SH2-155 - The Cave Nebula - also known as Caldwell 9 is a diffuse nebula found in the constellation Cepheus. It is actually a part of a much larger complex of nebulae n the region which includes emission, reflection, and dark nebulae. Sh2-155 is located 2400 light years away and is an ionized HII region with evidence of star formation activity.

I have described this image as my problem child. This is a faint region and you really need a lot of integrated exposure to show it well. I took 150x 2.5 minute exposures over two nights, thinking that I had enough to accomplish what I wanted to do with this image. After I stacked the images and began to process them I found what looking like a bullseye made of rainbows superimposed over my image? What was going on? First I found a problem with my flat exposures and sorted that out. Then I looked at the data more analytically. It turns out that the subs I took the second night has 3X worse noise than what I took the first night. This target is located to the north of me - an area of light pollution. I think some high level cirrus clouds came in and reflected the light form the polluted area and messed up my subs. The first night there was no evidence of cirrus clouds so they were much better. I ended up eliminate half of my exposures - which meant that I had to work like the devil to handle the noise on this image.

So not my best work, but at least I was able to salvage something from the exercise…

Thanks for looking and reading of my tale of woe!

Here are the image details:

75 x 150 seconds, bin 1x1 @ -15C. ( I was hoping for 150!)

45 Bias exposures

25 Dark exposures

45 Flats

Scope: William Optics 132mm FLT F/7 APO

Guide Scope: Apterna 60mm

Camera: ZWO ASI294MC-Pro

Guide Camera: ZWO ASI290Mini

Focus Motor: Pegasus Astro Focus Cube 2

Field Rotator: Pegasus Astro Falcon

Mount: Ioptron CEM60

Polar Alignment: Ioptron Ipolar integrated alignment cameras

Capture Software: PHD2 Guider, Sequence Generator Pro controller

Image Processing: Deepsky Stacker, Pixinsight, Photoshop, Coffee, extensive processing indecision and second guessing, and much swearing…..