Celestron CPC Deluxe 1100 HD Computerized Telescope - Manual (Page 27)

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CELESTIAL PHOTOGRAPHY
After looking at the night sky for a while, you may want to try
photographing it . Several forms of celestial photography are possible
with your telescope, including short exposure prime focus, eyepiece
projection, long exposure deep sky, terrestrial and even CCD imaging.
Each of these is discussed in moderate detail with enough information to
get you started . Topics include the accessories required and some simple
techniques . More information is available in some of the publications
listed at the end of this manual .
In addition to the specific accessories required for each type of celestial
photography, there is the need for a camera – but not just any camera.
The camera does not have to have many of the features offered on
today’s state-of-the-art equipment. For example, you don’t need auto
focus capability or mirror lock up . Here are the mandatory features a
camera needs for celestial photography. First, a “B” setting is required
which allows for time exposures . This excludes point and shoot cameras
and limits the selection to SLR cameras, the most common type of
35 mm camera on the market today . Second, the “B” or manual setting should NOT run off the battery. Many
new electronic cameras use the battery to keep the shutter open during
time exposures. Once the batteries are drained, usually after a few
minutes, the shutter closes, whether you were finished with the exposure
or not . Look for a camera that has a manual shutter when operating in
the time exposure mode. Olympus, Nikon, Minolta, Pentax, Canon and
others have made such camera bodies .
The camera must have interchangeable lenses so you can attach it to the
telescope and use a variety of lenses for piggyback photography. If you
can’t find a new camera, you can purchase a used camera body that is
not 100% functional . The light meter, for example, does not have to be
operational since you will be determining the exposure length manually .
You will also need a cable release with a locking function to hold the
shutter open . Mechanical and air release models are available .
>> Short Exposure Prime Focus Photography
Short exposure prime focus photography is the best way to begin
recording celestial objects. It is done with the camera attached to the
telescope without an eyepiece or camera lens in place . To attach your
camera you need the Celestron T-Adapter (See Optional Accessories
section) and a T-Ring for your specific camera (i.e., Canon, Nikon, etc.).
The T-Ring replaces the 35 mm SLR camera’s normal lens . Prime focus
photography allows you to capture the majority of the lunar or solar disk.
To attach your camera to your telescope:
1. Remove all visual accessories. (For the 9.25” and 11” tube you must
also remove the 3” adapter plate threaded onto the rear of the tube)
2 . Thread the T-Ring onto the T-Adapter .
3 . Mount your camera body onto the T-Ring the same as you would for
a standard camera lens .
4 . Thread the T-Adapter onto the back of the telescope while holding
the camera in the desired orientation (either vertical or horizontal) .
With your camera attached to the telescope, you are ready for prime
focus photography. Start with an easy object like the Moon. Here’s how
to do it:
1. Center the Moon in the field of your telescope.
2. Focus the telescope by turning the focus knob until the image is
sharp . Make sure the mirror lock knobs are loosened .
3. Set the shutter speed to the appropriate setting (see Figure 8-1).
4 . Trip the shutter using a cable release or self timer .
5 . Use your camera’s bracketing feature to automatically change
exposure time in order to find the best exposure.
The exposure times listed in table 8-1 should be used as a starting
point . Always make exposures that are longer and shorter than the
recommended time . Also, take a few photos at each shutter speed .
This will ensure that you will get a good photo .
• This technique is also used for photographing the Sun with the
proper solar filter.
FIGURE 8-1
Above is a listing of recommended exposure times when
photographing the Moon at the prime focus of your telescope.
Lunar Phase ISO 50 ISO 100 ISO 200 ISO 400
Crescent 1/2 1/4 1/8 1/15
Quarter 1/15 1/30 1/60 1/125
Full 1/30 1/60 1/125 1/250
FIGURE 8-2a
T-Adapter for 8” Optical Tube
T-Adapter
T-Ring
(camera
model
specific)
FIGURE 8-2b
T-Adapter for 11/14” Optical Tube
T-Adapter
T-Ring
(camera
model
specific)