiss refractors vs.
similar to slightly larger Maks, Meade and Questar the contrast was
still better in my refractors. This was always with well cooled down
optics from my light polluted urban environment and on the Moon and
planets. Small details popped out quicker and had more contrast on
these bright objects. Now, this is with 2.4" and 3" refractors against
3.5" Maks.
I am sure a 6" Mak and a 3.7" refractor will be different but one
cannot say with any objectivity that every 6" Mak beats every 4"
refractor. I always get a laugh when one fellow makes an observation
here and anyone who does not agree is somehow substandard or a
complete fool for not seeing it the same way. Say's more about the
accusers state of mind than the 'fool" he is chastising. Everyone's
milage may vary here, what works for you in your own eyes is what
counts.
I am with John Issacs on this one. Feel free to state your opinion and
be helpful but no need for name calling and "I'm smarter than you"
here.
Best,
Tony Miller (soon to be bashed I am sure <g>)
Chris1011
show you as much.
>>
Sorry, I don't give that kind of stuff away. You'll have to get yer own.
Roland Christen
Chris1011
The person in question has NOT a f/10 mak but rather a f/12 (with
might turn out to be anything in between f/11 to f/13 depending on
circumstances) 34.5% obstructed mak. >>
Well, if you want to split hairs, I have one also which has a 2.1 inch central
obstruction diameter, and a clear aperture measures just under 5.9 inches (the
opening measures slightly larger, but the clear part of the glass is 5.9").
That makes the obstruction 35.6%.
>>Even with such high CO it still
has far more concentrated energy within the first two dark rings(accounting for
nearly the totality of the focused energy) than a 4"
unobstructed scope>>
You must be assuming perfect optics in the Mak, which may not be the case here.
If the optics are only 1/4 wave with some edge defect, you could easily have an
Airy Disc peak of less than 60% with quite substantial energy in the first few
diffraction rings. In poor seeing, this could wipe out any contrast.
Roland Christen
DGM Optics
"andrea tasselli" <atas...@hotmail.com> wrote in message
news:ba9aa3a9.03012...@posting.google.com...
Hi Andrea,
I think this could be in the running;
http://users.erols.com/dgmoptics/Images/image006.jpg
Full aperture solar filter over the front of an OA-4.0, (98mm, F/10.3
off-axis Newtonian) 12 mm Plossl eyepiece, and a Sony Camcorder (handheld)
on an unguided dob mount. Courtesy of Mike Palermiti, Jupiter FL.
Dan McShane
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Chris1011
Full aperture solar filter over the front of an OA-4.0, (98mm, F/10.3
off-axis Newtonian) 12 mm Plossl eyepiece, and a Sony Camcorder (handheld)
on an unguided dob mount. Courtesy of Mike Palermiti, Jupiter FL.
Dan McShane>>
Very nice! Excellent resolution. Have him cut back on the USM a bit to reduce
that noisy look.
Roland Christen
DGM Optics
Thanks Roland,
I was wondering about the "graininess", but the resolution is clearly there.
I especially like the "fang"!
Zane
(snip)
>The visually weighted polychromatic MTF for an achromat is not as
>near a flat line as one might hope and at f/16 for a 93mm doublet
>would correspond to a strehl of between .84 and .9 depending on the
>design and specific glasses(asuming normal crowns and flints). Of
>course, in green light it can be as high as .99. At any rate, I would
>expect such a scope to be very good on planets, even if not quite
>the MTF equal of the same sized APO.
(snip)
It's been a while since I ran the numbers close to this size and f/no (93
mm is kind of an odd size), but for visual use on Jupiter there's a triple
spectral weighting involved -- the solar spectrum, cone vision spectral
response, and the dominant spectral reflectance in the main Jovian features
and transition zones/band edges.
I agree, though, that it's not a perfect MTF.
Zane
andrea tasselli
I already have my finders, no, thanks. Besides, it weighs too much.
andrea tasselli
> "andrea tasselli" <atas...@hotmail.com> wrote in message
> news:ba9aa3a9.03012...@posting.google.com...
> > chri...@aol.com (Chris1011) wrote in message
> news:<20030124160844...@mb-cu.aol.com>...
> > > >>Go around and shop for high resolution pictures of anything. My e-mail
> > > address
> > > is in the header. Post your findings and I'll post back mine.>>
> > >
> > > How about: http://www.celestialimage.com/page189.html
> >
> > It doesn't make it, for however good it is is too low in resolution to
> > compete. Besides, gimme that ST10E, a good mount an H-alfa and I'll
> > show you as much.
> >
> > Andrea T.
> >
> > My Astronomy Pages at:
> > http://www.geocities.com/andreatax/index.htm
>
> Hi Andrea,
>
> I think this could be in the running;
> http://users.erols.com/dgmoptics/Images/image006.jpg
>
> Full aperture solar filter over the front of an OA-4.0, (98mm, F/10.3
> off-axis Newtonian) 12 mm Plossl eyepiece, and a Sony Camcorder (handheld)
> on an unguided dob mount. Courtesy of Mike Palermiti, Jupiter FL.
>
> Dan McShane
Good try but still far too short of the target, I'm afraid.
Considering how was captured it's an amazing image however.
andrea tasselli
> >>
> The person in question has NOT a f/10 mak but rather a f/12 (with
> might turn out to be anything in between f/11 to f/13 depending on
> circumstances) 34.5% obstructed mak. >>
>
> Well, if you want to split hairs, I have one also which has a 2.1 inch central
> obstruction diameter, and a clear aperture measures just under 5.9 inches (the
> opening measures slightly larger, but the clear part of the glass is 5.9").
> That makes the obstruction 35.6%.
Well, since I have/had 2 and both had a CO of 52.2 mm on a clear
aperture of 150 mm I guess I have the upper hand on this. The CO is
34.7% therefore.
>
> >>Even with such high CO it still
> has far more concentrated energy within the first two dark rings(accounting for
> nearly the totality of the focused energy) than a 4"
> unobstructed scope>>
>
> You must be assuming perfect optics in the Mak, which may not be the case here.
Might well be. However the discussion was on whether *any* 4" or less
refractor can beat any 6" Intes. It's not the case and I want to make
that clear.
> If the optics are only 1/4 wave with some edge defect, you could easily have an
> Airy Disc peak of less than 60% with quite substantial energy in the first few
> diffraction rings. In poor seeing, this could wipe out any contrast.
In poor seeing it's hard to pick any contrast, I'm afraid.
andrea tasselli
> >>Besides, gimme that ST10E, a good mount an H-alfa and I'll
> show you as much.
> >>
>
> Sorry, I don't give that kind of stuff away. You'll have to get yer own.
Thanks. Sort I knew that already. APOs are good only if supported by
several 10000s worth of hardware I see.
Tony
>I already have my finders, no, thanks. Besides, it weighs too much
Somethings wrong somewhere!!!!!!!!!!!!!!!!!!!!
This guys as bad as Sick-Fried or whatever his name is. Two of a kind
Tony
DGM Optics
Damn, I guess I`ll have to lodge a complaint with the rules commitee on this
one !!!
:-))
clear skies,
Dan McShane
www.dgmoptics.com
SPaul21
> Were you, by chance, out last year the night before Thanksgiving? Right
> after a about a half foot snowfall, but the storm departed with sparkling
> clear skies and no wind that night. The seeing was about as good as it`s
> been around here in a couple years, or more. Saturn was magnificent. The
> Cassini division looked as if was drawn on with a fine black felt tip pen.
> The Crepe ring was easy but no Encke minima (that`s asking for too much).
> The planet itself displayed the obvious dark band around the equator then
> varying shades (not really bands, but hinting at them) up to the darkened
> pole.
Hi Dan,
Actually, that night I took my first picture of Saturn with the MX5-C
and the C8 at F20. I've tried in vain to do better. Although I haven't
given up. Unfortunately, I was so occupied with focusing and imaging
that I missed it visually. Ah well, I got a picture I'm pretty happy
with, for a beginner.
http://users.net1plus.com/spaul/AstroPhotos/Saturn3.jpg
I recently read that the MX5-C camera body fits inside a two inch
focuser. I hadn't realized that, and it didn't occur to me. I'm going
to see if I can sink her down into the focuser of the XT10 far enough
to reach the focal plane. If so, I might be in the market for an EQ
platform that can be autoguided. But anwyay....
> Hope the milky high junk doesn`t spoil your Jupiter look! I got a peek at
> Europa transiting around 11:00 pm.
I hadn't really done any research ahead of time for this session, but
I figured there must be a GRS transit coming up, since an astro friend
in Harvard suggested the previous day that we get together and observe
Jupiter. At the last minute we cancelled on account of the weather.
However, at home, I kept poking my head out to see if I could get a
window of opportunity. Well I could see Jupiter in the mist and
decided not to let the water vapor stop me, so I went out to see what
I could see. It turned out to be quite decent, but I couldn't push
300x and I was wishing I had a 5mm eyepiece, so that I could run at
250x. (I don't have anything in that range in this scope right now,
and the 8mm and 5mm Radians are on my wish list).
Anyway, while I was observing at 192x with the 13mm Nag and the Ultima
Barlow, I saw a bright spec departing from the west limb and was
thrilled by the sight. I dashed into the house and did an internet
search for one of the Juptier Moon applets. I wanted to know what was
going on up there and when the GRS was due to transit. Turns out it
was Europa, very cool, and so I observed for 10 to 20 minutes at a
time, taking warm up breaks in the house Each time out Europa was
further and further out from the limb.
Well, to make a long story short, before I knew it, it was 3AM and the
GRS was well accross the planet's disc. The seeing had been good
enough that I could detect swirls in the SEB and NEB most of the time
and there was a dark patch (barge?) at the south side of the north
polar region. Also a split in the SEB east of the GRS was obvious, as
was the pink-ish pastel of the spot itself. I'm not trying to paint a
mental image of a Hubble photo here, but some nice detail was visible.
Both polar regions were consistently shaded and occasionally I could
detect a distinct temperate zone, north and south.
It was a good night, considering the weather was supposed to be crap.
At 3AM the sky turned clear and transparent, and even though sleep was
beckoning me, I simply had to pull the Barlow and take a look at M51
at 96x in the 13mm Nag before I could put the scope away. Wow, do I
love that eyepiece. Nice wide field, and excellent contrast. If it
weren't so late and so cold, I could have spent another half hour
staring at M51. There was definite spiral structure visible, and the
cores were the brighest I'd ever seen them. (Of course, I've only
observed M51 a handful of times, and from the same backyard skies).
I can't wait for the first transparent and moonless night in Spring to
make the galaxy run with this combination. I also turned the scope
toward Leo and Virgo. I picked out M61 on a 20 second point and hope,
but I couldn't repeat my luck on any others, so I turned in.
-Stephen
DGM Optics
"SPaul21" <SPa...@msn.com> wrote in message
news:cbe98695.03012...@posting.google.com...
> "DGM Optics" <dgmo...@erols.com> wrote in message
news:<b0t5cq$gd1$1...@bob.news.rcn.net>...
>
> > Were you, by chance, out last year the night before Thanksgiving?
> Hi Dan,
> Actually, that night I took my first picture of Saturn with the MX5-C
> and the C8 at F20. I've tried in vain to do better. Although I haven't
> given up. Unfortunately, I was so occupied with focusing and imaging
> that I missed it visually. Ah well, I got a picture I'm pretty happy
> with, for a beginner.
>
> http://users.net1plus.com/spaul/AstroPhotos/Saturn3.jpg
> -Stephen
Hi Stephen,
You should be very happy with that pic! Very good beginners effort. Glad you
got a nice view of the Jupiter happenings over the weekend, too.
clear skies,
(And....., please, oh, PLEASE, warmer skies!)
Dan McShane
---
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Siegfried Gonzi
> You should be very happy with that pic! Very good beginners effort. Glad you
> got a nice view of the Jupiter happenings over the weekend, too.
The shot is really very good. It is also a testimony for the fact that
simply CCD imaging is entitled to exposure planets (imaging planets with
methods of normal photography is useless).
Is it just due to my hallucinations or is the white spot on Saturns body
at the upper right rim real? If so consign the exposure to
Sky&Telescope's gallery section.
S. Gonzi
Stephen Paul
> >>Go around and shop for high resolution pictures of anything. My e-mail
> address
> is in the header. Post your findings and I'll post back mine.>>
>
> How about: http://www.celestialimage.com/page189.html
Hi Roland,
I'm wicked impressed by h-alpha filter shots, and this is an excellent
example.
Can you describe what's going on with the star left of center? Is that a
double star?
Great desktop wallpaper, thanks.
Thanks,
--
-Stephen Paul
jerry warner
account for everything you describe.
Or the scope could be a lemon but that's less likley than poor
collimation.
-Jerry
Tony wrote:
> Hi
>
> I recently posted here about the 93mm F16 refractor that I threw together and
> put it up against my 6" Orion/Intes Mak-Cas and it seems to me the refractor
> easily beat it - on saturn - much sharper, more detail, much more contrast -
> cassini was at best gray and poorly defined in the Mak but black and razor
> sharp in the refractor and hinting at shading in the outer parts of the ring.
>
> Some people responded and said they would agree to this sort of thing but I
> guess the majority said its not possible or I'm a troll or something. (is troll
> a polite way of saying "A--Hole". I have had about 20 scopes over the years but
> nothing really high end and none cost more than $1000 so I'm not any kind of
> expert when it comes to judging scopes but being in this for over 15 years I
> think what I see at the eypiece counts for something. The scopes I had in the
> past range from several refractors up to 4" all F11 or under, Several
> newtonians up to 10" all F8 or under, an ETX90 etc. This homemade 93mm F16
> refractor in my opinion beats all those scopes all though I dont have them to
> compare side by side. To be fair though the larger newtonians were F4.5 so
> probably not a fair comparison anyway on planets.
>
> I bought the 6" Mak-Cas with high expectations of it based on the glowing
> reviews on the internet and S&T magazine which basically stated that other than
> some minor mechanical annoyances it performed flawlessly, competing with high
> end scopes and refractor like images and knows almost no limits on
> magnification. I bought it expecting a high end scope and for it to knock my
> socks off. $1000 for 6" aperture is somewhat high end in my opinion.
>
> Naturally when I first got it I was treated to 3 straight weeks of clouds. When
> I first got to use it the only god target available was the moon. It looked
> quite good but nothing spectacular. As time went on, looking at the moon and
> planets, I still was never impessed with it. Jupiter rarely showed more than 2
> bands with no detail, cassini was difficult in it, stars were not pinpoints. I
> attributed this bad performance to either poor seeing or the scope not being
> cooled down. As far as the latter I tried everything from leaving it in the
> garage all day (which is semi-heated) to actually leaving it hidden and
> unattended in the back yard all day. No difference. I soon became bored with
> the scope and lost interest in astronomy for the last couple of years until I
> came across this 93mm achromat in my drawer and decided to try it.
>
> With all that said where do I go from here. How do I find out if I'm crazy or
> the mak has something wrong with it? I hear people doing test reports on scopes
> and with one peek it seems they sum up the optics and say its 1/8 wave or
> something. What does this mean and how do they know with just a peek. Is there
> some kind of test I can do? Anyone near Johnston RI want to come see this for
> themselves. I want to add that the Mak has never left my property so it has
> not been banged around. If its got something wrong with it, it came that way
> from Orion.
>
> Also, I dont want to get off the main issue here or start a big debate, but
> since I have never had the pleasure of looking thru an APO, How would a 3 1/2"
> F16 refractor compare with a similar aperture APO besides the APO being better
> suited for deep sky.
>
> Thanks
> Tony