Image Processing in Light Pollution and Tutorials

Posted Thu, 02/25/2010 - 09:46 by Galactic

Hi All,

I get this a lot!

How do I deal with Light pollution gradients in my images?

I always get this question, again I've been asked by several club members, and
Since they know I image from light polluted Dayton or Yellow Springs Ohio.

Well my methods have changed over the years,

Currently I use Russell Crowman’s XT Gradient Plugin for Photoshop

but if you don’t own a copy of Photoshop

You can do they same thing in a Freeware program,
The Free Astronomical Image Processing Program is called IRIS,
Downloadable here (3.2MBytes)

http://www.astrosurf.com/buil/us/iris/iris.htm

At the bottom of the IRIS download page, you will see lots of tutorials on how to do specific tasks in IRIS.

Here is a tutorial on how to eliminate color and light pollution gradients from all types of image,

http://www.astrosurf.com/buil/iris/tutorial4/doc14_us.htm

I've used both Photoshop & IRIS with similar results.

Also IRIS does support many DSLR’s raws as well.

I hope this helps all of you get the most out of your images.

Best Regards,
John Chumack
www.galacticimages.com

Forums:
- Imaging

Once upon a time I had a huge

by John Graham - 02/27/2010 - 20:57

Once upon a time I had a huge problem with gradients from the light pollution I was struggling with from my back yard. I tried quite a few different processing techniques including Neil Carbonni's astronomy actions for Photoshop (which worked fairly well) and making my own synthetic flats (which was hit and miss). At last I found two things that together pretty much eliminated my problem with gradients. The first was getting a good light pollution filter designed for use with color imaging. I found both the IDAS LPS-2 and Orion Imaging Sky Glow filters work very well. The second was finally breaking down and building a light box to take real flats. This turned out to be fairly easy to do and it made a huge difference in my images. Applying real flats while the image data is in its native 16-bit format has proven to be very, very effective. Anymore, the last thing I do before bringinf my gear inside (or before I switch cameras) is I take a set of flats. This not only reduces my gradients, but it also does a great job removing dust motes.

Now, if we can only get some gosh-darned clear weather! Since December 1st I've had my gear out twice, and one of those wasn't a very good night. Grrrrr....

Have fun!

-John

================================================
Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
Rebel XT/XTi, DSI Pro I, II, & III, DSI I & III, LPI, Electronic