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ASTROMETRICALOG

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Amrum
ASTROMETRICALOG

Hi,

I wrote a tool to find *possible* variables in the reference stars of Astrometrica.

If you have a time series of 10 or more CCD images (same filter) and make an astrometric solution with Astrometrica (astrometrica.at), you get a long output with measured magnitude of the references atars. With PPMXL or other you get 1000 and more for each image. Those stars have a high SNR and you can find with this tool several candidates. Unfortuantely Astrometric gives not the designation, so that you get only the coordinates until know.

The tool ist written for the command line of Windows (so you must know, how to use the command line cmd.exe etc.) and the output  is written to screen. You can redirect it into a file with ">file.txt". The program has no option, it's just want the Astrometrica.log in the same path.

The program identifies the same reference stars in each image (using the FWHM for search radius). Then it looks using quartils for outliers. After this it checks all images, which have high outlier numbers (bad mags) and reject them. In a second run it find most of the possible variables using again the outlier method.

The tool looks the valid mags after outlier rejection and add the difference between each mag in time sorted series. For magnitude direction change for difference it adds the double. Then it divdes the sum by the mag interval and the number of values. If the resulting value is <20%/interval/entry, it's a very good indicator, that the variabilty maybe cause by the star itself. If it's lower 10% it's very sure.

Using some logs by me and a friend we found several known, but also unknown variables.

The tool is in development and you must update it from time to time. Later additions will be star identfication, a menu based program and changing of file names and parameters. Maybe I'll also add other software outputs to anlyze them this way.

Here's a part of the ouput

+-----------------------------------------------------------------------------+
|                                  star    3                                  |
+-----------------------------------------------------------------------------+
                    RA           dRA        Dec.        dDec     V      dV     
                  h  m   s        "       °  '   "       "      mag     mag    
20170523210011   17 55 50.151   -0.14   +21 47 41.58   +0.16   15.07   -0.09   
20170523215005   17 55 50.150   -0.15   +21 47 41.56   +0.15   15.16   -0.00   
20170523220639   17 55 50.153   -0.11   +21 47 41.58   +0.17   15.25   +0.08   
20170523222316   17 55 50.154   -0.09   +21 47 41.60   +0.18   15.35   +0.19   
20170523223950   17 55 50.154   -0.10   +21 47 41.53   +0.12   15.41   +0.25   
20170523225627   17 55 50.155   -0.08   +21 47 41.61   +0.19   15.42   +0.26   
20170523231302   17 55 50.156   -0.06   +21 47 41.54   +0.13   15.41   +0.25   
20170523232933   17 55 50.157   -0.05   +21 47 41.55   +0.14   15.39   +0.23   
20170523234612   17 55 50.159   -0.03   +21 47 41.59   +0.17   15.26   +0.10   
20170524000249   17 55 50.153   -0.11   +21 47 41.59   +0.17   15.19   +0.02   
20170524001925   17 55 50.158   -0.03   +21 47 41.58   +0.17   15.12   -0.04   
20170524003602   17 55 50.163   +0.02   +21 47 41.56   +0.14   15.09   -0.07   
20170524005244   17 55 50.160   -0.02   +21 47 41.53   +0.11   15.05   -0.11   
20170524010918   17 55 50.162   +0.02   +21 47 41.61   +0.19   15.02   -0.14   
20170524012558   17 55 50.167   +0.08   +21 47 41.58   +0.17   15.03   -0.14   
20170524014234   17 55 50.165   +0.06   +21 47 41.59   +0.17   15.03   -0.13   
20170524015908   17 55 50.166   +0.07   +21 47 41.59   +0.18   15.05   -0.11   
20170524021548   17 55 50.165   +0.06   +21 47 41.59   +0.17   15.08   -0.08   
******
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Quartils: 1442 1505 1514 1526 1589
All 21 measurements from 15.02 mag to 15.42 mag (range of 0.40 mag)
Without outliers 18 obs from 15.02 mag to 15.42 mag (range of 0.40 mag)
1st detection criteria: 81  202 11/meas.
2nd detection criteria: 619  62  3/meas.
3rd detection criteria: 83  40  207%  11%/meas.

 

After listing the coordinates, time and some other values, it presents a text based "lightcurve" - low values left, high values right - and some other parameters. The last one is the most interesting, here 11% and a really nice lightcruve for an until know unknown variable star (using the AAVSO database). Please note 3 outliers, because 3 images of the series are bad. That is listing in another part of the more longer output.

If you have problems, questions, please send your copy of Astrometrica.log to astrometrica@jostjahn.de with the output of your run and other details. I'll try to fix the problem.

Some virus machines means, it's dangerous using heuristic methods, but it's just a compiled Freebasic program: http://www.jostjahn.de/test/astrometricalog.exe

Have fun

Jost

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484