This Celestron piggyback mount is a handy accessory for all observers interested in wide-field deep-sky astrophotography. This lightweight mount allows you to attach your 35mm, DSLR, or point and shoot digital camera, with its normal lens attached, to the rear cell of all Celestron SCT telescopes. You can then take moderately long exposure wide-field constellation photos while your scope tracks across the sky to follow the motion of the stars.
Mounting holes in the base of the piggyback allow it to be installed in pre-drilled threaded holes in the rear cell of any of the above scopes, using the supplied mounting hardware. Because of the larger radius of curvature of the 9.25" to 14" optical tubes, there will be a slight gap between the rear cell and the center of the underside of the piggyback. This does not affect performance and is of no consequence if the piggyback mounting screws are threaded firmly in place.
The camera platform of the piggyback has a standard 1/4"-20 thread bolt with a hand-tighten knob in the platform to hold your camera in place. The camera can be pivoted from side to side to keep the telescope barrel out of the field of view of a wide-angle camera lens, but cannot tilt up and down.
The piggyback can be left in place permanently. If the piggyback is removed, however, the short screws that sealed the rear cell (that were saved when the piggyback was installed) should be used to reseal the mounting holes on the rear cell. Do not use the mounting screws that came with the piggyback to reseal the rear cell holes! These screws are long enough to potentially obstruct the movement of the telescope's primary mirror and possibly chip it. Damage caused by using incorrect length screws to reseal the rear cell holes is not covered by warranty.
Exposure times with a digital camera will be limited by the build-up of thermal noise within the camera's electronics, so some experimentation will be needed to see how long an exposure you can take before the image begins to get noisy and show excessive grain. The amount of light pollution in your area may also limit your exposure times.
Generally, with the normal lens on a camera, and the scope tracking in an altazimuth mode, exposure times will be limited to a maximum of five minutes or so for good full-frame images. After that, assuming your digital camera image has not become excessively noisy, the stars at the corners of the image will start to turn into short curved streaks because of the field rotation inherent in an altazimuth mount.
The field rotation and star trails can be eliminated with the NexStar 5SE by using the equatorial wedge built into the scope's tripod to convert the scope to equatorial tracking. The NexStar 6SE and 8SE and all other Celestron SCTs require the addition of optional equatorial wedge to be used in an equatorial tracking mode. In all cases, noise build-up in a digital camera would still limit your exposure times.
The unique design of the piggyback also allows you to fit a Celestron Star Pointer red dot finder on top of the piggyback as shown in the feature image below. This lets you accurately navigate your telescope and conduct astrophotography at the same time.
