58 ASTRONOMY • JUNE 2022
filter, then use a mask
paint where the noise
reduction should be
applied. You can adjust the overall power
of the noise reduction by adjusting the
opacity of the layer.
One of the great differences between
CCD and CMOS is that with a CCD, you
are stuck with whatever gain,
or sensitivity, is built into the
camera. With a CMOS cam-
era, you can adjust the gain, similar to
setting the ISO on your digital camera.
Be aware, however, that as you raise the
gain you forfeit some deep well capacity.
This means that your stars and brightThe author created this
image of the spiral NGC
2403 in Camelopardalis
with the QHY 600,
exposing through L, R,
G, B, and Hydrogen-
alpha filters. TONY HALLAS parts of your image can block up moreeasily, becoming pure white with no
detail in them.
On a target like a faint galaxy, increas-
ing the gain might be useful. I would
combine a medium increase in gain with
20-minute exposures to max out
recorded detail. I would also take a few
much shorter exposures to keep all the
stars colorful without washing them out.
These can be added to the final image to
replace the blown-out stars produced by
the increased gain.
My conversion to CMOS is an ongo-
ing learning experience. The QHY 600
is a good example of what is possible
today. It is a versatile camera that is at
home on many scopes, from a refractor
to a Cassegrain ref lector.
I look forward to creating
many excellent images
with it.NGC 206 is a star-
forming region in the
Andromeda Galaxy (M31).
The author created this
image by combining
exposures through R, G,
B, and Hydrogen-alpha
filters. TONY HALLASTony H allas is a
contributing editor of
Astronomy and one of this
planet’s finest astroimagers.