New scope

[neil groves]

I just tried a session last night on M25 open star cluster which are my fav object to image, I was a little dissapointed with my results in as much I have huge star bloat with a lot of colour fringing, I am using an ED120 skywatcher with a canon T3 DSLR, is this a good combo or would I get better results with a reflector telescope? also my star colours are burned out so what is the remedy for restoring the colours back?

advice on these issues would be greatly appreciated please.

Neil.

[MarsG76]

Are you imaging with your DSLR set to a high ISO? If you are you might be overexposing the stars creating excessive bloating.

[neil groves]

I am using ISO 1600 .

Neil.

[nicoscy]

Read this thread here. A bit old but very pertinent. Best of luck!

[kalasinman]

I wouldn't go over ISO 800 with that camera. More and longer subs, lower ISO. You're right, mirror based scopes don't get CA, are cheaper per aperture by far than fracs. Diff spikes are gone with curved spider kit.

Not being a frac fan, except for camera lenses, what aggravates CA? Lack of field flatness? Poor focus? Dunno

[wxsatuser]

How about posting an image so we can see whats happening.

Was focus spot on?

[neil groves]

Will I get better results from an 8" reflector instead of my ED 120? Are reflectors better than refractors for astro photography?

Neil.

[kalasinman]

It doesn't seem to be as simple as that.

Will I get better results from an 8" reflector instead of my ED 120? Are reflectors better than refractors for astro photography?

Neil.

Reflectors are inherently free from CA, but must have coma corrected, either by adding a corrector or by including counter curved mirrors as in the RC. Refractors require a field flattener, if a special lens for that is not added internally.

Obviously reflectors are much cheaper per increase in aperture, which is one reason I chose the GSO 150/750.

Besides the cost, big fracs are heavy and have a large moment of inertia . This means they may require premium mounts.

Much of the decision will be based on FOV. I plan very large objects with one of several camera lenses , prime focus newt. then a 6" RC . One mount will handle all of these and the lot will cover a wide range of targets at a total cost less than a premium mount alone.

s has been pointed out elsewhere, processing skills are the key to high quality images, once the data has bee properly collected.

[neil groves]

Thankyou that's makes a lot of sense, I'll save for the 8" skywatcher, it's just within my budget of $1000.

Neil.

[Scott]

Thankyou that's makes a lot of sense, I'll save for the 8" skywatcher, it's just within my budget of $1000.

Neil.

Are you sure your mount is up to an 8" newt ? there is no reason to go so big. a 130pds gets amazing results. look on the forum for some results. 

I would also recomend that you do a bit more research rather than act on the first post you read. many MANY imagers prefer fracs. do your reserch and find out why

[kalasinman]

Or a 6" newt? There are MANY imagers who prefer Newtonians, RCs, and other types of reflectors as well. There are reasons why the worlds largest refractor was first lighted in 1897, and why every professional observatory made since then has housed one type of reflector or other.

[Charic]

Neil.....there is a wonderful book available from FLO called Making Every Photon Count. The images are amazing and primarily imaged with a scope of less aperture than your ED120.

Your ED120  should therefore be  capable of similar if not better results, the only issue is that you would need to read the book?

At about $34  ( not sure of postage  to East Bay ~ speak with FLO )    you will have loads of change from your  $1000 and quite possibly a further saving once you know  your scopes  capability.

[Scott]

Or a 6" newt? There are MANY imagers who prefer Newtonians, RCs, and other types of reflectors as well. There are reasons why the worlds largest refractor was first lighted in 1897, and why every professional observatory made since then has housed one type of reflector or other.

indeed there is a reason large aperture scopes are reflectors. cost, human restrictions in ability to make large refractor lenses. did i mention cost? . but we're not really talking about 2 mtr aperture here are we? for the record, I use both fracs and newts and like them both but I still maintain that the op needs to do his own research. incidently, curved veins don't remove diffraction spikes, they just spreads them out over a larger area. whether thats a good thing or not, I've not used them so I won't comment

[wxsatuser]

Surely an ED120 cannot be that bad with CA, have'nt used one but it cannot be any worse than an ED80, can it?

You mention your stars are burntout, most likely you have over exposed, you don't mention anything about exposure etc.

I would'nt spend anymore money until you get to the root of the problem.

If it cannot be fixed then move on.

[Tim99]

I have been using an ED 80 Refractor for over a year now. (My first refractor).  I am amazed at the clarity of my images of the moon.  Simple snapshot photos with a prime set-up have yielded very nice results.   Now, I have read that many people use the ED 80 for their DSO photography.  Who wudda thought that was possible?  The more I read, the more I realize that I need to read some more!  LOL.  I decided I wanted more aperture and just bought a 9.25 SCT for planetary work mainly.  It seems that you can't have too many telescopes.