HEQ5 RA axis fix

[Kaptain Klevtsov]

Probably operator error on my part. I had a sticky RA axis, which i thought was going to be expensive. I think I have a cure which involves the setting circle ring. I could be wrong, if i am then I'll hold my hand up, as I don't know how the setting circle works. Let me know if I am wrong, then I can reassess and change the website.

www.gas.uk.net/HEQ5

HTH

Captain chaos

[Greg]

The RA setting circle ring is meant to be rotated for aligning on targets the small screw locks the circle.

It's the only way you can find celestial targets using RA and DEC.

Greg

[Kaptain Klevtsov]

Thanks greg for stepping up here, I'm very much working blind here as you will see from the following description of how I came to the conclusions that I did.

Now this is something that I don't understand, the whole setting circle thing I mean. If the small screw is used to lock the circle, without the screw being in the hole, it effectively locks the whole axis. Is it possible that the hole is in "the right place" and the adjustment is a one off?

If the ring needs to be turned to any random position and then locked, then two things need to be done.

a) A second screw oposite the locking screw to take the pressure from the locking screw(or better, two at 120 degree intervals).

The hole in the ring needs to be filled in.

I had assumed, initialy, that the setting was done on the large aluminium ring and the shiny (looks made for it) screw is the locking screw to save the adjustment. After I had diagnosed the stiffness, I reconsidered and assumed, this time, that the adjustment is with the index which lines up on the aluminium plate. This index is on a small ring around the polar scope. I am probably wrong with this newer assumption as this adjustment requires a screwdriver. This would work, however, if the RA setting is a once only affair.

I was guessing that the setting up was a one off calibration similar to levelling the tripod and that, once set, it would stay that way for ever. That would allow the small index ring to be adjusted and locked in position, but does not explain the big shiny screw. Because of the hole in the setting ring, I became convinced that there could be only one position for the ring and that was where my problem was, that I had moved the ring enough to disengage the ring from it's alignment hole.

Any and all comments, especially pointer st ohow the setting circles work, would be very much appreciated. The manual that came with the mount was less than helpful in this direction.

[moondog]

Hi CC

I would agree with you - the screw that locks the RA circle locks it to the MOUNT, not to the RA axis.

Pointing the scope to an object of known RA, locking the RA circle with the screw and then moving the mount in RA to a new object doesn't work. The RA circle moves a few millimetres then jambs.

I have taken the locking screw out of the RA circle. I can now use the setting circle as it was meant to be used as the (deliberately?) stiff RA circle moves with the axis

I have gone on to the HEQ5 website and users with new mounts say the same thing.

It may be that Greg's mount is an older one that works as it should.

I agree that you should be able to lock the RA circle to the axis. I could do this on my previous mount.

MD

[daz]

CC

The small index ring around the polar scope is for setting the East West off-set for your location. Without doing this, the polar alignment would always be wrong. In our case, this is 0.

Then, when you polar align, you:

1) Use the small hour-marked ring to align with the index marker on the RA axis to set the date

2) Use the big RA setting circle to set the time.

3) Rotate the RA axis until the zero lines up with the marker.

4) The polestar can now be aligned in the polarscope, and you now know it is correcty oriented.

When you need to polar-align, you start again from 1).

Now, the problem you are describing is one I have as well. The setting circle is set EVERY time you use the scope. This is because the earth has of course rotated since you last had the motors running!

What *SHOULD* happen is:

1) Find a target star / object of known co-ordinates e.g. Pole Star

2) Set the declination setting circle (this should not really move much) to 90.

3) LOCK the declination setting circle with the screw

4) Set the right ascension setting circle

Now, I assumed that I needed to lock the RA down so that it rotates with the mount. Apprantly not with the HEQ5. If I leave it loose then it rotates with the mount (as it should do), but I find that it 'slips'. If I lock it down, then it doesn't move. I am confused by this, as I would have thought that locking it down would ensure it does not move for that session. Come next session, I would reset and re-lock.

I'm not an engineer and I'm not confident in taking it apart to find out if I can do anything about it, so if you find something, I'd be very interested.

Does the above make sense?

[moondog]

CC / Daz

I used the setting circles on my last mount. To set the RA circle to the current 'celestial time' I looked up the RA time for say Rigel from a set of star tables. Rotated the scope to point to Rigel. Moved the RA circle so that it read Rigel's RA time against the pointer, then locked the RA circle. To find another star I would look up the RA in tables and rotate the scope in RA until the RA time for the new star was opposite the pointer.

It is not possible to use the HEQ5 this way as the locking screw goes through the fixed shroud to the mount.

My previous mount had the RA circle on the RA shaft below the mount shroud. The locking screw was fixed to a flange on the RA circle. So when you locked the RA circle and rotated the RA shaft the RA circle moved as it needs to do.

Daz - On the HEQ5, if I loosen the cover to the polar scope and slide the RA circle down slightly my RA circle works without the screw as it's pretty stiff.

Good luck!

MD

[daz]

MD

That's exactly how it's supposed to work!!

I'll try the little trick with the polar scope cover, though!!

Cheers

[Greg]

The only time I have to lock the scew is when i'm tracking an object for a long period of time during photography, when I don't want to lose the coodinates.

Captain,

I wrote this a while ago regarding the RA and DEC circles and finding stuff - hope this can be of use

http://stargazerslounge.co.uk/index.php?topic=2455.0

Greg

[daz]

Hmm, I defintely need to play with mine tonight....

[moondog]

The only permanent 'fix' that I can see for the HEQ5 RA setting circle is to tap a hole for a screw through the face of the setting circle (at say 'zero' hours) and that will lock it to the RA axis. The setting circle is a substantial thickness and should take a tapped thread.

At the moment my setting circle works OK due to the stiff fit. If the circle works loose over time I will have to fix it as above.

No such thing as the perfect mount or scope I'm afraid!

MD

[daz]

Here is a man who knows his mount!!

This is what I call an UPGRADE!!

This may help CC

[Greg]

Superb find daz:D

Good Googlin!!

[Chubster]

Here is a man who knows his mount

Is it just me who cannot acces this......or have all you EQ5ers crashed his site

[moondog]

Looks like the site has a temporary problem - It's been OK before.

MD

[daz]

Damn! That was a useful site - hope it comes back up soon!

I did strip down the polar mount and RA circle from mine, cleaned the 'glue' off and re-greased everything. This has made some difference. I also drilled a hole at 0 hours, and need to tap a thread into it. Trouble is, I am a Rubbish engineer, so I need to get my BIL involved in this!!!

BUT, the regreasing has made a difference - I can slew the RA axis around and the RA circle works pretty well....

[Chubster]

Up and running again Might give it a go even though there doesnt seem anything wrong with mine........B****r all else to do with it :D

[daz]

I also made the 'washer' that goes between the mount and tripod (for easy az adjustment) but, I used an ice-cream lid (all I had to hand), but it didn't work particularly well. Perhaps the butter / marg lids are slightly different material :?

Hmmm, site appears down again today........

[daz]

UPDATED LINK:

http://ozastro.dyndns.org/