The piggyback bracket is a shoe to put the same 1/4"-20 thread mount as a camera tripod on top of a telescope. This makes it possible to mount cameras and small scopes with a very simple installation.

Background

Celestron Schmidt Cassegrain telescopes are some of the most commonly found general purpose amateur telescopes. The C8 is fair sized for observing in the city. It has a mix of light grasp and focal length which lets an amateur astronomer do a lot of things. They come with various sorts of mounts, such as the NexStar8GPS I mounted this one on. The telescopes generally have fairly good mounts with drives, so piggybacking an SLR camera on one for wide angle astrophotography makes a lot of sense.

Another need these telescopes commonly have is for a small guide scope. Guide scopes are smaller telescopes used to check and make sure the main telescope is not drifting during long exposures. These also serve as wider-field visual telescopes in their own right. As a result, having a secondary mounting hard point on top of the main telescope is generally a handy thing to have.

Description

The Celestron Piggyback Bracket comes as a kit with everything needed to install it either on a C8, 9.25", or 11" tube. The bracket itself is very sturdily made from 3/8" thick aluminum. Clearly even large SLR lenses could be comfortably supported by this part.

Strangely enough, the bracket needs different screws depending on which telescope it is going on. This is not a problem, though, since all of the required parts are included. The telescope tube assembly has two screws installed in the holes this part uses to make sure dust doesn't get in through there.

The instructions indicate installing the bracket so the shoe part would hang over the end of the optical tube. In my case, this would make the telescope tail heavy (a problem I am fighting, anyway), so I turned the bracket around, which results in its payload being balanced over the axle. You will have to balance any fork mounted version of an SCT with this part in place. I am doing this the hard way, with a large Vixen rail on the bottom side of the optical tube to suppport weights and eventually an autoguider (a telescope with camera hooked up to a computer to automatically give tracking corrections to the telescope by watching the movement of the image).

The mount has a knob to turn the threaded camera tripod connector. This part is made to be captive, and when you do not have a camera mounted, it is possible to thread the bolt in so it is held against the bracket and does not rattle (which would cause the image to shake).

Usage

The piggyback mount is very simple to use for a camera- all you have to do is thread it on. The alignment will need to be manually adjusted if you want to have it exactly centered with the telescope. Remain calm- there are some very straightforward ways to do this.

First, take the telescope and with the drive OFF (so it will not drift while you are doing this), point it at a distant object with an identifiable centering point on it. An alignment target can be the light on a radio tower, a weather vane on a building, or even a distinctive point on a distant mountain. Get the main telescope sighted on the object and center it in the field of view. Now, put the camera or smaller scope on the piggyback bracket and look at where the object is in the field of view. Rotating left or right on the mount is easy to do to adjust for that direction. The hard part is getting the tilt correct.

To do this, I recommend using aluminum air conditioning tape (the shiney metal tape; NOT DUCT TAPE). To move the plane of the mount, all you have to do is put tape on the side of the shoe where the scope is low. So, for example, if you need to bring it up compared to the optical tube, put tape on the shoe at the front end. Try to get the contact area to be uniform, and keep in mind the further from the screw thread you put the tape, the more effective tilt you get. If you have several devices you want to mount, consider putting the tape on the camera or smaller scope instead of the piggyback shoe because you can't be sure different instruments will line up the same way. With this done, you can leave the tape on and the next time you attach to the adapter, the alignment will be nearly perfect.

When using the piggyback bracket in the field, the camera or telescope on it is over 8" from the centerline of the main scope. depending on where the telescope is pointed, this can mean the secondary instrument is difficult to get to. So, you will probably want to get a 90degree viewing adapter for SLR cameras used this way. Small telescopes can use star diagonals to do the same thing.

One thing to pay attention to is mounting on the piggyback bracket has a large effect on the balance of the telescope. Because it isn't practical to move the main telescope with other equipment and counterweights mounted on it, it is tempting to leave these items off until they are needed in a real setup. I recommend trying out installations inside in daylight before you attempt them in the field. For example, something as small as a 66mm telescope will appear to be a minor load when the main tube is level indoors, but will cause the main telescope to pitch up very strongly if it is pointed upwards. You will need to know what the correct counterweight setup is to correct for this, and that will be a lot easier if you can experiment where everything is available and you aren't in a hurry to be set up before dark. There is a bright side to the balance problem: the bit of standoff distance it has will allow the rotating focuser on my guide scope, an Astro Tech AT-66ED (www.astronomytechnologies.com) can sweep a full 360 degrees while attached, so it can be used to line up a camera with the orientation of objects in the sky.

Conclusion

The Celestron Piggyback Bracket is a simple, ruggedly made, and easy to use. It does lack some fine features like its own fine tracking controls to point a piggybacked scope away from the main field of view at a guide star. But this would introduce a lot of cost and complexity, and is a feature most guide scope setups do not support, anyway. Given what it costs and the value it delivers, I really have no good reason to complain about the Piggyback Bracket.

Recommended: Yes