iraf.net

I've noticed a minor bug in the aperture definition stage of doslit (at least in the ctioslit package), namely that if you go to define a second aperture (with "m") on another star that it occasionally gets marked as aperture 3 rather than 2. In other words, if it automatically finds one aperture, and you go to mark a second, the second one gets labeled "3" rather than 2. I've been using "i" to reset its number to 2.Oddly, this doesn't happen every time. My **impression** is that this happens
primarily when the first found aperture is at a low column number (<500) and the newly marked second aperture is at a high column number (>1500) but I'm not sure of that.I have put a test image on iraf.noao.edu pub, iff0054c3.fits. If you run doslit
on it from the ctio package with the default parameters (but dispaxis=1) it will
automatically find a star at around column 450. Now mark ("m") the other
peak around column 1600. It will come up as a "3".

There is a feature intended for fibers where if a new aperture is added and the separation from the neighboring aperture is greater than an amount specified by the parameter "maxsep" then the aperture number is adjusted for the number of gaps. The default for this parameter in apextract and the various "do" tasks is 1000 pixels. This was not a farsighted selection given that detectors can have more than this number of pixels (both at the time all this was done years ago and in the foreseeable future). I have changed the default values to 100,000 pixels.So what is happening with your data is when you happen to mark the second aperture more than 1000 pixels from the first one you get 3 instead of 2 as you report. Thanks for helping identify this problem which will be fixed for subsequent releases. Your work around is fine.Yours,
Frank

OK, that makes perfect sense. Thanks for checking on it...