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OK, I fess up straight away, this is about stellar astrometry (measurement of proper motion) but I’m guessing the most experienced people measuring positions are in the comet or asteroid sections 🙂 Hence seeking forgiveness for posting here….
I’ve started a little side project to measure the proper motion of some of our closest stars, (mainly out of curiosity, and my old mentor (Dick Chambers) RIP, sort of suggested back in the 1990’s that it was beyond what Amateurs could do – he was probably correct back then, but now it looks perfectly possible (and not that difficult?)
Having never done any astrometry I wanted to check with those who are experienced in it, if my approach is valid. I may be going about this completely wrong so didn’t want to get a year into the project to find that out!
I’m quite pleased that my measured positions are <20 milli arc seconds what I calculated the positions to be based on published data but have no understanding what should be achievable with amateur equipment, attached is my workflow and I would really appreciate any comments on how to improve it.
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Measuring stellar proper motions has been possible for amateurs for a long time now, though we will not reach Gaia levels of accuracy.
In particular, I really must update my track of Barnard’s Star with images from this year. Ok, that’s an extreme case but proper motions greater than, say, 100mas per annum should be fairly easy to measure over the course of a year or few.
The pipeline I use is MaximDL for taking images; local astrometry.net using the Gaia catalogue to put a WCS on each sub; SWarp for stacking if required; and then APT for photometry (my primary interest) and initial astrometry (if desired). The source list fed into APT contains Gaia positions and its output includes substantially sub-pixel precision on the stars’ centroids, in both pixel and sky co-ordinates. That’s good enough for me (and I repeat that my primary interest is in photometry rather than astrometry). Perhaps I could, and should, try harder to achieve ultimate accuracy in astrometrical positions.
Paul
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