Mounts and Payloads - EQ5

[darrellx]

Hi all

I actually have no problem at the moment, but I have a few questions just for clarification on mounts. Specifically Payloads.

I have an EQ5 GoTo, and depending on which site I go to, and which manual I read, the payload is reported as either 10kgs or 9kgs.

I also have a skywatcher 8inch reflector. The manual reports the "tube weight" as 7.98kgs This works with two counterweights that each weigh 5.1kgs.

So if I do the sums, the total weight is just over 18kgs (excluding the dovetail, rings, and eyepiece).

The whole system works well. It seems stable enough - except in windy weather. The tracking is okay, but not brilliant. This is probably more of a reflection on me and my alignment than the mount.

Am I misinterpreting some of the terms like "mount payload" or "tube weight"? How can my EQ5 (with a limit of 10kgs), carry over 18kgs? When reference is made to "tube weight" is that just the OTA?

I am at the point of considering a "bigger and better" mount - maybe the EQ6Pro. I want to make sure I get all the sums right.

Thanks
Darrell

[matt]

Hi Darrell.

I may be wrong but I think in this case the payload limit is given AFTER the weights have been added to the mount.

So, once the mount is fully set up with weights attached, you still have about 9 or 20kgs room to move.

I used to have exactly the same setup you describe and it all performed very nicely.

[dannat]

I agree, I think the payload weight is usually the tube not including the balancing counterweights

[BC]

Hi,

It is very tricky working out what the story really is. I have just bought the EQ6 Pro (which incidentally appears to have gone back down to $1,495 at http://www.telescopeshop.com.au/Telescope_mounts_and_tripods/Skywatcher_Go_To_Mounts/#35087 ). After reading about the EQ6 and it’s payload for the last 3 years since buying my 10” dob, I am very surprised to see only 2 x 6mm bolts which supposedly hang onto the potential 25kg payload. While the mount looks fantastic, I can’t see how to safely attach any weight to it. Perhaps top grade high tensile bolts will be fine. I’m sure other’s expertise on this forum will allay both my concerns and your wonderings. :shrug:

Bruce

[xelasnave]

If not doing photos dont worry too much... and then it is what works for you not what the manufacturer claims will work...but the eq5 is a great mount for the money I would not be rushing out just yet to improve if not into photos...when into photos no mount is big enough for die hards... I have seen 80mm on a paramount...that is like having a ten ton truck to move one ton of sand ... you gaurantee a smooth ride.

alex
alex

[tempestwizz]

I have noted on my recently acquired EQ6 pro that the head with the dovetail section and two knobs, is held into/onto the mount by three relatively small grubscrews. The part that inserts into the top of the Dec section has a taper, and these screws bite ino the taper. They are also all that prevents dec (rotational) slippage should the load be too unbalanced.

Apparently its supposed to work, but I personally will pay considerable attention to balance in any setup.

I propose to employ a 10" F5 newtonian (my Sutchting Dob mirror mounted in a lightweight frame) and SBIG camera setup. These weigh in at around 20 Kg without counterweights.

I am having an alternate head made up by Luke Bellani and do not intend to rely on the original dovetail attachment methodology, but I will still be stuck with the three grubscrews.

BC

[g__day]

I always thought the maximum weight was how much counterbalance you could have - so its approximately half of the total.

On my Vixen Atlux I removed the standard head and put a Losmandy TAK head on to give better grip - and on my C9.25 - the CG5 dovetail was the first to go - the 4" wide, 1/2 inch thick Losmandy C9.25 dovetail make the original look like a joke - which it is!

[rally]

This discussion has been had a few times !

I think you will find that a mount is rated for a given payload based on all the standard supplied counterweights being in use.
It is for mine !

Some manufaturers specifically state both the "Payload" and "Total capacity" separately (which spells this out quite clearly), most only state Payload and dont specifically state what defines the real Payload.

If you add more counterweight to the original OEM weights you are actually decreasing (not increasing) the usable payload in terms of scopes - as far as the manufacturers safe ratings are concerned.
These are based on bearing loads, gear contact surface pressures, motor torque loadings etc

If you can remove a certain amount of counter weight then you can add extra payload.

Most mechanical equipment is designed with some certain amount of safety margin built in, some isn't designed its just built !
That doesnt mean the ratings can necessarily be ignored.

Now I realise that this is not what everyone is doing - generally if more scope weight ends up on top then the common thing to do is to add more weight at the bottom and people have done this for a long time and assume its OK.
Its only OK till you wear out your mount prematurely (bearings, shafts bushes and gears) or things get overloaded - motors stall or burn out or otherwise compromise the tracking ability of the mount.
The truth is its not OK but we all overload our 6x4 trailers too - dont we !

If there is any argument, I suggest a letter of request should be sent to the manufacturer to clarify what is Payload and what is the Total Capacity including counter weights.

The exception to this is some of the new robotic mounts with harmonic drive motors where there are no counterweights. In these the actual torque load of your payload is more important than the simple mass of your Payload. eg - two payloads of the same mass - say a refractor and a large diameter mirror - the large mirror being over the rated capacity of the mount whereas the refractor will be OK simply due to torque loading as the mirrors centre of mass is much further away from the axiis of rotation. (its slightly more complicated than this - but its close)

Cheers
Rally