Posted by
ChristopheM. on
Feb 17, 2016; 8:12am
URL: http://astroimagej.170.s1.nabble.com/Perform-differential-photometry-on-an-object-moving-across-a-field-tp240p346.html
Karen,
I've been testing the moving object photometry in the last couple of days.
Here are a few comments and suggestion, if you don't mind.
That's true that moving objects are too oftenly loosed in the process, for some reason : nearby bright star, hot pixel, or … nothing else, maybe, than a need of freedom ?
The step by step is a good solution in the case the user only have a few dozen of images to submit ; but that's impraticable for hundreds of them.
What about performing a « semi-automated-step-by-step » photometry ?
As the telescopic displacement of a moving target is utterly linear and predictible, why not using the displacement vector as a check for the centroid position ?
The user click on the comps, then on the target, then he must click on the target on the second image of the sequence to get the displacement vector (or on the fifth image, or tenth image for better precision, if you like).
When the photometry is lauched, AIJ check the vector and must search for the centroid in the area defined by the vector. Add a target flux verification for each step and that's it. (you don't expect your object to be suddenly 2 mag brighter from image to image).
In case of problem, AIJ stops, the user click and drag the aperture on the target, Enter, and then the process resume until the next trouble or end.
There is also the possibility, as you write previouly, to defined the target on the first and last images and calculate the xy displacement for each image using timing. This works well on Christain Buil's Iris.
Astrometrica by Herbert Raab is a well know software used by asteroid and comet observers ; it's main feature is astrometry and MPC mailing. It has many capabilities in terme of stacking images in order to get better SN on faint objects, and other useful tools, such as finding known objects in a field or declaring a moving object is a new one, search databases and catalogues. It is often said by comet observers that Astrometrica is perfect for sending/publishing MPC submissions, but also that the photometry is far from perfect, with surprises magnitudes, from time to time. Hebert is a nice guy ; he used to answer any submitted question.
Maybe a source of inspiration … the soft can be used for free for 100 days.
http://www.astrometrica.at/Have a nice day,
Sincerely,
Christophe