How close must the balance be?

[Snaxmuppet]

I have a new mount and scope (AZ-EQ5 & SW 80ED). I set it up in my lounge but when I went to balance it in the dovetail mount I couldn't get the dovetail far enough forward to get an exact balance. It is very slightly heavy at the eyepiece end.

The obvious thing to do is to move the OTA forward in the rings but it is already as far forward in the rings as it can go. I guess this is a consequence of replacing the stock focuser with a Moonlight one which seems heavier (?).

It isn't out of balance a lot to be honest but before I look into other solutions, such as moving the rings on the dovetail get the forward travel for the OTA, I thought I'd ask your advice. Clearly an exact balance is desirable but how much of an issue would it be if the balance was slightly heavy towards the eyepiece. I am using it visually at the moment but intend imaging as soon as I get my camera back from being modded. If it is eyepiece heavy with just the diagonal and eyepiece now then it will be even worse when I attach a dSLR!

On a more general note... what are the consequences of not being in balance apart from things moving around when you release the clutches

[Matt Scunthorpe]

I am certainly no expert, but I believe the idea of being balance is so that the gears/motors etc of the mount, when you are tracking, don't have to fight against the weight of everything, if that makes sense. I think being out of balance a little bit is not a problem, but If it is out of balance with no DSLR, I assume that once you put an DSLR onto it, it will really skew the balance and then may be an issue.

But as you say the OTA is already as far forward as it can do, im not sure what else you could really do.

Hopefully someone will have a better idea of what to do.

Matt

[ianm2k4]

How about putting a counter weight at the front of the dovetail to counter the focuser/DSLR? It would have to be held well so it didn't move when the scope moves assuming the mount can take the extra weight?

Just a thought

[Snaxmuppet]

Thanks Matt. There are holes further forward on the dovetail so I could remove the rear ring and re-attach it to the dovetail further forward. But that would then mean that the two rings holding the OTA are then closer together and it also means that the adjustment screws for adjusting out cone error are not available as there are no equivalent holes for those screws at the forward ring attachment point. If I don't want to adjust for cone error then that might work providing having the rings closer together is not an issue (?).

How many people adjust for cone error anyway? I only found out what it is yesterday!

[Matt Scunthorpe]

I'm going to be completely honest in that I have no idea what cone error is lol.

Matt.

[Snaxmuppet]

How about putting a counter weight at the front of the dovetail to counter the focuser/DSLR? It would have to be held well so it didn't move when the scope moves assuming the mount can take the extra weight?

Just a thought

It is a good thought!

The mount can take up to 15kg for imaging but I wouldn't want to get close to that. I will have to weight it all and see!

[MattJenko]

I have an ED80 as well and bought a longer dovetail so you can balance it easier that way rather than adding extra weights! Balance is only really critical for imaging I feel, and even then, on a mount like the EQ6 and a scope like the ED80, you are significantly under the point where weight issues kick in. Also, there are arguments to be slightly unbalanced so the scope is always pressed against one side of the worm gear so doesn't wobble between gear cogs, but I have not concerned myself with such precision in my imaging and I have the smaller HEQ5.

I reused the original dovetail to put on top to attach the ST80.

[Snaxmuppet]

Ah yes, of course... a longer dovetail. Obvious when you think about it... ! That is probably the better solution.

Yes, I did wonder if it being very slightly off balance might help with imaging but to be honest... I am a beginner. I am not sure how much these little details matter until I learn more and get a bit more skilled (hopefully!).

[Ouroboros]

I've owned two SkyWatcher mounts and neither have had sufficient free movement with the clutches released for me to do anything other than set the balance approximately. Seems to work OK.

When imaging I initially set the balance with camera attached. I then set it slightly unbalanced re. Matt's comment above. I then remove the camera for polar alignment and finding the target before replacing the camera for imaging.

[RichM63]

I'm a bit 'nuts' when it comes to balancing, cone error, and collimation of a Newt, even down to balancing when I only have a DSLR and short zoom on an EQ3.

My ST80 + DSLR sits on a very long dovetail and is no bother to balance due to the increased slide length.

This rig is different from what you are likely to use as the camera is bolted to the dovetail and the single tube ring is left slightly loose to allow the OTA to slide forward and backwards for focusing. Used as a daytime photo rig.

But note the length of the dovetail, 36cm.

[Starlight 1]

I'm going to be completely honest in that I have no idea what cone error is lol.

Matt.

You do cone error by off setting the tube rings.

[jnb]

You could put an extra tube ring on the scope just to carry a small counter weight at the objective end. It would also give you an easy option for tuning the balance as you change setups at the eyepiece end.

[Wobbly Bob]

I did have a little dovetail clamp which weight could be added to, it is clamped to the objective end of the dovetail and slid back and forth to achieve balance, not to sure where I got it from though.

[Steve Ward]

Imaging-wise I recall that you want to be slightly 'east-heavy' so that the mount's RA gears are fully engaged when being driven , perfect balance means the gears could be 'floating' between two teeth and any flop or gentle breeze will result in nasty shaped stars.

[ollypenrice]

Imaging-wise I recall that you want to be slightly 'east-heavy' so that the mount's RA gears are fully engaged when being driven , perfect balance means the gears could be 'floating' between two teeth and any flop or gentle breeze will result in nasty shaped stars.

Perfectly correct but, for visual, a bit of imbalance is neither here nor there. I woudn't dream of rebalancing for a big change in eyepiece mass, for instance, on an EQ6 or whatever.

For imaging, with its nerdy insistence on near perfect guiding, balance does need to be fine tuned, for sure.

Olly

[Ouroboros]

How do you "fine tune" the balance when the mount is not particularly free moving when the clutches released? Or putting it another way, both my mounts have to be way out of balance before they will rotate without being pushed. To overcome the inherent static resistance in the mount I resort to making adjustments in weight and telescope position and then swinging the mount one way and then the other until it comes to a stop in about the same amount of time. In otherwords when it "feels" about right.

[D4N]

Dec you can do by taking the OTA off and balancing the dovetail on a pencil to find the balancing point.

RA you can set your latitude to zero so it will swing more easily.

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