My mount doesn't seem to like the South!!

[swag72]

Apart from the fact that everything is about to go outof the window ............ if the obs had one!!! Here's a strange one,,,,,,,,,,,

I have just completed a few subs on NGC1499 and the mount has guided absolutely fine, 600s subs with no problems. So I've decided to move to a target in the South and the mount will not give me a straight guiding graph and neither will it give me decent subs. I've recalibrated in Maxim - to no avail.

Nothing has changed between the 2 targets - Weights are East heavy as NGC1499 was rising and so is NGC2264 in the South. Earlier I disengaged the clutches and moved it all around freely, as I was having a similar problem last night.

So any ideas what it could be? Is there something that I could do to improve my mount performance in the South?

[Martin-Devon]

Sara although I have no words of wisdom on this issue - it seems it's yet another issue on top of all the other ones you're experiencing at the moment - you're having a dreadful run of bad luck & it must be a terribly frustrating time for you. Ideally you only want one thing to change or 'play-up' at a time so that you can minimize the areas to check-out, but when many components are simultaneously not playing ball as they should I can only dread to think what the situation must be like. Here's hoping you find the solutions quickly and get back to posting the nice images or even better ones very soon.....

[Merlin66]

Sara,

I'd double check the balancing. The position of the OTA relative to the mount axis will have changed and you may find to now have too much/ too little "pre-load"

[swag72]

Martin, it's frustrating to be sure!!!

Ken, How do I check the balance? WHat I mean is that if I check the balance at the beginning of the night and then guice on a target and it's fine, I slew southwards and it's all over the place - How do I balance? The way that I check it has no bearing on whcih way the mount is pointing if that makes sense?

[Merlin66]

Sara,

Ok.

Roughly orientate the mount and OTA to the position of your target object....

Balance the OTA on the Dec axis, so it will sit almost in position with no clamps..

Balance the Dec axis so it will sit in position with no clamps

and finally set the RA balance so that there is a SMALL out of balance towards the East

(I find with the Kg of spectroscope and cameras I have to do this check at least twice a night...)

[r3i]

My first thought when I started reading your post was to suggest you re-calibrate the guiding but it sounds like you've done that and if your balancing tests check out okay, it's clutching at straws time: Anything loose in the image train that only manifests itself when pointing south?; Any cables or other stuff that might be snagging when the scope is in a certain position?

Hope you get sorted quickly - imaging is hard enough without having to deal with these kind of annoyances.

[swag72]

Cheers Ken. I am really surprised at that - I thought that once the mount was balanced, it was balanced and that's it! I have now balanced it according to where I was pointing last night. So now it wil be out of balance for my Eastwards imaging? Why have I never encountered this phenomenon before? I knew balance was important, but Jeez, this is madness!!

[martin_h]

I re-balance mine when moving from east to west, so as to always make the east side heavy, I just put some tape on the counterweight shaft to mark the position of the weights

[swag72]

I always move the weights when I go from East to West, but moving to the South involved rebalancing the OTA along the DEC axis. Surely that's not right? Also, now it's balanced for the South. when I pointed it to the East where I'd normally start ............... it was no longer balanced.

[Astro_Baby]

Maybe I am missing something but I cant see why the DEC axis would change balance. I can see that with an offset camera or a heavy lens a newt would need potential rebalancing but as far as I recall your using a frac.

[swag72]

I don't get it either Mel.

I balance as per usual and all is fine and dandy. I move the scope southwards and it's no longer balanced. Nothing has moved or changed, the focus hasn;t changed so the drawtuve hasn't lengthened.

[Whirlwind]

Hi Sara

You don't seem to be getting any luck at the moment, I'm sure it will all come good though.

Is there anything else that could be generating some form of drag or change in the moment of the telescope? How is you wiring? Does any of it get tight in certain positions that could be pulling on the axis. How is you cable management, when you point further south is that 'lifting' any electrical components (thinking of something like a USB connector here) off the ground? Also have you checked your dewshield/dew heaters that they aren't slipping when you slew?

Have you tried just rotating the scope by hand to see if resistance changes as you move it?

Ian

[Lars]

I can't understand either why a refractor would change balance when moving south. The only thing I can think of is if your guide scope is very offset from the center of gravity?

/Lars

[swag72]

OK, this is so unscientific, but has potential!!

I balanced the scope today poiting south. This evening guiding was poor again. Like you I am bemused by how the weight of my refractor moves! I have been using 1 counterweight for ages, and so just stuck on another and weighted the east side like a goodun. Guided to the East for 600s no problem, Have now moved to the troublesome south - Showing potential!

Cables all slack, no pulling and the guidescope is on top of the scope. nice and tight. I'm just running off a 600s southwards - Wish me luck!

[Merlin66]

Sara,

How did your exposure go?

Any better?

[swag72]

Oddly Ken it went much better. I basically chucked on another 5kg counterweight in pure frustration, it's absolutely so East heavy as to be unreal!! But it's working. How bizarre!

[davew]

Take care. I heard of a mount that was left running without the tube on but with the counter weight on and it burnt the motor out !

We don't want that now do we ??

Dave.

[swag72]

Interesting Dave - I am still struggling withthis and have not had consistency from one night to the next. Oddly I was just starting to wonder if there is something terminal happeing with this mount - Just how to decide. I feel another thread coming on as I cannot get to the bottom of the issue.

[davew]

Seems odd.

The HEQ5 does have a very good reputation and I can't remember you having this trouble before.

Someone must know. Yep, start another thread with all details.

Dave.

[ollypenrice]

I think this is absolutely classic and par for the course. I can image down to about 20 degrees on the southern horizon but guiding is rarely if ever as good as it is higher in the sky. Possible explanations would be 1) poorer seeing at low elevations so you are chasing the seeing. One thing that can help is to increase the duration of the guide subs so the turbulence evens out. 2) You are likely to be nearer the Celestial Equator so an error in RA moves the object a lot further than it does nearer the NCP. (Think of imaging Polaris unguided. A sight easier than imaging Betelgeuse unguided.)

I do tend to balance for one particular image with ordinary mounts (Tak, NEQ6, iOptron.) I just estimate the object's position and check balance in that position. The Mesu Mount 200 couldn't give a gnat's crotchet about fine tuning. It just does its job and we never touch the weights.

The reason your scope's balance changes is likely to do with offset such as induced by an assymetrical finder maybe located on one side. Cables also tend to pull slightly assymetrically. It's worth rehearsing the mount's swing for a proposed image in order to suss out any balance oddities or cable issues/snags in advance.

And after all that there is the redoubtable Sod's Law which brings the darkness into the Dark Art...

Olly

[swag72]

Thanks for that Olly - I seem to be struggling at about 20-23 degrees. The guiding is terrible, but there seemed to be other odd things going on that just don't seem to happen as I move higher up. The pulse for example didn't seem to be getting to the mount consistently. At least I have eliminated all sorts of cable issues as I swapped them all over!! Just checked the power to the mount this morning and that seems OK. I was starting to wonder if it was something electrical that was faulty in the mount itself, but specifically with the guiding stuff as it will slew quite happily. I don't know what to do to check that.

2 frustrating nights on the bounce, lets see if we can't make it a third, surely there's no fun when it all works well.

Shame if I really can't get low to the south as that effectively rules M42 out for me.