Dohydra problem maybe with the trace?
greensilverfish wrote on Aug 08, 2009
I am having a problem with dohydra, I am reducing data from the WIYN telescope acquired in June 09. The program runs without any errors but for some of the extracted spectra there is a strange drop. See the following image: [img:3c7c1e875e]http://krysse.webs.com/photos/-Spectra/dohyra.jpg[/img:3c7c1e875e]
Why is this happening? and how do I fix it. Not every spectra does this but many of them do and all at around pixel 717. (somewhere between 710-730)
Why is this happening? and how do I fix it. Not every spectra does this but many of them do and all at around pixel 717. (somewhere between 710-730)
Francisco Valdes wrote on Aug 08, 2009
Yes this could be due to the trace. Be sure to do the extraction first with no cleaning or weighting to eliminate another possible source due to the profile fitting. If you get a reasonable extraction with simple extraction then you can turn on the more advanced features if needed.
Yours,
Frank Valdes
Yours,
Frank Valdes
Francisco Valdes wrote on Aug 08, 2009
Hello,
Daryl Willmarth just showed me something very similar. I was slightly swayed by your suggestion of a tracing problem. But now I think the more likely cause, because I've seen something like this years ago, is that the FITS file is corrupted in the sense that it is jumping into the middle of the first spectrum (because the offset from the header to the data is off by a FITS "block") and what you are seeing is a wraparound into the next aperture.
So I will be looking at why this happens with Daryl's example.
Frank
Daryl Willmarth just showed me something very similar. I was slightly swayed by your suggestion of a tracing problem. But now I think the more likely cause, because I've seen something like this years ago, is that the FITS file is corrupted in the sense that it is jumping into the middle of the first spectrum (because the offset from the header to the data is off by a FITS "block") and what you are seeing is a wraparound into the next aperture.
So I will be looking at why this happens with Daryl's example.
Frank
Last post on Aug 08, 2009