DIS III - Taking Lamp Calibration Spectra
Contact your Russet McMillan (primary) or your Observing Specialists (secondary) for additional information or corrections.
Contact Jack Dembicky for web page errors, corrections, ommisions, and/or additions.
This page last updated: June 8, 2005 - JMD
This page last checked: TBD - JMD
Contents
Taking Lamp Calibration Spectra
Taking Lamp Calibration Spectra
Cals are generally taken either off the primary mirror covers or off the primary itself, using lamps on the telescope truss as illumination sources. For observers concerned with color terms in flat field images taken off mirror covers, arrangements can be made to take twilight sky flats with DIS. Observers can control turning the lamps on and off, but actuation of the mirror covers is restricted to the Observing Specialists; ask your ObsSpec to close or open the mirror covers as needed for cals. Lamps can be turned on and off with the xlamps command issued from the tycho prompt under the visitor1 account. A simple graphical interface allows the user to cycle the lamps at will.
Exposure times have been determined from practical experience to maximize signal-to-noise while keeping the signal level well within the linear regime of the chip (62K)
The table below gives suggested times for Bright Quartz lamps
|
Grating
|
Exposure (s)
|
Counts
|
| Red Low |
|
|
| Blue Low |
|
|
| Red Medium |
180
|
~30K
|
| Blue Medium |
180
|
~12K
|
| Red High |
120(180/300)
|
22K
|
| Blue High |
240(300/???)
|
17K
|
(NOTE: Times in parentheses are "minimum" and "maximum" exposure times taken from results of testing of DIS after optics upgrades in 2002. The minimum times were chosen to yield S/N values of ~100 "at most wavelengths"; maximum times were chosen to avoid saturation.)
(Under Construction!) HeNeAr lamps are available on the truss for comparison arc exposures. Suggested exposure times for HeNeAr arcs are:
|
Grating
|
Exposure (s)
|
Counts
|
| Red Low |
|
|
| Blue Low |
|
|
| Red Medium |
30
|
10K
|
| Blue Medium |
|
|
| Red High |
30
|
11K
|
| Bleu High |
500
|
10K
|
(NOTE: Counts cited for arc lamp spectra are those in the brightest lines to reach a S/N of ~100K. Consult plots of arcs taken with DIS to determine whether these exposure densities are sufficient for your program. If taking arcs with the lamps separately, reduce exposures for Ne only by about half, increase exposures
Items that need to be inserted into these pages but the links may not yet work
DIS III Slits - desription: February 29, 2002
DIS III Slits - photos: March 5, 2002
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