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Celestron Powerseeker

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lot of difficulty in using the setting circles help !!! please?

i own a celestron powerseeker 127eq. i am facing a lot of difficulty in using the setting circles i.e. the R.A. and Dec circles to align the telescope with heavenly objects above. any kind of advice or name of a site which helps such as a telescope tutorial or such would be greatly appreciated.

More details of the precise problem you are having would help since it is quite a broad area. This article: http://www.skyandtelescope.com/howto/visualobserving/3304206.html?c=y&page=1 covers the process in more detail than anyone would be willing to do so here although the initial introduction is far too pessimistic in my opinion.

If your polar alignment is good then you can navigate over large portions of sky accurately enough that the object in question will at least be in the field of a low power eyepiece: the problems arise when people demand to the degree accuracy from their setting circles when their polar alignment is several degrees out.

However it also has to be said that the setting circles on your scope are not particularly good examples. Good setting circles tend only to be fitted to mid range to high end mounts these days - you would need to spend twice as much on the mount alone as you did on your complete set up.

The key thing to note is that the RA axis will drift away from the correct value as the sky rotates during the course of a night. Most people advocate regularly correcting the RA axis because of this but I always try to avoid it. Instead I adjust the scale so that it will give the correct reading at midnight. Then every time I need the circles I look at the time and calculate how long before or after midnight it is. The difference between sidereal and solar days is small enough that it can be disregarded, so I add or subtract that figure from the RA value I am looking for. In this way I calibrate my RA scale only once.

As for Bullseye's comments they are so wide of the mark I am hesitant to even call them wrong: it is akin to responding "Belgium" when asked "What is 2+3?" Dobs do not have traditional setting circles - they are fundamentally incompatible with polar circles and usually lack even altazimuth circles. The setting circle problem is one of the key disadvantages of the Dobsonian mount.

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