Creating an Astro Image Part II – The Software

So what kind of software ties all the equipment together, and makes it all do its job?

The “foundation” of it all is the ASCOM library.  ASCOM (Astronomy Common Object Model) is, essentially, a translater.  It presents a standardized set of commands (e.g. SetFocus(value) to move a focuser to some point) for all kinds of astronomy hardware, and then relies on the manufactures to provide it with the translation…meaning, the manufacturer of, say, a focuser can use whatever he wants as the command to “Move the focuser to 3000”, as long as his driver tells ASCOM what that command is.  Then, ASCOM simply ties that to “SetFocus(3000)” and that’s all my control software has to know.

Everything discussed in the previous post “speaks” ASCOM, so all of it can be controlled by, in theory, a single piece of software that does as well.  In my case, that software is Sequence Generator Pro from Main Sequence Software.  SGP is a fantastic interface that can control all aspects of an imaging session.  It can move the mount to any position, change filters in the filter wheel, automatically focus the camera, make sure the guiding is working, and take any number of frames of any exposure length I wish with the camera.

SGP can even help me plan out and execute an entire sequence for any given target.  I can tell it “For this target I want X many frames of Y exposure time through Z filter, then A frames of B length through C filter” and so on, and it will line them all up and make all the adjustments to shoot all those tasks.  It even has the ability to look up any given target, find its exact location, and program the sequence to know where that is.

Finally, SGP provides an interface to various “plate solving” engines.  Plate solving is the process of taking a single brief frame, and then analyzing the stars in the image.  The engine then compares the pattern of stars to a large index of known stars, and matches the pattern.  From this information, the software now knows exactly where the telescope is, and can send commands to adjust it slightly to the exact point in space the user has requested for this session.  This also allows sessions to now extend over several nights, since the next night we can come back, “plate solve” a frame from the night before, and tell the mount “Go here”, allowing us to maintain the same framing over multiple nights.

Finally, when all this amazing software has done its job and collected dozens of hours of data, processing begins.  My image processing software of choice is Pleiades Astrophoto’s PixInsight.  PixInsight is dedicated specifically to processing astronomical images, and does so from an extremely technical and mathematically based point of view.  The learning curve is very steep, but the results are worth the effort.  Harry Page’s PixInsight Tutorials are the defacto standard starting point for newbies learning to use PI.

Next time, we’ll begin getting into the meat of creating my next image, and select a target!


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