Decommissioned

The two-channel photometer is used at the Cassegrain focus to observe contemporaneously the variable and the comparison star. Two similar photometers are radially located on a rotating platform. The rotation of the platfom around the optical axis of the telescope allow to align the photometer heads with the line joining the two stars and then pick-up the star light by moving the two 90^o reflecting prisms on the star positions. All movements should be done manually at the telescope. Both photometers use EMI 9863QA photomultipliers cooled to -15 C. The same PC and software of the single channel photometer is used to operate the two heads as an option allowed by the Obelix program.

Star distance constraints:
minimum separation: 4 arcmin
maximum separation: 20 arcmin

Filters

Johnson system: U B V
Stromgren system: u b v y H-beta(N,W)

Time resolution:
0.1sec with 2-8 filters
0.01 sec only one filter

Limiting magnitude:

5<V<12 in UBV (limit given by the pointing and aligning optics)
3<V<12 in ubvy H-beta