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# Clarification on Equatorial Platforms?

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I've got too much time on my hands right now, I guess.I've spent a good part of the last few days threads related to Dobsonian equatorial platforms - both the very expensive models for purchase and some home made versions. I thought I had things figured out, but now I'm confused again and I'm looking for some clarification on the platform angles.Most of the platforms I've reviewed are canted at no more than 3-5 degrees (estimated). I live at 48 N and understand that this would be the required angle to align with the pole star. I've seen one particular example at such an extreme angle and it looks quite scary for the Dob!!These platforms are generally designed to allow for tracking for approximately one hour, equating to 15 degrees of arc, before resetting. That works out to 1/24th of a circle. Applying this to the latitude setting, then about 2 degrees of cant on the platform would make sense.My physics is pretty rusty, but I've managed to convince myself of this line of thought. Am I right or is there a fundamental flaw that I'm overlooking? :scratch: Thanks for any help you can provide.

Cheers,

Barry

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Most are designed to suit the lattitude of the observer with usually no adjustment. Close is good enough as they are not really suited to imaging and a very slight drift is acceptable for visual.

Although they look like they're at a small angle, most are designed to have a flat surface to put the Dob. on, but act at quite a big angle.

The way they work is not very obvious from a quick look, but if you can imagine a big cone lying on the ground with the point and the edge of the base both on the ground you start to get there. You then need to imagine cutting the cone so that you get rid of most of it with a cut parallel to the ground and thats the platform design. Rolling the cone, or whats left of it, follows the stars round the sky.

In the detail of the design, the axis of the cone points to Polaris, the point is fixed and the big end has wheels under it such that the whole thing rotates around an axis that passes through the North Celestial Pole. Most of the imaginary cone is not needed so you don't build that bit.

HTH

Kaptain Klevtsov

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thanks Kaptian,I'll have to keep looking at designs to get my head wrapped around things a little better.

Cheers,

Barry

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