Heq5 pro tripod question

[Thalestris24]

Hi all

Does anyone by any chance know what the minimum cut down heq5 tripod height / leg length is that will maintain stability (with a 150pds)? For example, the current actual leg length is ~800mm so, if I reduced that to, say, 600mm - would that still be ok (for imaging)? The reason I'm asking is that I'm currently using the mount on a 550mm Orion Optics pedestal and I have suspicions that it isn't as stable as I'd like it to be especially when the scope is pointing to higher altitudes.

Thanks for any input

Louise

[Tinker1947]

I don't think there's a minimum height other than stopping the primary end scrapping the ground, stability will be what the legs stand on, and surrounding area, if you move does the scope move due to ground movement, you could stack sand bags against the legs to keep them stable or cement them in the ground so there's no cutting down just dig a hole the right size and fill it with cement (i would use pea shingle) that will make it stable....

[Thalestris24]

I don't think there's a minimum height other than stopping the primary end scrapping the ground, stability will be what the legs stand on, and surrounding area, if you move does the scope move due to ground movement, you could stack sand bags against the legs to keep them stable or cement them in the ground so there's no cutting down just dig a hole the right size and fill it with cement (i would use pea shingle) that will make it stable....

I've always assumed that the further the legs are splayed out, i.e. the bigger the footprint, the more stable the mount will be. I guess I'll just have to try it. I can get better guiding on the AVX/tripod than I can on the heq5/pedestal but don't know why. Guiding on the heq5 gets erratic as the scope points higher. I'm talking about 30 deg alt. so not very high before it goes off. I figure it's something to do with the centre of mass changing but I could be wrong. It was doing it before I did the Rowan belt mod and nothing's changed after the mod. If the tripod legs were only 600mm the distance between them would be less than the distance between the feet of the pedestal are so I might still have a problem... I've put 10kg weights over the pedestal feet but they don't seem to make any difference so I'm not sure what's best to do.

Thanks

Louise

[Carina Lass]

The tripod feet are about a metre (guessing here hypothetical) spread from centre.

The balance point of ota/mount is probably 250 mm forward of centre

As the legs get shorter the weight on the back legs gets less.

I'd suggest putting a scale under each leg in turn and balancing the mount at the base.

This would stop those xhanges.

[Thalestris24]

The tripod feet are about a metre (guessing here hypothetical) spread from centre.

The balance point of ota/mount is probably 250 mm forward of centre

As the legs get shorter the weight on the back legs gets less.

I'd suggest putting a scale under each leg in turn and balancing the mount at the base.

This would stop those xhanges.

Hi

Sorry - I don't really understand....

Louise

[Carina Lass]

Do you have a bathroom scale?

If you do, put the rig together with the bathroom scale under one foot (levelled to compensate for the odd angle the scale produces)

Then do the same for the other two feet.

You'll find the weight is different for the front leg than the back two legs.

If you then shorten the legs, you'll find more weight transfers to the front leg - as the rig normally has its centre of mass forward of the boss in the foot of the mount.

Taken in extremis to a point where if the legs were any shorter, the rig may pitch forward.

So the balance for the rig can be quite important if the ground is soft or spongy as the weight transfers from one foot to the other.

[Thalestris24]

Hi

Ah, I see what you mean now I have my heq5/150pds on a pedestal at the moment. It's a 550mm one and I've had a suspicion that it might be flexing somehow but I'm not sure. So I came up with the idea of reinstating the original tripod but with legs shortened such that the mount would be at a similar height to the pedestal. The tripods have two front legs and one back leg in the northern hemisphere . However, I image to the East anyway. My heq5 has a belt mod and is perfectly balanced i.e. with clutches loose I can point the scope in any direction and it stays there. Yet guiding becomes erratic at 30 deg alt and it gets worse at higher values. That's led me to think that maybe something e.g. the pedestal is flexing to cause the problem. It also doesn't seem to hold PA very well even though it's permanently set up. I also have an AVX + 130pds on a tripod and that guides fine with the same finder guider. It could be a problem with the heq5 though I've adjusted the worm gears. The poor weather and atmosphere don't let me have many opportunities to test things... Sigh.

Louise

[Carina Lass]

The overall centre of mass is forward of the mount boss even when ra and dec are balanced.

That is where the problem arises.

[Thalestris24]

The overall centre of mass is forward of the mount boss even when ra and dec are balanced.

That is where the problem arises.

Hmm... I think I'll put the 130pds on the heq5/pedestal next session and see how it behaves. It's lighter and will only need one counterweight. Should tell me something!

Cheers

Louise

[MattJenko]

Hi Louise. Not sure what you mean about the northern hemisphere setup. I am in Essex and I always have my HEQ5 tripod setup with a single leg north pointing and the other two SE and SW. I always have the legs as short as possible, and only extend a leg or two to give a bit of levelling, so basically as low down as possible. I use an ED80 through, not a newt, but unsure if that would make a difference. It is not great when pointing up, but I am talking up here, ie almost straight up. Zenith up. Everywhere else seems ok.

[jambouk]

My tripod allows me to move the pin which the azimuth adjusters push against, so i can either chose to have one leg pointing north and two southerly, or two northerly legs and one pointing due south.

[jambouk]

Like this.

[Thalestris24]

Hi Louise. Not sure what you mean about the northern hemisphere setup. I am in Essex and I always have my HEQ5 tripod setup with a single leg north pointing and the other two SE and SW. I always have the legs as short as possible, and only extend a leg or two to give a bit of levelling, so basically as low down as possible. I use an ED80 through, not a newt, but unsure if that would make a difference. It is not great when pointing up, but I am talking up here, ie almost straight up. Zenith up. Everywhere else seems ok.

Yes - you're quite correct - my mistake!! I just went by my AVX which has two legs pointed north and assumed the heq5 was the same. Having just checked my folded away heq5 tripod, I can confirm my error!

As I mentioned before I was thinking about shortening the tripod legs to about 600mm so it would then be about the same height as the pedestal. However, I'll try the 130pds on it first and see what the guiding is like.

Cheers

Louise

[Carina Lass]

I would have the pin towards the single leg

[Thalestris24]

Like this.

Lucky you, James! Can't do that on the heq5 but it's not a problem, as far as I know.

Louise

[jambouk]

I do do

[Tinker1947]

There are 2 reasons for the North pointing leg, you can attach the weights and it won't fall over, then attach the scope, there is room between the legs to sit and get to look through the polar scope, i would have thought this applied to all mounts/ tripods not just the Skywatcher range....

[Thalestris24]

There are 2 reasons for the North pointing leg, you can attach the weights and it won't fall over, then attach the scope, there is room between the legs to sit and get to look through the polar scope, i would have thought this applied to all mounts/ tripods not just the Skywatcher range....

I think it's a bit academic, Tinker! FWIW, my AVX azimuth peg can optionally be put in the opposite position but, as it was delivered, the north-facing side has two legs and it's quite stable Similarly, the pedestal mount has two legs facing north.

Louise

[Tinker1947]

Just a thought on why they put the peg in the wrong hole are they assembled in the souther hemisphere where the legs would be opposite....( or would they)

[Thalestris24]

I don't think there is a right or wrong peg hole really - where there's a choice, it's surely a matter of personal preference? With the AVX (which is a different design to the heq5), having one leg pointing south doesn't stop use of the polarscope (though I don't have one on the AVX and have never used one on either mount anyway).

Louise

[Thalestris24]

Managed a quick test with the 130pds/1100d on the heq5 but still same problem with the guiding. I'm wondering if it's something mechanical with the heq5... I'll re-check all the adjustments tomorrow just in case...

Louise

[Carina Lass]

same peg hole in southern hemisphere too.

It's not a sundial!