Is there an approved way to do automated VSX searches? I have a list of a few hundred variables from APASS data and I want to see how many of them are known in VSX, but I don't want to add positions abd click on a web page that many times. Another solution would be to have a file of positions of the VSX stars that I can use my position matching code on.
The best way to do this is using the "List of Targets" function in VizieR.
We do it often when we have to add variables to VSX from newly published lists. Even though the authors say their variable stars are new, a lot of them turn up to be already in VSX so we don't want to add duplicates.
So go to the VizieR version of VSX (updated every Monday) available here.
Click on the List of Targets tab.
Be sure that the "add your input as first column" box is marked and upload a file with the positions of your stars.
Select the "target dimensions". It depends on the accuracy of the positions you are going to enter, and also on the accuracy on the catalogued positions.
E.g.: there may be a NSV variable that matches your object but has a poor position so it is 30" away or more. But if you work on crowded fields e.g. galactic bulge), too many results may come up.
I would do a first pass with a 20" radius (to include most ASAS and other survey variables) and then a second pass with a 60" radius including the objects that didn't have a VSX match in the first pass.
For large separations be sure to properly identify the objects. You may have a new variable even when there is another VSX variable nearby. This is not likely but it is good to double-check using magnitudes, colour data, light curves, etc.
Then you can choose which information fields you want to be displayed in the results.
Include the "Distance ρ" parameter (on the left panel) so you know how far from your position the VSX stars are and how reliable the cross-ID is.
I remember checking a list of potential new APASS variables a couple of years ago but they turned out to be close doubles causing photometry problems (you can also check for that using some of the astrometric catalogues with better resolution. E.g.: the UCAC4 catalogue. Vizier version here).
I hope you are luckier than me this time!
Thank you Sebastian. That will be a big help. And I too have seen "variables" caused by the close doubles. The PSF reduction code should help a lot with that.