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March 2009

Combined infrared flat field images now available to ANDICAM users

To assist you in reducing your infrared images, we are now providing combined infrared flat field images for each filter. These are created by combining all of the flat images that are taken at each dither position, producing one flat image for each filter. These can be downloaded from the ftp site in /home/ftp/pub/smarts13m/flatsir.

Separate flat field images (at each of the dither positions) will continue to be available from the same ftp directory as before (/home/ftp/pub/smarts13m/calibsir).

Please direct any questions to either Michelle Buxton or Suzanne Tourtellotte.

If you have to generate schedules for a telescope (or anything else) and are interested in streamlining the process, we recommend the software developed at NASA Goddard by the Science Goal Montior (SGM) group. The main website can be found here and you can download the specific software developed for SMARTS here. Email Michelle Buxton if you need help with creating the specific sun and moon files needed (this is currently done using another piece of software, XEphem).

The 1.3m/ANDICAM now has neutral-density filters installed for viewing bright sources in V, I, H, and narrowband He 1038nm. Tests with standard stars show that the V+ND combination has an attenuation of 4.6 (a factor of 39,000, or 11.5 magnitudes) over that of the V filter, and the I+ND combination an attentuation of 3.0 (1100, or 7.6 magnitudes).

The ANDICAM instrument has two optical neutral density filters, V+ND4 and I+ND4, and two infrared neutral density filters, H+ND4 and 10830+ND3. (The 10830+ND3 filter is a narrowband He filter.) The optical ND filters are 5-arcminute diameter round filters, and the IR ND filters are 2.4-arcmin square filters. According to the previous paragraph, the V+ND filter has an attenuation of 4.6 (a factor of 39,000, or 11.5 magnitudes) over that of the V filter, and the I+ND combination has an attenuation of 3.0 (1100, or 7.6 magnitudes).

From observations of Eta Car in the ND4 filters done by Alan Whiting, the FWHM generally ranges from 2.5 to 4.9 pixels in V. He also notes that flat fields taken through the attenuated filters have not been successful in calibrating the data. However, the flats from the unattenuated V, I, and H filters seem to work fine with ND filter observations.

We have spotted a peculiarity in observing the Landolt standard PG1323. It appears as though the light of a bright star (most likely Spica) outside the field of view is not properly baffled, causing the raised level of the background, as shown here:

In principle, this should not affect the count rate in the standard stars themselves, but, we do not recommend using this particular standard for your observations.

The 1.3m has been removed from the CTIO exposure time calculator. The values obtained using this calculator were found to be too optimistic by several orders of magnitude. Please estimate you exposure times using the values found at the ANDICAM detector website (http://www.astronomy.ohio-state.edu/ANDICAM/detectors.html#sens [9]).