Balancing an IOptron CEM70

[HydrogenBadger]

All, I have just taken delivery of an Ioptron CEM70G and a Williams Optics GT71 with a load of accessories. I cannot balance it.  Although I am very amateur, I believe it is because:

 

1. the counterweight is too heavy for the scope - impossible to balance in RA

2. the scope is too short when fitted with all other accessories and accessories clash with mount - cannot balance in DEC

Am I doing something stupid? Pictures attached  

 

 

 

 

[northantsnick]

Hi. I had the same issue with my Cem60 and the OTA I was using. 

Solved by increasing the weight of the OTA by buying some gym arm and ankle wrap round weights from Decathlon (very cheap). I bought a combination of 1.5 and 2.5 kilos weights. When wrapped around the tube they are very stable as they are secured to themselves with velcro

I agree the single 9 kilo weight you receive with these mounts is way too much and of course most retailers don't stock the smaller weight. The hole diameter is odd too at 28mm and other mount weights won't fit it. 

Nick

[Anne S]

The smaller the scope the more difficult it becomes to balance everything. I've been balancing my Altair 70EDT this week on my CEM 60ec which is very similar to your 70. Due to the length of the saddle I've invested in a 350mm Vixen dovetail Which allows me to use a Primaluce weight on the objective end. I run a filterwheel with my sx694 so have much more weight at the back. I can now use my 9.5kg counterweight. There's a screw hole each side of my weight so I've a threaded rod full of washers and nuts to add some off axis balance. I find the focus motor causes some imbalance.  I can't get my focus motor vertical due to lack of clearance.

One other thing, when you focus properly the fact the focuser tube comes further out will make the dec much more back heavy you need to keep the objective end heavier until then. Once you've got it nearly in balance the cabling need fitting as this may affect everything. I have a Hitecastro Mount hub pro mounted on top of the scope in front of the guider.

Hopefully someone more expert than me will chip in with other suggestions soon.

[Craney]

31 minutes ago, northantsnick said:

 

Solved by increasing the weight of the OTA by buying some gym arm and ankle wrap round weights from Decathlon (very cheap). I bought a combination of 1.5 and 2.5 kilos weights. When wrapped around the tube they are very stable as they are secured to themselves with velcro

 

I'm liking the innovation, but would it not be easier to wrap the weights around the counter-balance arm and adjust (slide) the position to suit ?   Saves anything hanging off the OTA..

Just wondering ?

 

[northantsnick]

23 minutes ago, Craney said:

I'm liking the innovation, but would it not be easier to wrap the weights around the counter-balance arm and adjust (slide) the position to suit ?   Saves anything hanging off the OTA..

Just wondering ?

 

Well I suppose you could. Didn't look at it from that perspective. 

Just worked for me. 

Might try your suggestion though

Nick

[HydrogenBadger]

Thanks all, from what I am hearing I am not doing something fundamentally wrong so my options for the RA problem is either buy a lighter counter weighted or buy additional weight to hand scope side. 
 

How do I solve the declination balance problem? As you can see from my photos I have pushed the tube as far forward as I can including having to rotate the auto focuser and ASI air pro so theY can pass over the mount - doesn’t feel it is supposed to be done like this. 
 

 

Edited August 4, 2020 by HydrogenBadger

[Craney]

Use one of these....

https://www.firstlightoptics.com/counterweights/baader-dovetail-bar-levelling-counterweight.html

Attach it to the underside of the dovetail  on the OTA sticking out above the mount clamp.  It is designed to be slide-able so you can fine tune the position.

This little bit of kit is very useful as the weight can detach and leaves you with a Vixen clamp which can be screwed onto the top of a normal camera tripod.... you never know the silver weight might screw directly into the end of the counter balance arm.... now that would be handy !!!... only speculation though, since I have an EQ-6 and cannot test it for you.

 

[Anne S]

9 hours ago, Craney said:

Use one of these....

https://www.firstlightoptics.com/counterweights/baader-dovetail-bar-levelling-counterweight.html

Attach it to the underside of the dovetail  on the OTA sticking out above the mount clamp.  It is designed to be slide-able so you can fine tune the position.

This little bit of kit is very useful as the weight can detach and leaves you with a Vixen clamp which can be screwed onto the top of a normal camera tripod.... you never know the silver weight might screw directly into the end of the counter balance arm.... now that would be handy !!!... only speculation though, since I have an EQ-6 and cannot test it for you.

 

I bought the Primaluce version as it's suitable for Losmandy as well as Vixen bars. Also stocked by FLO.

[Richie092]

I had a similiar issue with my Star 71. Purchased a longer rail and stuck my Pegasus up the front. Works like a dream now 🙂

 

[fwm891]

There are smaller CW's available: https://www.firstlightoptics.com/counterweights.html

I have a CEM60 and have a smaller 5Kg CW for when I use my WO ZS 73 and DSLR. Even then the CW is well up the CW arm.

As for balancing accesories keep things as near to the optical axis line as possible, above or below the scope.

[The Admiral]

15 minutes ago, Richie092 said:

I had a similiar issue with my Star 71. Purchased a longer rail and stuck my Pegasus up the front. Works like a dream now 🙂

 

Neat arrangement.

You've done what I'm planning to do with my new guide-scope, using the WO handle clamp to mount it on a dovetail between the scope rings. When it arrives, that is . Nice to see it for real.

Ian

[johnturley]

Mount seems a bit big for the scope

John 

[Richie092]

Ah yes, but as I have the older Star 71 I cant get the 105mm space between hole centres so I had to turn the gold dovetail over and "bodge it" with nuts and bolts, can't quite get my fingers under to use as a carry handle but is rock solid.

Are you going for the uniguide? This one was in stock so went for it but it doesn't have a focuser, was a bit of a faff setting it up.

I will admit it isn't quite as neat from the other side...

[Richie092]

3 minutes ago, johnturley said:

Mount seems a bit big for the scope

John 

Can't be overmounted 🙂. I also have an Edge 8HD that sits on it.

There is a fair bit of weight there.

[The Admiral]

16 minutes ago, Richie092 said:

Ah yes, but as I have the older Star 71 I cant get the 105mm space between hole centres so I had to turn the gold dovetail over and "bodge it" with nuts and bolts, can't quite get my fingers under to use as a carry handle but is rock solid.

Are you going for the uniguide? This one was in stock so went for it but it doesn't have a focuser, was a bit of a faff setting it up.

I will admit it isn't quite as neat from the other side...

Neat enough! (I think johnturley was referring to the original post though in his reply.)

Nothing is easy is it? I've got an Altair 102 and the dovetail is 200mm long, and nothing I've found in that length had intermediate holes to use, or the profile amenable to adding the WO handle. I have little space to increase the scope ring separation. The best I could find were the WO 210 dovetails, which as far as I can see should fit the bill. A little bit 'suck it and see' but until they arrive I can't be totally sure how it'll go together. I've ordered those, the saddle handle, and the Uniguide scope. I'm expecting they'll arrive in the next couple of weeks, according to FLO. Fingers crossed in this coronavirus world.

Ian

Edited August 5, 2020 by The Admiral

[Richie092]

My fingers are crossed for you. It does take a bit of tinkering to get the set up right doesn't it?!

[Stuart1971]

The counterweight should be nearer to the mount, then it may balance, it’s also better for the mount if you have more weight and have it closer to the mount head.. rather than less weight further away... 👍😀

[Stuart1971]

15 hours ago, HydrogenBadger said:

All, I have just taken delivery of an Ioptron CEM70G and a Williams Optics GT71 with a load of accessories. I cannot balance it.  Although I am very amateur, I believe it is because:

 

1. the counterweight is too heavy for the scope - impossible to balance in RA

2. the scope is too short when fitted with all other accessories and accessories clash with mount - cannot balance in DEC

Am I doing something stupid? Pictures attached  

 

 

 

 

You need the scope further forward than shown in first image, to balance in Dec, as ATM its all rear heavy, and to get RA balanced move the weight up the counter weight shaft to effectively lighten it...it may all work then... 👍😀

[RayD]

16 hours ago, HydrogenBadger said:

All, I have just taken delivery of an Ioptron CEM70G and a Williams Optics GT71 with a load of accessories. I cannot balance it.  Although I am very amateur, I believe it is because:

 

1. the counterweight is too heavy for the scope - impossible to balance in RA

2. the scope is too short when fitted with all other accessories and accessories clash with mount - cannot balance in DEC

Am I doing something stupid? Pictures attached  

If you have a look at my video here you will see the issue you are having is common (this in on my CEM120).  I added an ADM weight to the front of my longer dovetail which helped sort out dec (and it will help RA) but also allowed for trimming off centre balance on the third axis.

FLO does variousl types and styles of dovetail weights.

Edited August 5, 2020 by RayD

[HydrogenBadger]

3 hours ago, Stuart1971 said:

You need the scope further forward than shown in first image, to balance in Dec, as ATM its all rear heavy, and to get RA balanced move the weight up the counter weight shaft to effectively lighten it...it may all work then... 👍😀

The counter balance is a far up as is possible.

All of the equipment is now upside as otherwise it fails against the mount i.e. the autofocuser, ASI Air Pro and the fine foucuser.  Not sure if this is a problem.  If I move it any further forward the scope will only be connected by one clamp in the dovetail which does not seem like a very good idea.

[HydrogenBadger]

4 hours ago, Richie092 said:

I had a similiar issue with my Star 71. Purchased a longer rail and stuck my Pegasus up the front. Works like a dream now 🙂

 

Thanks, yes I have just order a losmandy style plate which I am hoping will do the same thing you are suggesting here.  Should the focuser unit be fixed in position?  Mine is allowed to rotated freely and I can't see how I fix.

[HydrogenBadger]

3 hours ago, RayD said:

If you have a look at my video here you will see the issue you are having is common (this in on my CEM120).  I added an ADM weight to the front of my longer dovetail which helped sort out dec (and it will help RA) but also allowed for trimming off centre balance on the third axis.

FLO does variousl types and styles of dovetail weights.

Thanks yes, I have beeen watching all of your videos in the run up to my scope arriving!

[Richie092]

Edited as I can see you have it fixed with the metal bracket, how is it rotating?

The focuser has given me more headaches than the rest of the system combined... including the RPi4 and Stellarmate that was as familiar as alien technology to me.

Edited August 5, 2020 by Richie092

[Anne S]

8 hours ago, Richie092 said:

I had a similiar issue with my Star 71. Purchased a longer rail and stuck my Pegasus up the front. Works like a dream now 🙂

 

It's a pity my MHP is so big! It has to go on top.

[Anne S]

7 hours ago, RayD said:

If you have a look at my video here you will see the issue you are having is common (this in on my CEM120).  I added an ADM weight to the front of my longer dovetail which helped sort out dec (and it will help RA) but also allowed for trimming off centre balance on the third axis.

FLO does variousl types and styles of dovetail weights.

I was looking at getting that counterbalance system but it looks as if it only fits Losmandy. I was planning on keeping my 70edt on a vixen bar.