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RA Calibration

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Hi All

Looking for some help with the RA setting and calibration on my Skywatcher 130.

There is a metal pointer fixed to the body of the mount that is currently set to zero, the dial moves when I move the RA but have noted that this can be manually moved by undoing the thumbscrew and swivelling it aound independant from the body.

On the mount there is 'R / A' the / denoting a pointer? - is this there for a purpose, or this to show the polar alignment direction of the RA?

If i'm calibrating, I presume I fix on a known star and then undo the thumbscrew and turn the dial to those co-ordinates, so eg Sirius 6h 45m and then would I move the RA dial to show this RA with the metal pointer then set on this co-ordinate?

At present I'm just finding objects with the find and pointing but what to use the scope to its full potential.


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You have the right idea about using the RA setting circle BUT the problem is that the setting circles on most mounts that are available today are pretty useless!! They are far too small and are very poorly mounted (I bet there is play of a few degrees in yours!). I would ignore them and continue using the finder and your knowledge of the sky.

(If setting circles worked who would buy goto mounts!!)?

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I totally agree with Bizibilder. The setting circle on my EQ5 is useless, so I can't imagine any mount below it to do any better. The vernier scales were stickers, and the one on the dec axis was so thick parallax error would render them useless. If they were precision machined like the one on my vernier caliper, I might have used them and wouldn't have bought a GOTO, but they weren't.

Just tick with the finder, or get a Telrad if you want to star hop.

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I agree with Bizi and Keith - the setting circles on the EQ2 aren't really accurate enough for anything but general direction finding in the sky.

More important is polar alignment - you can do that with reasonable accuracy on your mount. The benefit is that the motor will track objects in RA for you so you won't have to keep moving the scope with the fine tuning knobs. :icon_eek:

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I use the setting circles on my CG5 mount every time I use my scope and don't have any problems, I find them invaluable.

I usually calibrate the setting cirlces on a star near the objects I am going to be viewing to reduce error. The setting circles will get me close enough to see the object I am looking for near the centre of the view finder and then a minor correction will get the object in sight.

I find it saves a lot of time because rather than planning a route using star hopping, I can just write down some coordinates from stellarium before heading out.

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Thanks guys

To be perfectly honest I've found simly finding the object with the finder the easiest way to find things and since the scales are in increments of 10, accuracy is always going to be questionable.

I guess as long as I know where it is in the sky from maps or stellarium, I shoud find whatever I'm looking for...maybe!

Edited by Mez7000
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