Mounting a Skymax 90mm and ST80 together

[AstroNebulee]

Hi am wondering about mounting both my Skymax 90mm and ST80 together on my AZ5 mount.  I know the best way would be an expensive skytee on my tripod but just thinking is there a way on my AZ5? 

The weight combination with my dslr and heaviest ep would come in under the 5kg of the capacity of the mount as whn everything is on there it's 4.6kg. 

I'm thinking 2 options. Either mounting the Skymax on top of the ST80 or vice versa via tube rings on the Skymax. Or mounting the Skymax on the side of the ST80 via the mounting rings on the ST80 using my silver dovetail clamp bolted to the Skymax dovetail and fitting a dovetail on the ST80 tube rings. 

I am being totally thick as usual I thinking this is feasible? I would have to add some stabilisation weights onto the tripod help centre the loads. It's probably putting to much stress on the whole setup. So don't shoot me for being an idiot 😂. 

Lee 

 

Edited February 18, 2023 by AstroNebulee

[badhex]

Hi Lee, 

It might be pushing the limits of the AZ5 a bit but it's worth having a punt. Best configuration I can think of would be similar to your second picture.

You can buy a short dovetail and bolt it to the top of the ST80 rings, and you'll need to remove the camera mount bolt with the black disc to do so. Then you can clamp your Skymax 90 on to the new dovetail using the saddle that you have in the third picture. 

This is a very rough drawing as viewed from the top:

Ideally you'd want the heavier Skymax 90 on the inside, to bring the COG in, i.e. directly attached to the saddle, but without buying rings for it you have no way of attaching the ST80 in that case.

Worth giving it a try with the kit you already have anyway!

Edited February 19, 2023 by badhex

[AstroNebulee]

7 minutes ago, badhex said:

Hi Lee, 

It might be pushing the limits of the AZ5 a bit but it's worth having a punt. Best configuration I can think of would be similar to your second picture.

You can buy a short dovetail and bolt it to the top of the ST80 rings, and you'll need to remove the camera mount bolt with the black disc to do so. Then you can clamp your Skymax 90 on to the new dovetail using the saddle that you have in the third picture. 

This is a very rough drawing as viewed from the top:

Ideally you'd want the heavier Skymax 90 on the inside, to bring the COG in, i.e. directly attached to the saddle, but without buying rings for it you have no way of attaching the ST80 in that case.

Worth giving it a try with the kit you already have anyway!

Hi 

Thank you, that's a great drawing and something I should of done in the first place but I'm pleased you could fathom the plans in my brain 😂. 

Actually the ST80 (with finder and zoom ep) is heavier than the Skymax by nearly a kilo. 

I had another hairbrained thought this morning. I could attach tube rings to the Skymax. Connect it to the AZ5 with its own dovetail and then mount the ST80 on the tube rings via its dovetail.

Hope my drawing is clear. 

 

Lee

[badhex]

That could also work if your tube rings will fit the 90. I guess the main downside to having the weight on the top vs the side is that your COG will be above the the alt axis centre, so it might make things a bit unstable and you'd have to be very careful with the AZ5 alt clutch (I think it has one?). You also might find eye placement when using the 90 a challenge depending on how you set up the diagonals etc. 

Obviously you have a similar issue with the COG out to the side but at least if the clutch is looser than expected it won't flop over. 

[AstroNebulee]

52 minutes ago, badhex said:

That could also work if your tube rings will fit the 90. I guess the main downside to having the weight on the top vs the side is that your COG will be above the the alt axis centre, so it might make things a bit unstable and you'd have to be very careful with the AZ5 alt clutch (I think it has one?). You also might find eye placement when using the 90 a challenge depending on how you set up the diagonals etc. 

Obviously you have a similar issue with the COG out to the side but at least if the clutch is looser than expected it won't flop over. 

Yep agreed. It seems a better way to do a side by side setup thus avoiding a bigger imbalance when loosening the alt clutch thumbscrew (it does have one 😊) I've contacted flo for their help and suggestions too. I'll use your drawing to supply them if I may? 

Thank you 

 

Lee 

[Peter Drew]

Apart from balance issues, it looks like it would be awkward to use both telescopes if one above the other?

It would depend on your DIY facilities as there is probably no commercial one available, but I think I would make an L bracket such that the upright would fit the AZ  and the horizontal would accept the two telescopes side by side.  With the dovetail positioned vertically, the bracket could be moved up or down to better balance the rig about the horizontal axis.     🙂

[AstroNebulee]

50 minutes ago, Peter Drew said:

Apart from balance issues, it looks like it would be awkward to use both telescopes if one above the other?

It would depend on your DIY facilities as there is probably no commercial one available, but I think I would make an L bracket such that the upright would fit the AZ  and the horizontal would accept the two telescopes side by side.  With the dovetail positioned vertically, the bracket could be moved up or down to better balance the rig about the horizontal axis.     🙂

Great idea Peter. Thank you. Or some how make a T bracket set up? Tho an L bracket to bolt to a vixen dovetail maybe readily available in some shape or form. Edit... Another thought skywatcher do an l bracket, if I turn around and mount a losmandy plate I have laying about, across this and bolt it to the L bracket mount both scopes via the vixen clamps (I'd have to purchase another one) on that as an idea. Though potentially as badhex said that the cog vertically may be out to much. I have seen an issue with my losmandy mounting idea.. A  lash with the alt slo mo control even if I was using the flexible one too. Scrap that idea then haha. Just thinking from way outside the box here where my brain generally lives. 😂

Lee

 

Edited February 19, 2023 by AstroNebulee

[AstroNebulee]

52 minutes ago, AstroNebulee said:

Great idea Peter. Thank you. Or some how make a T bracket set up? Tho an L bracket to bolt to a vixen dovetail maybe readily available in some shape or form. Edit... Another thought skywatcher do an l bracket, if I turn around and mount a losmandy plate I have laying about, across this and bolt it to the L bracket mount both scopes via the vixen clamps (I'd have to purchase another one) on that as an idea. Though potentially as badhex said that the cog vertically may be out to much. I have seen an issue with my losmandy mounting idea.. A  lash with the alt slo mo control even if I was using the flexible one too. Scrap that idea then haha. Just thinking from way outside the box here where my brain generally lives. 😂

Lee

 

Just had a brainwave or a spark of idiocracy. If I mounted my losmandy plate to the ST80 tube rings then the Skymax 90 to the losmandy plate via the silver saddle I have, that could work? Bit more weight tho. 🤔

Lee 

Edited February 19, 2023 by AstroNebulee

[badhex]

You could use the losmandy but it will add quite a lot of weight as you said.

If you have DIY skills all you actually need is a flat bar or plate which you can bolt to the holes at the top of the rings. It would need two holes for that, and a further two holes (ideally tapped) so you can bolt the small saddle you have onto that, then put your Skymax in that saddle. 

Depending on the measurements between the two holes on top of the rings, you could also use something like this photography cheese plate:

Lightweight, fairly inexpensive (about £22) and plenty of holes to choose from. 

[AstroNebulee]

37 minutes ago, badhex said:

You could use the losmandy but it will add quite a lot of weight as you said.

If you have DIY skills all you actually need is a flat bar or plate which you can bolt to the holes at the top of the rings. It would need two holes for that, and a further two holes (ideally tapped) so you can bolt the small saddle you have onto that, then put your Skymax in that saddle. 

Depending on the measurements between the two holes on top of the rings, you could also use something like this photography cheese plate:

Lightweight, fairly inexpensive (about £22) and plenty of holes to choose from. 

Thank you badhex, that's a much better idea. I've looked through all my box of astro bits and thought I had a cheese plate but just to small. Though I have found a piece of stainless steel plate I could drill and tap holes in to attach hopefully. 

Thank you. 

Lee 

[AstroNebulee]

Just an update on this project. 

I fitted a longer rectangular cheeseplate to the ST80 tube rings. Then could attach the silver vixen dovetail clamp to this and then attach my SM90. 

I have encountered an issue when placing my dslr on the SM90 as my finderscope on the ST80 prevents me from having the dslr mounted in the correct fashion (or as my ocd leads to it being upside down or at 90 degree's) the lcd screen on my dslr is movable so not a great issue I guess just my ocd. 

Because the scopes are now well over the cog of the centre of the mount I figured maybe I could fit a 3/8 threaded bar to attach the mount to the tripod (excuse the abundance of nuts on the bar, just didn't want to lose them) and then fit counterweights to the threaded bar to increase stability to the set up. I have 2x1kg from an old Eq2. Mount so doable. 

Before fitting the counterweights the whole set moves really smooth with no signs of straining to the mount. (obviously the images are with the tripod unextended, so maybe more cw needed) 

I have yet to use it as I need to cut the threaded bar to length first and solve the dslr and finderscope clashing issue. I do have a 6x40 ra fs, which I found in my box of astro bits! (didn't know I had this) so could use this instead but I do really like my 9x50raci! 

The whole setup balances nicely on the alt side of things with no issues. 

Further update to follow, hopefully. 

Lee 

 

Edited February 26, 2023 by AstroNebulee

[LaurenceT]

That's quite some engineering Lee. Looks amazing, hope for great success.

[AstroNebulee]

1 hour ago, LaurenceT said:

That's quite some engineering Lee. Looks amazing, hope for great success.

Thank you Laurence. I will see how it goes, I've got to cut the threaded bar first before any serious observing but think it's worth a try and it seems very stable considering. 

Though tonight I just swapped the ST80 and SM90 around on the AZ5 when needed and this was a bit of a faff. 

Lee

[AstroNebulee]

Second to last update hopefully. 

I've fitted the 3/8 inch threaded bar and both counterweights. Those for a treat and add 2kg of weight to steady it. 

Refitted the cheeseplate and dovetail clamp so it's central to the ST80. 

Found a threaded nose piece to use on the dslr t-ring and the dslr misses the 9x50raci fs now. 

When I use the SM90 it will just be for lunar imaging and planetary atm. I can quickly hook up the SM90 onto the ST80 and then take off when not needed. It will save taking off the scopes to swap around too.  I'll probably swap out the 6x30 RA fs on the SM90 for the supplied rdf. 

It's all surprisingly sturdy even when the tripod is fully extended. There is a bit of minor flexing in the tripod itself but nothing to worry as I won't be spinning the setup around so fast. Maybe it's worth looking into some form of spreader plate to help cure the flexing. 

Anyway hopefully will get first light with this dual setup moro if  the forecast is correct. 

 

Lee

Edited March 1, 2023 by AstroNebulee

[AstroNebulee]

Last update to this thread. 

I've had first light tonight withbgthe dual set up and everything performed brilliantly. It was very stable with the legs of the tripod extended. Slo mo knobs were sdmooth and under no strain. 

Imaging with the SM90, I took off my zwo asi120mc-s from my guidescope on my imaging setup to grab some frames of Venus and Jupiter. Had to remember what to do in sharpcap again. 

Then swing around to the moon to take some frames and with the x2 barlow. Then hooked up my dslr to the SM90 and worked great on the moon. 

I took off the SM90 to jyst leave the ST80 on and a quick bit of visual. 

All very good and a worthwhile experiment until the sky tee falls in my lap. 

Lee 

Edited March 2, 2023 by AstroNebulee

[Naughty Neal]

Nice, a neat tidy solution.

[cajen2]

A possible (but not cheap) alternative mount to the Skytee could be a Berlebach Castor II, which has the option of a twin mount. Or even an AZ GTiX, which would give you go-to as well.

[Jasonb]

Excellent bit of work!

Just one small note, I have the AZ5 mount as well, and the manual says that its limit is 5Kg on the "portable" tripod and 9Kg on the "heavy" tripod. So, depending on how you class your tripod, you could be fine up to 9Kg. I think the distinction Sky-Watcher make is portable = aluminium and heavy = steel.

Either way, great engineering and a great solution!

[AstroNebulee]

7 hours ago, cajen2 said:

A possible (but not cheap) alternative mount to the Skytee could be a Berlebach Castor II, which has the option of a twin mount. Or even an AZ GTiX, which would give you go-to as well.

Thank you 😊, I have seen the Berlebach mount and the AzGtiX. The latter did pique my interest. But as astro finds are non existant at the moment I'm going to have to keep to the engineered set up for now until funds allow.

 

7 hours ago, Jasonb said:

Excellent bit of work!

Just one small note, I have the AZ5 mount as well, and the manual says that its limit is 5Kg on the "portable" tripod and 9Kg on the "heavy" tripod. So, depending on how you class your tripod, you could be fine up to 9Kg. I think the distinction Sky-Watcher make is portable = aluminium and heavy = steel.

Either way, great engineering and a great solution!

 Thank you that's very kind of you. 

The total weight of both scopes, finderscooes, dslr and zoom lens comes in just under 5kg. With using the celestron steel tripod and the additional 2kg under the centre of the mount hopefully provides enough stability. The skywatcher 1.75inch steel tripod would be much better for my setup. I think the portable tripod could be the one that comes with the AzGti or called the star adventurer tripod (which I do have). Hopefully I'm somewhere between the two with my celestron tripod. 

Thanks again, great to see other astronomers approve of the set up. It really did work well on first light. 

I will open up the both axis on the AZ5 and regrease it with white lithium grease. 

Lee 

[bosun21]

11 minutes ago, AstroNebulee said:

the manual says that its limit is 5Kg on the "portable" tripod and 9Kg on the "heavy" tripod.

Where did you get the 9kg payload capacity from? The Skywatcher site states that with the 1.75” steel tripod the maximum is 15lbs or 6.8kg.

[Ratlet]

8 minutes ago, bosun21 said:

Where did you get the 9kg payload capacity from? The Skywatcher site states that with the 1.75” steel tripod the maximum is 15lbs or 6.8kg.

It's in the manual believe it or not.  I'm not sure if they scaled it down or not at some point.

[bosun21]

3 hours ago, Ratlet said:

It's in the manual believe it or not.  I'm not sure if they scaled it down or not at some point.

This is from the Skywatcher website 

[Ratlet]

They must have dialled it back a bit.  Makes sense.  My 130pds is on the heavy duty tripod and is a bit wobbly bobbly at high powers and it probably only just gets to 5kg

[Jasonb]

3 hours ago, AstroNebulee said:

Thank you 😊, 

I will open up the both axis on the AZ5 and regrease it with white lithium grease. 

Lee 

Would you be able to document that please, I'd be curious about it! 

Thanks...

[Jasonb]

9 minutes ago, Ratlet said:

They must have dialled it back a bit.  Makes sense.  My 130pds is on the heavy duty tripod and is a bit wobbly bobbly at high powers and it probably only just gets to 5kg

Interesting, I hadn't seen that reduced limit. My 150 Reflector is 6.5Kg, so very close to it.