backfocus on 9.25 SCT
Doug Healy
I am curious if anyone has had any issues with backffocus using
microfusers/flip mirrors/ focalreducers on the 9.25 Celestron.
I would appreciate any feedback.
Am going to pick up the new 9.25 this afternoon and hope to have
it on the G11 tonight :-)
Doug H
Rockett Crawford
Doug Healy wrote:
> Hey All
> I am curious if anyone has had any issues with backffocus using
> microfusers/flip mirrors/ focalreducers on the 9.25 Celestron.
> I would appreciate any feedback.
I have heard that the 9.25 has less backfocus, although I have
no experience with one myself.
>
> Am going to pick up the new 9.25 this afternoon and hope to have
> it on the G11 tonight :-)
Sounds like a killer setup. :^)
Rockett
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Capella's Observatory (CCD Imaging)
http://web2.airmail.net/capella
Ron Wodaski
measured it, but I've used 5.5" of accessories back there, and never had
trouble coming to focus.
Ron Wodaski
"Doug Healy" <dhe...@teleglobe.net> wrote in message
news:38DB9F07...@teleglobe.net...
> Hey All
> I am curious if anyone has had any issues with backffocus using
> microfusers/flip mirrors/ focalreducers on the 9.25 Celestron.
> I would appreciate any feedback.
> Am going to pick up the new 9.25 this afternoon and hope to have
> it on the G11 tonight :-)
> Doug H
>
ToddG18522
the meades
RAnder3127
reducers might have a problem when used
with a diagonal, but accessories like cameras (not afocally mounted) will work
fine.
-Rich
Al Gore: "I don't care if gas hits $4 per gallon. The American people have
had
it too cheap for too long. How will we ever move to clean fuels like
methanol if gasoline remains inexpensive? $5000/yr is ok to get
cleaner air." :)
Ron Wodaski
Ron
"ToddG18522" <toddg...@aol.com> wrote in message
news:20000324183142...@ng-md1.aol.com...
Alessandro Vannini
> Sounds like a killer setup. :^)
I'm planning to purchase a new telescope for CCD hi-res planetary images
(no visual or photographic use, just CCD), and wondering what about this
9.25 Celestron SCT. Is this SCT a good telescope for my purposes? How
much is the central obstruction percentage? Since I'll use the CCD camera
along with a flip-mirror unit, the backfocus argument is greatly
interesting for me.
Actually, I'm thinking about a fully custom SCT, let's say a 10" or 11"
diameter SCT (I own a Losmandy G11 too), with a very very little central
obstruction, but would like to consider alternatives before commissioning
the building of the new planetary instrument. Ah, and yes, I've
considered the apo refractor solution, yet :-)
--
Alessandro Vannini - a.va...@mclinkBLABLA.it
http://www.mclink.it/personal/MC7872/index.html
<<Togli BLABLA per rispondere>>
Robert Deane
>The F6.3 reducer/corrector and other
>reducers might have a problem when used
>with a diagonal, but accessories like cameras (not afocally mounted) will work
>fine.
>-Rich
It is fairly easy to compute the back focus and effects of the focal reducer.
Anyone who is interested might like to look at my site and booklet on that
subject. <http://mypage.direct.ca/r/rad> Author of "The Design and
Calibration of Polpular Schmidt Cassegrain Telescopes"
Good viewing. Robert <r...@direct.ca>
Ron Wodaski
need a very special design, with the secondary not located at the corrector
plate, in order to gain any ability to change the size of the secondary. See
"Telescope Optics" by Rutten and van Venrooij to learn the details of this
and other designs.
The 9.25" is very good for planetary imaging; your seeing conditions are
likely to be your limiting factor.
You might want to take a look at the new long focal-length Newtonians coming
from Excelsior Optics, which are optimized for planetary imaging.
Ron Wodaski
"Alessandro Vannini" <a.va...@mclinkBLABLA.it> wrote in message
news:MPG.1346ceac8...@news.mclink.it...
RAnder3127
>Actually, I'm thinking about a fully custom SCT, let's say a 10" or 11"
>diameter SCT (I own a Losmandy G11 too), with a very very little central
>obstruction, but would like to consider alternatives before commissioning
>the building of the new planetary instrument. Ah, and yes, I've
>considered the apo refractor solution, yet :-)
You might be able to produce (at huge
expense) an SCT with a smaller secondary
mirror, but in order to get the focus out
the back, you will have to use a secondary
with more power, hence you will have a longer focal length and a slower
(f-ratio) scope. This will lengthen your exposure times. Using a relay lens
in the baffle to move the focus further out the back will
also make the scope slower.
You might consider a Maksutov instead.
-Rich
"Death warrants have been issued for N'Sync, S-Club 7, The Backstreet Boys,
Britney Spears, Aqua and Christina Aguilera. Anyone caught listening to this
music will be summarily executed."
-The Coalition Against Bad Music.
ToddG18522
It may not have _as much_, but it has plenty. <g>
Ron
Not really.. it has a lot fer sure..but I am just BARELY able to trick it into
being able to use a flip mirror plus a reducer when imaging. I had to pull out
all the stops.. such as 2-1.25" adapters that were totally flush, focus knob
all the way counterclockwise, different focal reducer, etc
also.. limitations involving binoviewer + reducer.
you can draw a case that I am pushing the limit anyway tho.
the meade has a bit more flexibility
teh takahashi has less
TG
RAnder3127
good quality relay lens that would
add a small amount of back focus
and not increase f.l. too much?
Doug Healy
Doug h
Ben Siemerink
> I am curious if anyone has had any issues with backffocus using
> microfusers/flip mirrors/ focalreducers on the 9.25 Celestron. I
> would appreciate any feedback. Am going to pick up the new 9.25 this
> afternoon and hope to have
> it on the G11 tonight :-)
Which Celestron 9.25" SCT did you buy? The CG or the Ultima?
What is the G11 tripod? Couldn't find it on the Celestron web page.
I'm thinking of buying the CG9.25 which comes with a G9 (according to
the spanish booklet in Spain) or with a CG-5 (according to their web
page). Does any of those ring a bell to you?
Thank you very much in advance!
Saludos, Ben.
--
Ben Siemerink
Madrid, Spain.
Rockett Crawford
Ben Siemerink wrote:
> Hi Doug!
>
> > I am curious if anyone has had any issues with backffocus using
> > microfusers/flip mirrors/ focalreducers on the 9.25 Celestron. I
> > would appreciate any feedback. Am going to pick up the new 9.25 this
> > afternoon and hope to have
> > it on the G11 tonight :-)
>
> Which Celestron 9.25" SCT did you buy? The CG or the Ultima?
>
> What is the G11 tripod? Couldn't find it on the Celestron web page.
>
The G-11 is an excellent extremely solid and accurate mount made by
Losmandy.
Celestron used to sell some of their scopes on these mounts until
recently.
Some vendors still continue to sell Celestron and Meade scopes on G-11
mounts however.
take care,