TAL-200K
Henrik Johansson
Has anyone here tried the TAL-200K Klevzov-Cassegrain telescope?
According to an ad you get lots of equipment for the money:
200mm (8") Motorized Klevzov-Cassegrain Telescope
Magnification Range: 69x, 139x, 177x, 357x
Diameter of Primary Mirror: 200mm
Diffraction Limited Optics
Telescope focal Length: 1735 (f8.7)
Eyepieces supplied (1.25"): 10mm Plossl & 25mm Plossl
2x Barlow lens
8x50 finderscope, field 7°
Light filters supplied: yellow, red, blue, green and neutral grey
(Lunar).
Equatorial Mount with built in electronic motor drive
Heavy duty pedestal stand with built in vibration suppression pads
Price: £699.00
Regards,
Henrik
ar...@selena.kherson.ua
Hi Henrik,
While this scope is really cheap, it has several major disadvantages.
They are:
1. Very tight tolerances for the proper collimation and centering of all
elements.
2. Huge coma (larger than in an SCT).
3. Much more reflections than in any another design on the todays
market.
4. Large central obstruction.
5. Very big field curvative.
6. Open tube (disadvantage vs SCT).
The only advantage is all sperical surfaces (light come through and
reflect) - totally six surfaces on a light pass (too many, I think). This is
very good for manufacturing. This is a reason of main advantage -
low price.
IMO, any todays 8" SCT ($300 more expensive) is better, especially
if we consider a quality of a filed tripod, coating. Above disadvantages
are not exist or less significant in an SCT.
Valery.
Sent via Deja.com http://www.deja.com/
Before you buy.
lude...@my-deja.com
> Hi Henrik,
>
> While this scope is really cheap, it has several major disadvantages.
> They are:
>
I see again Valery know anything, but really not to much about this
product. Valery know about something like this design from his
computer, but not about this specific modell.
Here some coments to Valery from first hand, the designers of this
system and a published production report from Moscow.
primary is spherical, secondary is an douplet corrector made from same
glas, the first lens is a negative meniscuslens with long f-ratio for
correction of spherical aberration and coma, yes Valery Coma is
corrected.The second element is a negative maginlens which make the
chromatismcorrection and bring the focus out of tube. Thanks to the
same dispersion of both lenses, the spherochromatis is reduced into the
size, smaller tahn the airydisc, so no visible color.
The photographic field is limited due fieldastigmatims and curved field
and the corrected size of field is between 30 and 40 arcminutes.This
fieldastigmatism and curved field can be corrected by a photographic
corrector.In SC systems you gettingstraylight, not in this system.
The tested sensitivity for misscollimation is far less than in all
commerical Schmidt Cassegrain ( Valery this is the second point where
your info is wrong), due the use of spherical optics.This was already
due practical tests.
The compactness, simple to manufactor optics, compact size and
relativly wide tolerance for misscollimation and decentering are the
most postive signs of this new system.
The douple corrector is held in a thermocompensation cell for
temeperature diffrences of + - 50° celsius. The spider is 3 van curved
spider, that results into nonvisible spikes even at bright objects.The
primary mirrors is fixed in the backpartof the tube , so that a
decentering of primary mirror is impossible, even by bad handling and
poor transport.
Practical tests by the manufactor showed that that this design in
serialproduction made, is much more lightweight, more simple to build
and much less sentitive for decentering and much much more easy to
collimate than a 8" MCT telescope.
> 1. Very tight tolerances for the proper collimation and centering of
all
> elements.
wrong , please read above
> 2. Huge coma (larger than in an SCT).
fully comacorrected, please read above
> 3. Much more reflections than in any another design on the todays
> market.
wrong, much les reflections than in any SC
> 4. Large central obstruction.
33% is not to much ( include secondary baffle), which is much les than
SC and same as F/10 MCT
> 5. Very big field curvative.
only a diadvantage for photographie, with corrector photographic field
increase to 1,3 degree at F/6,3
> 6. Open tube (disadvantage vs SCT).
, cools down much more quickly than a SC or MCT, is that a disadvantage
?
> IMO, any todays 8" SCT ($300 more expensive) is better, especially
> if we consider a quality of a filed tripod, coating. Above
disadvantages
> are not exist or less significant in an SCT.
>
The excisting SCT have the disadvantages of never keep the collimation
during mirrorshift, straylight from Schmidt plate, massproduction
quality.
Valery if you post something about another product, please check the
real product and his real design and dont simulate something in your
computer which is maybe total diffrent.
thanks
Markus
JS
information available about it.. "Soveitsky collection" markets it from San
Diago, only a few lines of info and a picture on the site, APM's website
has more in German (I don't speak). Somewhere I read it gives Mak like
images, than how come there isn't more drumming going on. 8" Maks are much
more expansive then Newt or SCT's, although claiming, it 's cheaper to make
(claim, everything is spherical). Seems cheaper to make, has a higher ticker
price.
JS
lude...@my-deja.com wrote in message <89liph$aod$1...@nnrp1.deja.com>...
valery_...@my-deja.com
lude...@my-deja.com wrote:
> I see again Valery know anything, but really not to much about this
> product. Valery know about something like this design from his
> computer, but not about this specific modell.
I know something and slightly more. Do you know something?
FYI, the original Klevtzov design does has only one meniscus
corrector in front of secondary mirror. If you and others, include
manufacturer call this given system as Klevtzov, then you are
wrong from the beginning.
> Here some coments to Valery from first hand, the designers of this
> system and a published production report from Moscow.
Am I understand that my words were commented by original designer of this
given system? Did you contacted him? he personally commented my words? Is
he live in Moskow? FYI, this is Novosibirsk (Siberia) optical plant product.
Not Moskow.
> primary is spherical, secondary is an douplet corrector made from >same
> glas, the first lens is a negative meniscuslens with long f-ratio for
> correction of spherical aberration and coma, yes Valery Coma is
> corrected.The second element is a negative maginlens which make >the chromatismcorrection and bring the focus out of tube. Thanks to >the same dispersion of both lenses, the spherochromatis is reduced >into the size, smaller tahn the airydisc, so no visible color.
No question about colors. These types of systems ( Popov, Klevtzov,
Argunov) are suffer from coma and field curvative. The coma is
a property of such systems without exception and no matter how many
lenses the small corrector use- one, two or three or four.....
>.In SCT systems you gettingstraylight, not in this system.
Interesting. How one YOUR cassegrain systems are differ
from anothers? May be they has curved main baffles? :-)))
Note, please, that only Markus said something about straight light
in cassegrain designs and now, when this is needed, he quickly
forgot his own words that any cassegrain-like systems are suffer
from a straight light. Whats about Intes' MAK-Cass ?
> The tested sensitivity for misscollimation is far less than in all
> commerical Schmidt Cassegrain ( Valery this is the second point >where
> your info is wrong), due the use of spherical optics.This was already
> due practical tests.
I never said something from practical tests of this given scope. The
design sensitivity has nothing to do with actual mechanical perfomance.
The radii of curvative here is much shorter (in the corrector) than in
SCT and therefore a higher sensitivity to any decentering is a property
of this design regardless what Great Teacher Markus said.
> The compactness, simple to manufactor optics, compact size and
> relativly wide tolerance for misscollimation and decentering are the
> most postive signs of this new system.
> The douple corrector is held in a thermocompensation cell for
> temeperature diffrences of + - 50° celsius.
The compactness is not a bit better than in any SCT. SCT optics is
same easy for MASS manufacturing as this one.
I never heard that any manufacturer does use a thermocompensation
cell for the design which is not sensitive to the decentering. It is
quite interesting to know why the cell is thermocompensited. What is
the reason? To make the scope more expensive - probably not if we
look on its price. So, Markus, what is the reason? You you simply
get entangled in your misleading of public?
>The
> primary mirrors is fixed in the backpartof the tube , so that a
> decentering of primary mirror is impossible, even by bad handling and
> poor transport.
Even Mak-newt which is much less sensitive to the decentering sometime need a
collimation. I clearly remember that 145mm MN I saw was required a
re-collimation, not much, but still required. And this design is also use
fixed mirror. Why the system which is much more sensitive to the decentering
is impossible to decollimate? You can't be sure in this. You simply try to
promote one of a next product you plan to make money on. I am not so biased
and therefore I am objective unlike you.
> Practical tests by the manufactor showed that that this design in
> serialproduction made, is much more lightweight, more simple to build
> and much less sentitive for decentering and much much more easy to
> collimate than a 8" MCT telescope.
He he! Markus, as I know, you never belive to any manufacturer's
words. No you said totally different. You can't go bothe ways.
Who will belive you that this system is easir to collimate than a simple
SCT. They both does has similar configuration and additional elements
can't simplificate a collimation - they can make a collmation more
difficult, but not in any case easier. To say this is the same if you say
that you can fall in upper direction. :-)))
> > 1. Very tight tolerances for the proper collimation and centering of
>> all elements.
>
> wrong , please read above
OK, when you will have such scopes in your hand, ask Thomas,
to whom you probably trust more, to simulate the tolerances for the
decentering in this system. Then let us know, please.
And your words about relative advantages/disadvantages of any
optical systems worth nothing - your knoweleges in this field is simply
absent. From practical point, it has a little sense to listen you, but not
in optics.
> > 2. Huge coma (larger than in an SCT).
>
> fully comacorrected, please read above
I already read. Thanks. But huge coma in similar systems can't be
corrected by any manipulations regardless what you or somebody else said.
Unless the revolution is optics and such excellent system was not required
for a practical realization unless one genius in Siberia understand to
realize it?! These type of systems are at least 40 years old, if not older.
For one such system the S&T published the article ( 70x - 80x) .
>
> > 3. Much more reflections than in any another design on the todays
> > market.
>
> wrong, much les reflections than in any SC
You definitely get entangled in twi trees. You said that this system
does has a meniscus corrector with 2x light pass + one more element.
Totally 8 reflections (two on mirrors and six on lens surfaces) vs
only four in any SCT.
Your explanations make me bore, really bore. And what is the most
poor is that some peoples will listen you and will be misleaded for
no reason.
> > 4. Large central obstruction.
>
> 33% is not to much ( include secondary baffle), which is much les than
> SC and same as F/10 MCT
Not much less. In 12" Meade and 14" Celestron c.o. is not larger
than 33% if not less.
> > 5. Very big field curvative.
> only a diadvantage for photographie, with corrector photographic field
> increase to 1,3 degree at F/6,3
At least four more reflections and light loss.
> > 6. Open tube (disadvantage vs SCT).
>
> , cools down much more quickly than a SC or MCT, is that a >disadvantage
I didn't said something about cooldown problems. You already told
to us that you never experienced this in any SCT. Now we all see that
you again change your mind (for public, of course) when this need for
you.
Open tube, as you know is a disadvantage in the sense of an air
turbulence. According to you, this system does has advantage
(in a cool down) even versus refractors? Or am I missing something
in your sentences?
> > IMO, any todays 8" SCT ($300 more expensive) is better, > >especially if we consider a quality of a filed tripod, coating.
> > Above disadvantages are not exist or less significant in an SCT.
> >
>
> The excisting SCT have the disadvantages of never keep the >collimation during mirrorshift, straylight from Schmidt plate, >massproduction quality.
If you will use a JMI focuser and fix the mirror by simple srew, you
also will have no problems with collimation lost.
A ha! Now you told to public that not only Mak-cass is suffer from
a staright light, but also SCT.
OK, now:
1. I don't remember that my former 10" Meade does has a straight
light.
2. Hey, guys, who own Intes' Mak-cass (especially through Markus)
does your scopes has a straightlight in your oculars?
3. How is possible for one cass-like system to be totally(!) free from
staright light and for another systems of a similar designs this is
impossible. Don't you think that you are GURU and all must listen
your sentences about each optical systems?
4. This scope is also mass production as any SCT - no diffrence at all.
> Valery if you post something about another product, please check the
> real product and his real design and dont simulate something in your
> computer which is maybe total diffrent.
I do't need your advices. What I know that all your "eaters" were loudly
choked, all your "killers" were failed with their "missions".
This one will be the next, for sure.
I simply forgot a main disadvantage of this design - too many surfaces
mean that total wave front can be far from excellent and the contrast
too. Too many surfaces with reflecion is a light loss too.
Again about decentering sensitivity.
It will be interesting to see that will be a total wave front degradation
if each element in this system will has only 0.02mm decentering.
Clear sky,
ar...@selena.kherson.ua
"JS" <sz...@jps.net> wrote:
> I was looking into this scope a while ago, and there is very little
> information available about it.. "Soveitsky collection" markets it from San
> Diago, only a few lines of info and a picture on the site, APM's website
> has more in German (I don't speak). Somewhere I read it gives Mak like
> images, than how come there isn't more drumming going on. 8" Maks are much
> more expansive then Newt or SCT's, although claiming, it 's cheaper to make
> (claim, everything is spherical). Seems cheaper to make, has a higher ticker
> price.
We can ask Markus why Intes' 6" Mak-Cass OTA only cost more
than this systems? In Intes' Mak-cass all surfaces are spherical and
has less elements, less diameter, less material etc etc. So, what is
the reason of such down to earth price of 8" scope (motorized!) ?
May be a mass production?
lude...@my-deja.com
ar...@selena.kherson.ua wrote:> > price.
>
> We can ask Markus why Intes' 6" Mak-Cass OTA only cost more
> than this systems? In Intes' Mak-cass all surfaces are spherical and
> has less elements, less diameter, less material etc etc. So, what
is
> the reason of such down to earth price of 8" scope (motorized!) ?
> May be a mass production?
Valery,
INTES is placed in Moscow, which is more expensive city than New York
or Tokyo, material is there very expensive and man/per hour work is
more expensive. The TAL Telescopes made by Novorsirbisk in Siberia, I
am not shure, but I expect on Russian country places, the prices are 10
times lower , yes ?
What do we know about this new TAL 200 K? Really nothing, the first
samples will be delivered sometimes in April, than we can check them.
What we can tell about the quality of this manufactor of the other
modells? Testreports all over the world confirmed, that they have a
very robust mechanic and excellent optics. The typical tested
wavefreont quality of the telescopes up to 6" is about 1/6~1/8
wavefront p.t.v. I sold a few hundret of them in germany and any time
we checked them , they showed such quality. So what we can expect on a
new modell from a manufactor who have such good reputation on optical
quality ? I think same quality for bigge rscopes, yes ?
For sample: what we know about AP or Tak quality? all excellent, so do
we expect in a new modell of scuh companys less quality ? For shure not.
Lets wait a few weeks more and we will say, how it comes out, okay ?
thanks
Markus
lude...@my-deja.com
>
> I know something and slightly more. Do you know something?
> FYI, the original Klevtzov design does has only one meniscus
> corrector in front of secondary mirror. If you and others, include
> manufacturer call this given system as Klevtzov, then you are
> wrong from the beginning.
Valery,
the describtion of this telescope I posted is from Mr. Yurij Andreevich
Klevcov, so you want to tell us now, that Mr. Klevcov self describe his
own system in a wrong way to us ? You are real magic!
> >
> Am I understand that my words were commented by original designer of
this
> given system? Did you contacted him? he personally commented my
words?
I have the original letter with descibtion in my hand, translated by an
Diplomtranslater from Russia, do you think he translate all wrong ?
>
>
> No question about colors. These types of systems ( Popov, Klevtzov,
> Argunov) are suffer from coma and field curvative. The coma is
> a property of such systems without exception and no matter how many
> lenses the small corrector use- one, two or three or four.....
coma maybe in your Zemax and your design, but Mr. Klevcov, describe his
original design comafree, now to whom we must believe , to you to the
original designer ? It would be about the same as if you tell to Al
nagler, Al your Naglers are diffrent made, than you describe.
> > > >
> I never said something from practical tests of this given scope. The
> design sensitivity has nothing to do with actual mechanical
perfomance.
> The radii of curvative here is much shorter (in the corrector) than in
> SCT and therefore a higher sensitivity to any decentering is a
property
> of this design regardless what Great Teacher Markus said.
Valery, to mean it seems you talking about your Idea of the design, not
about Mr. Klevcov design. Did you see only of his Telescopes ? Did you
measured all datas to be so shure ?
> >
> I never heard that any manufacturer does use a thermocompensation
> cell for the design which is not sensitive to the decentering.
you are not able to read ? Due this cell it is not sensitive ?
It is
> quite interesting to know why the cell is thermocompensited. What is
> the reason? To make the scope more expensive - probably not if we
> look on its price. So, Markus, what is the reason?
the reasons is like describted to keep the optics stressfree for
temperature variation of 50° celsius. Valery why you not just read ? ,
than you would not need to ask this questions.
You you simply
> get entangled in your misleading of public?
Do you want to protect your own products due making bad other products
? I am getting more and more this impression.
> >
> Even Mak-newt which is much less sensitive to the decentering
sometime need a
> collimation.
Please go to AP webside and tell me what is printed there as an
describtion about collimation of new Mak , than come back and reprint
it , okay ?
> is impossible to decollimate? You can't be sure in this.
Of course i can't be shure from a describtion, but you cannot be shure
of the opposite too, correct ? I know from the zeiss MCT that such
mechanical design is possible, so we don't talk about something
impossible.
>
> He he! Markus, as I know, you never belive to any manufacturer's
> words. No you said totally different. You can't go bothe ways.
I dont go both ways, I wrote here not my impression, please understand,
I wrote here a clear designer and manufactoring company describtion.
> >
> OK, when you will have such scopes in your hand, ask Thomas,
> to whom you probably trust more, to simulate the tolerances for the
> decentering in this system. Then let us know, please.
As long you don't know the excat design of optics and mechanics, you
can say nothing about the final product, correct ?
> >
> You definitely get entangled in twi trees. You said that this system
> does has a meniscus corrector with 2x light pass + one more element.
> Totally 8 reflections (two on mirrors and six on lens surfaces) vs
> only four in any SCT.
The meniscus figure is curved , yes ? this avoid reflections much more
than an nearly flat Schmidt Plate, correct ? any more questions ? I
thought you know a little more, Valery.
> Your explanations make me bore, really bore. And what is the most
> poor is that some peoples will listen you and will be misleaded for
> no reason.
better than to listen you, who try to make a product of another company
real bad, without knowning anything about it, without ever seens one,
how is this possible ?
> >
> Not much less. In 12" Meade and 14" Celestron c.o. is not larger
> than 33% if not less.
but this is 8" and how big is it in 8" SC ?, 36% or so, yes ?
> >
> At least four more reflections and light loss.
same for your MCT using a focalreducer, yes ?
>
> I didn't said something about cooldown problems. You already told
> to us that you never experienced this in any SCT.
please show me where I said this , please come on and show it !!!
> > >>
> If you will use a JMI focuser and fix the mirror by simple srew,
which can be done only in 10" and larger, yes ? the 8" dont have such
screw, sorry!
you
> also will have no problems with collimation lost.
but than you lost the big advantage of the SC, moving mirror focuser !!
> A ha! Now you told to public that not only Mak-cass is suffer from
> a staright light, but also SCT.
wrong again. Please show me that all MCT suffer from straylight ? Come
on and show it to me, or stop liering.
> OK, now:
> 1. I don't remember that my former 10" Meade does has a straight
> light.
because you are a very uncritical observer !!
> 2. Hey, guys, who own Intes' Mak-cass (especially through Markus)
> does your scopes has a straightlight in your oculars?
it have an large enough baffle, not so in most small C.O. MCT, correct ?
Please see post from Yuri to you about this point. When we talked about
straylight in MCT, we did it not about general MCT, we did it only
about secondary coated. I know later on you told me, that your
secondary is much bigger coated, than the used surface, but you did
never told this to Yuri, correct ?
> 3. How is possible for one cass-like system to be totally(!) free from
> staright light and for another systems of a similar designs this
is
> impossible.
who say : totaly free ?
> >
> I do't need your advices. What I know that all your "eaters" were
loudly
> choked, all your "killers" were failed with their "missions".
I see you know nothing again. 1 of my eater, was not presented as an
eater by the show, people did know before , it is not a eater. All
other scopes, excapt this one, have been eaters.
And I beat, that a simple INTES mak 6" beats all 6" maks of same
configuration you can do in you magic Ion Beaming champer.
.
>
> I simply forgot a main disadvantage of this design - too many
surfaces
> mean that total wave front can be far from excellent and the contrast
> too.
you are a little stupid now ? There are no more surfaces than in a
triplet airspaced apo, so you want to say, a triplet apo can be nothing
than bad, yes ?
Too many surfaces with reflecion is a light loss too.
How much , think about it ? We have 2 coated reflections and 3
multicoated glassurfaces. In your MCT we have 2 coated surfaces and 2
multicoated surfaces. So you want to tell us, 1 more multicoated
surface does all this damage, yes ? Become a little more realistic ,
please.
>
Valery , about you are worried in this scope ? Something must worry
you, otherwise you would not try with all your little power to make a
new product, a cheap beginner scope, not yet on the market so bad.
Please explain us this reason.
thanks
Markus
Paul Murphy
-Paul Murphy
lude...@my-deja.com
"Paul Murphy" <pa...@proseandcons.net> wrote:
> Who is going to sell the TALs in the USA?
>
> -Paul Murphy
>
>
Sovietsky Optics
valery_...@my-deja.com
lude...@my-deja.com wrote:
> > given system? Did you contacted him? he personally commented >>my words?
>
> I have the original letter with descibtion in my hand, translated by an
> Diplomtranslater from Russia, do you think he translate all wrong ?
I don't know what you speak about, but I received the original Klevtzov
design from Russian Patent Bureau. And this system simulation show a huge
coma. In any case, send me by FAX this letter from Mr. Klevtzov, OK?
> Due this cell it is not sensitive ?
The materials which is probably used here (Pyrex and K8) does
not require a thermocompensation cell. It is enough to use a
simple steel for a cell wall to eliminate any problems.
> the reasons is like describted to keep the optics stressfree for
> temperature variation of 50° celsius. Valery why you not just read ? ,
> than you would not need to ask this questions.
I read all what you wrote. Did you ever met a problem with stressing of
meniscus in your Intes scopes? As far as I know the tube and cells here are
made from aluminium and the meniscus is from K8 (BK-7). The difference in the
thermal expansion coefficient and their geometrical size are large enough vs
small secondary, small meniscus and their cell. So, no reason to make a
thermocompensation cell to eliminate a stressing. Much more probably that a
cell was made as thermocompensited to eliminate a decentering problem. FYI
instance, Markus, the thermal disbalance in a cell can cause unwanted
freedom for an optical (possible decentering) elements same easy as a
stressing, even more esy.
> You you simply
> > get entangled in your misleading of public.
>
> Do you want to protect your own products due making bad other >products? I am getting more and more this impression.
>
As always, you are wrong in your guess. May be you would like that
I will protect, but this is only in your imagination. Any optics we are
making are in different categories with this given mass production
one. No any reason for me to say something poor about this design
instead of real positive. To say "white" on a "black" is not my sign -
this seems to be your own sign. The problem with this design is almost
total absence of a positive sides except simple manufacturing and
terefore a price.
I only let public know that the design called "Klevtzov" is greatly
suffer from off-axis coma, has too many surfaces and very sensitive to
any, even smallest decentering.
The original K. design is:
1. Spherical primary
2. Spherical secondary
3. Thick small meniscus near secondary (convex surface directed
to the primary) . Light passed twice this meniscus. Meniscus fix a
spherical aberration of two spherical mirror system.
Any similar systems (no matter how many lenses in the corrector
1, 2, 3...) does suffer from huge coma and ffield curvative.
> Please go to AP webside and tell me what is printed there as an
> describtion about collimation of new Mak , than come back and >reprint it , okay ?
Don't tell me that Roland's mechanics is the same class as this TAL
or Intes' . Don't compare oranges and apples (your lovely words).
> > is impossible to decollimate? You can't be sure in this.
>
> Of course i can't be shure from a describtion, but you cannot be shure
> of the opposite too, correct ? I know from the zeiss MCT that such
> mechanical design is possible, so we don't talk about something
> impossible.
High-end mechanics still is not your field. Zeiss and AP can do what you
can't dream about at this moment. May be later.. 8" TAL is definitely the
cheapest possible design and it is compromised in ALL regards. Of course,
for the money $600 it may be a good thing, but I am not sure that the best
possible.
> > He he! Markus, as I know, you never belive to any manufacturer's
> > words. Now you said totally different. You can't go both ways.
>
> I dont go both ways, I wrote here not my impression, please >understand,
> I wrote here a clear designer and manufactoring company describtion.
Sure you try to going by two ways. If it will be possible, you will going
in three or even four ways. This is your strategy.
OK, forgot your "from paper" impression. Keep it for yourself.
Many scopes bofore were described as 600x power ( for 2" TASKO),
1/30 wave front, etc etc. So, no trust to manufacturer's unproved
claims. Let see all on a practice.
> > OK, when you will have such scopes in your hand, ask Thomas,
> > to whom you probably trust more, to simulate the tolerances for the
> > decentering in this system. Then let us know, please.
>
> As long you don't know the excat design of optics and mechanics, >you can say nothing about the final product, correct ?
Incorrect. If one know a principal design, he can easily try to simulate
this design and try to see what kind of perfomance such design can bring.
Any optical design software with automatic optimization will tend to
optimize the system for the best possible prefomance in one way or another.
It is impossible to miss such thing like possibility to fix coma. The
tolerancing will be quite similar too. So, we can't simulate exact design,
but we for sure can conclude, without a big risk to be mistaken, what kind
of perfomance a given system can has.
> > You definitely get entangled in two trees. You said that this system
> > does has a meniscus corrector with 2x light pass + one more >>element.
> > Totally 8 reflections (two on mirrors and six on lens surfaces) vs
> > only four in any SCT.
>
> The meniscus figure is curved , yes ? this avoid reflections much more
> than an nearly flat Schmidt Plate, correct ? any more questions ? I
> thought you know a little more, Valery.
Again and again, as always, your are wrong. Reflection is reflection.
Another reason is how they can damage a contrast.
About Shmidt correctors, if the corrector is tilted only for 0.5 degree,
you will never see any problem. Did you ever saw any similar problem
in your ARIES-INTES 16" Newtonian with flat optical window?
All in all in the 8" TAL there are too many reflections.
> >
> > Not much less. In 12" Meade and 14" Celestron c.o. is not larger
> > than 33% if not less.
>
> but this is 8" and how big is it in 8" SC ?, 36% or so, yes ?
35% . Not too different from 33%.
> > At least four more reflections and light loss.
> same for your MCT using a focalreducer, yes ?
No. Our one does has only two air-glass surfaces. You again wrong.
You also forgot that four less reflections and two less through glass
light pass. Totally enough diffrence.
> > I didn't said something about cooldown problems. You already told
> > to us that you never experienced this in any SCT.
>
> please show me where I said this , please come on and show it !!!
Easily! Read s.a.a. archive when you agrued with Roland about
cool-down problem. You each time cry that you never experienced
this problem with SCTs.
> > If you will use a JMI focuser and fix the mirror by simple srew,
> >
> which can be done only in 10" and larger, yes ?
> but than you lost the big advantage of the SC, moving mirror
> focuser !!
So, the TAL, as you indirectly said, does has a major disadvantage
vs SCT - no mirror focusing.
> > A ha! Now you told to public that not only Mak-cass is suffer from
> > a staright light, but also SCT.
>
> wrong again. Please show me that all MCT suffer from straylight ? >Come on and show it to me, or stop liering.
You can do this easily yourself - look on some discussions about
MCT vs MN . You were so loud there and one of your main ace was
wrong, as always, claim that MCT suffer from a staight light.
Who is always use a lie, depends present private interests, is you.
Read s.a.a. for two years and you will see your own portrait.
> > OK, now:
> > 1. I don't remember that my former 10" Meade does has a straight
> > light.
>
> because you are a very uncritical observer !!
You only think so. How you can figure how critical I am?
> > 2. Hey, guys, who own Intes' Mak-cass (especially through Markus)
> > does your scopes has a straightlight in your oculars?
>
> it have an large enough baffle, not so in most small C.O. MCT, correct ?
Incorrect again, as always however. The small c.o. MCT does has
smaller angular field, but not more straight light. They simply does
has no straight light at all ! You simply don't know the design of the
baffle system.
Two principal questions:
1. Why each time you try to connect any my estimation of any given
system with the AP's MCT ? We only making nice optics for this
instrument.
2. You sold several our 10" MCT . Did you ever saw a straight light
in them? Are were not your own words that these our scopes does
has better deep sky capabilities than significantly larger 12" SCT?
> see post from Yuri to you about this point. When we talked about
> straylight in MCT, we did it not about general MCT, we did it only
> about secondary coated. I know later on you told me, that your
> secondary is much bigger coated, than the used surface, but you did
> never told this to Yuri, correct ?
Correct. I don't have to say him something about our design and
Roland's tricks. Unfortunately he was too fast in his judgements
looking on the picture only. You also don't have to repeat his
wrong step.
> > 3. How is possible for one cass-like system to be totally(!) free from
> > staright light and for another systems of a similar designs this
> > is impossible.
>
> who say : totaly free ?
So, 8" TAL Klevtzov system does has a straight light? Interesting
quick point of view change. Reason?
> > I do't need your advices. What I know that all your "eaters" were
> > loudly choked, all your "killers" were failed with their "missions".
>
> I see you know nothing again. 1 of my eater, was not presented as an
> eater by the show, people did know before , it is not a eater. All
> other scopes, excapt this one, have been eaters.
Sure? Which type(s) of scopes were ate by them? APOs? You each
time cry that you will present a "NEW APO EATER!!!!!" And, as
always they loudly choked . Is this not a reason why you expanded
your apo program? Whats with your "APO eaters" ? Still try to eat?
Are their own teeth were not totally ate?
> And I beat, that a simple INTES mak 6" beats all 6" maks of same
> configuration you can do in you magic Ion Beaming champer.
You will never havea win. First- the ION-BEAM is too expensive for such
size like 6". Second - if we will ever need to make a 6" MAK, then any of
them will be better than any Intes' 6" in any regards from optics excellence
to mechanics. How quickly you becames critic of ION-BEAM. It is worth to
read your own words here, somewhat 18 months ago. And, if Roland will finally
deside to go with 12" MCT and will choose us as supplier, in this case only
you will be able to look through ION-BEAM figured optics. Then you will
speak, OK?
> > I simply forgot a main disadvantage of this design - too many
> >surfaces
> > mean that total wave front can be far from excellent and the
> >contrast too.
> you are a little stupid now ? There are no more surfaces than in a
> triplet airspaced apo, so you want to say, a triplet apo can be nothing
> than bad, yes ?
Markus, as a rule, one, who often use such word as "stupid" , very
probably is really stupid himself in one way or another. Exactly the case
with you. Fortunately, all know this for a long time ago.
FYI: air spaced triplet does has six (SIX!!!)
air-to-glass surfaces. This Klevtzov design does has two reflective
surfaces and at least SIX air-to-glass surfaces ( the light pass the
meiscus twice - FOUR surfaces + one correcive lens, as you said).
Totally 8 reflections versus 6 in air-spaced triplet. You definitely need
to study a simplest arithmetic. :-)))))
Also, I will always say that air-spaced triplets does has more
scattered light than oiled triplets and air-spaced doublets if the
coatings are same good. Some guys here already told that
an air-spaced triplets does has more scattered light vs doublets.
Their reports were based on practical recent comparitions.
A general rule: as more surfaces - as more scattering, is still valid,
and ever will.
> Too many surfaces with reflecion is a light loss too.
> How much , think about it ? We have 2 coated reflections and 3
> multicoated glassurfaces. In your MCT we have 2 coated surfaces >and 2
> multicoated surfaces. So you want to tell us, 1 more multicoated
> surface does all this damage, yes ? Become a little more realistic ,
> please.
Same in your MCTs and MN at first, then, in second - you need to
study a simplest arithmetic and then, in the case of a success, read
something in optics and how a given K. system does work.
You again seat in to a pool. :-))))
>
> Valery , about you are worried in this scope ? Something must worry
> you, otherwise you would not try with all your little power to make a
> new product, a cheap beginner scope, not yet on the market so bad.
> Please explain us this reason.
About power, especially personal one (knoweleges and manufacturing
capacity) you should be silent - better for you - you don't have both.
About imaginated (in your mind only) my worry. No worry at all. I only
let public know what the design K. is , what its main disadvantages
are and a weak advantages (if they in general exist except simplicity in
manufacturing) . I still fully convinced that any serial 8" SCT no
matter Meade or Celestron, having only 300$ high price, will be
better choise for a beginners.
Let see a direct abstract(!) conparition: If scope win in comparition,
this consider as + and vise versa, if loss, than - .
property 8" TAL 8" SCT
-----------------------------------------------------------------------------
---------- 1. Light grasp - + 2. Contrast - + 3. Coatings quality -
+ 4. Sensitivity to colimation - + 5. Filed aberration similar similar
6. Accesories availability - + 7. Acessories ability to use - + 8.
Tripod quality - + 9. Worm wheel size - + 10. Srability - + 11.
Compactness - + 12. Tube currents - + 13. Focus travel - + 14. Service
ability - + 15. oculars quality - + 16. Provided accessories quantity +
-
-----------------------------------------------------------------------------
-------- Total score : 1 : 15
Is not enough?
There are a huge amount of different scopes for a beginners and
one can make his own choise due to known only to him reasons.
But he must have as more info as possible for any given design.
Brendan
Wow, guys....
I'd been interested in the 200K, and in speaking to Sovietski, they've
shipped several so far with no complaints (but it hasn't been that long, I
believe). Unfortunately, it appears that none of these new owners belong to
this group, or we'd have some actual reports to ponder instead of verbal
assaults. I hope SOMEONE can settle this for those of us who just want to
know how the TAL 200K actually performs!
Brendan
<valery_...@my-deja.com> wrote in message
news:89pa7j$2on$1...@nnrp1.deja.com...
lude...@my-deja.com
>
> I don't know what you speak about, but I received the original
Klevtzov
> design from Russian Patent Bureau. And this system simulation
show a huge
> coma. In any case, send me by FAX this letter from Mr. Klevtzov, OK?
My version si the in german translated version , but you can read it in
russian language in the astronomical magazin Zvezdotcet October 1999
> ? ,>
> I read all what you wrote. Did you ever met a problem with stressing
of
> meniscus in your Intes scopes?
No !
As far as I know the tube and cells here are
> made from aluminium and the meniscus is from K8 (BK-7).
but the there is a 5 mm space between lens cell , filled with an
softmaterial during laserrotating collimation. Thei softmaterials
becomes strong enough to keep the lens perfectly centered but still
allow expansion of the glas.The big lens is far not such sensitive for
centering than 2 small power lenses.
> small secondary, small meniscus and their cell. So, no reason to
make a
> thermocompensation cell to eliminate a stressing.
I think, this must left in the hands of the manufactor, not on your
ideas, correct ? You are not responser for proberble working, they are
responser, correct ?
> >
> I only let public know that the design called "Klevtzov" is greatly
> suffer from off-axis coma,
not so correspondance to the original letter of Mr. Klevcov itself, so
maybe you Ideadesign is diffrence from his one ?
> > >
> Don't tell me that Roland's mechanics is the same class as this TAL
> or Intes' . Don't compare oranges and apples (your lovely words).
How you can talk about the mechanics of this 200 K if you have never
seen one, you can only think, but you cannot know it.
> >
> High-end mechanics still is not your field. Zeiss and AP can do what
you
> can't dream about at this moment.
thats your biggest dreaming yes ?
> > >> > > >>
> Again and again, as always, your are wrong. Reflection is reflection.
> Another reason is how they can damage a contrast.
> About Shmidt correctors, if the corrector is tilted only for 0.5
degree,
> you will never see any problem. Did you ever saw any similar problem
> in your ARIES-INTES 16" Newtonian with flat optical window?
yes i see
>
> So, the TAL, as you indirectly said, does has a major disadvantage
> vs SCT - no mirror focusing.
correct, but like in Vixen Cassegrain or INTES MK 91 , many people like
it that way.
>
> 2. You sold several our 10" MCT . Did you ever saw a straight light
> in them?
How big was the central obstruction ? 29%, big enough for well
secondary baffling , yes ?> >
> > > > >
> FYI: air spaced triplet does has six (SIX!!!)
> air-to-glass surfaces. This Klevtzov design does has two reflective
> surfaces and at least SIX air-to-glass surfaces ( the light pass the
> meiscus twice - FOUR surfaces + one correcive lens, as you said).
> Totally 8 reflections versus 6 in air-spaced triplet.
6 coated go through in the Klaevozov ( 1 lens and 1 mangin mirror) and
2 relection surface.
In Apo 6 reflections .>
Markus