Skip to main content

Issue with Aperture Photometry with Pixinsight and APASS catalogue

1 post / 0 new
omega.centauri@...
omega.centauri@gmail.com's picture
Issue with Aperture Photometry with Pixinsight and APASS catalogue

Dear All,

I am trying to do aperture photometry of the Landoldt field of M67 for calculating my trasformation coefficients.

For the automatic photometry I am using Pixinsight that, after plate solving the image, creates a table with the APASS name of the star and the calculated aperture photometry.

It looks easy and quick, but there is an issue. The same stars in the VSX and in the APASS look like have different names (coordinates).

Example:

The M67 Landoldt field as X25589YX, its photometry table contains the following star

AUID: 000-BLG-879
RA: 132.79925537
Dec: 11.75602818
Label: 100

However, on Pixinsight I can't find an APASS star with those coordinates; instead the aperture photometry tool finds a star at these APASS coordinates: 

132.799073 11.756131

Are those in reality two different stars, or the same one with slightly different coordinates because of different catalogues used for the chart? I can't know for sure...

My opinion is that they are the same stars with coordinates from different catalogues, but this is a problem because I would like to automate the extraction of the estimated fluxes for the stars selected for the standard field and reject those not part of that set.

Any idea on how to solve this?

Thanks a lot for your help

Nicola

 

 

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