Calibrating The Filter; Tilting The Filter; Troubleshooting - Baader Planetarium SUNDANCER II Manual

The SunDancer II has been calibrated at the factory and should give the best image
when the micrometer screw has been turned clockwise as far as it will go without
applying force and the heater has reached the preset target temperature, so that the
temperature difference display is also at "0". After about three to ve minutes of solar
observation, the lter has reached temperature equilibrium and you can assess its
performance.
For optimal performance on your particular system, you should calibrate the lter
to compensate for differences in aperture ratio, energy rejection lter and more. This
should require only small corrections to the factory setting, which was set at an effecti-
ve focal ratio of f/30. To do this:
1. Turn the micrometer screw clockwise as far as it will go (without applying force).
2. Set the temperature control box to a value of -5.0 as described above in the chap-
ter "Setting the temperature". Give the lter 3 to 5 minutes to stabilise and observe
the sun exactly in the centre of the image of the lter. You should now see it in the
blue wing of the H-alpha line.
3. Increase the target temperature by 1.0 degree (corresponding to 0.1 Å) and give the
lter a couple of minutes to stabilise again.
4. Increase the target temperature until you see the sun with the best contrast. The
solar disk is then darkest and you have centred the lter exactly on the H-alpha line.
Increasing the target temperature moves the lter to the red wing, decreasing it
moves it to the blue wing. A change of more than ±10 degrees is not advisable.
Increasing the temperature too much can destroy the filter.

Tilting the Filter

With the micrometer screw, you can tilt the lter up to 3° off the optical axis to quickly
shift the central wavelength into the blue wing. If the image improves when you tilt the
lter, this may have two causes:
1. The lter line is in the red wing of the H-alpha line at target temperature.
2. The micrometer allows the lter to be tilted past the neutral position.
The set point of the target temperature should be adjusted to give the best image
when the micrometer screw is turned gently clockwise to the stop. Then you can tilt
the lter towards shorter waves, into the blue wing of the H-alpha band, by turning the
micrometer screw back. In the blue wing, you can better observe rapid, high-energy
changes on the sun.

Troubleshooting

If the lter does not deliver the expected contrast, it is usually because it is not aligned
exactly to the optical axis. Even with a tilt of 0.5°, the lter can no longer work as desi-
red. A tilt can be compensated for to a small extent by increasing the target tempera-
ture, but this also increases its half-value width.
In case of tilting, rst check whether your focuser tube is correctly adjusted or whe-
ther it has play and gives way under load. Simple clamping screws on the focuser or
zenith mirror can also cause tilting.
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Manual: SunDancer II

Calibrating the Filter