Mosaic II FAQ
Frequently Asked Questions
- I identified an object exposure as a domeflat. How do I correct
this after the image is written to disk?
You need to do two things: (a) change the name of the file, and (b) change
the information in the header describing the "image type".
- change the name with something like
- change the image type in the header with the msccmd command, which
is needed to change the information in ALL extensions of the MEF file.
Use something like
msccmd "hedit $input OBSTYPE object"
- What is the linearity of the Mosaic CCDs like?
The linearity should be good to <1% up to 20,000 and 40,000 adu, depending on which CCD. The point at which each amplifier saturates is posted on the main CTIO Mosaic web page. The amplifiers probably begin to go non-linear within 10% of these values. Note that there are SIGNIFICANT variations, so one must be careful when specifying the saturation value.
- How do I fix bad headers? (when TCS & WCS info isn't present)
Before fixing any headers, save a copy of the original image.
Instructions on fixing bad headers is found here.
If you are sitting in the Blanco Control room, you may use the task 'fixhdr1'.
- To add parameters RA, Dec, Filter, epar fixhdr1
image = obs1011.fits Image to update header
ra = 05:13:02.71 right ascension
dec = +09:51:05.00 declination
filter = V c6026 filter
(epoch = 2000.) epoch of coordinates
(hdrpath = home$uparm/) Path to header files
(update = yes) update image headers
(verbosi = yes) verbose mode
(mode = q)
- To add any other parameters, epar ccdhedit
- How do I take apart MEF files (extract individual CCD frames)? How do I make an MEF file from individual CCD frames?
The tasks to use are mscsplit and mscjoin.
- How do I interpret the WCS in the Mosaic image headers?
Lindsey Davis described some of the details of the WCS calculations in this email about Mosaic WCS computations.
- How do I correct for the difference in pixel area for photometric measurments?
Frank Valdes described this correction in an email about
using the task 'pixarea' in the mscred package.
Last updated: April 2010 by AMK
Andrea Kunder (firstname.lastname@example.org)
Chris Smith (email@example.com)
Alistair Walker (firstname.lastname@example.org)