C100/ModSpec Observing Procedures

Instrument Setup

Make sure that spectral lines are aligned along the columns of the CCD
Set grating tilt to 18.20 degrees. Take a He lamp and make sure that the 5015 line lies at column 906, or that the 7278 line lies at column 3, or that the bright 5876 line lies at column 568. Adjust the tilt if needed. (the bluest line is 3888 at column 1356. Blueward of this line the sensitivity vanishes completely)
The spectrograph must be focussed. The collimator value is close to 515. When the central lines are focussed the blue end is out of focus. There is nothing to do but just check that the focus is better at 5000 A.
Set the slit width to 1" from low to high values.

Daytime Data Calibrations

The calibrations must begin at least 2 hours before sunset.
Open an IRAF window
Change directory to /export/data1/obs100/ccd_data/mario.
Create new directory in format 20020911_12
Start data acquisition window in this directory with 'ccd' command.
In dialog window set "uniblitz", "Site2", "16", "LCO-100".
Set gain to 1 in CCD window.
Take 15 bias frames. The bias level should be at 170 adu's.
Take 15 dome flats with slit=1" (~120 sec each). Set voltage to 480. You need 20000 adu's at maximum. Never reach the saturation level at 32000 adu's.
Take 15 dome flats with slit=5" (~20 sec each). You need 20000 adu's at maximum. Never reach the saturation level at 32000 adu's.

Night-time Observations

Operator begins by zero-pointing the telescope.
Start focus sequence using "multiple" option. Set loop to 7 and exptime to 10 sec. Place bright star on slit and take 7 exposures. Use implot to find the best focus, which is probably around 4445.
Take spectrum of two standards with 5" slit along paralactic angle. Check exposure times here.
Take SN spectrum with 1" slit along paralactic angle. Check exposure times here.
Right after the first exposure take a comparison lamp of He and Hollow Cathode. The total exposure is 30 sec but at t=10 sec you must turn off the Hollow Cathode. For details about commands see below.
Take another SN spectrum with same slit (1").

Comparison Lamps