Nordic Optical Telescope Text Size: Smaller Text Normal Text Larger Text  

The MOSCA web page

MOSCA Focus offsets

Telescope focus offsets for the optical filters.

In practice, the smallest meaningful focus-offset is about 20-30 TCS units.
The best telescope focus is dependent on the thickness of the filter, wavelength and type of glass.
The telescope focus offset is calibrated to be +19 TCS units per the thickness of the filter in mm. Luckily the 100mm broad band filters (#104-112, #120) have all almost the same thickness (5 mm), so the expected focus offset between these filters is small.
There is an indication of a slight difference between the focus offset between the CCDs.

MOSCA best focus (tc11) measured with "mosca.focus-auto"
U#104 B#105 V#106 R#107 I_int#108 SDSS g#110 SDSS r #110 SDSS i #111
Best focus 23259+-15 23248+-10 23250+-5 23245+-5 23240+-7 23250+-8 23238+-10 23238+-8



Fig 1: Focus offsets for U#104, B#105, V#106, R#107, I_int#108, SDSS g #120 SDSS r#110, SDSS i #111.


Dark-2700s

Back to top Last modified: 23-Mar-2010