Handbook for the SXVR-H18
Issue 1 March 2010
15
The ‘Pelican’ with an FSQ106 and deep red filter
A stack of 5 x 600 second images, using MaximDL
Although I have concentrated on the use of a telescope for deep-sky imaging, do not
forget that you have the option of using an ordinary camera lens for impressive wide-
field shots! A good quality 200mm F3.5 lens with an infrared blocking filter will yield
very nice images of large objects, such as M31, M42, M45 etc. If you cannot obtain a
large IR blocker for the front of the lens, it is often quite acceptable to place a small
one behind the lens, inside the adaptor tube.
Taking pictures of the Moon and planets:
The SXVR-H18 is not intended for planetary imaging, as a much smaller CCD is in
many ways much better for this. However, lunar imaging is a different matter and the
H18 can give impressive whole-moon pictures. Most deep sky objects are faint and
relatively large, so a long exposure is needed, while the moon is bright and needs very
short exposures. The shutter of the H18 cannot operate extremely quickly and so you
need to keep the image brightness down with an ND filter or aperture stop, so that the
exposure time is not less than about 0.5 seconds. A H-alpha deep sky filter often gives
excellent results as an attenuator for moon images.
The exposure time needed for good lunar images is such that the image histogram has
a peak value at around 127 and does not extend much above 200 (Ignore the major
peak near zero, due to the dark background). If you use too short an exposure time,
the image noise level will be increased, and if too long a time is used you will saturate
the highlights and cause white patches on the decoded image.
