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Hi all,I am working on some echelle spectra with 11 orders. I tried to normalize a combined flat with apflatten task. As a reference image for apertures i used an extracted spectrum of deneb with apall task. Now the problem is, though i tried again and again with different parameters, i can not decide whether my normalization is good or not. Is there any criteria for that? The parameters that have given the best (?) results are as follows(interac= no) Run task interactively?
(find = no) Find apertures?
(recente= no) Recenter apertures?
(resize = no) Resize apertures?
(edit = no) Edit apertures?
(trace = no) Trace apertures?
(fittrac= no) Fit traced points interactively?
(flatten= yes) Flatten spectra?
(fitspec= no) Fit normalization spectra interactively?(line = 150) Dispersion line
(nsum = 10) Number of dispersion lines to sum or median
(thresho= 0.) Threshold for flattening spectra(pfit = fit1d) Profile fitting type (fit1d|fit2d)
(clean = no) Detect and replace bad pixels?
(saturat= INDEF) Saturation level
(readnoi= RDNOISE) Read out noise sigma (photons)
(gain = GAIN) Photon gain (photons/data number)
(lsigma = 3.) Lower rejection threshold
(usigma = 3.) Upper rejection threshold(functio= spline3) Fitting function for normalization spectra
(order = 2) Fitting function order
(sample = *) Sample regions
(naverag= 2) Average or median
(niterat= 3) Number of rejection iterations
(low_rej= 3.) Lower rejection sigma
(high_re= 3.) High upper rejection sigma
(grow = 0.) Rejection growing radius
(mode = ql)
Any comment or advise?Thanks in advance,
Ozgur Basturk
Ankara University Observatory
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Hello Ozgur,It was not clear what I could say so I put off replying. The only way I could tell you if the result is good is to see the data. I you wish you can put some data some place that I can download it. Send me an email directly if you do this at valdes@noao.edu.Yours,
Frank Valdes

Dear Sir,I have sent an e-mail to your mail address. Thanks in advance...Ozgur Basturk
Ankara University

Dear Ozgur,Thank you for posting some data. It looks good and I think you are doing the right processing. My only comment is more about the data taking. The flat fields should be taken with a longer slit if at all possible. The goal is that the apflatten image should have order strips that are wider than the profiles of the science exposures so that the edge effects and any possible flexture (bending) shifts are covered.So I encourage you to continue as you are doing.Yours,
Frank Valdes
On Jun 2, 2008, at 8:31 AM, ozgur basturk wrote:Dear Sir,I'm a PhD student in Ankara University. I posted a question in a topic
on the iraf.net forum regarding the normalization of a flat fied for
reducing spectra on May, 14. Thanks for your reply on the forum. You
told me to put some data on some place so that you could have the
chance to have a look. I put some files on a web server located at my
department. Here is the address:http://dione.astro.science.ankara.edu.tr/~ozgur/The server does not allow directory listing. So I had to make links,
you will have to right click on the links and save the frames all of
which are in fits format. I am very sorry for the inconvenience.I obtained the data with TFOSC (TUG Faint Object Spectrograph and
Camera) which is one of the ten FOSC series instruments. It is
attached on the 150 centimeter Russian-Turkish Telescope RTT-150. When
it is used in echelle format, it reaches 5000 resolution maximum
(theoretically though). There is no document or pipeline for reducing
its data and we are trying to create a manual for ourselves.First of all, I have decided on the overscan region and trim
section.(both are declared in the headers) I made the corrections.
Then I created a masterbias frame which is the median of 10 bias
frames. I zero-corrected all my data using this masterbias frame. Then
I created a masterflat which is the median of 10 halogen flat frames.
I ran apall task for finding the apertures from a Deneb spectrum. I
have fit spline3 functions with the order of 3 to the apertures,
editted, resized and recentered them. Then I ran apflatten task for
the masterflat I obtained using the Deneb spectrum as reference. This
time I haven't interactively found the apertures again but just
flatten them. So I had the normalized flat (which is on the server
under the name normalized_flat.fits) I have put flatten and zero
corrected Deneb spectra and extracted and wavelength calibrated
spectra so that you could check them.Is anything wrong with the way I reduce spectrum? Is my normalization
to the flat frames correct cause I know that it's very important for a
clean reduction process?Thanks in advance,
Ozgur Basturk
Ankara University
Astronomy and Space Science Department