3dpan
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Contributing Member
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Posts: 734
Re: Keep Canon 300 f2.8 lens or sell and get telescope?
3
BigBen08 wrote:
I retire next year and will have more time for hobbies. I'd like to try my hand at astrophotography. I'm mostly interested in nebula and galaxies. Not so much planets.
I have the Canon 300 f2.8 IS II that I no longer use. I could keep it for astrophotography or sell it and put the money towards a telescope. Since I know almost nothing about astrophotography, I'm not sure what to do.
I also have the Canon 6D and R5. Would these be useful for astrophotography?
Besides the telescope, tracking device, and a bunch of accessories, I'd like to keep the total cost at $5,000 USD, or less.
Advice?
f/2.8 is very useful, especially for nebulae, dust clouds and similar faint "buried-in-noise" signals.
Very hard to find a telescope that fast.
300mm is also very useful, more than enough for a lot of nebulosity especially if you have a crop-sensor camera.
Fast optics mean shorter exposure times, less demand on your polar alignment, and more images collected in any given imaging time.
Don't underestimate the amount of imaging time that my be required, (see example below)
I can't speak for the optical quality of the Canon 300/2.8 and its suitability for astro, but looking at the test results from LensTip, I would say resolution across the frame, CA levels especially at f/2.8 and f/4, and coma levels, are very hard to beat for astro.
Personally I use the Nikon 300/2.8 because I already had it.
You will get a whole chorus from others who say the speed of your optics is not important because you can use auto-guiding to compensate for longer exposures/tracking problems.
And I say "Sure, if you have the extra imaging time needed, and are happy with the extra complexity associated with auto-guiding".
Also, I recommend a quality tracking mount. It will cost more, but will never (?) become obsolete, and will make achieving high quality polar alignment so much more enjoyable.
As an example I include an image of the Blue Horsehead Reflection nebula.
A stack of 164 x 2-min frames at f/2.8, 135mm on m4/3.
(More than 5 hours of imaging, over three nights).
Reflection nebulae are fainter than for example Emission Nebulae, and require deeper imaging techniques.
Reflection nebulas are actually made up of very fine dust that normally appears dark but can look quite blue when reflecting the light of energetic nearby stars. In this case, the source of much of the reflected light is a star at the eye of the horse.

PS,
I took early retirement about 30 years ago, abandoned city life and moved to a dark sky area.
Best move ever. And I discovered astro photography too.