Asteroid Photometry

[ghawkins]

Is anyone using AIJ for time-series asteroid photometry?  The challenge is how to do time-series photometry when the target is moving, without having to result to frame-by-frame analysis.

Best regards,

Gary

[AstroT]

Hi Gary, I just posted a similar question. Did you find a way on how to solve the moving asteroid problem?

[basilr]

A late answer to your question, yes, sort of. I almost always use AIJ for a first look at my images and try a quick plot of the lightcurve. The moving target issue can be a challenge. I use centroid aperture in AIJ and frequently (but not always!) the target is moving slow enough for AIJ to re-center on the asteroid, but not after a meridian flip, so I usually make a subset of images after the flip. One challenge is finding where the comp stars are in the subset. Also, when a background star becomes the "target" after the asteroid passes too close - because I'm using centroid apertures, well that's where I usually stop my first look, or use the single step method in AIJ.

My first post about using AIJ for asteroids was back in 2019, here:

http://astroimagej.170.s1.nabble.com/Subtracting-background-stars-for-asteroid-photometry-td1197.html

I am very happy the AIJ team and Karen have decided to re-visit using AIJ for moving targets. I recently sent her a few nights of images for 2 targets in hopes they will help move their project forward. You may want to check this thread to hear of progress. I will try to let you know if I hear anything.

http://astroimagej.170.s1.nabble.com/Aperture-photometry-of-moving-asteroid-td2499.html#a2522

Doing the measurements is one thing, period analysis is another. I do not know if they will take AIJ into the period analysis ballpark, that would be a pretty big (time consuming coding) enhancement to AIJ and may come at a later date.

Basil

[Fred]

Hello

For asteroid photometry, I use pictures centered on the asteroid ; all the stars are moving.

You can request the (dRAcosDEC ; dDEC) drift vector to drive your telescope mount on this site.

Then AIJ performs photometry as usual.

Fred

[karenacollins]

Moving object photometry is now supported in AIJ's multi-aperture setup panel. Turn on the moving object option. Place apertures will then ask the user to identify the object in the first image and the last image. The feature works best with plate-solved images, but will also work with un-plate-solved images if movement is consistent from image to image.

Karen

[basilr]

Indeed it is supported now! Thank you and the team for adding this ability. I almost always use AIJ as a "first look" at my images to get an idea what I'm dealing with, mostly hoping for rapid rotator with a large amplitude - an "easy one". I then switch to another program (Tycho Tracker, MPO Canopus) to look for rotation periods, possible moons, with Fourier analysis, etc. - which I don't think AIJ can do?

I didn't know AIJ could work on non-plate solved images, as long as there is consistent movement between images, I'll have to give that a try. However the images must be plate solved at some point in my process.

Thanks again
Basil

[karenacollins]

Yes, AIJ now supports periodogram analysis, including BLS (Box Least Squares for transit searches in long baseline time-series photometry), TLS (Transit Least Squares for transit searches in long baseline time-series photometry), and the mode I think you'd need, Lomb-Scargle. To use, create or open a measurements table, then go to Multi-plot Main > Table > "Create periodogram using table columns", select the measurements table you want to analyze and the mode ( Lomb-Scargle in your case) and follow the prompts from there.

This recent feature was contributed by Greg Srdoc. Thank you Greg!

Karen

[basilr]

Oh wow, really wonderful news! I am looking forward to giving this a try and "following the prompts". I'm guessing many of the things you mentioned are pretty new and it sounds like a LOT of work has recently been done with time-series analysis, so the docs may still be in process. I'll let you know how it goes

Thank you Greg, Karen, and the AIJ team very much !!

Basil