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Dear IRAF help,I haven't heard back from Lindsey Davis on these questions; perhaps she is
away (or recently come back) so I thought I'd send this to the general
IRAF help.Someone else may be able to answer the DS9 questions just as well as she.Thanks, -- Stuart---------- Forwarded message ----------
Date: Fri, 6 Sep 2002 17:38:35 -0400 (EDT)
From: Stuart Taylor <taylor@chara.gsu.edu>
To: Lindsey Davis <davis@noao.edu>
Cc: iraf@noao.edu
Subject: "psf" and Input psf star list
Hi Lindsey Davis,Thank-you for responding to my earlier question.I think I've got my crowded field photometry to work well at identifying
the appropriate number of stars using your suggesiton and following the
manual for photometry, but things seem to have changed for the "psf"
function since the manual was written by Massy and yourself in 1992.I am confused about entering an "Input psf star list" as I don't find that
in the manual (p48 +/- a page or two). I was also uncertain how many PSF
stars I need to find beforehand; my field is very crowded and I've only
found about six that look okay, though I'm unable to get any of the
viewers ds9, saoimage, and ximtool to show more than the central part of
the image unless I do a "fill+" which reduces the quality too badly such
that too much is interpolated into each pixel so "zooming" does no good.
I've made subsections of my image using "magnify" and displayed those;
that works but is kludgy and takes disk space.So I've explained my main question plus two side questions: 1. How do I
enter all the files "psf" now requires that aren't show on p.48 of the
photometry manual?, and 2.How to display smaller parts
of the image in good detail? and 3. How many PSF stars do I need to find?A question #4 is that ds9 and saoimage (imtool gives error mssgs and
fails) say they don't support the mesh grid that is used on p.49.I hope I've made my questions clear; it seems that there are actually two
files that I need to enter that aren't shown in Fig. 38 on p. 48.Thank-you for your earlier reply. -- Stuart Stuart Taylor, http://www.chara.gsu.edu/~taylor
office 404-651-2287 (Fax: 404-651-1389)
Center for High Angular Resolution Astronomy (CHARA)
Georgia State University (GSU)
1 Park Place South SE Rm 700, Atlanta GA 30303Input psf star listOn Wed, 19 Jun 2002, Lindsey Davis wrote:>
> Hello Stuart,
>
> Sorry for the long delay in getting back to you concerning your daofind
> problem. I have only just got back to my office and I am wading through a
> backlog of mail. It sounds as though your original problem went away on its own.
> Is this the case ?
>
> With regard to the too many detections issue I think the problem
> is that your datamin value is too high. The value you are using is 2000,
> the sky value is closer to 1000, and the recommended value is something
> like 5-7 sigma below background. The high datamin setting will produce
> a biased density image and biased detections.
>
> Let me know if this is not the problem and I will look into it further.
>
>
> Best regards,
> Lindsey Davis
>
>

Hi Stuart,As Mike already told you, Lindsey Davis is no longer available to
provide consultation on the DAOPHOT package. We are trying
to find a substitute consultant. We will give what help we can
but we may no longer be able to provide detailed guidance. Often
the questions are easy for us to answer. However, occasionally
it may not be obvious. This is the case with the details of what
all the new parameters are useful for in a general sense. Don't
hesitate to ask questions but understand we may not always have
the definitive answer.You will need to consult as much documentation as you can yourself.
In particular, you should read the on-line help pages for the tasks
you are using and which are mentioned in the guide. As you noted, the
package has evolved somewhat since the manual was written. To
read the help you use "help psf", "phelp psf", or "help psf dev=gui".
The help may also be read on the web through the IRAF home page
"iraf.noao.edu".Here are some hints. When new parameters are added to tasks they
usually have default values that preserve the previous functionality.
For the pstfile it looks like you should use the value "default". Also
just using the default hidden parameters (those in parenthesis in epar)
is usually the right thing to do initially. Looking at the help for
each of the new parameters I think you will be able to figure out what
to do.As far as how many PSF stars you need, that is a matter of scientific
judgement and the data. Obviously the more the better but if the
data is very crowded you may have to limit this. I would expect that
six is an acceptable number.Yours,
Frank Valdes

Hi Stuart,I forgot to mention that there is a more recent document on the
DAOPHOT package. This is not as "user friendly" but appears to
be very useful.http://iraf.noao.edu/iraf/docs/daorefman.ps.ZFrank