Star positions via Stack -> Lights aka access to the Astrometry in ASTAP

[Jesse Goldbaum]

I'm interested in a parsable text file of pixel coordinates for identified stars in a set of images. I've used a few programs to do this and have no idea how in ASTAP. I try stack -> Lights -> Analyse and organise and lo, I get a spreadsheet style view that looks rather similar to what I can get using DeepSkyStacker (DSS), including a column labeled 'Stars' which I assume indicates the number of stars identified in each image. So far so good. In DSS I get something very much like this after registration at which point DSS also writes a text file for each input file that includes, among other things, the center coordinates of each star identified. ASTAP has a STACK button which seems close enough, but when I click it I only get, well, a Stack. So where's the Astrometric (text) info advertised in the program's name :)

My goal in this is to compare (ideally average) star positions (well, relative distances actually) from different codes to get a slightly more accurate estimate of the 'true' distances.

Jesse

[han.k]

My goal in this is to compare (ideally average) star positions (well, relative distances actually) from different codes to get a slightly more accurate estimate of the 'true' distances.

Not fully sure which information you want. You can have the X, Y position in pixels or the RA, DEC positions of the stars. The most powerful command in ASTAP is in the popup menu "Star info to clipboard" See attached screenshot.

You get then the data as the table below.

The detected star X, Y positions and flux you can get also via the command line.

Han

Limiting magnitude is 16.2   (16.2< m <16.2, SNR=7, aperture ⌀1.5)
Passband filter used: Luminance
Passband database=V
Magnitudes are only valid if passband filter and passband database are compatible. E.g. CV=BP, G=V, R=R, B=B.
Option 1) Select in tab photometry a local database and in tab alignment the local database (standard=BP or V50=V)
Option 2) Select an online database in tab photometry.

Saturated stars are excluded to avoid photometric errors. For photometry purposes ignore stars with a low SNR value (SNR<30).

fitsX   fitsY   HFD α[°]    δ[°]    ADU SNR Magn_measured   |   Gaia-V  Gaia-B  Gaia-R  Gaia-SG Gaia-SR Gaia-SI Gaia-G  Gaia-BP Gaia-RP
1166.07 498.95  1.870   70.194631   73.986005   10146   19  15.316  |   0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000
1246.22 500.65  2.679   69.990707   73.981129   6561    11  15.789  |   0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000
1160.54 504.28  2.788   70.207239   73.990154   95636   134 12.880  |   12.845  13.406  12.503  13.068  12.696  12.564  12.707  13.010  12.238
908.00  507.99  1.991   70.848472   74.010576   8813    15  15.469  |   0.000   0.000   0.000   0.000   0.
................

[Jesse Goldbaum]

Thanks for getting back. I've got a lot of files, and it looks like astap_cli -f (filename) -extract will give me what I'm looking for. -Jesse