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Solar Imaging Tips:
Daystar recommends
MONOCHROME CCD
imaging whenever
possible for best
results. The recent
availability of CCD
cameras and DSLR
cameras has offered a
simple opportunity for
solar observers to image
the Sun in Hydrogen
Alpha with a Digital SLR camera. Please be advised, however, that due
to the nature of monochromatic light and its effects on a CCD camera,
certain negative effects are likely to occur.
The DSLR imager must be aware that most camera manufacturers
(Canon and Nikon) use an IR blocking filter which greatly reduces the
transmission of Hydrogen Alpha light. DSLR cameras without this IR
blocking filter will have better sensitivity imaging in Hydrogen Alpha.
The imager should also appreciate that even after considering IR
blocking filters, that the COLOR CCD chip is constructed in a way that
only 1 in 4 pixels detect red light. The other 3 sensors only detect blue
and green because the pixels are actually permanently covered with a
colored dye for each corresponding color. So a color CCD chip (in a
DSLR or a CCD camera) will only offer 1/4 the sensitivity and 1/2 the
resolution of a monochrome chip.
Another effect present in CCD imaging of
monochrome light of Hydrogen Alpha is the
interference pattern - or Newton's Rings. The
effect is similar to interference testing of an optical
surface between two flat surfaces. The sensor
and cover slip cause a small interferometer inside
the camera and cause a Newton's Ring moire'
pattern. The CCD chip must be tilted to a minor
degree to prevent this pattern. Recent advances
in aftermarket adapters offer a simplified solution for the issue. This
effect is a concern for both color and monochrome sensors.
An optional accessory is available from DayStar (MG-0408 or IECC)
which can be used between the DSLR and Scout telescope to adjust the
light angle and extinct the interference pattern.
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