Help please! DSOs appear colorless :(

[Costas Soler]

Hi! 

I have finally managed to get deep sky stacker up and running on my computer (a macbook pro) and I have collected quite a bit of data with my Orion 8" Newtonian Astrograph. I have stacked 104 images of M27, and the results appear reasonably OK. (At least to me, I am very much a beginner and only about one or two weeks into the hobby...) I am also including an image I took of the Eagle nebula, a stack of 52 images of the same exposure and ISO (I'd like to know what you think of this as well in regards of how I could improve it). Pillars of Creation.TIF I was wondering if you have any tips on how I could tease out more color from this image, or if I just need more data. My subs have been taken at ISO100 at 30 second exposures. I know this is a to lower sensitivity than most use, but any more than that and light pollution tends to degrade the image. This seems to be the sweet spot for my images until I can get out somewhere dark. 

[bendiddley]

If you get yourself a light pollution filter you'll be able to up your ISO and take longer exposures which will help with capturing more data. I live in a moderately light polluted area and I can get about 90 sec subs before trailing and no issues with LP because of the filter, I have my ISO at 800. Also what post-pocesing software are you using, I use photoshop and find it is very good at teezing out hidden data using the levels and curves features. Nice image of M27 by the way!

[Stub Mandrel]

There's loads of detail in there, you have the usually-missed outer envelope.

What did you use to stack it? If DSS, which settings did you use?

[uhb1966]

Hm! ISO100 at 30 second exposures= ISO200@15= 400@7.5 = 800 @ 4 = ISO1600@2 secs. Being a noob, i believe you need more data, or maybe you could try start with an object with a higher surface brightness? Nevertheless , not a bad start at all! Some people claim the Baader UHC S Filter helps... what Bortle scale is your observation point? What camera are you using? And tell us a bit about your workflow. Also, you might want to share the result data from DSS, some people on SGL do wonders with Pixinsight ...

 

[calli]

You did not say what camera you use. For that detail there must be color. Maybe DSS did not like your RAW images or there is some missconfiguration. Dare to show us a raw frame? Or let us play on the autosave.tif

I can see a faint color in my lightframes which really suck, nut at least there is some color. See my sig for the crappy results (used my MAK127 which is not "really" a DSO hunter :-)

Carsten

 

[gremlin750]

In terms of colour - you could try boosting the saturation in whatever editing software you use. It worked for me but you have to be careful not to overdo it otherwise it looks a bit false.

Just play around with it and see what looks good.

Iain

[dph1nm]

On 27/06/2016 at 15:53, uhb1966 said:

Hm! ISO100 at 30 second exposures= ISO200@15= 400@7.5 = 800 @ 4 = ISO1600@2 secs.

No it doesn't. ISO does not affect the sensitivity of the camera to photons, so 30sec at ISO100 collects as many photons as 30sec at ISO1600.

NigelM

[uhb1966]

dph1nm has a point here, but photon collection is also only a part of the equation. I googled SGL and i quote a good post about short vs long exposure stacking from opticalpath in the thread :

opticalpath: "Read noise is the same for any length of exposure and accumulates with each exposure added to the stack; it doesn't in any sense cancel out or level out - it diminishes the S/N ratio of every individual frame and the S/N of the stack.   So 3600 one-second exposures will contain SQRT(3600) i.e. 60 times the read noise of a single 3600-second exposure... A good quality image generally means aiming for a high S/N ratio and you get that by increasing signal and/or reducing noise, so the key question is: how does 60x read noise compare with the accumulated signal from my faint object? .  Often sky background is the major source of noise and the usual advice is to expose each sub-exposure long enough so that camera read noise is very small compared to sky background and does not start to make a significant contribution.   So you can see why, if going for 3600 x 1 sec, you need to be shooting with a high-efficiency, very low-noise imaging system.  "

While opticalpath is referring to another special situation, he brings the point home: stacking multiple short exposure images helps, but it is not the same as one long exposure image in terms of signal-noise ratio.