Star Selection for Plate Solving

[Sean Curry]

I'm using AIJ V5.2.0.09 and have a question about plate solving. I'm currently plate solving from AIJ using Ansvr on another PC on my local network, and that has been working well in the past. I now have a set of challenging images that won't solve with Ansvr, so I tried sending them to astrometry.net through AIJ, and those solves failed as well. I then tried solving the same images manually through nova.astrometry.net. and they solved successfully.

The difference is that it seems as if AIJ pre-selects the stars that are sent to Ansvr or astrometry.net for solving, and in this case only 6 or 7 stars are found on each image. However, when the images are uploaded to astrometry.net, and astrometry.net selects the stars, it finds a lot more, and can plate solve the images.

If I'm correct in my assumptions, is it possible to control the star selection parameters in AIJ so that more stars are found before sending the list of stars to the plate solving program? I've tried playing settings on the DP Astrometry Settings dialog in AIJ, but they don't seem to help in this case.

Thanks, Sean

[karenacollins]

Sean, the controls in the Astrometry Settings panel are the ones that might need to be tweaked. If you want more stars selected, you'd either need to reduce the "Noise Tol"  setting, maybe as low 0.10 or 0.05, depending on how faint the stars are in the images. Also, you'd of course need "Max stars" set to at least the number of stars you want considered for the plate-solve. If tweaking the above numbers fails, and you will have many of these type images in the future to solve, you can send a link to an example and I'll give it a try. If it is a one-off case, then I'd recommend just using the ones from astrometry.net.

Karen

[Sean Curry]

Karen,

Thanks! That did the trick. I set the Noise Tol to 0.1, and AIJ then selected 27 stars, many of them very faint. The plate solve worked fine in Ansvr at that point. I hadn't realized the the Noise Tol setting affected all star selection - I thought it only applied to the stars that were ignored because of the Max Peak setting.

Thanks again for your help. AIJ is a very productive tool for the projects I'm working on.

Sean