Is it the light pollution creating the noise

[acharris77]

Hi all, being still new to editing and astrophotography I was wondering if I could give me some advice. I use levels in PS CS6 and adjust the sliders each side of the graph. Then I apply that and go back in and click the background dropper and select an area to make the background darker.

When I do that, I get the effect in the attached image with the left side of the image looking grainy and brighter. I was wondering if anyone knew if it was the light pollution as I need to order a 2" filter or is it some noise from the long exposure? I can edit it darker, but when I do I lose detail like in the pic. As in that pic you can just see NGC 6207, but when I adjust it I lose that little detail.

Would I need to take more darks to help with that effect or would more subs be more useful. Any advice is appreciated as I am trying to learn new techniques so I can take better photos when I get my EQ5. Any advice is greatly appreciated.

Many thanks.

[cathouse42]

That is light pollution.

A very inexpensive LP filter is the Skywatcher LP filter, it is very very similar in effect to the Baader Neodymium filter and cheaper.

1.25" http://telescopehouse.com/acatalog/Skywatcher-Light-Pollution-Filter-1.25-inch.html

2" http://telescopehouse.com/acatalog/OVL-Light-Pollution-Filters-2.0-inch.html

This filter won't break the bank to dip your toes in them

Here is a comparrisson

http://stargazerslounge.com/topic/33706-skywatcher-lpr-filter-vs-baader-neodymium-filter/

This is a good book on image processing for astrophotography using Photoshop (or similar).

http://www.amazon.co.uk/gp/product/0943396913?colid=XSTNWGKBQMMX&coliid=I16FV63BIG5AEN&ref_=wl_it_dp_o_pC_nS_img

This book has been updated and is inexpensive. You can always get your library to get this for you before you buy.

[acharris77]

Thanks for the reply and confirming what it is. That review link to the comparison of the two filters is what I have been looking for. When I take my images, they look like the shot with no filter orange. I will buy one from FLO I think and give it a try. I got a 1.25" Baader neodymium filter, but no got for my 2" attachment the 1000D uses.

Thanks again.

[cathouse42]

Thanks for the reply and confirming what it is. That review link to the comparison of the two filters is what I have been looking for. When I take my images, they look like the shot with no filter orange. I will buy one from FLO I think and give it a try. I got a 1.25" Baader neodymium filter, but no got for my 2" attachment the 1000D uses.

Thanks again.

I  use the 2" filter with a 58mm to 48mm  step down ring on my Canon 58mm filter ring lenses.

http://www.amazon.co.uk/58mm-48mm-STEP-DOWN-RING/dp/B0013UTYG2/ref=sr_1_1?ie=UTF8&qid=1433785827&sr=8-1&keywords=48+58+ring+step

The bad thing about your image is it is a gradient, not even light pollution.

[acharris77]

I am unsure what causes gradient. And is there any way in software to reduce some of gradient?

Thanks. 

[cathouse42]

I am unsure what causes gradient. And is there any way in software to reduce some of gradient?

Thanks. 

Lots of tutorials.

https://www.youtube.com/results?q=astrophotography+gradient+removal

I could spend hours watching YouTube tutorials

[ollypenrice]

I can't say that I know that that is light pollution. Think of the sky gradient due to LP, then think of the size of your chip and how much sky it covers. Bit of a coincidence, no? I image from one of the best sites in mainland Europe and I am perfectly used to gradients along those lines. It might be LP but I get gradients which aren't and, like all imagers, I'd love to know where they come from! Yours would be a cynch to remove in processing, though. I run all colour stacks through DBE in Pixinsight. That is the top tool. Gradient Xterminator for Ps comes in a strong second. You will, in my view, never remove gradients at source. Everybody get s them. (At least, all amateurs do.) Olly

[cathouse42]

https://www.google.com/search?q=light+pollution+gradient&biw=1914&bih=868&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIxuX844eBxgIVRGvbCh2TVgDN#tbm=isch&q=light+pollution+examples+astrophotography

Here is a bunch of light pollution example pictures on Google Images.

[wxsatuser]

An LP filter will help with the LP of course but it won't stop gradients.

I get some real doozies even with the best LP filters.

As Olly, I use DBE in PixInsight, it's the dogs.

[acharris77]

Thanks everyone for the great advice and insight into what is going on in my images. Some great links provided for me to look at and learn from.

Thanks again.