Sunday, September 17, 2017

NGC 7822

NGC 7822 is a young, star-forming region in Cepheus - some of it's regions are no more then a few million years old. It is 40 light years across and lies 3000 light years away above our galaxy. Inside the region is a supernova remnant - which indicates that a massive star in it has already exploded. Also, it contains one of the hottest stars discovered near our sun - it has a surface temperature of 45000 Kelvin (the surface temperature of our sun is 5778 Kelvin). It's luminosity is about 100,000(!!!) times that of the sun.

(click for full resolution)
I took the LRGB data (4.5 hours) at OSP and Ha and OIII (13 hours) in our backyard in San Jose. I used the Ha to enhance Red and Luminance and OIII to enhance Green and Blue.

When processing this image, I ran into something that I haven't experienced before. After stacking, color correction, background extraction and enhancing the images with my narrowband data) I ended up with the following RGB and Luminance image (stretched):
But when I combined them (using LRGBCombination in Pixinsight), I got this:

Zooming in reveals that applying the Luminance image indeed increased the detail, but it took out almost all color!

I tried this several times, finally asked around. And it turns out that LRGBCombination only works on stretched images! I have no idea why I didn't encounter this before - I am sure I had done this before. But once I did this, everything else went smoothly!!!