Re: Re: [Utah-astronomy] Re: A Solution
From: Chuck Hards <chuckhards@yahoo.com> Date: 2004/10/26 Tue AM 06:57:05 MDT To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] Re: A Solution
Hi Joe:
Balancing a SCT can be tricky because of the very short moments of inertia involved. I really can't post a quick method of balancing - but I can say that most commercial telescopes don't have the ability to be completely balanced in every accessorized situation and SCT's are no exception. Even those weights that slide for-and-aft on a rail only address balance in one dimension, and you have to think about balance as a radial function around each particular axis as well. It's a dynamic balance you're after, under any orientation, not just a static balance in a few orientations. And of course whenever you change an accessory the balance will change. It can be a trying procedure, don't be frustrated into a "good enough" mentality. When your telescope gets back, I'll meet you somewhere and we'll give it a look.
--- Joe Bauman <bau@desnews.com> wrote:
I want to try again. I have a balance bar that runs along the bottom, and some weights that can be extended out from the tube on their rods. First, can you give me a quick primer on how to balance in dec (it's fairly obvious how to do it in RA). I'm assuming moving the weights up or down on the bars would do it, but I'm having trouble picturing how. More importantly, I feel certain I would have to set up and align on north first and then balance. There's just no room between the tube and the wedge for anything sticking out while it is going through the motions of aligning. But I am hesitant to loosen the settings in RA and DEC after it's set up in order to balance it -- won't that throw off the tracking? Thanks, Joe
That is why I got a GEM mount. It is much easier to balance. I have one question for Chuck. When you say the gears should be working uphill, do you mean towards the telescope side or towards the counterweight side?
Debbie
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Hi Debbie: --- astrodeb@charter.net wrote:
That is why I got a GEM mount. It is much easier to balance. I have one question for Chuck. When you say the gears should be working uphill, do you mean towards the telescope side or towards the counterweight side?
If you can't achieve precise balance: Telescope side should be slightly heavy when looking west of the meridian, counterweight side when looking east of the meridian. The load should always be against the direction of rotation. When the telescope isn't "working" against the gears, it's acting as a governor, not a drive, and it was not designed to do this. The result can be erratic tracking if the mount is loaded to near it's limit or was designed poorly from the outset. _______________________________ Do you Yahoo!? Express yourself with Y! Messenger! Free. Download now. http://messenger.yahoo.com
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Chuck Hards