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Trouble importing Gaia Stars into AIJ

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WBY's picture
Trouble importing Gaia Stars into AIJ

I tried importing a Gaia aperture list downloaded from the link on the TTF for the first time using the instructions in appendix D of the TFOP Observation Guidelines Rev 6.3.1. The images were plate solved using the AIJ ANSVR plug-in for AIJ. The apertures appeared on the image before I opened the multi-aperture tool and they appeared in the wrong place. Then when I select the target star (left click) in the multi-aperture tool, instead of locating the the imported stars in the correct location it adds the target star as a comp,C5. I checked the Image center coordinates added by ANSVR in CRVAL1 and CFVA2 fits header fields and they appear to be correct J2000 decimal coordinates. The coordinates in the loaded radec file also appear to be correct J2000 coordinates. I am using the latest AIJ including the latest daily build. 

Can anyone explain why this isn't working and how I can fix it? In this case there are only 4 Gaia stars within the 2.5' "contamination radius" and they are easy to identify and select by hand. Frequently, however, that isn't feasible and I need to use this feature. I have used "Use previous apertures" and  "Use RA/DEC to locate apertures" features before to reuse apertures entered from an earlier plate solved run on another plate solved run without issue. 

A screenshot of the aperture placement, a text version of the fits header file and the gaia aperture file are attached. I added the .txt suffix to the radec file name to upload it to the forum. 


dennis-conti's picture
Gaia Stars and AIJ

Hi Brad,

So we don't burden the forum with back and forth, I will contact you via email and then report back to the forum the results.



WBY's picture
Resolved Trouble Importing Gaia Stars into AIJ

The problem was resolved by Karen Collins. She discovered that our telescope control program was installing an EPOCH fits header field and populating it with the epoch of observation. This is now a deprecated fits header field replaced by EQUINOX but it is defined as containing the epoch of the WCS solution not the observation. AIJ then interpreted the J2000 coordinate plate solution as the Jnow solution at the epoch of observation and transformed the J2000 Gaia aperture table coordinates to the 2020.xx epoch before placing them in the field. The plate solution was correct but the value in the EPOCH field made AIJ think they were for a 20.xx year different epoch. 

The solution which included in daily build and later overwrites an EPOCH field value if present when AIJ plate solves with the value 2000, which is the correct epoch of the WCS plate solution. 

Brad Walter, WBY


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