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) which can be
used between the DSLR and SolaREDi 66 to adjust the light angle and
extinct the interference pattern.
