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advantage of telescope versus dslr and prime lenses

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#1 Clayk59

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Posted 08 April 2021 - 11:49 AM

I hope this is not a stupid question but here goes.  I have a dslr and a lot of experience with terrestrial photography.  I would like to take a crack at some imaging.  My plan is to mount a dslr with prime lens, 200mm f2.8 or 300mm f4 to my cem25p mount and not attach the dslr to a telescope, say a 80mm.

 

My question is, what is the advantage of a dedicated refractor over a similarly speced prime lens?  The lens would be a high quality Canon L series lens.  I realize that this would not work for visual observing but I intend to only image.

 

Your thoughts are much appreciated.

 

Clay



#2 BlueMoon

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Posted 08 April 2021 - 11:54 AM

Quite a few people start off with a camera/lens combination for AP. My thoughts: one advantage is simplicity. The camera with a well-chosen lens provides few, if any, optical or mechanical compatibility issues. Another is that you don't have to match the camera sensor size to the optics train as you do with a telescope. Again, the lens is suited to the camera so no compatibility issues. Yet another is that you don't have to invest in more gear to adapt and mount the camera to a telescope. items like adapters and field flatteners and/or reducers (unless the telescope is already specced for AP use like a WO Redcat 51 for example) are an additional cost. There are other advantages but those 3 are what mattered to me.

 

 

My plan is to mount a dslr with prime lens, 200mm f2.8 or 300mm f4 to my cem25p mount

That sounds like a good workable plan using either lens. If your not having to work out problems with your imaging train because your using camera and lens is already compatible, you can focus more on content, technique and image stacking and/or processing. More fun, less hair-pulling. waytogo.gif

 

Clear skies.


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#3 Rocketrat1

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Posted 08 April 2021 - 11:55 AM

Probably not the best person to answer this but as far as I know a lens will probably have a bit less time dedicated to making all the color channels line up and so chromatic aberration is a bigger problem. Not to mention the focuser of a dedicated refractor is built more for astronomy and so will be easier to use. 

That being said lenses do perform great for astrophotography too! I would definitely recommend for someone starting out to use a lens they already have until they’re sure about getting into the hobby.



#4 meansrt

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Posted 08 April 2021 - 11:56 AM

Longer focal length I would say is the biggest one along with better chromatic aberration correction (depending on the scope or the lens). Your DSLR with those lenses will be an excellent choice though I started out in the same situation. It's too bad M31 is set now because that would be an excellent target for those focal lengths. 


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#5 bobzeq25

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Posted 08 April 2021 - 12:04 PM

I hope this is not a stupid question but here goes.  I have a dslr and a lot of experience with terrestrial photography.  I would like to take a crack at some imaging.  My plan is to mount a dslr with prime lens, 200mm f2.8 or 300mm f4 to my cem25p mount and not attach the dslr to a telescope, say a 80mm.

 

My question is, what is the advantage of a dedicated refractor over a similarly speced prime lens?  The lens would be a high quality Canon L series lens.  I realize that this would not work for visual observing but I intend to only image.

 

Your thoughts are much appreciated.

 

Clay

The lens is an excellent way to start.  The L series are very popular.

 

But you asked what the advantage of a scope.  Since it need focus only at infinity, it's cheaper.  And has fewer elements to absorb light.

 

But a fast lens is a better way to get started.  <smile>  Learning imaging and doing imaging are two different things.

 

Beware of being unduly influenced by a terrestrial background.  Terrestrial and astro are even more different.  For example.  An astro specific calibrating/stacking/processing program like Astro Pixel Processor has significant advantages over trying to add on to and warp a terrestrial photo editing program to do astro.

 

The low signal to noise ratio in astro changes _everything_.  A cautionary tale.

 

"I've been into photography for 20 years so how hard can AP be?"  He found out.  <smile>


Edited by bobzeq25, 08 April 2021 - 12:10 PM.


#6 Clayk59

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Posted 08 April 2021 - 12:05 PM

maybe it was not so stupid.  Thanks to all for the fast and excellent responses


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#7 Sandy Swede

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Posted 08 April 2021 - 12:08 PM

You will find that many here started with a dslr and lens.  I started with the popular Rokinon/Samyang 135mm f/2 (usually stopped down to 2.8), but found the same model 200mm f/2.8 that I believe you have and sold the 135.  Of course, with 'planetary season' just around the corner, you need to get out there an buy a very expensive long FL telescope!  lol.gif  



#8 Clayk59

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Posted 08 April 2021 - 12:16 PM

The whole processing aspect is what makes me want to go slow and inexpensively until I see how I like the process


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#9 bobzeq25

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Posted 08 April 2021 - 12:30 PM

The whole processing aspect is what makes me want to go slow and inexpensively until I see how I like the process

Reading that, I even more strongly recommend Astro Pixel Processor.  It will do _two_ things.

 

1.  Work better.  2.  Let you actually see how much you like the process, without distractions from inferior software that would interfere with that.

 

It's $200.  You're spending thousands on the first 50% of DSO AP.  Spending $200 to do the second 50% better is _completely_ trivial.  It should not be a barrier.

 

The "free" alternatives are not free in terms of your time, your image quality, and best revealing what this business is actually all about.


Edited by bobzeq25, 08 April 2021 - 12:34 PM.


#10 psugrue

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Posted 08 April 2021 - 12:50 PM

OK I will take a stab at this.

First, go ahead with your plan. It's totally legit. People do it all the time. I have done it myself with Canon lenses but not as nice as the one you are talking about. You will get great results.

Now to try to answer your question. What are the advantages of a dedicated astro telescope over a decent Canon prime lens.

Well I think first you will find that if you compare apples to apples. You would for example be looking at a 75 mm (objective lens) refractor compared to the Canon 300mm. The Canon is going to run you $1350 and you can get a pretty decent 75mm triplet for $850 so you can save some money. Or you can spend the $1350 to get into a bigger refractor. For $1400 you could be going up to something as big as 115 mm triplet. So basically you get a lot more scope for your money. Which is hardly surprising because you don't get image stab, autofocus, and adjustable aperture that you don't need for Astro. Also the focus on a telescope is very fine, often 2 speed and easy to lock. Also it comes with hardware on the back to attach dedicated mono cameras and filter wheels right out of the box. This will give you superior results to a DSLR when using NB or stacking video for example. Also the telescope will often include mounts for finder scopes and guide scopes included in the price. I may have forgotten some things but rest assured people will chime in.

 

Regards,

 

Patrick    


Edited by psugrue, 08 April 2021 - 12:54 PM.

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#11 Islander13

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Posted 08 April 2021 - 12:58 PM

+1 for Astro Pixel Processor. I'm very new to astronomy and AP and only wanted to dip my toes in to see how I like it. I'm just on the trial version of APP, but I will be purchasing it. So far I have just used default settings and have been really impressed with the results. I bring the image into adobe lightroom after for tweaking, though I know that APP has some finishing tools that I haven't explored yet. 

 

I came from a strong terrestrial photo background, but had sold off my 70-200 2.8 lens before I got into astro. So I went with the refractor instead of a new long lens after researching the options. If I had a longer lens, I would have definitely just started with that. Having said that - there is little in common between AP and terrestrial photography.  

 

But I can say that I am hooked on AP. The challenge of finding, and framing DSO - the extracting all of those photons with long, tracking exposures - and then having APP do the heavy lifting in processing, and bringing out details that aren't visible to the naked eye, or appear only as smudges though binocs or telescope - all makes for a pretty rewarding experience.     




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