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M31 and advice needed


Johnnyaardvark
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Hi all,


 


This is a first attempt at M31. Was taken on Friday with the moon blazing away and is mostly from short 30s subs with Nikon D5000.


 


24 lights 30s ISO1600 + 1 188s ISO400 (a test really) tried one other after some refocusing but that had a step/jump in frame?


30 Darks 30s ISO1600


No flat frames as I've not really sussed out a good way to do it yet so have a few rather annoying dust bunnies! (Not sure this astro lark is doing my camera body any good?!


 


 


Is there anything else I could/should be doing with post/pre processing?


Should I try and push this data a little further?


Or is it just a case of more data and longer subs?


Will I achieve much just by adding more 30s subs on a darker night with no moon?


How does DSS cope with longer subs e.g 2-3 minutes if they are not quite equal length?


 


Thanks in advance for looking and comments.


 


Steve


 


15341767120_707a504bd0_h.jpgRaw M31 24 and 16  Frame Stack by sja88, on Flickr


 


 


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DSS will cope.


 


Always more data.


Always less moon.


Always avoid anything over 800 ISO.


Do some flats.


 


Going over 800 ISO is a bit of a no no, you aren't getting any more light in nor is the sensor getting any more sensitive, the camera merely amplifies the signal so any noise gets amplified too.


 


Flats, for my ED80 I use my laptop screen, it's good enough for now even though not ideal. It should get rid of most of the vignetting and dust bunnies.


 


More data always helps, you can never have too much.


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that's not bad at all for what is only 12 minutes worth of exposure time, keeping the ISO down will help with the noise, and also it`s not really worth doing more than 15 darks as most of the noise will be taken out with around 15 darks so doing loads more will not get you much more benefit.


flats are very easy to do and will help, pointing the scope at a evenly lit light source and taking exposures times until the histogram is about 1/3rd to 1/2 the way along the graph which should be fairly quick exposure times.


the p[processing is the real hard part.


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Thanks all,


 


Mike great idea with the PC screen and I can do that (at least for the ED80) with everything in place.


 


Rob, I was not sure how many darks to do... just had left it snapping away in the cold (with the lens back on) while I was doing other stuff.


How many flats? Thanks for the info re: using the histogram.


 


Had wanted to keep my ISO's lower but did seem to get more data (of course with more noise) at the 1600 setting especially with shorter exposures. I'll definitely be aiming lower when I am happier that everything is working.


 


Thanks


 


Steve


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I do 16 darks and 21 flats.


 


More data will allow you to pull more detail from the short subs. 30 secs is good for the core, prob 90 would be better for the spiral dust lanes. Then you layer mask the core into the outer in PS. There are many great video tutorials on the You Tube


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Thanks for the info. When we get assume clear nights I'll try and get more and cleaner data. Have ordered something that should allow me to plan a set of longer subs.

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