Photometry of Sloan r images

Affiliation

American Association of Variable Star Observers (AAVSO)

Fri, 07/12/2019 - 15:11

Hi, I am having difficulty processing the sloan r images in VPhot. It delivers a magnitude of 0.0. I tried using the same comp stars as my R filter images. Also, Vphot delivers the following when I attempt to load comp stars:

"Comp stars/sequence exist, but none was imported due to no photometry for this particular filter, or too faint to be detected.0X24546AHW"

Thanks.

Aaron

MZK

Affiliation

American Association of Variable Star Observers (AAVSO)

Fri, 07/12/2019 - 17:33

No Comp Sloan Mags

Aaron:

The AAVSO comp data base does not yet have Sloan gri mags, only Johnson-Cousins BVRI. So VPhot cannot find any mags from VSP for the sloan r filter, thus it yields that error message.

However, if you find the Sloan R mag for your comps (e.g., from seqplot), you can edit your sequence and add the SR (sloan r) mag for your comps, measure your target and report as SR.

HTH, Ken

PS: IF your images came from a BSM scope with an SR filter, you can rename the filter as R and use the known transform coeffs that change SR to transformed R.

mcneely

Affiliation

American Association of Variable Star Observers (AAVSO)

Fri, 07/19/2019 - 14:38

Thanks MKZ: Edit Sloan r image FITS header

Thank you for the information. Would I need to edit the FITS header to change the filter setting for the Sloan r images?