RA scale and polarscope

[Kevdan]

Hi,

Even though clouds are blocking my view Im having a play and have noticed that me RA scale doesnt turn with the mount as it should I have removed the polarscope holder and there isnt anything holding the RA ring in place apart from the polarscope holder.

Whats missing?

Kev

[West End Wendy]

May have the wrong end of the stick here, but on my mount (eq5), the RA scale is locked when used as a date scale for use in polar alignment.

There's a little nut that locks it at zero which you unscrew when the scale is in use as an RA setting circle.

Tim.

[Kevdan]

hi,

Yes it's got the locking screw for use with date/time but when this is undone and the scope is moved on its mount the scale sometimes moves and sometimes doesnt, I have stripped it down and there's nothing inside that connects with the RA scale to move it.

Kev.

[glowjet]

Your RA scale is a free spirit until you use it for polar alignment when it will be locked against the zero mark.

[killer10971]

hi

i have the eq5 and im having the same issues , should the scale move with the mount or should it be set and then locked so it dosnt move again

completely new to this and the skywatcher instructions are not too good

many thanks

[West End Wendy]

Lock it for polar aligning.

Unlock it when used as a setting circle (it should then move freely with the mount).

You will find that it will only actually lock in one position (at zero).

Tim

[killer10971]

thanks for the reply

when you say it should move freely with the mount do you mean it just sticks using the greasey stuff against the ra shaft?? and the thumb screen only locks it up against the 0 ??? i have a def wobble on my ra scale and a 4-5mm gap

how many people have knocked/moved the scale during observing if thats the case ,

[West End Wendy]

when you say it should move freely with the mount do you mean it just sticks using the greasey stuff against the ra shaft??

Yes that's my understanding. I don't think anyone would claim the setting circles are beautifully engineered - I think the Chinese manufacturers have realised that very few people use them.

The lock cannot be used to hold the setting circle at a specific RA co-ordinate. It locks at zero and turns the RA scale into a date/time scale. See Astro Baby's tutorial on polar alignment if you're interested - that's how I learned.

http://www.astro-baby.com/HEQ5/HEQ5-1.htm

Tim

[killer10971]

many thanks

do you use your circles for finding stuff or goto

[West End Wendy]

do you use your circles for finding stuff or goto

Neither - I have a manual mount and I find stuff using a Telrad and a right-angled correct-image finderscope (and a decent star map, of course).

I looked at using the setting circles when I first got the scope, but as you have obviously found out yourself, they're not really precise enough on modern mounts. I think setting circles were much bigger and much better made 10-20 yrs ago, before goto started to make them redundant.

Tim

[killer10971]

we have been finding stuff with a planispere and just random pointing and working out what it is later

cheers

[West End Wendy]

we have been finding stuff with a planispere and just random pointing and working out what it is later

cheers

Yes I'm all for that approach. Saw Globular cluster M53 a couple of nights ago for the first time - didn't have a clue what it was at the time but checked the star map later and struck it off my Messier list.