Two-channel photometer PDF Stampa E-mail




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 90o 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



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