11
Most deep-sky objects have a large angular size. Therefore, low-to-moderate
power is all you need to see them. Visually, they are too faint to reveal any
color. Instead, they have a black and white appearance. And, because of their
low surface brightness, they should be observed from a dark sky location.
Light pollution around large urban areas washes out most nebula making them
difficult, if not impossible, to observe. LPR filters enhance deep sky viewing
from light polluted areas by blocking unwanted light while transmitting light
from certain deep-sky objects. You can, on the other hand, observe planets
and stars from light polluted areas or when the Moon is out.
Your Celestron can be used for both terrestrial and astronomical photography.
Celestron telescopes have fixed apertures and, as a result, fixed
f/ratios. To properly expose your subjects photographically you need to set
your shutter speed accordingly. Most 35mm cameras offer through-the-lens
metering which will let you know if your picture will be under or over exposed.
This is more of a consideration when doing terrestrial photography where
exposure times are measured in hundredths of a second. In astrophotography,
the exposures are much longer requiring that you use the “B” setting on your
camera. The actual exposure time is determined by how long you keep the
shutter open.
To reduce vibration when tripping the shutter, use a cable release. Releasing
the shutter manually can cause vibration, something that can produce unsharp
photos. A cable release will keep your hands clear of the camera and tele-
scope, thus eliminating the possibility of introducing vibration. Mechanical
shutter releases can be used, though air type releases are best.
In addition, remember the focusing hints described earlier in this manual.
After looking at the night sky for a while you may want to try photographing it.
If you do, start with a nice, bright object like the Moon.
Load your camera with film that has a moderate-to-fast speed (i.e., ISO rating).
Faster films are more desirable when the Moon is a crescent. When the Moon
is full, and at its brightest, slower films are more desirable. If photographing
during the full phase, use a yellow filter to reduce the light intensity and to
increase contrast. To attach your camera to the F80 AZ or C102-AZ, you will
need the Celestron T-Adapter (#93634-A) and the T-Ring for your specific
camera. On the F70 AZ, the T-Adapter is built in and you only need the T-Ring
to attach your camera.
Consult the Celestron accessory catalog for a list of recommended exposure
times. These exposure times should be used as a starting point. Always
make exposures that are longer and shorter than the recommended time.
Also, try bracketing your exposures. Take a few photos at each shutter
speed. This will ensure that you will get a good photo.
Keep accurate records of your exposures. This information is useful if you
want to repeat your results or submit them for possible publication in astro-
nomical magazines!
Photography Hints
Photographing the
Moon
