Flats and arcs are acquired in polarimetry mode for flat fielding and wavelength solutions. Below you will find two tables that list typical exposure times for flats with the dome used as the illumination source and for arc lamps on both the red and blue side. Note that all filters are not available on both the red and blue sides. Optimal exposure times differ significantly from normal LRIS observing modes.Currently, there are two slits available in LRISp mode. Typical exposure times are provided for both slits.

Arc Lamp Typical Exposure Times

Lamp Exposure Time (sec)
Red side Blue side
using 1.0" slit using 1.5" slit using 1.0" slit using 1.5" slit
Hg 3 2 5 3
Neon 3 2 - -
Argon 4 3 - -
Cadmium 2 1 5 3
Zinc - - 5 3
Internal Halogen lamp 18 sec 12 sec 220 150

*be sure to let this lamp warm up before taking the exposure!
Warm up times listed here.

Dome Flat Typical Exposure Times

Filter Exposure time
Red Side Blue Side
U NA ??
B 80 ??
V 20 ??
R 10 NA
Rs ?? NA
I ?? NA