Building & Using a Tracking Mount for Astrophotography

Building the Mount

For the most part I followed Gary Seronik's plans carefully. Since I intended to install the mount on an equatorial wedge, I modified the size and shape of the bottom plate to match the circular outline of the wedge as shown below. Also since my supply of scrap plywood did not include any 1/2-inch plywood as called for in the plans, I used some nice 3/4-inch plywood. This change could make the mount a bit heavy for installation on a photo tripod. So in that case it might be best to stick with the plan's use of 1/2-inch plywood.

One of the keys to this type of mount is the hinge between the two plywood halves of the mount. The upper plate with camera moves relative to the lower one via that hinge. In the Northern Hemisphere the hinge pin must be pointed at the North Celestial Pole (near the North Star) for the mount to track accurately. Of course for those located in the Southern Hemisphere, the pin must be directed to the South Celestial Pole.

 Gary's plan uses what looks like a pair of door hinges. I chose to use a single piano hinge, which allows the hinge to be the full width of the upper plate. I also relocated the ball-head camera mount from the center of the upper plate to the top edge, as shown in the above photo. This was necessary to avoid the problem of my articulating camera monitor not being accessible when the camera was pointed up.

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views and opinions held by dpreview.com or any affiliated companies.

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Comments

Total comments: 4
NancyP
By NancyP (Jan 17, 2013)

What is the maximal load the home-made barn-door mount can accommodate?

What is the minimal wattage on the green laser? I understand that these green lasers often emit eye-cooking infrared, and would like to use the least powerful laser that can be used for polar alignment. I know some people use more powerful lasers for group lectures during star parties, but that capability I don't want.

0 upvotes
RustierOne
By RustierOne (Mar 25, 2013)

Hi Nancy,
I don't know the minimum wattage, since that would depend on circumstances. The visibility of the laser beam depends not only on its wattage, but also on the amount of particulate matter in the air available to reflect the laser beam. I purchased my Laser from Orion Telescopes for around $40 US PPD. It's rated at <5mW, which seems to be very bright in a dark sky. One important use consideration is to be very sure not to point the laser beam at anyone's eyes or at any aircraft. To do otherwise would risk eye injury and would be violation of the law.

Best Regards,
Russ

Comment edited 2 minutes after posting
1 upvote
Leif Goodwin
By Leif Goodwin (Dec 25, 2012)

This mount was invented by George Haig of Glasgow, and originally known as the Scotch or Haig mount. In North America it became known as the barn door mount. The original version had a straight drive arm which accumulated tracking error, which was corrected in later versions with various modifications. The original article appeared in Sky and Telescope, April 1975 according to Wikipedia, where there is a discussion of some of the variants.

0 upvotes
the jimmy
By the jimmy (Dec 20, 2012)

Good article, thanks

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Total comments: 4