Truss Dob with a 16" f4.5 Ed Beck Primary
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Structure Type: | Truss Tube Dobsonian; Kriege-based, standard teflon/ebony star bearings, strong and smooth |
| Primary: | 16" f4.5 1.75" thick Meade, refigured by Ed Beck (this is a pretty special mirror) | |
| Mirror Cell: | 9-point floatation with six perimeter retaining clips | |
| Secondary: | 3.1" on a 4-vane spider | |
| Upper Cage | Lightweight, aluminum with flocked interior; Orion Low-Profile 2" Dual Speed Crayford, Orion 50mm straight-thru on standard Orion mount and foot, Telrad. | |
| Misc. | 7/8" trusses with very good lower truss clamps (similar to Aurora Precision). Very nimble quick-release handles and wheels. Stable enough that leaving wheels on does not degrade tracking. |
Observing Log from Thursday 12/18/2014
A great mirror surrounded by surprising nimble structure.
The mirror is much better than any of the mirrors I used to own (including a 17.5" and my beloved refigured Nexstar 11 GPS (I miss that scope, even though I'd probably always used a dob instead)).
This is a Kriege-based Obsession clone with some interesting differences.
The mirror box and rocker box combination are well-built: very stable with smooth motions. Top-shelf lower tube clamps. The rocker box is perfectly symmetric, front and rear. The altitude bearings are well-done. My impression is that the upper 4-inches aren't necessary (you really don't need -20 degrees to 200 degrees swing in altitude), but they do make good secure handles when having to move the box. Nicely done, snug round mirror cover.
The mirror cell is solid and does its job. Views are excellent. Collimation is easy. The connector between the cell and the mirror box is round. It provides adequate ventilation, but it looks a bit weird. I'd consider buying some good birch plywood and making it square, mounting a fan. Probably a one-hour project (plus varnish).
The upper cage is the biggest departure from standard. Aluminum, flocked on the inside. It's very lightweight. The truss tubes are 7/8" and use bolts and non-captive thumbscrews.
Note that some of the pictures show a the original gear on the cage. That has been replaced with an Orion Dual-speed Crayford focuser and a straight-thru Orion 50mm optical finder. The Telrad remains.
The handles and wheels are ingenious. The handles slide right into the frame. It takes 10 seconds to put them both on or off. The wheel assembly comes right off, but I never take them off. They do not degrade tracking or stability with them on.
| The mirror box is considerably smaller than the 17.5" Telekit that I had. This dob fits in the house just fine, where the Telekit simply was too large. The fact that the handles come right off make it easy to take them off when stored in the house or the garage or during observing (no accidentally kicking the handles).
If you choose to roll the dob into a van or truck, you only need one plank instead of two (this is surprisingly much more convenient). |
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Rolling Out the Ed Beck dob (1 minute)
Running a Telescope from a Tablet: Demo with a dob and Nexus (3 minutes)
SkySafari on iPad 2 Quick Planetaries + Instant Info
Summary of Computer Equipment dob-to-iPad (1 minute)