iraf.net

Hello IRAF experts,I use apall for quick-look analysis of long slit data while I'm
observing; there's generally only one star I'm interested in, so I set
it to look for the star automatically and strip out the spectrum. I
run this from within a little bitty script. Been doing it for years,
works great.Well, until this observing run I'm on now; about half the time, for no
reason I can tell, it fails to find the star in the slit profile, even
when the star sticks way up over the background, and proceeds to strip
out the wrong columns of the chip. I've unlearned apsum and typed
everything back in, and I can't see anything different from what I've
done for years. The weird thing is that it's completely unpredictable
when this happens, sometimes it works fine and sometimes it doesn't.This isn't a killer problem, since I can always re-run apall
interactively to get it right, but it's a bother and a mystery and I
thought you might want to know about it. For the "real" reductions
I've been running apedit interactively with "find" on, and that is
behaving properly -- it always finds the highest peak in the slit
profile. Does anyone have any idea what might be happening? I'm
running PC-IRAF v 2.12 export (version May 2002) on a nearly-new PC
under RedHat 7.3.Thanks,
John Thorstensen-- Here's the lpar for apall, in case there's a clue somewhere: -- input = "x302" List of input images
nfind = 1 Number of apertures to be found automatically
(output = "") List of output spectra
(apertures = "") Apertures
(format = "multispec") Extracted spectra format
(references = "") List of aperture reference images
(profiles = "") List of aperture profile images\n
(interactive = no) Run task interactively?
(find = yes) Find apertures?
(recenter = yes) Recenter apertures?
(resize = yes) Resize apertures?
(edit = yes) Edit apertures?
(trace = yes) Trace apertures?
(fittrace = no) Fit the traced points interactively?
(extract = yes) Extract spectra?
(extras = yes) Extract sky, sigma, etc.?
(review = no) Review extractions?\n
(line = 514) Dispersion line
(nsum = -20) Number of dispersion lines to sum or median\n\n
(lower = -5.) Lower aperture limit relative to center
(upper = 5.) Upper aperture limit relative to center
(apidtable = "") Aperture ID table (optional)\n\n# DEFAULT BACKG
(b_function = "legendre") Background function
(b_order = 3) Background function order
(b_sample = "-50:-10,10:50") Background sample regions
(b_naverage = -3) Background average or median
(b_niterate = 1) Background rejection iterations
(b_low_reject = 3.) Background lower rejection sigma
(b_high_rejec = 3.) Background upper rejection sigma
(b_grow = 0.) Background rejection growing radius\n\n# APERTU
(width = 5.) Profile centering width
(radius = 10.) Profile centering radius
(threshold = 0.) Detection threshold for profile centering\n\n#
(minsep = 5.) Minimum separation between spectra
(maxsep = 1000.) Maximum separation between spectra
(order = "increasing") Order of apertures\n\n# RECENTERING PARAMETERS\n
(aprecenter = "") Apertures for recentering calculation
(npeaks = INDEF) Select brightest peaks
(shift = yes) Use average shift instead of recentering?\n\n#
(llimit = INDEF) Lower aperture limit relative to center
(ulimit = INDEF) Upper aperture limit relative to center
(ylevel = 0.3) Fraction of peak or intensity for automatic wid
(peak = yes) Is ylevel a fraction of the peak?
(bkg = yes) Subtract background in automatic width?
(r_grow = 1.5) Grow limits by this factor
(avglimits = no) Average limits over all apertures?\n\n# TRACING
(t_nsum = 30) Number of dispersion lines to sum
(t_step = 30) Tracing step
(t_nlost = 5) Number of consecutive times profile is lost bef
(t_function = "spline3") Trace fitting function
(t_order = 1) Trace fitting function order
(t_sample = "*") Trace sample regions
(t_naverage = 1) Trace average or median
(t_niterate = 1) Trace rejection iterations
(t_low_reject = 3.) Trace lower rejection sigma
(t_high_rejec = 3.) Trace upper rejection sigma
(t_grow = 0.) Trace rejection growing radius\n\n# EXTRACTION
(background = "fit") Background to subtract
(skybox = 1) Box car smoothing length for sky
(weights = "variance") Extraction weights (none|variance)
(pfit = "fit1d") Profile fitting type (fit1d|fit2d)
(clean = yes) Detect and replace bad pixels?
(saturation = 60000.) Saturation level
(readnoise = "8") Read out noise sigma (photons)
(gain = "3") Photon gain (photons/data number)
(lsigma = 4.) Lower rejection threshold
(usigma = 4.) Upper rejection threshold
(nsubaps = 1) Number of subapertures per aperture
(mode = "ql") --
-------------------------------------------------------------
John R. Thorstensen Professor of Physics
Department of Physics and Astronomy and Astronomy
6127 Wilder Laboratory
Dartmouth College voice: 603-646-2869
Hanover NH 03755-3528 USA FAX: 1446
-------------------------------------------------------------

>From valdes Mon Jun 23 08:36:34 2003
From: thorsten@partita.dartmouth.edu (John R. Thorstensen)
Subject: "apall"-ing problem ...
Date: 21 Jun 2003 22:07:31 -0700
Hello IRAF experts,I use apall for quick-look analysis of long slit data while I'm
observing; there's generally only one star I'm interested in, so I set
it to look for the star automatically and strip out the spectrum. I
run this from within a little bitty script. Been doing it for years,
works great.Well, until this observing run I'm on now; about half the time, for no
reason I can tell, it fails to find the star in the slit profile, even
when the star sticks way up over the background, and proceeds to strip
out the wrong columns of the chip. I've unlearned apsum and typed
everything back in, and I can't see anything different from what I've
done for years. The weird thing is that it's completely unpredictable
when this happens, sometimes it works fine and sometimes it doesn't.This isn't a killer problem, since I can always re-run apall
interactively to get it right, but it's a bother and a mystery and I
thought you might want to know about it. For the "real" reductions
I've been running apedit interactively with "find" on, and that is
behaving properly -- it always finds the highest peak in the slit
profile. Does anyone have any idea what might be happening? I'm
running PC-IRAF v 2.12 export (version May 2002) on a nearly-new PC
under RedHat 7.3.Thanks,
John Thorstensen-- Here's the lpar for apall, in case there's a clue somewhere: -- input = "x302" List of input images
nfind = 1 Number of apertures to be found automatically
(output = "") List of output spectra
(apertures = "") Apertures
(format = "multispec") Extracted spectra format
(references = "") List of aperture reference images
(profiles = "") List of aperture profile images\n
(interactive = no) Run task interactively?
(find = yes) Find apertures?
(recenter = yes) Recenter apertures?
(resize = yes) Resize apertures?
(edit = yes) Edit apertures?
(trace = yes) Trace apertures?
(fittrace = no) Fit the traced points interactively?
(extract = yes) Extract spectra?
(extras = yes) Extract sky, sigma, etc.?
(review = no) Review extractions?\n
(line = 514) Dispersion line
(nsum = -20) Number of dispersion lines to sum or median\n\n
(lower = -5.) Lower aperture limit relative to center
(upper = 5.) Upper aperture limit relative to center
(apidtable = "") Aperture ID table (optional)\n\n# DEFAULT BACKG
(b_function = "legendre") Background function
(b_order = 3) Background function order
(b_sample = "-50:-10,10:50") Background sample regions
(b_naverage = -3) Background average or median
(b_niterate = 1) Background rejection iterations
(b_low_reject = 3.) Background lower rejection sigma
(b_high_rejec = 3.) Background upper rejection sigma
(b_grow = 0.) Background rejection growing radius\n\n# APERTU
(width = 5.) Profile centering width
(radius = 10.) Profile centering radius
(threshold = 0.) Detection threshold for profile centering\n\n#
(minsep = 5.) Minimum separation between spectra
(maxsep = 1000.) Maximum separation between spectra
(order = "increasing") Order of apertures\n\n# RECENTERING PARAMETERS\n
(aprecenter = "") Apertures for recentering calculation
(npeaks = INDEF) Select brightest peaks
(shift = yes) Use average shift instead of recentering?\n\n#
(llimit = INDEF) Lower aperture limit relative to center
(ulimit = INDEF) Upper aperture limit relative to center
(ylevel = 0.3) Fraction of peak or intensity for automatic wid
(peak = yes) Is ylevel a fraction of the peak?
(bkg = yes) Subtract background in automatic width?
(r_grow = 1.5) Grow limits by this factor
(avglimits = no) Average limits over all apertures?\n\n# TRACING
(t_nsum = 30) Number of dispersion lines to sum
(t_step = 30) Tracing step
(t_nlost = 5) Number of consecutive times profile is lost bef
(t_function = "spline3") Trace fitting function
(t_order = 1) Trace fitting function order
(t_sample = "*") Trace sample regions
(t_naverage = 1) Trace average or median
(t_niterate = 1) Trace rejection iterations
(t_low_reject = 3.) Trace lower rejection sigma
(t_high_rejec = 3.) Trace upper rejection sigma
(t_grow = 0.) Trace rejection growing radius\n\n# EXTRACTION
(background = "fit") Background to subtract
(skybox = 1) Box car smoothing length for sky
(weights = "variance") Extraction weights (none|variance)
(pfit = "fit1d") Profile fitting type (fit1d|fit2d)
(clean = yes) Detect and replace bad pixels?
(saturation = 60000.) Saturation level
(readnoise = "8") Read out noise sigma (photons)
(gain = "3") Photon gain (photons/data number)
(lsigma = 4.) Lower rejection threshold
(usigma = 4.) Upper rejection threshold
(nsubaps = 1) Number of subapertures per aperture
(mode = "ql") --
-------------------------------------------------------------
John R. Thorstensen Professor of Physics
Department of Physics and Astronomy and Astronomy
6127 Wilder Laboratory
Dartmouth College voice: 603-646-2869
Hanover NH 03755-3528 USA FAX: 1446
-------------------------------------------------------------
>From valdes@noao.edu Wed Jun 25 14:02:22 2003
Date: Wed, 25 Jun 2003 14:02:20 -0700 (MST)
From: Frank Valdes <valdes@noao.edu>
To: thorsten@partita.dartmouth.edu
Subject: Re: "apall"-ing problem ...Hi John,I'm sorry I didn't catch "this observing run I'm on now". This should have
led to a quicker response.In a project of observing a large number of stars I also did much as you
are doing. I had an automatic postproc script that produced quicklook
extracted spectra and then printed min/max counts for estimating S/N.The automatic finding of the highest peak has be extremely reliable and
I can't imagine why you find that sometimes it defines an aperture that
is not centered on the peak. The only potential problem is cosmic rays
but I see that you correctly use a negative "nsum" to compute a median
vector in which to find the star. Looking at the rest of the parameters
I can't see anything wrong. Are you reusing image names so that maybe
there is an aperture definition in the database from a previous time?Do you have the "logfile" which would give some brief information about
the finding and other steps?I don't have any other thoughts. So more info than just the parameters
would be needed to give you an answer.Yours,
Frank
>From thorsten@partita.dartmouth.edu Wed Jun 25 20:01:05 2003
Date: Wed, 25 Jun 2003 23:01:02 -0400 (EDT)
From: "John R. Thorstensen" <thorsten@partita.dartmouth.edu>
To: Frank Valdes <valdes@noao.edu>
Subject: Re: "apall"-ing problem ...
Hi Frank,Thanks for the reply.I'm home again now and it was just a mystery -- which somehow
gradually got less frequent over the next night or two. I
wasn't reusing image names, so that's evidently not the cause --
and since I'm gone now it'll just have to remain a mystery,
I guess! Until it happens to someone else so it can be tracked
down ... ! Best,
John
On Wed, 25 Jun 2003, Frank Valdes wrote:> Hi John,
>
> I'm sorry I didn't catch "this observing run I'm on now". This should have
> led to a quicker response.
>
> In a project of observing a large number of stars I also did much as you
> are doing. I had an automatic postproc script that produced quicklook
> extracted spectra and then printed min/max counts for estimating S/N.
>
> The automatic finding of the highest peak has be extremely reliable and
> I can't imagine why you find that sometimes it defines an aperture that
> is not centered on the peak. The only potential problem is cosmic rays
> but I see that you correctly use a negative "nsum" to compute a median
> vector in which to find the star. Looking at the rest of the parameters
> I can't see anything wrong. Are you reusing image names so that maybe
> there is an aperture definition in the database from a previous time?
>
> Do you have the "logfile" which would give some brief information about
> the finding and other steps?
>
> I don't have any other thoughts. So more info than just the parameters
> would be needed to give you an answer.
>
> Yours,
> Frank
> --
-------------------------------------------------------------
John R. Thorstensen Professor of Physics
Department of Physics and Astronomy and Astronomy
6127 Wilder Laboratory
Dartmouth College voice: 603-646-2869
Hanover NH 03755-3528 USA FAX: 1446
-------------------------------------------------------------