M81 and M82 newbie

[Bikingbill]

Here is my image of M81 and M82 taken on the 17th April. My 2nd attempt at a DSO, so be kind! I used a Canon 750D, RVO 60ED, Starguider pro and autoguiding. 40x60 second exposures at ISO 1600. Only 5 darks. Stacked in sequator and then Ps for processing. I'm under Bortle 5 skies. 

Any advice welcome... do I need to take longer or more exposures? Is my ISO right? Do I need more darks? 

[Rustang]

Great image, lots of good points to talk about. I would definitely recommend taking some 'flats' to help with the gradients, they can be tricky to get right sometimes but once you have managed to, they will help greatly. It could be worth adding a few more darks, also see if some 'bias' frames help, they are very straight forward to take.  ISO 1600 seems to have worked ok with the shorter exposures, the noise in the image isant taking over to much. Have a go with iso 800 when you start taking longer exposures and in regards to this, try going up to 2 min subs and see how your mount performers without guiding, if your stars are still nice then your good to keep going with two minutes and maybe longer!? Great job so far though. 

Edited April 18, 2021 by Rustang

[Adreneline]

This is a really good image and nicely framed up too.

I agree with all of the points suggested by @Rustang.

I took the liberty of removing the gradient and performing a tiny bit of noise reduction. If you're using PS it might be worth taking a look at GradientXterminator to help with gradient removal; there is a free trial so you can assess if it is worth buying.

It might also be worth trying DeepSkyStacker (also free) to calibrate, register and integrate your images, especially once you've taken bias, dark and flat frames.

Great result considering you are imaging under Bortle 5 skies.

Adrian

Edited April 18, 2021 by Adreneline
Clarification

[AstroAndy]

Hi

Like everyone said, flats, bias and darks are the way to go. Having said this, for a while now, I haven't done flats as they are best shot at the same focus and temp. after an image session, and when you have to work the next day, you can't hang around 'till morning twilight.

So, I made them myself (synthetic flats): Here are a few simple methods (they apply to Photoshop, but the workflow can be used with other processing programs, I'm sure):

https://www.youtube.com/watch?v=a-Zuo5hMxJs

Andy

[Bikingbill]

Thanks @Adreneline and @Rustang for some great feedback. Definitely going to try longer exposures and will add in more darks and look at flats and bias as well. I'll have a look at Deep Sky Stacker.

I like your point about work the next day @AstroAndy which is why I'm only taking a few darks. It took me forever to find the objects, I suppose this is practice . A GOTO mount is a bit beyond the budget at the moment.

Thanks again

Bill

 

[wavydavy]

Yeah the dark circle is a dust speck, in the imaging train. the sharper it is the closer it is to the imaging chip. Ie........on the optical window, or even worse its got inside between the glass and the chip, typicaly done when changing dessicant in the chamber if its a cooled CCD or CMOS ). if its a larger fainter circle its usualy on something like the filters ect......its a really good first attempt, and you should be happy with your result. Always keep your early images, and as you progress go back over them to see how much better you get, you will be surprised!  Well done.