DSLR Imaging - Std Lens Vs Refractor

[AntHart]

I’ll keep this one short and to the point for once

If I’m using a DSLR (full frame Canon 6d) why should I use a refractor telescope,  plus flattener, plus an adaptor ...and not just use something like a 150-600mm f5-6.3 zoom lens instead??

is it because a telescope is designed to perform better (baffles/coatings and what not)?

is it down to the quality of glass?

is it because telescopes have finer focus control?

As a beginner I’ve more questions than answers!ha! 
 

Anyone out there using a big zoom camera lens (400-600mm) please post some photos ...plus any ED80 guys would be ace to 
 

Be great to hear some pros and cons for each 👍🏼
Cheers, Ant 

[cuivenion]

It depends on the quality of the telescope and the camera lens. Zoom lenses tend to have poorer optical quality than prime lenses. A telescope with a flattener will give better performance than most zoom lenses unless you're spending a hell of a lot of money on the lens.

Try having a look on the Astrobin site where you can look up images taken by different telescopes and lenses.

https://www.astrobin.com/

 

[wxsatuser]

The refractor will need to be able to cover the full frame chip for a start, at least a 44mm imaging circle.

Most wide range zoom lenses will likely give poor results depending on what you can put up with and can vary in quality and speed.

A very good fast zoom lens will cost an arm and a leg same as a very good fast scope.

There is one very good fast Canon zoom, Canon EF 70-200mm f/2.8L IS III USM Lens, or the II version.
These can run wide open across the range with good results but expensive, they also work fine on APS-C.

[rickwayne]

Certainly people have done outstanding images with zooms. But you don't get something for nothing, and optical design, like in any discipline, is all about compromises. A general-purpose camera lens, especially a complex optomechanical one, has to play off all manner of constraints against each other. By comparison, a telescope has a very simple job: Provide sharp, contrasty, aberration-free images at a single focal length, at a single distance (infinity).

One of the major advantages to a camera lens is of course that it's FAR more useful for terrestrial photography too. And your point about focusing is well-taken. An astro-suitable telescope will have a geared-down fine focuser operating at a 10:1 ratio, because there is no depth of field and stars are incredibly unforgiving of even tiny focus errors. (We are talking about linear movements in the 10-micron range!)

[Knight of Clear Skies]

If you already have lenses for your camera they are well worth a try but most primes will give better results than zoom lenses. A particularly good AP lens is the Samyang 135mm f2, you might not require as much focal length as you expect. To give an example, this is the Rosette and Cone at 135mm.

[AntHart]

On 09/04/2020 at 04:49, cuivenion said:

It depends on the quality of the telescope and the camera lens. Zoom lenses tend to have poorer optical quality than prime lenses. A telescope with a flattener will give better performance than most zoom lenses unless you're spending a hell of a lot of money on the lens.

Try having a look on the Astrobin site where you can look up images taken by different telescopes and lenses.

https://www.astrobin.com/

 

What an awesome website!! Thank you mate  I’ve signed up..no images yet but I’m on there as AntHart 👍🏼

[AntHart]

On 09/04/2020 at 05:45, wxsatuser said:

The refractor will need to be able to cover the full frame chip for a start, at least a 44mm imaging circle.

Most wide range zoom lenses will likely give poor results depending on what you can put up with and can vary in quality and speed.

A very good fast zoom lens will cost an arm and a leg same as a very good fast scope.

There is one very good fast Canon zoom, Canon EF 70-200mm f/2.8L IS III USM Lens, or the II version.
These can run wide open across the range with good results but expensive, they also work fine on APS-C.

I’ve been looking at the Canon 200mm f2.8 L prime...plus the Samyang 135mm f2...both around £400 ..prices are for Canon used VGC, Samyang new.

Cheers for the reply  

[AntHart]

On 12/04/2020 at 15:01, Knight of Clear Skies said:

If you already have lenses for your camera they are well worth a try but most primes will give better results than zoom lenses. A particularly good AP lens is the Samyang 135mm f2, you might not require as much focal length as you expect. To give an example, this is the Rosette and Cone at 135mm.

That’s one I’ve been looking at mate, the Sam f2 looks epic for the price! My only worry was the 135mm vs 200mm FL , I know it’s not much but being full frame every little helps  The 200mm I’m looking at is the Canon 200mm f2.8 L (black one red ring) it’s a prime not the 70-200 like I might have given the impression 👍🏼
Cheers

[wxsatuser]

1 hour ago, AntHart said:

I’ve been looking at the Canon 200mm f2.8 L prime...plus the Samyang 135mm f2...both around £400 ..prices are for Canon used VGC, Samyang new.

Cheers for the reply  

The Canon is a good lens, can even be used wide open but most stop it down a bit.

The Samyang is most likely the best out there overall and should run wide open.
Not used it on a full frame but it's superb on an APS-C sensor, should be ok as it is
made as full frame lens.