Astrotrac wedge adapter for Questar

The Questar is light enough to be mounted on any sturdy tripod and mount. An adjustable astronomical wedge makes precise drift alignment practical for long exposure astrophotography.

My earlier SkyWatcher wedge was the first that I could reliably drift align with. That design perched the Questar on the single dovetail rail, I wasn't comfortable extending it far enough for good balance on the tripod. Also, I didn't care for having to attach a dovetail wedge to the Questar. Thanks to a prize from the Astonomical League and OPT astrophotography competition I have an Astrotrac TW3100 wedge. This is my take on an adapter plate to mount the Questar on the Astrotrac wedge.

I've seen several beautiful examples Astrotrac adapters from other Questar owners: Ralph Encarnacion (started me down this slippery slope), Kevin Barker, and Don Elledge. I also had learned a few lessons from my other wedge designs. I decided that I wanted a design that:

  • I could build myself with basic power tools such as a drill press and saw.
  • Placed the balance point of the Questar close to the middle of the tripod at mid-latitudes
  • Supported an alignment device such as the QHY PoleMaster camera or a smart phone (for live view opposite celestial pole alignment)
  • Looked as good as the Questar and the wedge it connected.

Plans for Questar Astrotrac wedge adapter plate.

I still have all my fingers and both eyes, so it is possible to do this yourself with simple tools. If you have any doubts, it should be an easy job for a local machinist with the plans above. My wife thinks that I should have had such doubts. Also, be sure to check the dimensions with your parts.

I decided on 1/4" aluminum stock, because it was comparable to the materials in the AstroTrac wedge which can hold 33 lbs. The Questar, cameras, and adapters are less than 10 lbs.

I roughed out the shape, using a metal blade on a circular cutoff saw, with tangent cuts around the circular area. I finished the circular cut for the telescope base with an end mill in a drill press. I made a wooden jig with a screw through a pilot hole and very carefully milled the extra metal left by my tangent line cuts with the circular saw.

After some cleanup with a metal file and sandpaper, I drilled and tapped the holes for the screws. The large hole for the Powerguide connection cable was made with the drill press and a hole cutting saw. You will want longer M4 screws to attach to the wedge. I have a couple of small rubber feet/bumpers that I will mount at the bottom sides to center the telescope when attaching it to the adapter with an 1/4 x 20 thumb screw.

You can finish the plate in lots of ways, including a mirror finish polish, anodizing, bead blasted, and powder coat finishes. I'm partial to brushed aluminum, easy to do and easy to repair if it gets scratched later.

In addition to the smoother action of the Astrotrac wedge, advantages to this design include:

  • Better balance and less vibration - With the broad plate supporting the rigid rim of the Questar base, I shifted the mounting to the Astrotrac wedge so that the telescope is close to balance above the tripod center at mid-latitudes.
  • Convenient mounting for alignment devices on the shelf behind the telescope which attaches to the wedge.
  • The teardrop shape is beautiful, strong, and light.

Here are a couple of other views of the mount and adapter:

I've added a couple of extras to the basic design. Rubber bumpers make it easy to line up the mounting screw with the Questar drive base. The flat area below the scope is perfect for mounting a PoleMaseter. I prefer to do a compass/live-view alignment to the opposite celestial pole with SkySafari. This allows me to polar align during daylight or with the pole star obscured. It's more than good enough for planetary astrophotography and a great starting point for a drift alignment.

Content created: 2018-07-08 and last modified: 2018-07-10




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