Balance in DEC problem

[ian_bird]

Hi

I have a WO 98 FLT on a CGEM DX. On top of that I have a WO 72 Megrez on a Baader Stronghold.

I balance in DEC with the RA horizontal. I can get it spot on when DEC is horizontal - but when I swing DEC up to the vertical it is badly out of balance until it gets back to horizontal on the other side.

Is it the cables?

Any ideas gratefully received.

Cheers

Ian

[ollypenrice]

Dynamic balance! What a treat!!

No side by side plates in operation here?

I suspect that the issue will arise from an assymetry in your piggybacking arrangements. You have quite a gap between the smaller and larger scopes so if one is even slightly left or right of t'other you are going to know about it.

Do the cables play equally in all directions?

Let's assume you've done a basic balance pointing at Polaris in RA and Dec.

So, if you now set the CW bar to horizontal and the scopes to vertical, do they stay there? I bet they don't. If I'm right, you need to add some weight somehow to make sure they do. Maybe you have a finder or something well off axis? Or off axis cable drag?

Without the setup in front of me I'm seriously not very good at this. Steve Richards is very coherent on balance, though, and may join in.

Olly

[Freddie]

With the DEC horizontal you will be moving the scopes left/right on the mount connection or through the rings. With DEC vertical and the scopes pointing up/down in front of you, you have a misbalance to the left or right side of the scopes. This can either be wheel position or cam position or cables if they are all on the left or right side. One of the astronomy shed youtube vids shows this quite well. I'll see if I can find it.

[ian_bird]

Hi Olly

"No side by side plates in operation here?"

e

Nope, don't like them.

"Without the setup in front of me"

Well it will be in October!

Will look into your suggestions. But it's a bit odd that the balance gets worse as it gets closer to the vertical - and then gets better as approaches the horizontal on the other side.

Cheers

Ian

[Freddie]

Here it is. I think this will show your problem.

[ian_bird]

Basically I can start off horizontal in perfect balance - flip the scope over the vertical - and it will stop by itself on the horizontal on the other side.

But it takes a fair old flip - as you get close to the vertical - the load goes up. Not massive - but obvious.

[ian_bird]

Thanks Freddie. Will be studying that. Much appreciated.

Cheers

Ian

[ollypenrice]

Hi Olly

"Without the setup in front of me"

Well it will be in October!

Cheers

Ian

Oh dear. At this point you'll discover that I'm not much good when I DO have the setup in front of me...

Most embarrassing, most embarrassing... I'll have to offer you the well established 'discretion discount!'

Olly

[ian_bird]

I'll have to offer you the well established 'discretion discount!'

Olly

Monique's cooking means you will never have to play that card!

Clouds or no clouds!

Give Monique my regards!

See you in October.

Cheers!

Ian

[Freddie]

About 5min 40secs through is where you want.

[ian_bird]

Thanks Freddie. But my rig seems fairly well balanced with regard to the kit hanging off it or on top of it.

Not sure where I go from here.

Cheers

Ian

[swag72]

I have had some issues with what I thought was balance - My subs would start off OK lower down and while I was asleep and everything was travelling towards zenith, the guiding and perceieved focus got worse. Last night I decided to tackle it and make the scope very east heavy while guiding at Zenith. The guide graph was straight and the mount seemed happy enough. I set my target later, low in the east and went to bed!

This morning, the proof is in the pudding - Much better! There is a small issue with the stars (which I can tweak tonight I'm sure), the the focus has remained very stable. Demonstrating to me that the focus drift that I was seeing was more to do with the balance (who would have thought it?). I've learnt over time that my mount likes to be east heavy. When people say slide the counterweights down by 1cm, for my mount that means 10 cm's!!! But it is happy and will guide. I'd also like to say that the guiding lower down is spot on - so looks like I can adjust the balance a little more in favour of zenth imaging before having any adverse effects low down.

This has surprised me - Just how much weight and balance alone can affect things. Whether it is the same for your mount, I don't know, but I have certainly learnt the idiosyncracies of my HEQ5 over time!!

[ian_bird]

Freddie, Olly - thanks!

You were spot on. My Wo 72 Megrez was offset by about 4mm. Causing exactly the effect shown in the video.

Just have to figure out how to center it. Drilling time I think!

Thanks for all the help guys. Really appreciated.

Cheers! Big time!

Ian

[andrew s]

Ian, not that elegant but you can always tape some weighs to the light side. I find a bit of roofing lead works well. You will need to adjust the other balance planes unless you tape the weigh inline with the RA axis.

Regards Andrew

[Freddie]

No problem. Glad you got it sorted.

[ian_bird]

Thanks Freddie - you were a big help. Really appreciate it!

Andrew - great idea! Will certainly investigate that. Beats drilling!

Cheers

Ian

[ian_bird]

Dynamic balance! What a treat!!

You have quite a gap between the smaller and larger scopes so if one is even slightly left or right of t'other you are going to know about it.

Olly

Hi Olly

Took your suggestion - and bolted the guide scope directly to the losmandy plate.

DEC balance is a whole lot better. Thanks.

Cheers

Ian

PS - Recently moved to Australia. Hence the upside down picture. Honest.

[SnakeyJ]

Ah suddenly it dawns! Have to check my guide scope centre of mass and remount - Cheers Freddie and all contributors!