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Dear Iraf Help team,I am an experienced user of stectra software but I find myself unable to
solve the following problem.I have echelle observations where the star was out of focus. As a result,
a cut perpendicular to the dispersion direction shows 24 orders, all
double-peaked (usually one peak is higher than the other). I want to
extract the entire order (both peaks) using an aperture wide enough to
encompass the double-peak. However I cannot set the aprecenter and
apresize paramters such that the center of the apertures are in the trough
between the split peaks (ie in the middle of the order), and the aperture
boundaries are on either side of the split peak, wide enough to encompass
both peaks.I know how to do this manually, but I need to do it in automatic mode
since I have a lot of orders and a lot of stars. So far I have only been
able to place the center of the aperture on one of the two peaks, and one
of the apertures sides is always too close to the aperture center to
encompass the entire order...Can you help?Thanks, Orsola++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Orsola De Marco, PhD Tel: +1 (212) 496-3444 Department of Astrophysics
Fax: +1 (212) 769-5007 American Museum of Natural History
research.amnh.org/~orsola/ Central Park West at 79th Street New York, NY
10024
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Hello Orsola,I can make some suggestions though the details would require me to have more knowledge of what the spectra look like.First, the profile centering width is a key parameter. This should be the width of the entire order independent of the structure of the profile. Basically this is the scale at which the code looks for edges. The centering is much less sensitive to feature which are either much wider or narrower than this width.The other parameters which should be useful are ylevel and peak. These control how the aperture width is set initially or during resizing. Whether you resize or just recenter depends on how much the actual width is varying from exposure to exposure. It may be that you just need to interactively sets the apertures for one exposure and then use that as the reference and do the recentering only. In the recentering only case it comes back down to making sure the width parameter is wide enough. You can also constrain the centering to be a shift for all apertures rather than independent recentering for each order.This probably will require some experimentation but I think the parameters I've mentioned can be adjusted to do what you want.Good luck,
Frank Valdes[/img]