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Domeflats: can be done
with telescope pointing to the zenigh. Bear in mind that domeflats can have unwanted spectral
characteristics due to the lamp and/or the reflected light from the painting in the dome.
SYS> petals open
There are five topring lamps 1) 9w, 2) 25w, 3) 150w 4-5) 500w. To switch them all on
SYS> fflamp all on
to switch them all off
SYS> fflamp all off
or if one needs less light, there is a possibility to switch on only the desired lamps
SYS> fflamp 1 on
the same way one can switch off the topring lamps. The number of lamp can be 1 to 5 (see the
power of the lamps above).
SYS> fflamp 1 off
To close the mirror petals
SYS> petals close
Orientative exposure time values. Always test before running the hwflats script.
Ks fflamp 1,2 on, exposure time 1.5 s
H fflamp 1,2 on, exposure time 0.9 s
J fflamp 1,2,3 on, exposure time 0.9 s
Y fflamp 1,2,3 on, exposure time 0.8 s
z fflamp 1,2,3,4 on, exposure time 0.8 s
Hc fflamp 4 on, exposure time 1 s
Jc fflamp 4,5 on, exposure time 0.8 s
Kc fflamp all on, exposure time 1 s
Skyflats: Before sunset ask the OSA to point the
telescope away from the Sun and at elevation of 20 degrees. Ask the OSA to switch off
tracking. Since the read-out time of LIRIS is short you can easily afford to take a
sufficiently large number of flats, such as 20 per filter.
For all kinds of flat fields, choose the exposure time such
that you reach about 20000 counts in the image (post-read minus pre-read).
It is important that you take flat fields since the
effective quantum efficiency of the LIRIS detector shows variations of up to 20% across the
field. The flat field itself, however, is very stable with time.
Put the desired polarimetric setup
SYS> lipol <filter>
Flat fields can be obtained with the command
SYS> hwflats.bsh
<int time> title <nmult>
nmult is the number of flats per one setup i.e. 1) with orthogonal half-wave plate and 2) with parallel half-wave plate in use. Thus using 5 for nmult
will give 10 flats.
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