Difficulty Prosessing

[Shiinsuh]

Hi all.

On Sunday I was out with my scope and spent the evening imaging M81 / M82. Everything was fine and I took 55x180s subs, 7 of them were subtracted in stacking (from trails mostly), I also took 80 Flats and 80 Bias (no darks).

Anyway the data looks fine but I'm seriously lacking in the skill to process it, one major head ache for me is the I am using a CCD-CLS filter this is causing me to get a blue hue and I'm finding it difficult to equalise the colours.  I'm getting the background and stars to be colour equalised but this is throwing the colour of the galaxies out.

Could anyone provide me some help on what steps I should be doing?
I am processing it in Photoshop. I do had nebulosity and pixinsight trials but I have verY little knowledge on how to use them so would prefer to use Photoshop at the moment.

Any help would be appreciated. The stacked tif file I have been working on can be found here so if you want to make sure I'm actually able to get the colour out of it! of if you simply wanna play about and see what you get.

Shiin

[Leveye]

Your really should be taking dark frames and using them. Same exact ISO and at the same exact ambient temp as the lights. I use HLVG filter in post to remove the color cast from the LP filter. That or you can use Gradient Xterminator.

After playing with your Tif I found that Gradient Xterminator worked. I would reprocesses the original files again in DSS and bring up the mids more. The original Tif is pretty dark. 

[Shiinsuh]

Your really should be taking dark frames and using them. Same exact ISO and at the same exact ambient temp as the lights. I use HLVG filter in post to remove the color cast from the LP filter. That or you can use Gradient Xterminator.

After playing with your Tif I found that Gradient Xterminator worked. I would reprocesses the original files again in DSS and bring up the mids more. The original Tif is pretty dark. 

Shiinsuh_150308_M81M82_03.jpg

Thats for the reply. That images was actually the wrong one, I do have one that has been processed in DSS a bit Here. I have used both GradX and HLVG to some effect but I just can't seem to get data out of it without getting clipping around the core of M81.

As for Dark frames, I do usually take them though because I'm using a DLSR, I'm not sure how effective they are due to the wide temperature range. I will try stacking some previously taken darks though that had the same EXIF temperature to the lights are.

Once those are stacked and i've played around, I will report back.

Thanks

Shiin

[wxsatuser]

The blue hue is normal with the clip filter, make sure you use Align Channels in DSS.

Also use Kappa Sigma Clip stacking and you should be able to use the subs with trails.

I assume your exposing correctly, get your exposure in the range of 20 to 40% on the histogram.

Like mine below, see the white peak on the lower luminosity histogram, mine is around the 25% mark.

[Shiinsuh]

The blue hue is normal with the clip filter, make sure you use Align Channels in DSS.

Also use Kappa Sigma Clip stacking and you should be able to use the subs with trails.

I assume your exposing correctly, get your exposure in the range of 20 to 40% on the histogram.

Like mine below, see the white peak on the lower luminosity histogram, mine is around the 25% mark.

Thanks for the reply.

I am a wear that I would have got the blue hue from the clip filter, so its not that I wasn't expecting it. I'm not sure if I do or do not have align channels on in DSS I will check later, however I did try using kappa sigma clip, but this seemed to apply the trails to the final image. I will be having another go once I get home after work though.

The exposure time was ok but not the best, it was about 20% (180s). I will try with longer exposures,see if this helps with processing, then I'll know how much a difference that makes.

Thanks for the advice.

Shiin

[Jokehoba]

Hi Shiin,

You mention Nebulosity and PixInsight... Nebulosity has some basic post-processing options - including auto colour balance and auto-background correction - which you may find useful. It's also great at stacking and won't automatically reject subs.

I prefer to post-process with PixInsight since it's Dynamic Background Extraction and Colour Correction processes clean up my images with a few clicks. there are lots of tutorials. Try http://www.harrysastroshed.com/pixinsight/pixinsight%20video%20html/Pixinsighthome.html. Indeed, many use PI for the DBE alone.

I am sure those proficient in PS can achieve everything PixInsight can do but I would recommend you take a closer look.

John