Processing the Combined File Dataset

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There are many good tutorials and some books available on processing your astronomical images. I have Jerry Lodriguss' "Photoshop for Astrophotogra-phers" and I also check out Rob Gendler's http://www.robgendlerastropics.com/ processing tips, as well as Steve Cannistra's http://www.starrywonders.com/ on a regular basis. Ron Wodaski http://www.newastro.com/wodaski/ also has some very nice image processing tutorials on his website.

However, when all is said and done, there is no substitute for getting the colour-converted raw image into an image-processing package and simply having a go at some digital image processing. There are probably more than 3 "Golden Rules", but I find these three must be adhered to at all times. Golden Rule number 1: Do not clip the light point. Golden Rule number 2: Do not clip the dark point. Golden Rule number 3:

When (nonlinearly) stretching your data using "curves" to bring out the faint stuff - use the "Magic Curve".

I think the only way to see how to use the available tools is by practical example. So you will be able to download some raw data and try these things out for yourself. Be advised, the data I will provide you with isn't too bad, so you will not be plagued by gradients or terrible vignetting in these examples, I don't want you to be scared off too early : I will also supply you with two basic processing routes, the first a "cheap and cheerful" i.e. reasonably quick route that will give good overall results without using Photoshop at all, but it will result in non-optimal stars. The second route will be a little more "formal" using Photoshop for all the main digital image processing and which will end up with a better overall result. Lastly, we shall have a try at putting together a 5-frame Hyperstar mosaic!

Before getting on with the practical work I should say that the consensus of opinion is that you should get your stacked image file out of the acquisition package (Maxim DL or AstroArt) and into a "proper" processing package such as PhotoShop as quickly as possible. In other words, any pre-processing (beyond colour-conversion and stacking) should be minimal or even zero in the nonPhotoShop packages. Having looked at the alternative processes quite extensively, I have to agree with the consensus opinion on this occasion. That being the case, this first "quick and dirty" processing routing is really only for initial practice, and to get an image out as quickly as possible with minimal effort. It is not recommended for creating an astronomical work of art.

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