DSLR telelens vs newton f/5 telescope for astrophotoraphy?

[mislav]

Hello, what do you think is better for astrophotography?- DSLR with newtonian f5 (150/750) or clasical dslr telelens (100-300mm cca)? Asking about DSO imageing-not planets...

[vlaiv]

I would say newtonian, but it really depends on several factors.

What mount are we talking about? How good lens? Intended targets?

Telephoto lens: needs to be well corrected for infinity with sharp stars, suitable for low resolution work like large nebulae, wide field shots, largest of galaxies. Less accurate mount acceptable. Non standard mounting for lens on mount (large lenses need additional support like suitable rings). No additional corrective optics needed. No star spikes (if you care about it).

Newtonian will probably need very decent mount (I would say HEQ5, you might get away with EQ5 but just). You will need coma corrector. You will probably want to guide at some point. Needs collimation. Will be suitable for mid to high resolution work (so everything DSO except wide field, which you can do by mosaic technique).

So unless you know your requirements / desires it is hard to label any of mentioned as better. In general I would be inclined to say that 6" F/5 newtonian is going to be better (but that is only based on number of different things that it will have an edge over lens).

[mislav]

well if its FD lens it needs corrective optics.... My telelens is 100-300mm F5.6 Canon FD, and its ok on day imageing...but dont know about starimageing... Newtonian is 150/750 and its on alt/azt goto mount (so i asume no way for more than 30sec exposures)..

[vlaiv]

18 minutes ago, mislav said:

well if its FD lens it needs corrective optics.... My telelens is 100-300mm F5.6 Canon FD, and its ok on day imageing...but dont know about starimageing... Newtonian is 150/750 and its on alt/azt goto mount (so i asume no way for more than 30sec exposures)..

Alt/Az mount is not really suitable for astro photo, but yes, people do use it with short exposures, you can find on this forum, there was even thread with challenge for AZ mount astro photo - there you can see some results.

As for lens, I'm not expert, so I can't really say anything clever for that. I guess your best bet is to do some research on internet, try to find reviews of that lens and see sharpness on far targets - ideally look for review for astro photo.

[happy-kat]

FD lens as far as I'm aware (I have several) will generally reach focus with a canon eos-m camera but not a canon with a mirror. Personally I have found that to get around the soft middle of the image when using the corrective optics adaptor the lens has to be fairly heavily stopped down which isn't ideal for astro imaging. I do find the my 70-135mm FD lens with a element with no corrective optics adaptor makes a great macro lens on my canon 1100d. If you are into diy there is a page on the internet showing how it might be possible to modify an FD lens to then reach focus with a mirrored canon. I think if you already own the lens then have a go there is nothing lost in trying with what you already own.

But from your posts you own a Sony camera isn't that a mirrorless camera? Why do you need an FD adaptor with corrective optics for that camera?