Setting Dec setting circles

[Astroman (Andrew Wall)]

Hi all,

I dont want to get into some debate on whether this is necessary or not, I just want to know if this procedure is the correct method for setting the declination setting circles on a GEM.

Firstly polar align the mount, including leveling of the base, this can be accurate or close enough for visual work. With the OTA on, rotate the scope in declination till is is horizontal, looking at the east-west horizon. Use a spirit level to get it exactly horizontal. Move the setting circle until it reads 0 declination, and tighten screws.

Is this correct?

[Dennis]

Hi Andrew

Off the top of my head, I would have thought that Dec 0 degrees would be the Celestial Equator rather than your horizon?

Your E horizon would be the Dec angle corresponding to your latitude?

Cheers

Dennis

[Dennis]

Hi Andrew

I’ve just opened The Sky and clicked the E horizon and you are correct, it is indeed Dec 0 as can be seen from the panel in the attached screen print.

Back to celestial mechanics school for me!

Cheers

Dennis

[Astroman (Andrew Wall)]

You know you are going insane when you try and close a picture that has a red square with a white cross in it.

No worries Dennis, thanks for that, I was starting to believe you hehehe.

[Geoff45 (Geoff)]

The other way is that once you are correctly polar aligned, go to a star with known dec and centre it. Then adjust the Dec circle until it gives the correct reading for the star.
Geoff

[Geoff45 (Geoff)]

Originally Posted by Astroman

Hi all,

With the OTA on, rotate the scope in declination till is is horizontal, looking at the east-west horizon. Use a spirit level to get it exactly horizontal. Move the setting circle until it reads 0 declination, and tighten screws.

Is this correct?

I think this only works if the Dec axis shaft is accurately positioned in a vertical plane i.e. counterweight is at its lowest possible point.

[ballaratdragons (Ken)]

Because I am hoping to buy a portable EQ mount soon I have been reading up on this exact subject.

The method I keep coming across is: Once you are polar aligned, find an easy bright object and track the object. Then turn both RA and Dec setting circles until the co-ords of that object are set. Then you are ready to use the setting circles on any objects co-ords as long as you don't alter the settings. If you accidentally move a setting circle, just find a bright object and set it's co-ords again.