Stacking subs from various nights with different bias frames

[julian489289]

Hi

I want to get many hours of data for my next target, Andromeda Galaxy.  In the UK, I will need to do this over a number of nights though! 

Firstly,what would be the best ISO for this target, 800??  I use a Canon 650 D, so need to keep the noise down.  I am looking to take shorter duration lights for the core.  What duration would best sort this, 90 seconds?  Then for the fainter, spiral arms, i was thinking, 300 seconds?  

The next issue I can see is stacking these subs in DSS.   For each night, I will need different flats, as I usually remove the camera and therefore the exact orientation may be different between separate nights.  How do I stack the final subs.  Do I stack each night's results, lights flats dark & bias then stack each of those separate nights together?  OR do I just stack the whole lot together with the differing flats?

Also, what do I do with the different ISOs.  Do these need initially stacking separately then stack the results together?  Then, how would I combine the different stacked  ISO's, by layers in PS?.

Could you please help me with some advice, thanks 

[tingting44]

do not use different iso's, if im at my dark site i use ISO800, if im imaging from my garder i use ISO400.....

and this is how to stack multiple nights using DSS...

File Groups
File Groups may be used to simplify multiple nights on the same object file management by logically grouping files for each imaging session.
If you use only the Main Group DeepSkyStacker is working exactly like before the introduction of File Groups.

There are two kinds of File Groups: the Main Group and all the others groups.

• Light Frames from the Main Group may only be associated with Dark, Flat and Offset/Bias Frames from the Main Group. 
  This is the behavior of DeepSkyStacker before the introduction of the File Groups.

• Dark, Flat and Offset/Bias Frames from the Main Group may be associated to Light Frames of any group.

• Dark, Flat and Offset/Bias Frames from others groups may be associated only with Light Frames of the same group.

You can create as many File Groups as you want knowing that a file may belong to only one File Group.
When you start DeepSkyStacker only the Main Group is available. As soon as you add a file to the last available group a new empty group tab is created.

Example:
You shot the same subject two nights in a row. 
For each night you have a set of Light, Dark and Flat Frames but the temperature was not the same each night and the Dark Frames are not compatible and the orientation was slightly different so your Flat Frames are also different between the two nights.

To associate each Light Frame with the good Dark and Flat Frames you just need to put all the Light+Dark+Flat Frames from the first night in one File Group and all the Light+Dark+Flat Frames of the second night in another File Group.
Since Offset/Bias Frames are common to all the nights they must be put in the Main Group.

DeepSkyStacker will automatically associate the Light Frames of the first night with the Dark and Flat Frames of the first night and the Light Frames of the second night with the Dark and Flat Frames of the second night. 
The Offset/Bias Frames from the Main Group will be associated with the Light Frames of the first and second night.

[julian489289]

Thanks for the reply.  But could you just clarify the following for me please;

I too suffer from LP in my garden.  So if I use 400 iSO would I need to increase the exposure time to compensate from not using 800ISO?

What about imaging the core, would 60 or 90 secs suffice and how would you combine the different exposure times in the final result?

I can see on DSS the bottom left hand corner tab "main group" .  I note that when I add a picture file to the main group a second other tab opens up.  I take it that when I add a picture file to other tab and further tab opens??

Am I right in thinking then, that I add all of the same night's lights, darks, flats and bias frames to each of these separate tabs and DSS stacks them for me without me having to do anything?

That would be Fab if I am right!!

Thanks again

[tingting44]

this is just what i do, im still learning also

from my garden the max i can shoot at due to LP is ISO400 and 4min subs

from my dark site i shoot ISO800 and 10 min subs

its quite hard to blow out a core with 10min subs, i would not worry about taking subs for the core and bright core can be dealt with easy enough during processing...

as to DSS....i have not stacked several nights worth of data yet, i will be getting my 2nd session of M31 data as soon as i can so i can not wait to have a go at stacking multiple nights

here is my M31 from last weekend

M31 by tingting44, on Flickr

but yes it would seem you put all your bias in the main group in DSS, then for each nights data you would put the darks/flats/lights all in their own group for each night, click stack and waaa laaaa its as easy as that or so i hope lol

[jgs001]

That's correct. Any calibration frames (like Bias) that you want applied to all the images in the stack (across multiple groups) go in the Main group. Any calibration frames, that are specific to a set of lights, go in the same group as those lights. DSS then processes them all, in the correct manner to produce an end result.

I've used this technique on many an occasion to do just what you're describing, stacking multiple nights data, with specific darks and flats. 

[Psychobilly]

AFAIK , provided you have the calibration frames to match you can vary ISO as well... I know I have done this in the past...

Peter...

[julian489289]

Thanks Guys, just need some clear nights now. 

VIP that's a fab result for Andromeda.  How many subs did you take and what software do you process the images in?

[tingting44]

Thanks mate

i did try copying the shot details but I can't seem to do it on my phone.... If u click on the image it will give u the shot details

edit, I used photoshop cs5 to process

[julian489289]

Probably a silly question but how do you work out what is the max ISO and exposure for any given location?  I note that the higher the ISO or exposure in my LP area the image becomes more orange but that can be processed out later.

Should my light subs be a darker sky rather than an orange one in order to obtain the best results??

[tingting44]

Tia is just how I do it.... I exposure to saturate about 1/3'rd of the histogram for the light frame, so for my garden that is 4 mins, at my dark site it is 10mins

[julian489289]

Whats sort of processing workflow do you use VIP?  I am fairly new to this game and am on that steep learning curve.  What is the order of things to do process wise?

[tingting44]

I wish I could give u a precise workflow lol I do bits and pieces over several days, when I get on the PC tomorrow I'll type up my workflow best I can

[julian489289]

Thanks VIP

[tingting44]

Thanks VIP

Call me Martin lol

[julian489289]

Thanks Martin, I look forward to reading the workflow.

[tingting44]

Thanks Martin, I look forward to reading the workflow.

oopps i forgot i will type it up tomorrow after work

[julian489289]

No worries

[tingting44]

right then, the 1st thing i do after getting the final stacked image from DSS is load it into Ps, i then give it a slight crop to remove any stacking artifacts around the edges which sorts the histogram out.

i then give it a tweak in the levels, then a tweak in curves (i do many curves back and forth till im happy with the result), i then run through a few of Astronomy tool actions like space noise reduction, color blotch reduction, increase star color, local contrast enhancement, then onto Annie's astro actions, enhance dust lanes, dynamic enhance, brighten color & sharpen and then a gradient removal, and thats about it for the actions (all the actions i adjust the fill layer as they are pretty full on, so this is a good way to tone them down by using each action in its own layer.

i then play about a bit with color balance and getting the background sky looking ok (this usually takes days for me as im far from fast at processing lol) i then frame and add a title to the image and upload to Flikr

My M31 image above, is my 1st proper picture lol of which i am happy with for now, hope this is of some help to you

[julian489289]

Thanks Martin.

I hate levels and curves as I have no clue in how to go about what I am trying to do.  I watch tutorials but their initial stacked images appear to show no target detail then hey presto, after a few tweaks the image looks much better.   My exports from DSS, show quite abit of detail but the more I tweak levels & curves I don't seem to get the same results!!

Where do you do actions like space noise reduction, color blotch reduction, increase star color, local contrast enhancement, are they in CS5?

I have downloaded Noel Carbonis' action, I take it these actions are similar to Annies??  What actions enhance the dust lanes, do the dynamic enhance and brighten colours?

I have seen a separate software for Gradient removal, the name slips me at the moment, do you use a separate program or is that in Annie's tools?

Sorry so many questions but for the look of your results with M31, (just as good as the processing I have seen with guys who use the expensive PixInsight!) I feel you are the man to advise!!

[tingting44]

Thanks Martin.

I hate levels and curves as I have no clue in how to go about what I am trying to do.  I watch tutorials but their initial stacked images appear to show no target detail then hey presto, after a few tweaks the image looks much better.   My exports from DSS, show quite abit of detail but the more I tweak levels & curves I don't seem to get the same results!!

Where do you do actions like space noise reduction, color blotch reduction, increase star color, local contrast enhancement, are they in CS5?

I have downloaded Noel Carbonis' action, I take it these actions are similar to Annies??  What actions enhance the dust lanes, do the dynamic enhance and brighten colours?

I have seen a separate software for Gradient removal, the name slips me at the moment, do you use a separate program or is that in Annie's tools?

Sorry so many questions but for the look of your results with M31, (just as good as the processing I have seen with guys who use the expensive PixInsight!) I feel you are the man to advise!!

here are the actions i have got mate

http://www.prodigitalsoftware.com/Astronomy_Tools_For_Full_Version.html

http://www.eprisephoto.com/astro-actions

i love them but you cant just rely on them, how ever they are great if your not sure where to start, also a few actions walk you through in steps as what to adjust

tbh i just play about with more or less all of them, if i like one i use it, if not i go back to the previous state by pushing Ctrl Z

i did have the trial for GXT for gradient removal and that is awsome! 

thank you for your kind comments, i am very new to this tho thanks again and do not worry if you have any questions i will try to answer if i can

[Scott]

Hi Martin,

Don't know if this applies to later versions of dss but it's worth a look anyway

[tingting44]

Hi Martin,

Don't know if this applies to later versions of dss but it's worth a look anyway

whats that Scott?

[Scott]

oh bother....forgot the link

[julian489289]

Thanks Martin, just need some clear nights to get some subs to process!!    Thanks for the advice, it's appreciated.

Thanks Scott for the update re DSS

[ollypenrice]

Personally I'd want to take control of the blending of long and short subs myself. Truth to tell I think the claim that you need short subs for M31 is questionable but that's in CCD with a greater well depth. This is the method I use for blending long and short subs, which I hardly ever do, be it said. http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

Often the over-exposed looking core contains far more buried detail than you think. Separate stretches of the same data often reveal what's there and can be combined in layers.

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/i-xbvjFDF/0/X3/M31%20Outer%20HaloLHE-X3.jpg

Olly