Be Ready For The Next Celestial Event
Don't get caught unprepared when then next great comet comes
You can get ready for some piggyback astrophotography by making the simple
piggyback camera mount described on this web page. With it you can get some
great astro images of the next comet, or many of your favorite wide-field
stellar objects like galaxies and star clusters. An example is this photo
below of the Comet 17P Holmes, which graced our skies in 2007.
Comet 17P Holmes, 2007
If the concept of
astrophotography is new to you, check out the introductory book Getting
Started: Budget Astrophotography. It will give you the essentials. The accessory
described on this page is one of the more basic ways to get into
While commercial piggyback mounts are available, they tend to be specific to
some of the popular telescopes. But the DIY piggyback mount on this page will
work with any 35mm camera (SLR's are best) or any digital camera capable of
taking time exposures. The mount described on this page clamps around the
telescope's tube, and so can likely be tailored (by selecting the right sized
hose clamps) to fit almost any telescope. However, check out the tailored
mounts if you have a popular telescope design. It'll save you some work and
maybe mount easier.
To take the photographs, you'll need an astrophotography camera. As
mentioned, a great camera for the job is a 35mm camera, something like my
trusty old 35mm SLR. The
camera you choose doesn't even have to have a removable lens as does my old
SLR, as some great pictures can be obtained with the camera's stock lens. But
the camera must be able to take time exposures, or allow the shutter to be
locked open. Most likely, you won't be able to take exposures of over a few
minutes unless you live on a remote mountain top somewhere, but a few minutes
will be sufficient for many targets. Some DSLR's (digital cameras) can even
deliver results with a few seconds of exposure.
You'll need a telescope or at least a sight of some kind for guiding. For
the long exposures, you'll need a clock driven telescope or sight. It doesn't
need to be a giant telescope. One whose drive could handle the additional
weight of a camera is all. I currently have 3 telescope than can do the job
admirably, my old Meade
ETX 90, my Discovery f/5
Newtonian, and my Celestron NexStar
5SE. Each has a clock drive, allowing me to use the telescope to keep on a
target as the camera gathers the image.
Start with a 2 by 4 (No Kidding)
The piggyback camera mount shown above 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
Using a table saw, radial arm saw, or a circle saw, and 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 area not touching your telescope.
Add a Camera Mounting Screw
Using the above illustration as an example, 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 to hold it in position.
Finish Off with a Hose Clamp
Go to a hardware store and purchase a hose clamp, shown above, that is long
enough to go around your particular 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 buy two or three clamps 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 resulting 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 to secure the mount.
The Piggyback Camera Mount Fastened to Telescope
Above is an image of my piggyback mount on my 6 inch f/5 Newtonian
You can see the hose clamp band extending 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. The camera shown
is taking advantage of the SLR's ability to exchange lenses, as the
original lens is replace with a 135mm telephoto lens.
This particular telescope doesn't have electronic controls in the RA and
Declination axes. Rather 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 of my eyepiece.
If I need to make a tracking adjustment with the manual controls, I cap the
lens of the shutter-locked camera while 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
Hale Bopp with Piggyback Mount
Above 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. 3 to 5 minutes
will do wonders.
For some of your favorite star objects you may need to go up to 10 or 15
minutes, if your site is dark enough to allow it. If not, you can still get
some nice photos of most objects with just a few minutes.
This Hale Bopp image is also shown on the 2 Inch Photography page of this site.
Cygnus Nebula with Piggyback Mount
Above you see another example of what can be captured with just a
piggyback setup and a small telephoto (135mm) lens. It's an image of the
North America nebula in Cygnus. The bright star in the image is Deneb. You
can see that my inexpensive little telephoto has a wee bit of coma near the
edge of the field of view. The North America shape is not well resolved
at this magnification, but it is the nebulosity at the lower left of the
Contrast this with what you see when looking at Cygnus with either naked
eye or telescope. The nebula just doesn't show then. But with just a
regular camera and a minute or two exposure, it registers clearly. A
book I recommend, even though it is a very old one, is
Skyshooting: Photography for Amateur Astronomers. I have an even older copy
by the same authors which inspired me so long ago. Cameras have changed,
but the information on techniques is still relevant, and the images obtained
with modest equipment are inspirational.
Some Astophotography Tips
Obviously, to make use of the simple piggyback 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. As the photo below illustrates, if I use
my NexStar 5SE for piggyback photography, I need to use it with its built in
equatorial wedge. NexStar 5 SE in EQ Mode
Any telescope of 5 inch diameter or bigger will likely have a beefy enough
mount to do the job, and some smaller ones may also. You need the equatorial
mount for several minute time exposures because such exposures on a
computerized altazimuth mount will lead to a rotating field of view. A
telescope much like the one I use is the Celestron
Omni XLT 150mm Telescope Newtonian Reflector 31057. It is large enough to handle the weight of the
camera, and large enough in aperture to be able to find adequate guide stars
near your targets of interest.
If you want to go digital, be sure you choose a camera than can do time
Once the camera is attached to the telescope, the procedure I use is as
Cap the camera lens.
Set lens for infinite focus, open aperture to maximum diameter (smallest
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 to target in the telescope view.
Defocus telescope to let guide star illuminate reticle, then center.
Alternately, purchase an eyepiece that has an illuminated reticle.
Once any tracking backlash is gone, Uncap the lens.
If you see a guiding adjustment is necessary, cap the lens, make the adjustment, wait for stable tracking, then uncap the lens.
This procedure, simple though it is, can give very good results in that you
are generally seeing a magnified image in the telescope versus what the camera
sees, and tracking errors will be easily detected and corrected before becoming
big enough for the camera to record.
Pleiades with 135mm Telephoto
To make a point about developing, notice the image above of the
Pleiades. It was taken with the apparatus described in this web page,
using a camera and a 135mm telephoto lens. It shares an issue with my
Holmes image shown previously, that of enlarged star images.
You may notice that the star images aren't pin-point images, but disks.
I've wondered about this for some time. Usually my star images are point like,
or if guiding was a problem, small trails. This disk phenomenon is new to me.
I suspect it is a developing anomaly, probably caused by an automated system
trying to make a good print. I got my images for the website from the photo
store developed prints.
It reminds me that there is a step you should take with your film
camera as a standard procedure. Make the first 2 or 3 frames some general,
simple, day-time photograph. An everyday type of photograph, say of your
dog or something. Leave an instruction with those doing the development
that the film has star pictures, but they can use the first couple of
frames to set their equipment. They should not let an automated system try
to determine best exposure times for prints on each individual photograph.
I believe it was my failure (or their failure to note my instructions) that
lead to these enlarged star images.
As to star trails from poor guiding, note that guiding is most important in
the first minute or even the first 30 seconds, if you are using a film camera.
Film suffers what is called reciprocity failure. That is, film loses its
sensitivity to light as it is exposed. So it is very sensitive to light in the
first few seconds, and becomes less so over time. So any guiding error in the
first few seconds will cause a star trail. Small guiding errors that average
out aren't as critical after the first 1/2 minute or so.
This isn't so true if you are using a digital camera. Digital cameras,
while having their own problems, don't suffer from reciprocity failure.
Barn Door Mount
Even if you don't have a telescope with a clock driven mount to use as a
base for a piggyback mount, you can consider building a barn door mount,
sometimes called a hinge mount. These simple mounts use a few common
things you likely have in your garage or workshop plus maybe a couple more.
There are motorized versions and manual versions.
The idea of such a mount is to have a simple device that can sit
on a regular camera tripod and track stars well enough for a camera to collect
great star photographs. You can't use a telephoto on such a camera with
much luck, but you can get wide field star pictures that are impressive.
Check out the Build
a Hinge Tracker site for how to construct a manually driven model, and the
a Motorized Barn Door Tracker for instructions on how to build a simple