Lesson from the Experimental Aircraft people: "You take the proposed accessory and hold it straight out at shoulder height.  Let go.  If it falls to Earth, it doesn't belong on your airplane . . ."

Feb 22. I have spent the morning working out ways of mounting the guidescope. Figuring out what I have and what can be rearranged has let me solve the problem for the 10-inch and simplify rigging the 5-inch into the bargain. I have replaced steel with aluminum and aluminum with its absence.

I removed the Losmandy collimating rings from their bases. Then I cut a section from a long Losmandy DMM plate of the length actually needed by the guidescope and re-attached the rings directly to that. That leaves me with two Losmandy mounting blocks which can be left mounted on the 10-inch and on the 5-inch to receive the guidescope in its rings on its severely shortened dovetail plate. I can dispense with the DSBS when using the 5-inch and reserve it for the 200mm.

The 5-inch when ready for deepsky photography with the focal reducer, ST2000XM, guidescope and DSI now weighs 37 pounds, down from 49. The guidescope, rings, dovetail, finder, and DSI combined weighs 8.5 pounds.

The 5-inch and 10-inch packages will weigh almost exactly the same when ready to image. The 200mm with the guidescope and the DSBS will be approximately the same weight. The CG of the 10-inch will be quite a bit higher.

It needs an additional 11 pound counterweight. Drat. I tried mounting the guidescope low on the side of the center frame, but this still didn't avoid the need for the additional weight and introduced a strong declination imbalance, too. So back to the top of the tube location and just live with the extra weight.

Surprise! The diagonal allows the 35mm Pan to come to focus, also a 12mm Nagler. Probably others.

Black box / red bag: The guiding electronics go into a red stuff sack. Wires go in; wires come out. The bag hangs from the G11 for any optical suite.

In twilight, I set up the ST2000XM and gave it a try on the Moon. Time to cut metal again and lock the mirror right where it is.

Mirror trusses need to be shortened and the receiver for the focusser needs to be rendered immobile. Then we'll see what it can do. Fine adjustments can be made, if needed, by moving the focus-receiver ring in or out, making it longer or shorter, etc. At least a modicum of light-shielding needs to be in place. The flocking material may arrive tomorrow. If so, I'll shield the top end at least and think about the mirror end.

While there was still light, I took down the 10-inch and replaced it on the G11 with the A-P to try out the extension I made some time back for the focal reducer and to try the new guidescope mounting scheme. The former focuses easily; the latter lets me drop a 22 pound weight in favor of an 11 pounder. I aligned everything on the Moon and then dialed in M81 and M82. For variety's sake and because there is a waxing almost quarter Moon in the sky, I shot through the H-a filter. Wind and truly dreadful seeing are problems tonight. Their combined effects look like poor focus, but that's not it. It's a balmy February evening and the ST2000XM would not reach its usual -35C set point, so I'm using -30C. Which means I need a dark frame, which means I didn't want to shoot 30 minute subs.

For tonight's imagery with the 5-inch, hit the button below labelled "Back to Cameras Behind Telescopes."

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Text & Photos by David Cortner
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