777 geek,

After over 50 years of doing this I hope I have some idea of what I'm doing.

Today's digital equipment has completely change the "rules" of astrophotography. When I was a kid they were just building the 200" Palomar telescope which cost only 6 million dollars in depression era dollars. When completed in 1949 it was 4 times larger in light collecting area than the next largest scope and was to answer "every" astronomical question thanks to its big eye. When I finished my 6" scope in 1954 I remember dreaming of what it must be like to use the 200" telescope. Things are very different today. Now for less than the cost of most of the pontoon boats seen on my lake you can take images that rival those of the 200" back in that era that so enthralled the public, and me, back then when published in magazines like Life and National Geographic. Thanks to today's technology I'm able to live that dream I had some 55 years ago and at a tiny fraction of the cost. Of course the big scopes now use the same technology so are again far ahead but as far as "pretty pictures" are concerned we are still pretty equal. I just need far more exposure time than they do.

The key today isn't so much in taking the image but in processing the data you do get. A computer screen can only reproduce a very limited brightness range that is divided into only 256 levels. A monitor has difficulty even reproducing all of these. So you have to process an image that may range in brightness from 8th to 21st magnitude, a range of about 160,000 times into those 256 levels. I've still got a lot to learn about that and about color balance of an image.

The bottom line just tells the telescope and that it was used at its native f/10 rather than use a compressor as is commonly done with such a long focal length scope, next is the exposures used, 4 luminosity images of 10 minutes each and two of similar duration for each of the three primary colors; red, green and blue so the image consists of 40 minutes of luminosity data (used for detail) and an hour of color data (colorizes the luminosity image). You could forgo the luminosity data and just use color data but that means far more exposure time. Since only 1/3rd the light gets through a color filter you need 3 times the exposure to go as deep as an unfiltered luminosity image so I'd need 2 hours per filter or a total of 6 hours to do what I do using a luminosity layer in only 100 minutes and achieve the same signal to noise ratio. During that extended time the atmosphere will tend to distort the image so the end result will often be worse due to all the time the atmosphere has to mess me up. Major observatories are usually located where seeing is far above average. I don't have that luxury. The next field is just the sensor used and lastly the mount the telescope is on. This is usually far more important than the telescope. Since you have to track the object across the sky and do so with extreme precision for 100 minutes in my case, longer with a smaller telescope, the quality of the mounting is of "paramount" importance. I fought average mounts into submission for decades, it was no fun. I was always wanting to do more than the mount was capable of doing. I finally had enough and got this mounting. Still my total cost is about that of a basic new car, less than my wife's Honda CRV. So I drive a pickup with 245,000 miles on it but have my observatory. We all have to have our priorities!

Rick