Building a Dual Camera Mount for Astrophotography

For sometime I’ve been intending to build myself a sturdy dual mount and all the recent cloudy weather has left me with the opportunity. I wanted to be able to put 2 cameras onto my CG5 equatorial mount, both with similar alignment. The system needs to be rigid yet very quick to change over between configurations. Typical immediate combinations might be:

  • Digital SLR plus Starlight Video Camera
  • Digital SLR plus Lodestar guide camera

In the future it might also be asked to carry an astro CCD camera attached to a Canon Lens. Having been pleased with Manfrotto equipment for my daytime photography, I decided to base the plan on their accessories; here’s the starting point:

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  • Over length dovetail to fit mount – in my case the CG5
  • 1/4 inch 20tpi & 3/8 inch 16tpi UNC head cap screws or bolts (to fit std & pro photographic tripod fittings)
  • Manfrotto 323 Quick Change Plate Adapter
  • Manfrotto 357 Universal Sliding Plate

The Manfrotto quick fit plates are really very secure devices with safety clips too. If any slippage does occur there are also compatible Manfrotto anti-twist spotting scope plates available. At this point can I also recommend Stagonset fasteners to anyone in the UK who is looking for good quality fixings like the UNC cap screws.

Now to put it all together. I drilled an extra hole in the dovetail at one end to take the slide plate fixings. Originally I had intended this to be 3/8 but I decided that might weaken the dovetail too much, so the slideplate thread was reduced to 1/4 with a bronze insert and then a 1/4 fixing was used. Spring washers were used to ensure a substantial hold. I also replaced the smaller screws that were supplied with the dovetail, these give extra purchase to remove any risk of movement. Here’s a picture:

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Next the procedure was repeated at the other end of the dovetail, to mount the quick change plate but on the underside this time. The whole setup was now checked for alignment and then the fixings tightened right up. Here’s a picture of the complete assembly:

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I was then really lucky, in that the next night I had just a one hour break in the clouds so I could briefly try the thing out. Everything seems very secure, the slide plate allows me extra adjustment to find good balance with a large lens & DSLR whilst the bottom quick change plate works well giving plenty of clearance for the smaller camera. Below are two images of the setup that I tested it with, Canon 20D 100-400L plus Mintron & C lens:

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A quick word about the Mintron starlight camera, this is a fabulous piece of kit. If you have children who want to see the view or maybe a group of friends around for a party, this really beats everyone queuing up & squinting through the eyepiece. It is highly sensitive & can internally stack up to 128 frames realtime whilst outputting this video to a TV screen. Below is an image of the plough (big dipper) on TV from the other night (apologies for poor quality but TV screens don’t photograph too well)

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The Mintron’s C lenses are interchangeable & it can also be attached to the back of a scope too. Perhaps I’ll do a separate write up on it, after I’ve captured some video with a capture card. I have seen a perfectly respectable M27 with it on the back of the C6SCT and Tamsin certainly loves viewing with it.

So that’s that for now, I’m currently waiting for the arrival of my adapter to mount the Lodestar & 300mm mirror lens together. Once that’s made it here from Australia, I should be able to start guiding. If only the skies would clear …

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