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Use shiny face of male dovetail?

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#1 tfield98

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Posted 28 July 2009 - 07:37 PM

I just got a Lunt telescope that came with a male dovetail.

1. One of the bevel faces has a thin, shiny (stainless?) metal facing added. Is this the face that the dovetail set-screw should press against, or is this face intended intended to be a low friction face on the other side from the set screw, allowing easy balancing?

2. (See picture) Is there any advantage/convention on whether the setscrew should point up or down when mounting the telescope? I'm in Seattle and the sun doesn't get very high in the south... I thought perhaps, since I'm not aiming at the zenith or north, that perhaps orientation #1 was more secure?

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#2 mclewis1

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Posted 28 July 2009 - 08:39 PM

The strip of metal is intended to provide a hard strip that the set screw won't mark up. Normally the set screw digs into the aluminum dovetail bars a bit and leaves some unsightly marks on the bars. The metal strip prevents that marking.

I don't think it matters whether the set screw points up or down but do think about which way it would be easier to ensure that it's tightly screwed in. If the set screw stays tight there should be absolutely no movement or shift in the position of the dovetail bar in the saddle. Sometimes the set screw will loosen slightly ... this is when you get some of the horror stories of a scope suddenly sliding out of the saddle onto the ground. There are two ways to prevent this ... keeping the set screw tight (and checking it occasionally) and adding bolts to the ends of the dovetail bar to prevent the bar from sliding out. Yes with the additional bolts you can't slide the dovetail into the saddle, you either have to tip the bar into the saddle from the side (only possible with saddles with a moving side plate) or take the bolt off of one end of the bar. These bolts that prevent sliding often have a plastic knob on them making it easy to add or remove them.

#3 tfield98

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Posted 28 July 2009 - 11:03 PM

Thanks, Mark, for the clear explanation!






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