Don't get caught unprepared when then next great comet comes
You can make the simple piggyback camera mount describe on this web page for
your telescope and get some great astro images of the next comet, or many of
your favorite wide-field stellar objects like galaxies and star clusters.
This will work with any 35mm camera (SLR's are best) or any digital camera
capable of taking time exposures.
Of course, you'll need a telescope with a clock drive.
It doesn't need to be a giant telescope. One whose drive could handle the additional weight of a camera is all.
Start with a 2 by 4 (No Kidding)
The piggyback camera mount is nothing more than a specially cut piece of 2
by 4. Cut off about a 3 1/2 inch length of 2 by 4, giving a square block.
Using a table saw, radial arm saw, or a circle saw, cut out the center
section to a depth suitable for your sized telescope.
It's best to make these cuts with the grain of the wood.
The idea is to have a block that will sit on its side rails with the
middle (cut out) area not touching your telescope.
Add a Camera Mounting Screw
Drill a 1/4 inch diameter hole through the center of the block.
Run a 1/4 inch screw through the block and tighten on a nut to hold it
securely. This screw will be used to hold your 35mm camera or digital
Be sure the screw is long enough to go through the block, a wing nut, and
still have a 1/2 inch or so of threads left to mount to your camera.
Thread on a wing-nut in an upside-down configuration. This wing-nut will
be tightened against the bottom of the camera.
Finish Off with a Hose Clamp
Go to a hardware store and purchase a hose clamp that is long enough to
go around your telescope. You can likely use a single clamp to go around
a small Maksutov cassegrain or refractor.
If you can't find one long enough because you use a bigger telescope, such
as an SCT or Newtonian, you can by two or three and fasten the ends together.
Just thread the tongue of one clamp into the screw of another.
Cut the clamp and drill a hole through the ends (or one end of each of
your numerous clamps).
Mount the non-tongue ends of the clamp(s) to the wood block with screws.
Now you can run the clamp around your telescope and tighten the hose-clamp
screw whenever you want to take star photographs.
The Piggyback Camera Mount Fastened to Telescope
Here's an image of my piggyback mount on my 6 inch f/5 Newonian
You can see the hose clamp band going around the telescope tube, securely
holding the specially cut 2 by 4.
The 35mm camera camera is turned several times onto the protruding screw,
and then the inverted wing-nut is tightened against the bottom of the camera,
allowing me to align the camera lens with the telescope.
This telescope doesn't have electronic controls in the RA and Declination
axes. It uses manual screw controls.
To get the best pictures, I use a reticle eyepiece and defocus on a
moderate to bright star in the field near my object of choice (or the center
of a comet). If a guide star is bright enough, defocusing it slightly lets it
better illuminate the reticle lines.
With the manual controls, I cap the lens of the shutter-locked camera
whenever I make a pointing adjustment, then uncap the lens when finished.
This ensures that any vibrations I cause or mistakes I make in adjusting
do not affect my photograph.
And Finally, the Proof
At left you see an image of Hale Bopp that was taken with the camera
and 135mm telephoto lens shown in the previous picture. I had a different
telescope then, but the setup was the same.
How long an exposure is necessary? For comets not that much. 5 minutes
will do wonders.
For some of your favorite star objects you may need to go up to 15 or
Obviously, to make use of this simple mount you will need a clock driven
telescope on an equatorial mount. Almost any will do, though if you use 35mm
camera equipment as I do, you may not be able to use a small telescope because
of the weight of the camera.
For example, I'm not sure my ETX 90M mount would handle the weight of
a 35mm camera and telephoto lens.
But any telescope of 5 inch diameter or bigger will likely have a
beefy enough mount to do the job. You need the equatorial mount for several
minute time exposures because such exposures on a computerized altazimuth
mount would lead to a rotating field of view.
If you want to go digital, be sure you choose a camera than can do time exposers of at least a few minutes.
Once the camera is attached to the telescope, the procedure I use is as follows:
Cap the camera lens.
Set lens for infinite focus, open aperture.
Set shutter on B (bulb) setting.
Lock shutter open. Some cameras, like my Exa and Zenit allow this. For
others, use a shutter cable with lock.
Get the closest guide star in the telescope view.
Defocus telescope to let guide star illuminate reticle, then center.
Uncap the lens.
If I see a guiding adjustment is necessary, I cap the lens, make the adjustment, then uncap the lens.