daofind problem
Jayme Derrah wrote on Aug 02, 2010
Hi, I'm trying to run daofind on some images with a large field of view. However it is returning way too many stars regardless of how I set my parameter files. It also doesn't seem to matter what I have my detection threshold set to, it still detects pretty much every pixel.
I have three exposure lengths, 30sec, 60sec and 120sec, and all three are detecting the same amount, which also doesn't make sense.
Can anyone think of something that could be going wrong?
I have three exposure lengths, 30sec, 60sec and 120sec, and all three are detecting the same amount, which also doesn't make sense.
Can anyone think of something that could be going wrong?
Mike Fitzpatrick wrote on Aug 02, 2010
Please post your parameters (e.g. "cl> dpar datapars") and a link to a sample image (or upload to the anonftp at ftp://iraf.noao.edu/pub), there's not enough information in your post to determine what might be wrong. I suspect there's a problem in the 'datapars' parameters, e.g. the 'scale' is too small for your data and so you get too many detections. See also the 'Docs' link on the banner bar for photometry cookbooks that might help.
Jayme Derrah wrote on Aug 02, 2010
My image file is 33MB in size (the field of view is 19.5 square degrees), so it's difficult to upload it. How do I upload it? (It won't let me post anything)
My parameters are:
(scale = 1.) Image scale in units per pixel
(fwhmpsf= 2.328) FWHM of the PSF in scale units (from imexam)
(emissio= yes) Features are positive ?
(sigma = 0.9888) Standard deviation of background in counts (from imexam)
(datamin= INDEF) Minimum good data value
(datamax= INDEF) Maximum good data value
(noise = poisson) Noise model
(ccdread= ) CCD readout noise image header keyword
(gain = ) CCD gain image header keyword
(readnoi= 0.16) CCD readout noise in electrons (calculated)
(epadu = 0.) Gain in electrons per count (calculated)
(exposur= ) Exposure time image header keyword
(airmass= ) Airmass image header keyword
(filter = ) Filter image header keyword (only have 1 filter)
(obstime= time-obs) Time of observation image header keyword
(itime = 120.) Exposure time
(xairmas= 1.2) Airmass
Do you want to see any of the other parameter files? My threshold value is set to 4.
My parameters are:
(scale = 1.) Image scale in units per pixel
(fwhmpsf= 2.328) FWHM of the PSF in scale units (from imexam)
(emissio= yes) Features are positive ?
(sigma = 0.9888) Standard deviation of background in counts (from imexam)
(datamin= INDEF) Minimum good data value
(datamax= INDEF) Maximum good data value
(noise = poisson) Noise model
(ccdread= ) CCD readout noise image header keyword
(gain = ) CCD gain image header keyword
(readnoi= 0.16) CCD readout noise in electrons (calculated)
(epadu = 0.) Gain in electrons per count (calculated)
(exposur= ) Exposure time image header keyword
(airmass= ) Airmass image header keyword
(filter = ) Filter image header keyword (only have 1 filter)
(obstime= time-obs) Time of observation image header keyword
(itime = 120.) Exposure time
(xairmas= 1.2) Airmass
Do you want to see any of the other parameter files? My threshold value is set to 4.
fitz
Please post your parameters (e.g. "cl> dpar datapars") and a link to a sample image (or upload to the anonftp at ftp://iraf.noao.edu/pub), there's not enough information in your post to determine what might be wrong. I suspect there's a problem in the 'datapars' parameters, e.g. the 'scale' is too small for your data and so you get too many detections. See also the 'Docs' link on the banner bar for photometry cookbooks that might help.
Mike Fitzpatrick wrote on Aug 02, 2010
To upload the image:
% ftp iraf.noao.edu
....login as 'anonymous', use your email as the passwd
ftp> cd pub
ftp> put myimage.fits
ftp> quit
AnTaR3s wrote on Aug 02, 2010
Hi
I find the daofind routine also very annoying...I remember playing around with the parameters as well...bah
A guy at the university told me to try a different task in IRAF which yields basically the same results and is much easier to use.
It's the starfind task in the images.imcoords package.
give it a try
cheers
I find the daofind routine also very annoying...I remember playing around with the parameters as well...bah
A guy at the university told me to try a different task in IRAF which yields basically the same results and is much easier to use.
It's the starfind task in the images.imcoords package.
give it a try
cheers
Jayme Derrah wrote on Aug 02, 2010
It wouldn't let me upload the image. it gave me this error:
local: hyades102mf.fit remote: hyades102mf.fit
227 Entering Passive Mode (140,252,1,86,235,122)
553 Could not create file.
[
quote="fitz"]To upload the image:
local: hyades102mf.fit remote: hyades102mf.fit
227 Entering Passive Mode (140,252,1,86,235,122)
553 Could not create file.
[
quote="fitz"]To upload the image:
% ftp iraf.noao.edu
....login as 'anonymous', use your email as the passwd
ftp> cd pub
ftp> put myimage.fits
ftp> quit
Mike Fitzpatrick wrote on Aug 02, 2010
Try using 'sftp' instead of 'ftp'. Otherwise, I can't find a record of your connecting to our ftp server recently (from UCalgary, right?) but I did verify the directory has the right permissions. Are you sure you did a "cd pub" before trying to upload the file? Can you otherwise put the image at a site I can access?
Jayme Derrah wrote on Aug 02, 2010
Hi, I finally got the image uploaded. Still using ftp, earlier I was trying to transfer the file from an airport, which is probably why is wouldn't work. But it's there now, the filename is hyades102mf.fit (2 minute exposure and corrected for darks & flats)
fitz
Try using 'sftp' instead of 'ftp'. Otherwise, I can't find a record of your connecting to our ftp server recently (from UCalgary, right?) but I did verify the directory has the right permissions. Are you sure you did a "cd pub" before trying to upload the file? Can you otherwise put the image at a site I can access?
Last post on Aug 02, 2010