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philsail1

Understanding scales on Setting Circles

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Can anyone help! I have a Skywatcher Explorer 200mm Newtonion Reflector. It's a great scope. I want to use the setting circles. (I've managed to do the "Polar Alignment - on a distant pylon during the day time). I've downloaded various items of information on how to use the setting circles, but I still can't understand the what the divisions mean on the circles. Are they in hours and minutes or degrees? - and what is on where! Sorry for appearing so thick! (I don't want to give up and "Go-To!")

Philsail1

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Hi Phil,

The DEC axis is in degrees, the RA axis is in hours. Forgive me, but how have you polar aligned on a pylon?

Gaz

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The RA circle will have long divisions interspaced with shorter ones. The long ones are the hour marks, the smaller ones are the minutes.

Count the small divisions If the are six, then each division represents 10 minutes 10 would be 6 minutes and so on. The longer ones may even have slightly shorter ones midway between, they would be the half hour marks.

Ron. :)

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Thanks for your replies "Daz" and "Barkis". Daz, I must have confused you! I should have said I "set up" the polar scope for alignment using the pointed tip of a distant pylon. First I lined it up as near to the correct position (near the bottom of the target circle) then turned the mount on its polar axis (if I am explaining right!) through 180 degrees and checked where the tip of the pylon rested within the target circle. It was out a little bit so I adjusted the polar scope a tiny bit, then turned the mount back to its original position (through 180 degrees in the opposite direction) and checked again. Did this "too and froing" a couple more times until I got the tip of the pylon to stay as near as "dammit!" to the right position in the target circle.

I hope I have explained a bit clearer!

I will study your replies and apply them to my setting circles. Thanks again.

Philsail1 :)

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Yes, Thanks Trevor - I've downloaded the info and will study it later - it looks really useful.

regards,

Philsail1

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Thanks for your replies "Daz" and "Barkis". Daz, I must have confused you!

Nope, not me. Might have confused GAZ though!!

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Thanks for your replies "Gaz" and "Barkis". Gaz, I must have confused you! I should have said I "set up" the polar scope for alignment using the pointed tip of a distant pylon. First I lined it up as near to the correct position (near the bottom of the target circle) then turned the mount on its polar axis (if I am explaining right!) through 180 degrees and checked where the tip of the pylon rested within the target circle. It was out a little bit so I adjusted the polar scope a tiny bit, then turned the mount back to its original position (through 180 degrees in the opposite direction) and checked again. Did this "too and froing" a couple more times until I got the tip of the pylon to stay as near as "dammit!" to the right position in the target circle.

I hope I have explained a bit clearer!

I will study your replies and apply them to my setting circles. Thanks again.

Philsail1 :police:

Philsail1, you do realise that the pylon goes on the cross in the centre and not in the little circle I assume? The little circle is offset from the mount axis as much as Polaris is offset from the NCP (North Celestial Pole).

Captain Chaos

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Sorry "Daz." it was "Gaz" - but I doubt if he'll be confused. "Captain Chaos" - Yes, I did position the tip of the pylon right on the centre of the cross hairs. Am I right in doing the same when lining up the Pole Star? I have tried it, and the Pole Star seems to remain right on the centre of the cross hairs. (it must be there, as I could not see it until actually moving the scope off the star slightly!

Thanks everyone, for all your help and advice - it's very reassuring when one is struggling all alone on a dark night at some ungodly hour!

Regards

Philsail1

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The reticle alignment needs to get the cross hairs centred on the 'scope axis, so pylon on cross hairs. Polaris however is not where it ought to be for polar aligning as its out of position by a tiny bit. The reticle therefore has a way of getting the offset correct. It has a circle such that the radius is equal to the offset necessary for polaris, and a few constellation sketches to allow the direction of offset to be worked out. On the circle mentioned previously, there is a tiny circle set on the circumference. This tiny circle is where Polaris needs to be put once the constellation diagrams have been rotated to look like they do in real life.

Captain Chaos

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Ah, thanks Captain Chaos! that's a good clear explanation. I've managed to download the "Polar Finder" program, which Trevor suggested. I will apply this to positioning the Pole Star. Just one more thing though. If I set my polar finder's reticule, with the tiny circle (on the rim of the bigger circle) positioned at the "bottom" (which is where Polaris is at its highest position) and the Polar Finder "clock" shows the Pole Star at a different position, do I adjust the telescope until the Pole Star corresponds to the "clock" - or leave it where it is in the little circle. (am I complicating things unnecessarily?)

Regards,

Philsail1

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Just turn the mount so that the little constellation pictures are oriented the same way as the ones in the sky then put Polaris in the little circle. The plan with the constellation pictures is that you don't need to look up Polaris to see where it is in relation to NCP, the diagram sorts it all out for you.

Captain Chaos

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