Problems Counter Balancing the Sky Watcher Star Adventurer

[Astro Buer]

Hi,

I will be the first to admit I'm a complete novice when it comes to equatorial mounts but I am hoping to find the advice I need on here as scouring the net for the last few days has brought me no joy.

I recently bought a Sky Watcher Star Adventurer Mount with the Astro Bundle (equatorial wedge, mounting plate, 1KG counter weight and shaft)

I am primarily going to use this for wide field as this is what the product does best, but one of the reasons I bought the Adventurer is that it is advertised as being able to handle a 5KG payload, and as I also own a Sigma 150-600mm lens I was hoping to be able to mount this and crack at shooting at longer focal lengths. I don't expect the results to be amazing, and I do expect to throw a lot of the subs away! but I still want to give it a try.

My setup entails:

Sony A7R2 - 625g

Sigma 150-600 - 1930g

Manfrotto XPRO Ball Head - 500g

Plus mounting bracket for Star Adventurer 

All in all this weighs in at just over 3kg, so tops 3.5kg with bracket. Still under the 5kg payload...

But I cannot counterbalance the setup with the weight supplied with the Star Adventurer! it is WAY too heavy on the camera side - it just doesn't balance at all... I've even tried removing the screw on the shaft to slide the weight as far down as it can go but still grip, and it's still way off being anywhere near balanced.

It is advertised as being able to balance a 5KG (or 11lb) payload with this weight and shaft setup... as I said I don't expect it to be perfect and I know you should never overload a mount but I thought being 1.5Kg under the threshold would at least give me a chance of being able to balance in sufficiently.

As I said I'm a complete novice so apologies for my naivety if it's a simple fix?! but when you counterbalance a setup you should be able to turn the mount 90 degrees and the equipment sits happily in the equilibrium... correct? but physics says this just isn't going to balance without adding more weight to the shaft, which will surely overload the mount?

Any advice on this would be great.

Thanks,

Nick

[Peter Drew]

The direct solution would appear to be some extra weight or a shaft extension. Probably the latter would be the better option. 

[Davey-T]

I use my Lunt LS60 on mine with a door stop from Screwfix drilled out to slide over the rod.

http://www.screwfix.com/p/dome-weight-door-stop-satin-stainless-steel/44030

Dave

 

[Astro Buer]

Quote

The direct solution would appear to be some extra weight or a shaft extension. Probably the latter would be the better option.  

Thanks, are the threads across the Skywatcher range the same? I have looked into this but haven't found something I am confident is correct. If you have any recommendations that would be great (sorry I'm rubbish!)

Quote

I use my Lunt LS60 on mine with a door stop from Screwfix drilled out to slide over the rod.

Oh my! what a fantastic fix! Thank you! What's the weight of your scope setup? Do you have pretty consistent results?

 

Also, I was wondering, what is an acceptable amount to tighten up the clutch knob? as long as it still rotates, is that OK for the motor still?

Thanks so much

[Davey-T]

Doubt if it's the same as other SW mounts, I drilled the doorstop out to 12mm

The solar setup weighs nearly 6Kg, tracks the Sun OK.

I tighten mine up pretty much as tight as I can with thumb and one finger.

Dave

[Astro Buer]

7 hours ago, Davey-T said:

Doubt if it's the same as other SW mounts, I drilled the doorstop out to 12mm

The solar setup weighs nearly 6Kg, tracks the Sun OK.

I tighten mine up pretty much as tight as I can with thumb and one finger.

Dave

Sorry for my naivety but are you saying that with the clutch knob fully tightened, I.e locked, the tracker will still rotate and track?

i thought this was locking it upright to obtain alignment then loosened for tracking so it will rotate? 

Am am I wrong here as well?!

[Davey-T]

Yes, I look up the polar scope and rotate it so 6 o'clock is at the bottom and lock it to polar align then unlock it and rotate to aim at the target, relock and start imaging.

Dave

[Astro Buer]

4 hours ago, Davey-T said:

Yes, I look up the polar scope and rotate it so 6 o'clock is at the bottom and lock it to polar align then unlock it and rotate to aim at the target, relock and start imaging.

Dave

Thanks Dave. I think this is where my naivety shows. I thought the clutch knob was a lock for everything, and that it should be released to counter balance freely and track.

If I can lock this up, and not even all the way, I can achieve a good balance... (puts hands over face)

Thanks for all you help! 

Nick 

[Axunator]

On 25.8.2017 at 15:42, Astro Buer said:

Thanks Dave. I think this is where my naivety shows. I thought the clutch knob was a lock for everything, and that it should be released to counter balance freely and track.

If I can lock this up, and not even all the way, I can achieve a good balance... (puts hands over face)

Thanks for all you help! 

Nick 

You should still try to balance the mount with the clutch open. Try to do it with the counterweight shaft approximately horizontal - if it's well balanced, the shaft remains horizontal even with clutch open. For tracking the clutch should of course be locked, as Dave said.

In addition, note that you can adjust the balance somewhat also by sliding the dovetail bar of the declination axis-counterweight assembly in the clamp. By having as little overhang as possible on the camera side naturally helps with balancing a heavy setup. Of course, if you slide it too much you cannot see through the polar scope anymore, but if necessary you can manage by polar aligning without the dec/cw assembly and install that after PA (but be careful not to bump the mount out of PA when doing that).

If you can't achieve perfect balance without extra counterweight or shaft extension, I'm sure your mount will not break even if you track with slightly unbalanced 3.5 kg payload, but the tracking accuracy may suffer, as well stability (it will be more prone to vibration etc.).

And one more note of caution, since I saw that you are planning to use a 150-600 lens. 600 mm fl will likely be WAY beyond the tracking capabilites of Star Adventurer, even guided. 200 mm and less are fine even unguided, 300-400 mm with autoguiding. This is not to say SA is a bad tracker, I think it's quite amazing for what it costs and weighs, but it's still a really, really lightweight mount. And very nice also for visual solar/lunar/planetary mount with a small scope (like 4 inch Mak) 

[Astro Buer]

On 27/08/2017 at 18:12, Axunator said:

You should still try to balance the mount with the clutch open. Try to do it with the counterweight shaft approximately horizontal - if it's well balanced, the shaft remains horizontal even with clutch open. For tracking the clutch should of course be locked, as Dave said.

In addition, note that you can adjust the balance somewhat also by sliding the dovetail bar of the declination axis-counterweight assembly in the clamp. By having as little overhang as possible on the camera side naturally helps with balancing a heavy setup. Of course, if you slide it too much you cannot see through the polar scope anymore, but if necessary you can manage by polar aligning without the dec/cw assembly and install that after PA (but be careful not to bump the mount out of PA when doing that).

If you can't achieve perfect balance without extra counterweight or shaft extension, I'm sure your mount will not break even if you track with slightly unbalanced 3.5 kg payload, but the tracking accuracy may suffer, as well stability (it will be more prone to vibration etc.).

And one more note of caution, since I saw that you are planning to use a 150-600 lens. 600 mm fl will likely be WAY beyond the tracking capabilites of Star Adventurer, even guided. 200 mm and less are fine even unguided, 300-400 mm with autoguiding. This is not to say SA is a bad tracker, I think it's quite amazing for what it costs and weighs, but it's still a really, really lightweight mount. And very nice also for visual solar/lunar/planetary mount with a small scope (like 4 inch Mak) 

Thanks for this, Axunator. The problem is with the clutch open, I cannot get anywhere near counterbalanced. Even when sliding down the dovetail bar. I'm 'supposed' to be able the counterbalance 5kg but there is no way the SA with take my 3.5kg setup with the clutch open. Quite frustrating. 

Obviously with the clutch locked up it's solid as a rock when turning 180 degrees but that doesn't help my issue?

I'm fully aware of the limitations of this rig! I know I'll be lucky to get anything useable over 200mm but as I have the long lens, I was hopping have a go at least. 

Thanks for your help ? 

[Axunator]

If that's the case, and you want to use such a heavy setup on a long-term basis, it will be a good idea to get an extra CW. In itself, it's not unheard of that an EQ mount is supplied with less counterweights than what is required to balance maximum or near maximum advertised payload. In fact, it's quite usual, even with premium mounts costing xyz times more than SA...

I would be happy to try to balance SA with a supplied CW and 3-4 kg payload to confirm your observation (just to make sure there's no other potential issues with your gear that might explain this), but I recently sold mine after getting HEQ5 (forget about grab and go with that one!!).

Actually, one potential thing comes to mind: how tall is that Manfrotto ball head that you're using? It may shift the center of gravity of your camera gear too much away from the pivot point, thus aggravating the balance problem by increasing the leverage on the camera side (remember, to achieve a balance, the product of the mass and the distance of c-o-g of that mass from the pivot point should be equal on both sides). Since you have the 1/4-20" screw in the dec shaft, try attaching your lens/camera combo directly to that, omitting the ball head altogether, and see if it helps. You can still aim your lens anywhere you want by adjusting the RA and dec axes.

Even if balance could be achieved, I would use a ball head only with shorter and lighter lenses.

Good luck and clear skies!

[Astro Buer]

On 30/08/2017 at 17:40, Axunator said:

If that's the case, and you want to use such a heavy setup on a long-term basis, it will be a good idea to get an extra CW. In itself, it's not unheard of that an EQ mount is supplied with less counterweights than what is required to balance maximum or near maximum advertised payload. In fact, it's quite usual, even with premium mounts costing xyz times more than SA...

I would be happy to try to balance SA with a supplied CW and 3-4 kg payload to confirm your observation (just to make sure there's no other potential issues with your gear that might explain this), but I recently sold mine after getting HEQ5 (forget about grab and go with that one!!).

Actually, one potential thing comes to mind: how tall is that Manfrotto ball head that you're using? It may shift the center of gravity of your camera gear too much away from the pivot point, thus aggravating the balance problem by increasing the leverage on the camera side (remember, to achieve a balance, the product of the mass and the distance of c-o-g of that mass from the pivot point should be equal on both sides). Since you have the 1/4-20" screw in the dec shaft, try attaching your lens/camera combo directly to that, omitting the ball head altogether, and see if it helps. You can still aim your lens anywhere you want by adjusting the RA and dec axes.

Even if balance could be achieved, I would use a ball head only with shorter and lighter lenses.

Good luck and clear skies!

Thanks so thanks so much for all your advice. I tried this last night (omitting the ball head) but still no luck. I am going to have to add some more weight to the shaft. 

It's worth a go but I think this camera lens combo may just be a little too much for the SA... it's a great little mount that will serve me well with shorter lenses.

Again, thank you all for your help. I really appreciate it! 

[SAW]

On 24/08/2017 at 23:35, Davey-T said:

I use my Lunt LS60 on mine with a door stop from Screwfix drilled out to slide over the rod.

http://www.screwfix.com/p/dome-weight-door-stop-satin-stainless-steel/44030

Dave

 

Hi,

Whats the weight of that door stop ? I'm looking for some extra count weight but don't need another 1kg one that comes with the Star Adventurer.

Thanks.

[Davey-T]

38 minutes ago, SAW said:

Hi,

Whats the weight of that door stop ? I'm looking for some extra count weight but don't need another 1kg one that comes with the Star Adventurer.

Thanks.

Weighs more than a kilo about 1.2 kilo I think.

Dave