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The RCX400 optical design consists of a h
yperbolic secondary and corrector lens/pri-
mary combination that performs as one hyperbolic element. The corrector plate advan-
tage, aside from the obvious optical correction that the lens produces, allow astropho-
tographers to make images free of diffraction spikes, with diffraction spikes being the only
real negative to a traditional Ritchey-Chrétien design.
Y
ou may perform through-the-telescope photography with any 35mm camera body with
a removable lens.You may connect a camera to a #62 T-Adapter. Using this method, the
telescope effectively becomes the lens of the camera.
The #62 T-Adapter connects to a T-Mount for the particular brand of 35mm camera
being used, followed by the camera body.
To orient an object in the viewfinder of the 35mm camera body, use a small jeweler’s
screwdriver to slightly loosen three adjustment screws around the outer knurled ring
of the T-Mount. Rotate the camera body to achieve proper orientation of the object;
then re-tighten the adjustment screws.
The #62 T-Adapter permits close-coupling of a camera body to the telescope. In this
f
ormat vignetting occurs: The photographic image appears on film with a slight dark-
ening (vignetting) at the corners of the 35mm frame (
Fig. 34).
Photography through a long lens such as the RCX400 requires special technique for
good results, and the photographer should probably expect to waste a roll or two of
film in acquiring this technique. Long-lens photography has its own rewards, however,
rewards that short-focus lenses cannot duplicate.
A few tips on photography with the RCX400 telescopes:
1. Use the Field Tripod for the telescope. At an effective focal length of 2000mm or
more, even small external vibrations can easily ruin an otherwise good photo.
For best results in photographing celestial objects, a wedge and One-Star polar
alignment is recommended. See
APPENDIX A, page 57.
2. Use a cable-operated shutter release. Touching the camera body to initiate shut-
ter operation almost certainly introduces undesirable vibrations.
3. Focus the image with extreme care. While observing the subject through the cam-
era’s reflex viewfinder, focus the telescope. Note that some 35mm cameras may
have an optional focusing screen (available from the manufacturer) for use with a
long telephoto lens. This screen provides a brighter and clearer image to focus,
and is highly recommended.
4. Correct shutter speeds vary widely, depending on lighting conditions and film
used. Trial-and-error is the best way to determine proper shutter speed in any
given application.
Note: The camera used with your telescope may have an exposure meter
that is still active when the standard lens is removed and the body is con-
nected to the telescope with the T-Mount. If used for terrestrial photogra-
phy, the camera meter should be acceptable. If used for astrophotography,
the meter probab
ly will not pro
vide good results since camer
a meters are
not made to compensate for a dark sky.
5.
T
errestr
ial photog
r
aphy through the
RCX400 is sensitiv
e to heat w
a
v
es r
ising from
the Ear
th’
s surface. Long distance photography is best accomplished in the early
morning hours before the Earth has had time to build up heat.
6.
Photog
r
aphy of the Moon and planets through the
RCX400 can be especially g
r
at
-
ifying, but points 1 through 4 should be particularly noted in this case. If you wish
to take photographs using polar alignment, see
APPENDIX A, page 57.
Fig. 34: Example of vignetting.
PHOTOGRAPHY
45