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[ Mariner Home | Introduction | Optics | Plans | Final |
Construction I | Construction II | Construction III | Construction IV ]
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Construction I

Construction started in January of 2011. Things started a bit slow, owing to the fact that I had to also acquire some new tools. The last time I did this (when I built Equinox) I had used my friend Don Nisewanger's home shop in Bozeman. Without that resource, I had to get a table saw (Ridgid R4510 10" Table Saw) and a drill press (Ridgid DP1550 15" Drill Press) of my own. I already had a router and other hand tools.


Mirror Cell

The first thing to constuct was the mirror cell. My cell is an 18-point floatation cell, more of less of the Kriege & Berry design, but using PLOP to size and locate the parts.

We don't have a machine shop in the Physics Department here at Utah State (Norm Williams, in the Physics Department at Montana State had helped me make the mirror cell for Equinox), so I contracted my mirror cell out to a local machine shop.

Shawn Bindrup and the folks down at Reed's Precision Machine Shop in Logan did a great job on my cell. It was built out of stainless steel (per the advice in The Book --- I know some folks among the ATMs at Cloudy Nights complain bitterly about using stainless, but since RPM was doing it for me, I didn't have any qualms about this). They were kind enough to take some photos for me during fabrication.

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Once the mirror cell came home, there was a never ending cycle of assemble, test fit, measure, disassemble, etc.

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As with Equinox, I wanted a permanent, tough coating on the mirror cell. So I had the entire cell powder-coated a flat black at Cache Valley Coating in Logan. I then repeated the assembly game to make sure it all worked!

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All the rage these days has been around putting cooling fans on your mirrors, either to scrub the boundary layer, or to bring the mirror to equilibrium with the ambient air more quickly. Gary Seronik has some good posts about this (Part 1 | Part 2). Cloudy Nights contributor sixela had a thread (thread link) about a series of tests studying different fan configurations, and I decided to follow the conclusion of that study: a rear pulling fan. I have a mirror baffle just above my mirror, so we'll see how this works. I purchased the quietest fan I could find, in this case a Silenx iXtrema Pro 120 fan; it is rated at 9 dBA for noise, and moves 38 cubic feet per minute. I power the system using the Cooling Fan System from Astrosystems.

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Mirror Box

As with Equinox, I wanted the secondary cage to nest inside the mirror box for transport. This defines the overall size of the mirror box to be the size of the secondary cage rings + 1/2" clearance on each side.

The walls of the mirror box are 3/4" baltic birch, a lower baffle made out of 1/2" baltic birch on the inside (just over the surface of the mirror), and a set of triangular gussets near the top edge to provide strength, but enough space for the secondary cage to nest down insde the box.

The mirror box was the first piece I built, and gave us our first sense of how big Mariner was going to be! I had to build extension tables around my table saw to handle the 5x5 sheets of baltic birch.

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Something I didn't do on Equinox was trim the lower front corner of the mirror box to be able to make the swing profile lower; the mirror on that scope is fully inboard and protected, and I can view at zenith flat footed so there was no need. Here the eyepiece is much higher, so I did the cutout to give myself the extra breathing room.

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I used corner widgets to square up the frame while I was gluing and screwing it; I used the completed mirror cell to make sure it was all square and going to fit together right. The box is big, so working in/with it was always interesting!

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The mirror box was built around the mirror cell. Somewhere along the way, I didn't quite get the box wide enough, so the cell was a tight fit. I didn't like having to wedge it in, so I took my router to the mirror box and put 1/16th inch deep channels on both sides of the box. The mirror cell is held in place by six 5/16" machine screws, countersunk into the walls of the mirror box, through holes in the sides of the cell, and secured with locknuts.

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I detest having a large separate piece for a mirror cover. It always ends up laying in the field and getting walked on! When I built Equinox I had designed an integral mirror cover which folds up and out of the way. I've always loved it, so I did the same with this scope. Because the mirror is large, I made the mirror cover fold in half to keep the box profile smaller.

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[ Mariner Home | Introduction | Optics | Plans | Final |
Construction I | Construction II | Construction III | Construction IV ]
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Last Updated: 25 September 2012