EQ6-R Pro + Evostar 80ED balancing issue

[badhex]

Hello all,

Have finally got around to setting up my EQ6-R with my 80ED and found that I can only just balance it on the DEC axis with focus wound all the way in, no finder and no EP (2" diagonal only) - I simply can't move the scope far enough forward in the saddle/tube rings.
Below you can see why - the tube rings are as far back as possible before hitting the focuser bolts, and the saddle is so meaty that the (vixen) dovetail is as far forward as possible before hitting the tube ring bolts.

Part of the problem is that the tube ring bolts are not recessed into the dovetail (though it looks like the new 80ED green dovetail does) and the Vixen-compatible bit of the saddle is at the bottom of the saddle and so has no clearance unlike the Losmandy part (see second picture).

I'd like to avoid any ankle/strap on weights on the tube or similar solution, so I'm guessing the best option will be some sort of replacement parts/modification of the tube rings/dovetail (e.g. perhaps this losmandy dovetail) but wanted to check in here first for advice and recommendations, as always.

I am sure I can't be the only person to have run into this issue!

TIA
Joe

[KP82]

The protruding bolts beneath the dovetail bar are anti-sliding safety measures.

Your best bet is get a longer dovetail bar.

[Laurieast]

Had this on my AVX, removed the two lower safety bolts in the dovtail, they are not threaded into the rings. Slide the bar up the mount as far as the you can go whilst still getting grip on the lower securing bolt. 

Balanced now with a DSLR on the back, electric focuser motor, and the heavy 9x50 finder.

Also, ordered a longer bar.

 

Edited April 19, 2021 by Laurieast

[Laurieast]

Also put a photo thread bolt into one of the dovetail threaded holes from underneath, which on the AVX mount  conveniently fits into a recess in the head in just the right place, so that is now the added safety. I don't know if there is similar on an EQ mount.

[badhex]

6 hours ago, KP82 said:

The protruding bolts beneath the dovetail bar are anti-sliding safety measures.

Blimey, I hadn't noticed that they were just safety bolts! I had this on a much smaller mount before which ironically wouldn't balance on the RA axis, so never had much need to closely examine the tube ring assembly.

Need to have a look tomorrow but assuming it's a single bolt attaching the ring to the dovetail, I might even be able to move the back ring forward to the next hole, hopefully meaning I can move the scope far enough forward to balance. Thanks! 

5 hours ago, Laurieast said:

Had this on my AVX, removed the two lower safety bolts in the dovtail, they are not threaded into the rings. Slide the bar up the mount as far as the you can go whilst still getting grip on the lower securing bolt. 

Balanced now with a DSLR on the back, electric focuser motor, and the heavy 9x50 finder.

Also, ordered a longer bar.

Great, thanks. Presumably the longer bar just means the objective-end tube ring is further forward/closer to the objective - does this help shift the center of balance substantially forward? 

[Laurieast]

9 hours ago, badhex said:

Great, thanks. Presumably the longer bar just means the objective-end tube ring is further forward/closer to the objective - does this help shift the center of balance substantially forward? 

Remove the safety bolts, and you can now slide the dovetail bar forward.

[badhex]

Thanks! I've moved the back ring up a touch which allows me to slide the scope forward an inch or so, and will remove the safety bolts as well if it still won't balance. Will check it later in the week when I get chance.

Thanks so much everyone for the advice - can't believe I hadn't noticed that they were just safeties! 🙄😂

Joe

 

[badhex]

Got everything set up this weekend to test balancing again (although no clear skies, naturally) and I'm able to balance it for the most part; the original problem is solved but I now have a couple of new ones! 

First issue is that I usually balanced my old mount with whatever EP I think I'm going to use most, and rack out to approx focus, but also quickly check my heaviest and lightest EPs for reference. Currently, the difference between the two is at least 500g so it's pretty much not possible to balance it for both so I'm not sure what the best thing to do is. 

Second issue is that I managed to balance it pretty well without the finder (SW 50mm straight-through supplied with the 80ED) first of all, then added it afterward and made a few adjustments. I could get it to broadly balance whilst the scope was horizontal, but after turning it maybe 60° *in either direction* it would want to flip completely and come to rest upside down, i.e. finder on the lower side. I assume this is because the finder alters the centre of mass/gravity (not sure which is correct here) upwards and makes it top heavy but I'm not sure why I didn't experience this on my old mount, nor what the best approach to fix it is!I

'm going to do some digging on balancing tutorials but any suggestions appreciated. 

 

Thanks 

Joe 

[KP82]

Could it be that the DEC axis in your old mount was a bit stiff? Maybe that's why the slight imbalance was not detected.

When imaging I always rack out the focuser to the same position where it achieves the focus after attaching the camera and guiding setup first, then double check the balance in both RA and DEC. I actually mark the position on the counterweight bar and dovetail bar to save time. I even take a few pictures of the whole setup as a reference when it's fully balanced in case the marks get rubbed off.

For visual precise balance isn't crucial, so I normally just use my most used eyepiece (ES68 20mm) for reference. Fortunately the majority of my eyepieces (except for ES68 34mm) weigh about the same and I only need to move the focuser a couple of mm to achieve focus with different ones.

[badhex]

1 hour ago, KP82 said:

Could it be that the DEC axis in your old mount was a bit stiff?

Yeah, this is my assumption. I also didn't have the Panoptic 41mm then, and wouldn't have attempted balancing even if I did as it was already undermounted. 

1 hour ago, KP82 said:

I actually mark the position on the counterweight bar and dovetail bar to save time

I've used electricians tape for this in the past, works pretty well. The counterweight bar is stored inside on the eq-6 though so I might go with pen to be safe. Pictures are also a great idea, thanks! 

1 hour ago, KP82 said:

For visual precise balance isn't crucial, so I normally just use my most used eyepiece

I guess I'm probabky worrying unnecessarily about balance in this scenario. I know it's crucial for AP and not good for mounts to be unbalanced long term but I guess the EQ-6 will be absolutely fine with the occasional light or heavy eyepiece. 

 

RE the finder I'm wondering if repositioning it directly above the rings i.e. On the same plane as the scope and dovetail bar is the right approach? That way the centre of mass should be down the middle of the scope. Not a physic genius so I might have the terms wrong! 

[KP82]

16 minutes ago, badhex said:

I guess I'm probabky worrying unnecessarily about balance in this scenario. I know it's crucial for AP and not good for mounts to be unbalanced long term but I guess the EQ-6 will be absolutely fine with the occasional light or heavy eyepiece. 

 

RE the finder I'm wondering if repositioning it directly above the rings i.e. On the same plane as the scope and dovetail bar is the right approach? That way the centre of mass should be down the middle of the scope. Not a physic genius so I might have the terms wrong! 

The moment arm of the ED80 is pretty short, so I doubt the slight imbalance due to different eyepiece weight would do any harm to the DEC bearing and stepper motor.

If you can already achieve balance with the finder mounted on the focuser, moving it forward onto a bar/saddle between the tube rings won't make any differences (well ok for imaging this does help reduce flexure). Personally I only mount my guiding this way when using the 72EDF as it's way too tail heavy.

[badhex]

6 hours ago, KP82 said:

If you can already achieve balance with the finder mounted on the focuser, moving it forward onto a bar/saddle between the tube rings won't make any differences

Ah, maybe I didn't explain well - I mean to move it so that the finder is on the same plane as the axis, which also happens to be in line with the top of the scope rings i.e. Not forward but essentially rotated about the scope. 

[KP82]

2 hours ago, badhex said:

Ah, maybe I didn't explain well - I mean to move it so that the finder is on the same plane as the axis, which also happens to be in line with the top of the scope rings i.e. Not forward but essentially rotated about the scope. 

I see what you mean. Placing the centre of mass of the finder close to the axis is definitely going to minimise its influence on the DEC balancing.

[badhex]

Thanks, thats what I was thinking. I will try it all again with the scope rotated so that the finder is closer to the axis. Unfortunately I think that will mean the focuser clashes with the end of the dovetail now I moved everything up but I'll see what I can do. The longer term solution given all these modifications may end up being to remount the rings onto a losmandy plate anyway, adn the vixen dovtail can be used for the finder rings perhaps.

 

[KP82]

15 minutes ago, badhex said:

Thanks, thats what I was thinking. I will try it all again with the scope rotated so that the finder is closer to the axis. Unfortunately I think that will mean the focuser clashes with the end of the dovetail now I moved everything up but I'll see what I can do. The longer term solution given all these modifications may end up being to remount the rings onto a losmandy plate anyway, adn the vixen dovtail can be used for the finder rings perhaps.

 

Rather than moving the whole OTA up in the rings I'd recommend getting one of these: https://www.firstlightoptics.com/william-optics/william-optics-120mm-saddle-handle-bar.html

Very handy for mounting finder/guider closer to the axis. I've got one on my 72EDF.

[blameTECHIE]

I've the same setup (80ED + EQ6-R) and was looking for solutions to the same problem - was going for a longer (double the length) mounting rail but didn't know how to mount the guide scope properly.  Thanks @KP82 for the link, that's now in the basket.

[badhex]

Nice! Look like a good option, thanks. Am I right in thinking that it will accept the synta-style finder foot? Looks like it might.

[KP82]

Just now, badhex said:

Nice! Look like a good option, thanks. Am I right in thinking that it will accept the synta-style finder foot? Looks like it might.

It does. I mount my synta made SW evoguide 50 in it.