Any new EQ8 Reports?

[Starlight 1]

Why did you want the counterbalance closer to the mount? The further away gives more stability as the moment of  inertia increases the farther out from the pivot point, thus decreasing the susceptibility to movement by wind etc. I'm a bit puzzled over that?

Derek

I do not have this mount, I would say with the counter balance closer to the mount will be better when it flips from East to West  Save moving balance for DEC.

[libraryman]

I have my heavy weight (10kg) closer to the head, and a lighter weight lower down to get balance correct, i find this better but i am open to suggestions that this i technically incorrect?

Ray

[Physopto]

Hi ,

 Maybe I'm reading it wrongly but it would appear that some are under the impression that the counterweights should be as close to the pivot point as possible.

This would  require a heavier weight moved further in towards the pivot point to compensate. The loading on the bearings is then greater, as the overall weight increases. The resistance to movement by wind etc., is increased, as the moment of inertia is decreased.  If the counterweight is further out, i.e. use the smallest weight possible to balance, then the loading on the bearings is lessened. At the same time the moment of inertia is increased as it is a function of radius². (For a point mass the moment of inertia is just the mass times the square of perpendicular distance to the rotation axis, I = mr2).

It also depends upon the shape of the weight, may sound stupid but if the weight was made up of balsa wood then it would be huge and form a wind sail. If made of depleted uranium then it would be very small (compact) and not be affected so much by wind.

So smaller weight further out reduces loading on bearings and decreases susceptibility to movement by wind or knocks by wires because of the increased inertial mass.

Regards,

Derek

[trazor]

I have my heavy weight (10kg) closer to the head, and a lighter weight lower down to get balance correct, i find this better but i am open to suggestions that this i technically incorrect?

 

Ray

Yes it is best to get the weights as close to the head as possible, this reduces the Kinetic energy, so reducing inertia,

and possible flexure of the weights bar.

When setting up a scope/scopes on a mount, compactness is King, this also enables better balancing.

[Physopto]

Yes it is best to get the weights as close to the head as possible, this reduces the Kinetic energy, so reducing inertia,

and possible flexure of the weights bar.

When setting up a scope/scopes on a mount, compactness is King, this also enables better balancing.

I see your point but maybe it's half a dozen and six of the other. Kinetic energy is due to movement of  its mass (1/2 mv²). If  the movement is resisted initially  then the kinetic energy is reduced. So back to weights less and further out.

Derek

[Zakalwe]

Yes it is best to get the weights as close to the head as possible, this reduces the Kinetic energy, so reducing inertia,

huh? if it's balanced then it's balanced. I always struggle with this bit though....

and possible flexure of the weights bar.

Have you ever seen an EQ8 CW bar? It's 30mm (or thereabouts) thick. It ain't going to bend with the weights that we are talking about.

When setting up a scope/scopes on a mount, compactness is King, this also enables better balancing.

I don't understand this? As far as balance goes, a 10Kg weight has the same effect as, say, a 5Kg weight at half the distance.

[trazor]

I see your point but maybe it's half a dozen and six of the other. Kinetic energy is due to movement of  its mass (1/2 mv²). If  the movement is resisted initially  then the kinetic energy is reduced. So back to weights less and further out.

Derek

Moving the weights outwards, does not reduce the weight at the pivot point if the scope is in balance.

A 20lb weight at 250mm out, will have the same effect as a 10lb weight at 500mm.

Interesting discussion............

[libraryman]

yes it is interesting, and the EQ 8 bar aint gonna flex too much, however; i find that if i put the heavy weight lowdown, it appears to me that as i rotate the head so that the weights rise, balance is difficult to maintain (not sure what i am trying to explain here) with the lighter weight lower, it just feels better??

Ray

[trazor]

huh? if it's balanced then it's balanced. I always struggle with this bit though....

Having the weights further out will make balancing more difficult

Have you ever seen an EQ8 CW bar? It's 30mm (or thereabouts) thick. It ain't going to bend with the weights that we are talking about.

Accepted, but I was talking in general about all mounts

I don't understand this? As far as balance goes, a 10Kg weight has the same effect as, say, a 5Kg weight at half the distance.

I think you mean the other way around.

But the further out a weight is, the greater the momentum for a given slew speed.

[Physopto]

Yes 10 Kg at 6 inches or 5 KG at 12 inches, same thing. But lower weight better for more even tracking, less bearing wear and less prone to vibrations. (inertial resistance). Just think of it this way 10 x 6 = 60, or 5 x 12 = 60 

On the point of bearing wear; all bearings will Brinell to some extent if---- a) the weight is too great. left in one place for too long with a weight on them.

Brinelling is the metal deformation of the bearing surface due to the ball or roller bearing pressing on  it. Metal bearings are tested to specific Brinell hardness. So, less loading less deformation.

Oh! I feel the need for a whisky coming on

Derek

[trazor]

Yes 10 Kg at 6 inches or 5 KG at 12 inches, same thing. But lower weight better for more even tracking, less bearing wear and less prone to vibrations. (inertial resistance). Just think of it this way 10 x 6 = 60, or 5 x 12 = 60 

On the point of bearing wear; all bearings will Brinell to some extent if---- a) the weight is too great. left in one place for too long with a weight on them.

Brinelling is the metal deformation of the bearing surface due to the ball or roller bearing pressing on  it. Metal bearings are tested to specific Brinell hardness. So, less loading less deformation.

Oh! I feel the need for a whisky coming on

Derek

Yes, but as you said 10kg at 6" is the same as 5kg at 12", thus the same bending moment is at the pivot point/bearings.

[Zakalwe]

huh? if it's balanced then it's balanced. I always struggle with this bit though....

Having the weights further out will make balancing more difficult

Sorry..I still dont get this (Im being thick here) .How exactly is it easier? The only difference that I can see is that a lighter weight will have to move more along the bar to get into balance.

Have you ever seen an EQ8 CW bar? It's 30mm (or thereabouts) thick. It ain't going to bend with the weights that we are talking about.

Accepted, but I was talking in general about all mounts

I don't understand this? As far as balance goes, a 10Kg weight has the same effect as, say, a 5Kg weight at half the distance.

I think you mean the other way around.

Sorry..it was the way that I punctuated that sentence...its not very clear. A 10Kg weight will have the same balancing effect at half the distance of a 5Kg weight. So, if the mount is in balance with a 5Kg weight at X distance from the pivot, then a 10Kg weight will also achieve balance at 1/2 X

But the further out a weight is, the greater the momentum for a given slew speed.

Agreed. But that won't affect the balance. Only the torque required to stop it.

Oh! I feel the need for a whisky coming on

LOL...you and me both. There's a very good reason why i am bad at maths, and talking about moments of force and inertia gives me a headache!

Yes 10 Kg at 6 inches or 5 KG at 12 inches, same thing. But lower weight better for more even tracking, less bearing wear and less prone to vibrations. (inertial resistance). Just think of it this way 10 x 6 = 60, or 5 x 12 = 60 

More weight would make it less prone to vibrations as the increased mass will present a greater inertia which must be overcome.

The Brinelling is a good point, but I guess for the speeds thatwe are talking about it's inconsequential?

[trazor]

Oh! I feel the need for a whisky coming on

Derek

Sending you an E-whiskey now............

[Physopto]

yes it is interesting, and the EQ 8 bar aint gonna flex too much, however; i find that if i put the heavy weight lowdown, it appears to me that as i rotate the head so that the weights rise, balance is difficult to maintain (not sure what i am trying to explain here) with the lighter weight lower, it just feels better??

Ray

Hi Ray,

 I must admit what ever does it for you is best. You are the one with your equipment. When you are happy then you only need to change things if something goes wrong. I was an engineer for a long time, then in physics and doing things by the book were not always the best solutions. I am just pointing out the engineering physics of the problem.  The counterweight bar is substantial and you will not really see flexture in it on an EQ8. But it does exist. What you are describing I think is the effect of centre of balance in different planes. The EQ8 is not really balanced properly because of the motor positions. Maybe that is at the hub of the problem. Your solution is what works for you so stick with it I would say.

Regards,

 Derek

[Physopto]

Sending you an E-whiskey now............

Thanks got the glass out ready.

Derek

[Zakalwe]

Sending you an E-whiskey now............

Can you fax me a £50 note too? :grin:

[libraryman]

Can you fax me a £50 note too? :grin:

Love it:)

[Physopto]

Sorry..I still dont get this (Im being thick here) .How exactly is it easier? The only difference that I can see is that a lighter weight will have to move more along the bar to get into balance.

 No you are not being daft at all. The lighter the weight the further out the weight from the pivot point. This also means that you can be more accurate in placement of the weight for balance. A 10 KG weight out of position by 1mm at say 150mm  or a 5 Kg weight out by 1mm at 300mm . The 5 KG weight will have half the error. In the silly extreme say a 1 KG weight at 1500mm but only 1mm out of position would have only tenth of the error. This is in balance only Inertia error would be proportional to the r² difference.

Anyway what ever happens I'm willing to bet most of you are getting better images than me. I'm still on a long learning curve.

Derek

[trazor]

Can you fax me a £50 note too? :grin:

I'm sorry, I have spent  all my money on weights...............  |

[libraryman]

Hi Ray,

 I must admit what ever does it for you is best. You are the one with your equipment. When you are happy then you only need to change things if something goes wrong. I was an engineer for a long time, then in physics and doing things by the book were not always the best solutions. I am just pointing out the engineering physics of the problem.  The counterweight bar is substantial and you will not really see flexture in it on an EQ8. But it does exist. What you are describing I think is the effect of centre of balance in different planes. The EQ8 is not really balanced properly because of the motor positions. Maybe that is at the hub of the problem. Your solution is what works for you so stick with it I would say.

Regards,

 Derek

Yes Derek, i agree, i think what i am trying to say is that the heavier the weight further down the bar, the harder it is to lift and the faster it appears to fall, even though logically it does not sound right.

but thanks for an interesting debate and a little education...enjoy your tipple!!

Ray

[Physopto]

Ah!!

Methinks I hear a Glenkinchie calling.

Night all.

Derek

[Zakalwe]

Sorry..I still dont get this (Im being thick here) .How exactly is it easier? The only difference that I can see is that a lighter weight will have to move more along the bar to get into balance.

 No you are not being daft at all. The lighter the weight the further out the weight from the pivot point. This also means that you can be more accurate in placement of the weight for balance. A 10 KG weight out of position by 1mm at say 150mm  or a 5 Kg weight out by 1mm at 300mm .

Aha...I see what you mean now.

Having said that, I find it difficult to get the EQ8 to balance correctly. No matter how loose the clutches are, the mount doesn't really move that much. I don't think that it particularly cares about being in perfect balance to be honest. After all, it's rated at 50Kg, so a few grams here or there won't be noticed!

Yes Derek, i agree, i think what i am trying to say is that the heavier the weight further down the bar, the harder it is to lift and the faster it appears to fall, even though logically it does not sound right.

but thanks for an interesting debate and a little education...enjoy your tipple!!

Ray

Libraryman to the red phone. Galileo is on Line 1 for you.....

[Sp@ce_d]

Blimey, little did I realise my last throwaway sentence would cause such debate 

Very interesting. The only reason I got into the habit of doing this is because ...

a) I picked it up along the way when I was learning (still am) as the way to do it...

  and....

because it's a good way to jam the first weight up against the top of the bar to stop it moving on the EQ6 & 5.

The bar is different on the EQ8, screws in & very substantial. However, on the 6 & 5 it slides in & out & is only locked into place by a single thread. So it pivots. With a heavy load & the weights are lower down there's a danger of a "clunk" at some point!

Besides, I need the extra weight anyway as I have an ADM triple bar that I'm going to have another go at getting balanced with both Esprits & the C925 or something similar for long FL work.

As an aside, one thing I will say about guiding. I've found now I'm using ACP it guides so much better than just using Maxim on it's own, as I did before. I know ACP uses Maxim but it seems to smooth it out. The other thing I stopped using with the EQ8 is PEC in EqMod, It seems to be better with out it! Whereas the EQ6 was definitely better with it.

Slange Derek

Enjoy it....  Glenkinchie is just down the road

[Zakalwe]

because it's a good way to jam the first weight up against the top of the bar to stop it moving on the EQ6 & 5.

The bar is different on the EQ8, screws in & very substantial. However, on the 6 & 5 it slides in & out & is only locked into place by a single thread. So it pivots. With a heavy load & the weights are lower down there's a danger of a "clunk" at some point!

The EQ6 CW bar is a rubbish design. No matter how tight I clamped mine it would wobble like a Saturday night drunk on his way home. It's even worse with the added extension bar.....that was ridiculous.

The EQ8 is a quantum leap forward....it's rock solid by design.

Regarding PEC, I had the same experience. It is probably down to user-error on my part (again!  ) but I get better results with PEC disabled too. Now if we could only get some clear skies I could have another play with recording PEC, but I am getting good enough results at 700mm to not worry about it.

[dazza1639]

All good stuff, but back on topic how are you all getting on with the EQ8? What's good? What's bad? What would you change? Are these show stoppers, niggles or just require minor tweaks? What is the issue with the early problems have the gone / been resolved? The EQ8 looks like a perfect fit for me so I'm curious about how people get on with it, you only seem to hear about the problems, but I'm sure that 99% of users must have a great experience otherwise there would be a lot more debate. It would be nice to hear the positives, this would help people on the upgrade path make an informed balanced choice. I have been researching mounts for a couple of months now and if I was to goby the reports on the forums I wouldn't bother with astro imaging mounts at all because most of the posts are about problems. It's a difficult decision I'm just after some balance, I can understand the reluctance of posting positive info when sometimes the thread turns into a "why did you buy that you're just trying to justify your purchase" type thread. No judgement I just want to hear some of the positives!

Thanks

Darren

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