Reducing GRB Data at Steward Observatory.
Jochen Greiner's GRB Page
Steward Observatory Telescope Schedules
MMT Observatory Telescope Schedules
USNO Photometric Data
USNO Finder Charts
The STScI Digitized Sky Survey
GCN Bursts of Special Interest
- Make a data directory and include both raw and processed subdirectories.
[ggwilli@grb ggwilli]$ mkdir /home/ggwilli/data/GRBYYMMDD
[ggwilli@grb ggwilli]$ mkdir /home/ggwilli/data/GRBYYMMDD/90inch
[ggwilli@grb ggwilli]$ mkdir /home/ggwilli/data/GRBYYMMDD/90inch/raw
[ggwilli@grb ggwilli]$ mkdir /home/ggwilli/data/GRBYYMMDD/90inch/proc
- Get the GRB coordinates of the burst from the
GCN Circulars or the
GCN Bursts of Special Interest.
- Check the image quality with ds9.
- Download a finder chart from the STScI DSS.
- Download an 11x11 arcmin finder chart from the USNO Finder Charts.
- Calculate the scale between the DSS image and one of the science images.
This can be done a number of ways:
- Use the science image first. Start the iraf task imexam.
Place the cursor over a reference star and type 'y'. This sets the
coordinates of that star as a reference position. Put the cursor over a
different star and type 'x'. The output values correspond to:
col line pixval xorign yorigin dx dy r theta
Origin: 357.50 494.00
632.50 546.00 1945. 357.500 494.00 275.00 52.00 279.87 10.7
Repeat the procedure for the second image.
Origin: 439.50 494.50
555.00 522.00 17492. 439.500 494.50 115.50 27.50 118.73 13.4
Use the ratio of the radii to get the scale factor:
scale = 118.73 / 279.87 = 0.4242
Use the difference of the thetas to get the rotation:
rot = 10.7 - 13.4 = -2.7 (NOTE: the order of the difference)
Perform the transformation on the DSS image:
im> imlintran test1.fits test10.fits -2.7 -2.7 0.4242 0.4242
If the scales were different in x an y one could first rotate the image
and then calculate xscale and yscale and then scale the image.
- Essentially the same as above but using the "Regions" capability in
ds9. Click on "Region" in the task button bar. Choose "ruler" from the
resulting shapes button bar. Click on the first star and drag the mouse
until the cursor is over the second star. Select the region (or line) you
just drew by clicking on it. From the "Region" menu at the top choose
"Get Info...". The dx, dy and theta are given.
- Download the USNO field photometry data file.
- Plot a finder chart using the USNO field photometry data.
- Match the USNO stars with visible stars in data field.
- Make a revised USNO field photometry file containing only the stars
that will be used with the data.
- Calculate the offsets.
- Plot the curve of growth. Adjust magnitudes accordingly.
- Determine the radius to use based on errors. Explain in greater detail.