Telescope Reviews: Sometimes I really feel so stupid...

I am way too much of an impulsive person. I tend to take up hobbies/things and just run with them...sometimes without knowing the simple basics that will help me out in the long run.

I have learned a heck of a lot of things in the past couple of months since I started this astrophotography thing, I did drill down and learn the basics about scopes and equipment when I decided to buy, but I am constantly coming up short in the basics department when dealing with processing of images.

Typically something doesnt come out right, I obsess over why for way too long, and then I have a forehead slapping moment where I realize...OMG YOU ARE SO STUPID about something basic that explains everything. I tend to read what everyone does, try to replicate what they do...but without knowing WHY they do so and the basics on what makes those things work.

For example: When doing some stacking and processing of light images, I was trying to figure out how I could process images from two different imaging sessions. I was making things seem more complicated than they were. When someone mentioned how to do it, I said to myself "that cant work, I took subs 30 sec one day and 1 min another....that shouldnt work!." The headslapping moment came when I finally realized that when images are stacked...each pixel value is ADDED to the a stack (of course some methods are used to discard wayward pixel values). For some unknown reason, when I saw the words "median combine" or "sigma median" my brain thought that the final stack was an average of all the pixel values for an image.

Fast forward to the last couple of nights...I was reprocessing some of my images, this time using DSS instead of Iris, and the final images I was getting out of DSS weren't quite right. When I started to do gradient removal and stretching, there was a hole in the middle of my images. It was missing the red there. Thought it had to do with my flats....I did underexpose my flats, but it shouldnt have been that much of a problem. I tried several different ways of processing the stack in DSS (at about 30min a pop in processing time) only to get the same results.

Then came the forehead slapping moment.

I was clipping the red channel because it was running out of the 16 bit color space. The 75 sub stack I was processing I guess caused an overflow in the red and that data just got thrown out. It didnt help because I also realized that the problem was exacerbated by the color adjustment parameters in the DSS settings were multiplying the red values by nearly 2.

For some unknown reason I forgot how things were stacked to begin with, and that....yes you can run out of color space in a 16 bit image. I never really figured this out before mainly because 1) I thought that the 16-bit color space was large enough that I could basically stack an infinite number of subs without overflow and 2) I sort of avoided this previously by using iris. In iris, I would usually process a stack, do a gradient removal, set black point, and then do color adjustment....I just wouldn't run into the 16bit barrier this way.

Now so many other things that people on the forums say here makes sense. About limiting exposure times so the histogram on the camera isn't too far right, and the loss of dynamic range if you did get things too far right. I never heeded this advice mainly because I thought I would never run out of dynamic range in the final stacked photos.

Stupid me.

Now I wonder what my next forehead slapping moment will be.

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Celestron C6-N 150mm f/5 Newtonian
Celestron CG-4 mount
Canon 300D unmodded
Meade 70AZ-Z + Philips SPC900NC for autoguiding