2008-09-12T05:28:00.000-07:00

Open all the frames acquired of the picture in question. Look them over and discard those with blemishes, trailing, excess noise, satellite tracks etc.

Open Tools/Preprocessing, click Files and make sure the relevant directory is listed in the top left pane and the files are in the bottom left pane, and click Reset to clear the working panels. Highlight all the light files in the bottom left panel and drag them into the Images panel. Highlight your flat frames and drag them into the Flat Frames panel and your Darks into the Dark Frames panel. Click Options, at the top and set your parameters.

In Images, click Average or better, Median. Median will also help with disposal of hot pixels. In Align, click Auto, then All Stars, then OK, to return to the Options page. Alternatively, if your frames contain nebulosity, use the Add button to add the data rather than average it. If you're more interested in star colour, the Average, or Median would be the better choice.
Click the CCD Colour Synthesis box, bottom left. There are other parameters but ignore them for now. Click OK, and AA will stack and calibrate the files. If not well stacked, try other parameters in the Align, and finally try Manual. If successfully done, you should now have the file on your screen ready for processing. This is a single colour file and can be processed by clicking on the Colour tab on the top line of the main screen. The drop down menu allows you to carry out further processing in LRGB or RGB or CMY form. My preferred method is to use L R G B, as this puts all the work of stretching and sharpening etc. into the Lum file, and the colour ones can be processed indentically without complications. But first, having split the file into L, R, G and B, you must file them with sensible names, I use L, R, G, B , as I keep them in the folder of the date they were taken, so they don't get mixed with other similarly named files. See the Acquiring page.

Processing the frames.

Now that you have your L, R, G, B files, you must process them singly, the colours exactly the same as each other with no sharpening, even some blurring, and the Lum separately, as the colours are just colours, but the Lum carries all the detail and contrast, so must be stretched and sharpened, to bring out all the nebulosity and detail you can.

I generally start with the Red file, so with that on the screen, set the Background (B at the bottom left of the picture) to 100. To do this click Arithmetic/Add Offset and enter an amount that will bring the “B” to 100, probably a minus amount. It will likely darken the picture. Then click, View/View Range/User Defined, and set the Min to 50, then OK. This will change the “V” at the bottom left of the picture to 50. Neither of these numbers is critical but they must be the same for all the colour files.

With the mouse cursor, move the White triangle in the long vertical sliders, the Visualisation sliders, on the right of the screen, up and down, this changes the “Log” number at the bottom, till the picture’s background is darker and the picture looks “pleasing”. You will find this will need some experimentation. Err on the dark side. Re-click View/View Range/User Defined and set the Max to the new “Log” number. The Min should still be 50. Then click OK. Then, if you wish, you can click Filters/Low Pass and set the strength to 2, then OK. This is to blur the frame a bit. Resave the file as R.fit, this is your Red Master file.

---------------------------------

The same processing steps, with the same parameters must then be carried out on the Green and Blue files, adjusting background etc. then finally saving them as G and B, your master Green and Blue files. It is important that all the parameters are the same to ensure the colour balance isn’t disturbed, so make notes of the Min and Max numbers in the User Defined panel, though AA4 does that for you.

Now put the Lum files through the processing steps, as you did with the Red, Green and Blue. But this must be done differently, as, with LRGB processing, the R, G and B, carry only colour data, all detail is in the Lum, so you must do all your sharpening and stretching for nebulosity and other fiddling, and there can be a great amount of it, frequently in other software, on the Lum file. When satisfied, save it as your master Lum file, L.fit

-----------------------------

Most workers in this field use either AstroArt or Maxim to acquire and the same and/or many others for processing. My very general work flow is AstroArt for acquisition and for colour processing, then Photoshop for detail work on the Lum and Paint Shop Pro and Photoshop to finish off. But the picture dictates the software. Processing is a bit of a Black Art. Moving from one programme to another isn’t a problem if you use non-lossy fits or tiff files. Jpegs too, if minimum compression is used. AA will accept any when doing the next step.

----------------------------------

Open all the masters onto the screen, minimised. Then click Colour/Trichromy. This will give you a panel where you must enter the names of the Red, Green and Blue files, by clicking them. AA4 will do this automatically if the masters are on the screen. You are offered other parameters but set it to Auto this time and click OK. AA will then stack the three files and screen them as an RGB file, with a panel for you to make adjustments from. Lighten the background with one of the panel’s vertical sliders, so you can see the background clearly. A grey background indicates a good balance of the colours. If not grey, adjust the colours to make it so. When satisfied, darken the background to the original degree, and a bit more. Save it as RGB.fit. Click Colour/LRGB Synthesis to bring up a list of the files that are on screen and click the Lum file and OK. This will bring it onto the stack, to complete your picture.

Now you can marvel at your handiwork. And save it with your choice of name.

Then review it and think where you can improve it!

The second time will be easier, and the third easier still.

By the fourth you'll be looking for short cuts and improvements.

Processing Colour Pictures in AstroArt