Astrophotography Scope

[mick pinner]

After keeping an eye on the pics that our resident astrophographers have been submitting it has become apparent that the medium sized scopes seem to be the scope of choice, and to a large degree l know this is dictated somewhat by the mounts available to carry them.
What l would like from the group of photographers out there is opinions on what would be the optimum photographic scope, l know opinions will vary greatly but all opinions appreciated, keep in mind that this scope will be purely for photography so size for visual observing is not a factor. Thanks guys.

[matt]

Celestron 9.25

Pound for pound the greatest in its weight division

[JohnG (John)]

Boy, you have opened a can of worms there, what mount are you looking at, like you say, the mount quite often dictates the scope.

My opinion, APO refractor and a premium mount.

JohnG

[janoskiss (Steve H)]

From a 100% theorist (i.e., zero experience ): Decide on what is the smallest detail you want to be able to resolve. This will set a minimum for the aperture for the scope. As a guide consider:

minimum aperture in inches = 4.6 / required resolution in arc seconds

Multiply by 1.4 if you want to image red things, double for infra-red.

[matt]

Sorry Mick

I misunderstood. Were you only asking about our opinions on which scope or do we also have to factor mount into the equation?

If that's the case maybe you could specify what you're likely to mount this scope on.

[mick pinner]

l really wasn't going to get into mounts but for the sake of argument lets say a G-11.
My idea is the optimum scope for all around photography, there is always comprimises between deep sky and planetary stuff so a scope that works well taking these comprimises into account.

[bird (Anthony Wesley)]

Hi Mick, I think the optimum scope for deep-sky is different to the optimum scope for planetary imaging... are you looking for something that will be good both of these, or just optimum for one of them?

For planetary work it seems the optimum scope is somewhere in the 10" - 14" range, but for deep-sky I guess the larger the better (as long as you have the EQ mount to take it!).

Planetary work on larger scopes quickly becomes problematic. Large mirror take longer to cool and the seeing conditions required for high res work and large mirrors are harder to find.

For deep-sky I think it comes down to the largest weight that your mount can take and still track accurately...

regards, Bird

[mick pinner]

thanks for the reply Bird and herein lies the problem, l appreciate that each scope and viewing/photographic object has it's good and bad points but surely there must be a scope that crosses the border between the deep space / planetary objects and can produce satisfactory images of both keeping in mind l'm not talking award winning images just reasonably good images of a wide range of objects.

[matt]

Bird

You seen Dennis' Jupiter captured with the 9.25? About the best Jupiter image I've seen with a scope in the 8-12" bracket. Better than a lot with larger aperture too! IMO

He's also posted some nice DSO pix too, by the way.

Rob's also done some great planetary work with his 9.25.

Obviously seeing is King, but that's the same wherever you happen to be imaging and with whatever scope you have.

[janoskiss (Steve H)]

Originally Posted by mick pinner

... there must be a scope that crosses the border between the deep space / planetary objects and can produce satisfactory images of both ...

I think that's one reason why 10-14" SCTs are so popular. Your 12" LX200 should be super, Mick. That's the sort of scope that semi-pros, like postgraduate students doing astronomy research, are using at some of the big universities.

[bird (Anthony Wesley)]

For the best of both worlds sort of scope I'd suggest something in the 10" to 12" size, that also keeps the scope nice and portable.

For the last year ot so I've been using a 10" f/6 newtonian, and it has given me first class results both visually and photographically.

regards, Bird

[Striker (Tony)]

Mick,

This will depend on what Camera and target imaging you will be doing.

Small chip CCD's will need something like an ED80 or even shorter focal length where a large CCD or CMOS chip like a DSLR or dedicated SBIG camera's can be used on larger aperture and longer focal lengths scopes for DSO's.

A small ccd chip is not optimal for a large aperture long focal length scope.

This will also depend on what you want to do regarding widefield or longer focal length imaging.

If you had a camera in mind and what you plan on imaging then we could offer a good match.

There is no such thing saying a particular scope is great for Astrophotography.

[iceman (Mike)]

You seen Dennis' Jupiter captured with the 9.25? About the best Jupiter image I've seen with a scope in the 8-12" bracket. Better than a lot with larger aperture too! IMO

As you say Matt, seeing is king..

Obviously the scope makes a difference, and the C925 is no slouch in that department, as proven by Damien Peach. But on a night of fantastic seeing that Dennis obviously had, I think anything in the 8-16" range would've produced an incredible image.

Wes Higgins (arguably one of the finest lunar imagers in the world) does his imaging with a servocat driven 18" starmaster (newtonian).

I don't think there's an ideal - the best at their art will pull the best images within the limitations of their equipment.

[matt]

I'm not so sure "anything" would have achieved "incredible" results Mike.

Even with great seeing you still need high quality optics and a fair degree of skill to achieve optimum results. As you know there's a fair number of variables that come into play in achieving superb planetary/DSO images.

Great images don't just fall in your lap because the seeing's good. Let's not dress it down too far!

But having said that, I've already stated how large a part seeing does play.

And I think given the standard of most mass produced optics these days (mirrors and lenses) most telescope owners are in possession of an instrument "capable" of high quality images.

Obviously there is no ideal telescope. That goes without saying.

[janoskiss (Steve H)]

Aperture is king until you have at least 5" of it.
Seeing and aperture compete for first place between about 5 & 10".
Seeing normally rules over 10", but sometimes aperture can make the best of exceptional seeing up to 16".
Beyond that it's all about trading light for time, and the more light the better. Aperture rules! Viva la republic!!!

[matt]

Well ... here we go!!!

This is one debate that could go all night. Aperature ... aperture...aperture.

Not for me though. Mick asked us to put forward our suggestions for an optimum photographic scope.

Do I need to be told aperture rules? NO

If it's a debate about aperture size, count me out. That's too much of a ***** contest for me.

I like the path Bird is heading down though vis-a-vis size and portability. If that's an important consideration, and it is for most of us, then you'll have to trade off some inches.

14" IMO would be the upper limit? Even that's getting beyond most people for moving around.

[Dennis]

Working up to the C9.25 has been a long, at times frustrating, apprenticeship for me, and I have had good people to learn from, and help me when I made mistakes.

I started off with a 4” refractor and a Pixcel255 (320x240) ccd camera. The 918mm focal length of the refractor was very forgiving. But, in the early days, it was still very frustrating acquiring the target (before I had GoTo) and then laborious and time consuming doing the multitude of other things such as polar alignment, focusing etc.

If I had started my apprenticeship with the ST7 and the C9.25 I would probably have given up. My slow and steady build up via the 918mm focal length refractor gave me the patience, techniques and skills to move up to the longer focal length of the C9.25, and learn the art of auto guiding. Even so, I still have my moments!

I don’t want to put anyone off, but it can be a steep learning curve and quite tough going as you master the basics of polar alignment, GoTo set up and alignment, finding the target, finding a guide star, getting good focus (changes with every 5 deg C drop in temp), setting up and integrating scope, mount, camera, computer, etc. Not forgetting the flat fielding, dark frame subtraction, image stacking and processing.

However, going in with both eyes wide open and the determination to succeed can overcome all these learning obstacles, so dive in and you’ll be well rewarded!

Cheers

Dennis

[janoskiss (Steve H)]

No peeing contest intended Matt. I was just meaning to say that you need enough aperture to resolve fine (angular) detail, before seeing becomes an issue (and trying to crack a joke at the same time ). For visual at sea level, about 5" seems to be the borderline where seeing is ordinarily is more limiting than aperture at high power, on bright targets like the Moon or the gas giants.

Mick, did you see the Hubble-esque photos taken with a 60mm Tak and posted here by ausastronomer?

[davidpretorius]

ok, I love my 10" newt, but in 5 to 10 years time, i believe that sct will be on the cards. the bigger the better and with a wedge to boot. I will also want an arsenal of cameras from canon dslr thru to sbig and artemis / dragonfly etc.

Dennis has proven it for me, his c9.25 is doing great work across the range.

If i were setting up my observatory and money was no object then meade rcx series etc in 14" or 16" will be on the cards.

I also want a ed80 as well down the track!!!

[matt]

No worries Steve. Knew exactly what you meant.


Was more a general comment about the perils of an aperture debate when ol' Mick was looking for specific scope recommendations. Or at least that's the way I read it.

Bit surprised that slipped through the language filter, actually

Anyway ... debate away.

I'm off to bed.