Telescope Data Center

Observing Protocol

as of 2005-11-14
Hectospec Image
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In order to facilitate the TDC Hectospec reduction pipeline script as well as to produce consistent, high quality data, we strongly recommend that the following observing protocols be followed when observing with Hectospec.

Check the Observers' Responsibilities page to find out more, and read the Observers Manual.

  1. Take 10 biases at the beginning of the evening

  2. Take darks every night, at least five at 15 minutes each.
    These are usually taken at the end of the night.

  3. Take ten domeflats at the beginning of the evening. The exposure time for domeflats is 2 seconds.

  4. Take comps (henears) right after domeflats if possible. There should be five 300 second exposures, or, if that is not possible, a minimum of three 300 second exposures. The comp exposures must be contiguous as they will be combined to make one file. It is important to take comps and domeflats close in time because the domeflat extraction profile, without any shift, is used for the comp extraction and there can be a small drift in the fiber positions over the night.

  5. Take sky flats every night when possible. These are usually taken right after sunset but they can be taken just before sunrise. We recommend a series of up to ten sky flats in increasing exposure times after sunset or in decreasing exposure times before sunrise. So, for example, you might have a series of sky flats with exposure times of: 2, 5, 5, 8, 12, 20, 25, 30. The increase or decrease in exposure time is made because of the rapidly darkening or brightening sky. Sky flats are used for the fiber throughput correction in the reduction pipeline.

  6. At least three contiguous observations should be made of your science fields. We need a minimum of three to do a good job of removing cosmic rays in the combine program.

  7. A minimum of thirty fibers must be used for skys, more if you can do so without losing a significant amount of data/observing time. Set the parameter for the number of skys in the fitfibs program to 30 or higher when you are preparing your observing fields. Skys are subtracted separately for each chip so a total of thirty or more skys increases the liklihood of having an adequate number on each chip.

  8. If you are observing stars, don't mix faint and bright stars in the same field. Stars should vary by no more than four magnitudes. You do not want to saturate the bright stars to get the faint ones. Make more than one configuration, if needed to separate stars of different brightness.

  9. Check with quick look after each new target exposure to make sure you have an adequate integration time and to check your positions: image and skys.

Modified 5-April-2007 by Doug Mink

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