EQ5 Mount Altitude Adjutment Bolts

[Steve789]

Hi, I've recently purchased a secondhand skywatcher 150P on a EQ5 mount and have been playing with it today in preperation for my first attempts at observing with it tonight.

The altitude adjuster just above the azimuth adjustment knobs seems to work fine but the one on the opposite side of the mount rotates about a quarter turn before coming to a stop. It doesn't go tight but just comes to a solid stop whichever way I turn it. Is this a fault or am I missing something in the way I'm supposed to use it? I'm very much a beginner when it comes to astronomy having only done a few nights with a cheap reflector scope a couple of years ago before the mount on that broke.

Also hidden inside the mount just above the seemingly broken altitude adjuster is a recessed bolt with an allen key head. What is this for?

[szymon]

The weight of the mount may be stopping the adjuster from turning; it rests on this when all the way back. Try moving the mount forward so it rests on the other screw, which might free it up...

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[Steve789]

Thanks for the reply but I've taken the mount off the tripod and its still jamming. Is it possible to take the end caps off the axle that is the altitude pivot point so I can have a look at what's going on inside? It doesn't feel like the bolts bent as it doesn't get tighter as you turn it so I'm curious to see what's going on.

[Steve789]

Ok correction the bolt is very bent - just used a torch to look through the small gap in the mount and I can see its bent to almost a 25 degree angle!

Any suggestion how I can take the mount apart so I can cut the bolt and unwind it from the other side?

[szymon]

You might need to loosen the thrust bearings a little, or your bolt might be bent (apparently quite common with the EQ5).  Not sure how similar your EQ5 is to my NEQ5, but here's a strip-down guide by Astro-baby:

http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

She's a wonderful stripper, has done one for the EQ6 too.  Perhaps they'll help you get at the internals?

-simon

[szymon]

Oh, you replied as I was typing.  Sorry, you're another person with bent bolts :-(  You'll need to get it out and replace -- there are lots of stronger replacements out there (which kind of indicates that there is a general problem with the bolts).  Try comparing astro-baby's HEQ5 instructions for strip down, good luck!

[JamesF]

If you take the two covers off the alt axis you should be able to separate the upper half of the mount from the lower, allowing you to remove the bolt.

Sadly it's a common problem in the UK because we're pretty much right that the limit of the mount design in terms of latitude.  You can replace the bolts with harder ones, and there are all sorts of DIY modifications to help stop the problem.

One of the important things I think is to do most of the alt/az adjustment with the weights and OTA off the mount, then put those on once you're happy and then do a final check.  That way the load on the bolt is much lower.  Possibly it may also help if you work downwards from a higher latitude rather than upwards from a lower altitude, as you won't be trying to push the weight of the mount with the south alt bolt.

James

[ronin]

Take care as it is easy to strip the threads in the actual head and then that means getting the head redrilled and tapped or a insert put in. Both generally meaning a small engineering workshop action.

Bent bolts are so normal that it is more odd not to have a bent bolt at one time or another. Considering that Synta must buy these in bulk another few pence for better bolts would be much better for the end user and they even if they passed the whole cost on it is minimal.

[JamesF]

Considering that Synta must buy these in bulk another few pence for better bolts would be much better for the end user and they even if they passed the whole cost on it is minimal.

Harder bolts might make stripping the threads in the mount more likely.  It's far less pain to replace the bolts than the mount castings

James

[ronin]

Aren't we putting harder bolts in and so back to the same position of stripping the threads.

Seems to be if Synta do it then bad, if we did it then good, but the same resulting combination.

[Herbig]

The bolts are very soft and the design is flawed allowing the load to be applied sideways, if you don't release one bolt as you tighten the other it results in one of the bolts bending. Once you have hot the mount in pieces you will have to cut one side of the bent one off and then unscrew it from the mount.

[Steve789]

Well and truly bodged...

Getting the cover plates off the alt axis was by far the hardest part.

I managed to bend the bolt straight enough to unwind so avoiding the need to cut it. Cutting it would have been a real pain. I did however damage the thread on the mount as I unwould it but fortunately I have an M8 tap so I was able to clean it up nough to be serviceable. I'll have to be careful not to strip the thread in the future...

[szymon]

Well done!  Now you can replace with better bolts (but then you have the problem that the better bolts can eat the thread).  Either way, nice rescue :-)