EQ3-2 Alt tune up

[wimvb]

Hi all,

I'm quite new to stargazing, and am now starting with astrophotography.

My mount is a Skywatcher EQ3-2 GoTo with Synscan.

When I do the Synscan polar alignment after a 3-star alignment, I have trouble adjusing the altitude of my mount.

Yesterday I looked into this and found the following:

The Alt can't be set past 62 deg North (I'm at 59.5 deg)

The whole weight of the assembly (EQ head, scope and counterweights) is held in place by the Alt-adjustment bolts. For my location this means that the entire weight more or less presses down on the longer of the two bolts. No wonder these tend to bend with time.

The Alt is quite smooth at lower altitudes, but starts to tighten as I set it higher; as if the central bolt is tightening itself. This in itself means that the assembly takes some of the heads weight off the adjustment bolt, but it also means that polar alignment per Synscans way is almost impossible. Is this self-tightening at high Alt a bug or a feature?

I opened up my mount (took off the cover plate) and had a look inside.

As I understand from discussions about (H)EQ5- and EQ6-mounts, these have  3 bolts for lining up the head of the mount. The EQ3-2 does not have these.

It seems that the people of Skywatcher assembled the mount by putting plastic shims between the head and the fork and then just tightened the bolt until they got rid off all sideways motion.

My idea is to loosen the central bolt so the alt adjustment runs smoothly, and to prevent any sideway motion by putting in 3 smaller bolts.

So, my question is; has anyone tried to drill and tap holes for these bolts in a similar mount? Is it doable? The wall of the fork is only about 6 mm (1/4 inch) thick. I'm not sure if that's enough.

Thoughts please...

Regards,

Wim

[JamesF]

Does the alt movement appear to tighten up if you just move the mount by hand, or only when you use the adjustment bolts?  If the latter then I suspect the effect is due to the fact that the end of the bolt is by that time pushing diagonally on the adjustment lug on the bottom of the mount, making it even more likely that the bolt will bend.

James

[Alien 13]

As James has mentioned, the angle of the lug is all wrong for uk skys so the bolt action gets less and less efficient with increasing alt, the only real fix is to glue/weld/screw a wedge of metal to the lug making the contact square on.

Alan

[JamesF]

There was a post some time back showing pictures where someone had screwed an entire second lug onto the bottom of the mount to make adjustment easier.  It wasn't an EQ3-2, perhaps a HEQ5, but I'm sure the same could be done.

James

[brantuk]

It was the EQ6 Alt plate mod by Gunnar - see here:

http://stargazerslounge.com/topic/215270-eq6-altitude-mod/?hl=%2Beq6+%2Balt+%2Bmod#entry2309060

You'd need to contact him for specific details for your mount. Hth

Here's the actual mod thread: http://stargazerslounge.com/topic/161907-neq6-tuning-kit/

[wimvb]

Follow up on my previous post.

I loosened the central bolt of the Alt adjustment and found out that the fork and head are threaded. I.e. the bolt and nut tighten independently. This also has the effect that increasing the altitude setting, will tighten it. Originally, if I set the altitude to its maximum setting (62 deg), even with the T-bolts removed, the mount would tighten to such an amount that it was really hard to turn it back to a lower Alt setting.

I solved my problem by loosening the central bolt and nut (on the opposite side) slightly. The Alt adjustment is much smoother now at high setting, and really loose at low setting. Probably so much that there may be a sideways motion for lower altitude.

I will definitely look into adding a small wedge.

Thanks for the replies!

Regards,

Wim