Help/Advice from Celestron AVX mount owners please.

[Feral Rabbit]

Hi everyone,

Well I have finally got to grips with my set up and alignment and am very impressed with the GoTo system. But I'm not sure if I'm doing something wrong or if I'm missing something blatantly obvious or whether I have a fault with my mount.

Last night whilst out I had the fortune of having Orion come into view, for the first time for me, from the east south east about 35-40 degrees above the horizon (the eastern sky is quite polluted with Gatwick Airport and trees block my view). I entered M42/3 and the unit slewed around but then it stopped moving but the motors were still whirring away. I noticed that the top clutch lever (sorry for my ignorance I don't know what this one is  ) had been knocked by the declination motor housing and had loosened the clutch lever. I am unable to tighten the clutch as the lever is butted right up to the housing.

Do my clutches need to adjusted to make them tighter so the lever doesn't have to be wound so far around thereby avoiding the housing as it slews around? Out of the box they seemed quite loose even when wound right around but I assume this is a safety feature to stop damaging the clutch mechanisms.

Am I trying to get the mount to do something it is not supposed to do?

Is this a design fault of this mount?

Have I missed something?

I probably haven't explained myself clearly but I am sure if someone has had the same issues then they will know what I am getting at.

Regards and as always thank you all in anticipation.

Martin

[Thalestris24]

Hi

My lever sits parallel to the housing when tightened. If yours doesn't then I expect the lever position needs adjusting.

HTH
Louise

[Feral Rabbit]

Thanks Louise, mine sits just low of parallel. As it's new I will take it into the shop I got it from and let them adjust it. I would only have to show it a screw driver and a leg would fall off the tripod. My DIY is not far off appalling tbh.

[Feral Rabbit]

Just an update.

Went into Astronomia and had a chat with Neil (the owner) and he has told me that the clutches just need tightening up a bit. Remove the levers and adjust then re-attach the levers. Apparently they should be tight 45 degrees from the stop. Mine are tight at around 180 +.

Louise, I think yours are therefore right on the limit too and could probably need a slight adjustment at some point.

Regards

Martin

[Thalestris24]

Just an update.

Went into Astronomia and had a chat with Neil (the owner) and he has told me that the clutches just need tightening up a bit. Remove the levers and adjust then re-attach the levers. Apparently they should be tight 45 degrees from the stop. Mine are tight at around 180 +.

Louise, I think yours are therefore right on the limit too and could probably need a slight adjustment at some point.

Regards

Martin

Hi

It's ok, mine are fine and do their job!

Thanks anyway

Louise

[NotSoSuperNova]

I would recommend to anyone doing this adjustment manually that the screws that you make this adjustment to are not the best quality. I like to make sure mine are locked off nice and tight and when I made the adjustment I twisted the head off the screw. Bearing in mind that I'm talking nice and tight, not Hulk tight, if I were doing the same again I would 1. take it easy with the stock parts and 2. think about replacing the screw with a decent one before doing it. Just my experience.  

[Feral Rabbit]

Ah thanks for the heads up Ryan. I may just take into the shop for them to do then. I will mess up as my DIY is atrocious 

[mbristol]

Hi Martin,

It's about 3 years down the road, but this morning the same thing happened to me as to you November 1, 2014.

A slewing to the low east "unhinged", loosened, the declination.

It was indeed the declination clutch lever that had been loosened while passing too close to the declination motor housing.

As Louise said the lever needed adjusting, so that while tight, when needing to pass by the declination drive housing, it would not touch that housing at all.

As for her, so for me, I found that a good position for the lever when tightened is parallel to the declination housing.

When loosening the drive, the lever should be going towards and into the stop.

You can check that the lever passes the declination housing OK, by loosening, moving the drive over the declination housing and then tightening.

Nothing should be touching, there should always be a gap between the tightened lever and the housing, for the whole of the travel over the housing.

Thanks for the posting above.

Michael

[jefrs]

Old thread similar problem.  Clutch slipping. But not because the knob had loosened. I could not get the thing to align, the motors were running but the axes were slipping on the clutches.

By tight I mean tight like gorilla, I know I can snap knobs off so I go easy on them, but they're tight.

So I took it apart - There's a plastic button below the screw as a friction pad against a drum. Drum and button were slathered in grease. That is never going to grip.

Presumably excess bearing/bush grease had oozed out making an unholy mess.

The top dec  plate comes off the AVX, so it came off to reveal the drum.  Degreased by wiping in naphtha (Zippo lighter fluid).

The bottom ra doesn't want to come apart, or at least not easily.  Degreased with WD40 ('orrible stuff) squirted in, not too much as I don't to wash grease out of the bearing/bush where it belongs. Then tissue wipe soaked in naphtha poked down the clutch screw hole and turned. A lot of black muck came out. Repeated a few times.

(I often mix up the terms ra and dec because I don't need to use them to move the mount, forgive me if I've switched them about)

Degreased the clutch screws and buttons. The dimple side of the button should provide most friction.  I roughed that side up a little on a fine file. A little, just to roughen it, not to remove material,  and washed off in the naphtha.

Reassembled and arranged the knobs tight at ≥90° from stop. Frees off, locks absolutely solid with no undue effort.