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Old 26-04-2010, 08:25 PM
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pvelez (Pete)
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Balancing - aaarrrggghhh!!!

Is it just me, or is it really, really difficult to balance a scope?

My trusty LXD-75 has served me well. Its an 8 inch schmidt -newt and sits very happily on my EQ6.

Not content with my trusty Canon, I picked up a SBIG ST-8300M. A ripper of a camera - but its heavy.

So to my problem, I can't get everything balanced so I can access all parts of the sky. Looking at my graph in PHD, on some occasions I find the Dec wandering off, despite the best efforts of the software.

The boys at Bintel suggested I rotate the camera so it is facing the counterweight - I have a short tube 80mm guidescope mounted on the outside of the OTA. This should balance the camera - he thinks hopefully.

So I find that the scope can be balanced well so I can access the eastern sky and the zenith now seems to work ok. Also, it seems to balance well to the north. But the west and south west - forget it! The scope seems to always want to rotate towards the north.

I am sure I can balance it to suit that part of the sky - which means I need to rebalance if I want to access anywhere else.

Is this normal?

I fear I amy need to go to a side by side arrangement - though I've been warned that is another nasty alternative as it requires 3 axes rather than 2.

So is it just me?

Pete
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  #2  
Old 26-04-2010, 08:50 PM
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peter_4059 (Peter)
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Pete,

I've got a starstuff SBS setup and find it quite easy to balance if that helps!

Peter
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Old 03-05-2010, 07:22 AM
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For we newbies who also have balance problems, what is a 'Starstuff SBS setup'?
Thanks
Mel
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Old 03-05-2010, 10:57 AM
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bmitchell82 (Brendan)
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if you are running your equipment in a piggy back configuration ( scopes all stacked ontop of each other) this is the easiest BY FAR setup and yields the best balance system.

SBS is a Side by Side bar, this can be hard for most people as you have to think about whats happening and be very good at understanding what it is your seeing. From my understanding a SBS bar is to reduce the leaver arm. but then it spreads the weight over a large axis and you have to offset the weight anyhow....

I had a issue recently with my 10" i had to rotate the OTA so that the camera/finderguider balanced each other off and pointed them when in the Park position to the ground. this instantly made my balance work.

So my thoughts without seeing what you have actually got.

1. Make sure everything is laying in the axis of the mount and not hanging off the side.

2. you run in a piggy back arrangement.

just for a idea.
if the mount swings to a direction the largest weight will pull to the bottom via gravity (larger mass will pull more). so adjust or move the weight towards where its pointing aka, if it swings to point straight up and down, move the OTA up. retest keep going till it doesn't move
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Old 03-05-2010, 11:51 AM
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peter_4059 (Peter)
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Quote:
Originally Posted by MelD View Post
For we newbies who also have balance problems, what is a 'Starstuff SBS setup'?
Thanks
Mel


Mel,
this is it...

http://www.starstuff.com.au/eqsbskits.html

It allows independent movement of each scope in x and y axis making balancing quite simple no matter what is hanging off the scope.

Mounting the guide scope beside the imaging scope keeps the weight closer to the axis of the mount however this bar is quite heavy so an additional counterweight will probably be required.

If the guide scope is mounted on top of the imaging scope the centre of gravity moves further from the axis of the mount so you will probably need additional counterweight in any case.

Peter
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Old 03-05-2010, 12:07 PM
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madwayne (Wayne)
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For Mel's benefit, here's one I prepared earlier .

My EQ6 with telescope control centre (USB hub, imaging scope focus controller and dew controller), ED80 and Tak FSQ106N mounted side by side with CCD cameras and even my old 20D on top of the FSQ.

It works for me the whole side by side setup but it really is horses for courses and at the end of the day it is what you think will work best for you.

Wayne
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Old 03-05-2010, 12:43 PM
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Hi Pete.
If you are finding the the camera end of the SCT is too heavy to achieve Dec balance then you might want to consider a counterweight to go under the nose of the SCT. https://www.bintelshop.com.au/Product.aspx?ID=7588

As you would have a vixen style dovetail already under your scope you would only need the counterweight and saddle. Though having an extra dovetail is always handy
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Old 05-05-2010, 12:19 PM
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Quote:
Originally Posted by bmitchell82 View Post
if you are running your equipment in a piggy back configuration ( scopes all stacked ontop of each other) this is the easiest BY FAR setup and yields the best balance system.

SBS is a Side by Side bar, this can be hard for most people as you have to think about whats happening and be very good at understanding what it is your seeing. From my understanding a SBS bar is to reduce the leaver arm. but then it spreads the weight over a large axis and you have to offset the weight anyhow....

I had a issue recently with my 10" i had to rotate the OTA so that the camera/finderguider balanced each other off and pointed them when in the Park position to the ground. this instantly made my balance work.

So my thoughts without seeing what you have actually got.

1. Make sure everything is laying in the axis of the mount and not hanging off the side.

2. you run in a piggy back arrangement.

just for a idea.
if the mount swings to a direction the largest weight will pull to the bottom via gravity (larger mass will pull more). so adjust or move the weight towards where its pointing aka, if it swings to point straight up and down, move the OTA up. retest keep going till it doesn't move
Thanks for the tips - been out of action for a few days with work.

Glad you mention switching the focus arrangement. I now have the focuser and camera facing down towards the ground with the guidescope sitting on the opposite side which has made a difference.

What has me puzzled is that if I balance when the scope is parked ie pointing at the SCP, all is fine to the south and east close to the horizon. However, when I am pointing from the zenith to the west, it all goes haywire - judging by my graph function in PHD.

My guidescope sits mid way between front and rear of the scope while the imager is at the back. Perhaps if I shift it forwards so there is more weight directly opposite the camera on the OTA, there is less prospect of it all swinging around?

I find that the scope wants to pull the camera around towards the ground, even if well balanced when positioned on the mount ie I have slid the OTA sufficiently back to ensure that the primary and front of the scope are balanced.

Perhaps I should take some photos and post them - its hard to explain.

Pete
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Old 05-05-2010, 12:25 PM
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Quote:
Originally Posted by [1ponders] View Post
Hi Pete.
If you are finding the the camera end of the SCT is too heavy to achieve Dec balance then you might want to consider a counterweight to go under the nose of the SCT. https://www.bintelshop.com.au/Product.aspx?ID=7588

As you would have a vixen style dovetail already under your scope you would only need the counterweight and saddle. Though having an extra dovetail is always handy
Thanks for the thought Paul. My scope is a schmidt newt so it has the focuser/camera in the same place as a newt rather than at the back like a SCT.

But I think you are right about getting the weight-distribution right. I'm now thinking of adding weight on top of the scope directly opposite the camera.

So if the primary end of the scope is A and the secondary/focuser end B and the focuser is 1 and the guidescope side 2, I suspect I need to add weight to position B2 which I can achieve by slipping the guidescope up. That said, when the scope swings oddly, I feel I should add weight to the A2 end. It may well be that the weight distribution will change depending on where in the sky I am pointing.

I expect SCT people don't confron this issue.

Or perhaps I am trying to talk myself into a new OTA!

Pete
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Old 05-05-2010, 02:01 PM
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I always offset my weight balance and i generally set it for a area of the sky and that area being from East to aproximately Zenith as i cant be bothered doing maridian flips .

Also when i balance, i release both RA and Dec clutches and swing it all around when i find a sticky point i make a small adjustment. I have also found that balancing a EQ6 perfectly is bad joo joos because of the backlash they have using the offset like I mentioned above loads up the motors. and when guiding you dont get the backlash/bounce happening.
In saying that my dec has always acted a bit funky, but i get round stars with the finderguider! happy days!

I should make a note that i don't balance my scope in the park position, i never image there well... i don't image directly at the SCP so why would you balance there?

my routine is, PUT EVERYTHING ON THAT YOU WILL USE FOR THE NIGHT BEFORE YOU START :d i have not heeded my own advice and had to pull down because my guiding wouldn't work... note to self.!

1. lay the scope over so the counterweight bar and telescope are laying horizontally.
-while its like this you can slide the counter weights around untill your balanced with a slight bias to the counterweights side (trying to lift the scope back to the park position)

2. once thats licked put the scope back into the horizontal position, release the RA clutch, this gives you the backwards forwards adjustment. if you find you run out of adjustment undo the rings and slide the OTA forwards or backwards what ever is needed. then repeat the process untill you have a slight bias wanting to drag the front of the scope to point to zenith.
Flip it so that the counterweight is on the other side, and see if your balance is still the same, if its not youll have to center the OTA accessories better so rotate the tube around then repeat the process untill everything is honky doory.

3. once both of these axis's have been balanced you should be able to release both Dec and RA clutches flip it anywhere and it has that slight pull you introduced in the bias but otherwise happy!

Keep up the questions.

Brendan
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Old 05-05-2010, 02:27 PM
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Quote:
Originally Posted by [1ponders] View Post
Hi Pete.
If you are finding the the camera end of the SCT is too heavy to achieve Dec balance then you might want to consider a counterweight to go under the nose of the SCT. https://www.bintelshop.com.au/Product.aspx?ID=7588

As you would have a vixen style dovetail already under your scope you would only need the counterweight and saddle. Though having an extra dovetail is always handy
Is that a Vixen dovetail? It doesn't say and I suspect it might be a Losmandy.
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Old 05-05-2010, 03:41 PM
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LOL Sorry Pete, sometimes i read too fast for my own good.


You can get them for both the Vixen and the Losmandy dovetails Andrew. Produced by Losmandy of course
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Old 05-05-2010, 04:10 PM
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Quote:
Originally Posted by bmitchell82 View Post
I always offset my weight balance and i generally set it for a area of the sky and that area being from East to aproximately Zenith as i cant be bothered doing maridian flips .

Also when i balance, i release both RA and Dec clutches and swing it all around when i find a sticky point i make a small adjustment. I have also found that balancing a EQ6 perfectly is bad joo joos because of the backlash they have using the offset like I mentioned above loads up the motors. and when guiding you dont get the backlash/bounce happening.
In saying that my dec has always acted a bit funky, but i get round stars with the finderguider! happy days!

I should make a note that i don't balance my scope in the park position, i never image there well... i don't image directly at the SCP so why would you balance there?

my routine is, PUT EVERYTHING ON THAT YOU WILL USE FOR THE NIGHT BEFORE YOU START :d i have not heeded my own advice and had to pull down because my guiding wouldn't work... note to self.!

1. lay the scope over so the counterweight bar and telescope are laying horizontally.
-while its like this you can slide the counter weights around untill your balanced with a slight bias to the counterweights side (trying to lift the scope back to the park position)

2. once thats licked put the scope back into the horizontal position, release the RA clutch, this gives you the backwards forwards adjustment. if you find you run out of adjustment undo the rings and slide the OTA forwards or backwards what ever is needed. then repeat the process untill you have a slight bias wanting to drag the front of the scope to point to zenith.
Flip it so that the counterweight is on the other side, and see if your balance is still the same, if its not youll have to center the OTA accessories better so rotate the tube around then repeat the process untill everything is honky doory.

3. once both of these axis's have been balanced you should be able to release both Dec and RA clutches flip it anywhere and it has that slight pull you introduced in the bias but otherwise happy!

Keep up the questions.

Brendan
Cheers Mr B - will have another go tonight.

Its cool and clear (at the moment) so I will dash home and experiment

Pete
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Old 12-07-2010, 01:13 AM
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balancing a fork mount?

hi,
would you'll have any tips on balancing a fork mount?
I've built a fork mount for an F6 Newt, which I guess is unconventional, but then it was easier to build than a GEM and I can't get an EQ6.

I read that for forks, you first point the scope at zenith so it is not top heavy or bottom heavy, then point it horizontally and balance it.

these two steps are fine in my setup, but issue is when the scope is not parallel to the RA axis, and the fork arms are around 45 deg from the ground. it tends to swing back to parallel to ground. does this mean I'll need another set of counterweights for this angle on either side of the scope to acheive proper dynamic balance?
I'm just trying to balance it with an slr at the focusser and no other equipment. have got weights near the secondary on the other side of the focusserl
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