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- Request that your Instrument Assistant or Telescope Operator do a
knife-edge telescope focus at the start of your run. Also do a telescope focus
run using just the TV and compare the focus values. After a
telescope move of 15-20 deg, refocus the telescope using the TV.
- Cosmetically the F3KC chip is among the best CCDs we have.
The area around 837,78 (in full format)
is an area of depressed sensitivity and should be avoided.
- To get a rough idea of your signal-to-noise, try the following. Do a
row plot in the wavelength
area of interest. Integrate the profile above bias with the "i"
option in the cursor package. Multiply this by 2.8 electrons/ADU and by
3 pixels/resolution element (unbinned)
to get the signal per resolution element.
The square root of the signal SNR/res. element .
- If you require the best radial velocity precision, take a
wavelength calibration exposure before and after each object exposure
at the object position.
- As mentioned earlier, the spectrograph shutter takes a noticeable time
to open/close. The actual time the shutter is open is 100-250 milliseconds
shorter than the advertised time. Exposure times of a minimum of 20
seconds are suggested if 1% or better timing accuracy is desired.
Wed Aug 2 13:05:25 MST 1995