DSO Imaging with a Mak

[Dazzyt66]

I know this isn't what you should be doing with a Mak, but I'm experimenting using Ekos atm and with my move to Ubuntu on my laptop, my HEQ5 permanently setup outside I'm really enjoying the fast setup and am trying to use what Ive got until I can afford an ED frac. So:

I'm using a Canon 1100d unmodded with my 150 pro Mak, Fl 1800. I'm using either ISO 800 or 1600 (I'd read 1600 was optimal for 1100d). I'm unguided so am limiting my exposures to around 60s to be safe (although my polar alignment using Ekos is spot on). Last night I did 40x60s lights of M81 iso1600, with bias, darks and flats. I haven't got much in the way of swirl detail at all (and I'm not expecting miracles) but do I do more subs? Change the ISO? Or just accept that this target isn't achievable? I'm also in bortle 7/8 which I guess isn't helping either? My gut feeling is I should've done more subs at iso800 rather than 1600.

I've had a decent image of the ring nebula in the past using the mak and Canon (just using a camera remote), so I know some DSOs are possible - I just don't want to waste precious clear nights trying to do the impossible! I would like to get a nice image of a whirlpool though!

Oh, and as you can probably tell, I know nowt about photography in general so its all a learning curve atm! 😂

Any help much appreciated!

Edited April 13, 2021 by Dazzyt66

[Avocette]

To catch enough photons from M81 you will need significantly more time. With your 150 SkyMax Pro with the DSLR mounted, the actual focal length probably measures around 1900mm and the actual (measured) mirror aperture is 140mm, so the focal ratio is f13.5 or so. That means you will need about four times more exposure than what you would with an SW ED80 with its matching focal reducer/field flattener (~f6.5 510/80). I spend no less than an hour on a target like M81 and typically two hours or more with my ED80 and ASI 533MC pro.

[Dazzyt66]

1 hour ago, Avocette said:

To catch enough photons from M81 you will need significantly more time. With your 150 SkyMax Pro with the DSLR mounted, the actual focal length probably measures around 1900mm and the actual (measured) mirror aperture is 140mm, so the focal ratio is f13.5 or so. That means you will need about four times more exposure than what you would with an SW ED80 with its matching focal reducer/field flattener (~f6.5 510/80). I spend no less than an hour on a target like M81 and typically two hours or more with my ED80 and ASI 533MC pro.

Thanks, this does make perfect sense - I realise I will need to do more subs but just wanted an idea of how many more - I didn't want to waste several hours to no avail. very useful.

🙂