Difficulty obtaining balance with a small scope and heavy camera+powermate+diag

[ram]

The short version is: has anyone had problems obtaining balance with a small scope (5lbs) and a diagonal with a heavy camera + glass (3-4 lbs total) on one end with the L shape of the diagonal causing issues with balance?

Normally I don’t have a problems with balance, even obtaining it with the same scope with the same camera but with a straight through setup (i.e., scope -> t-adapter -> camera). I’ve gotten this to work for many scopes of different weights, including the one in question which is a 70mm SV70T which weighs ~5 lbs without the camera. Normally my balance is “perfect” — I can swing the setup around axes and stop it at any position and it stays there. The moment I achieve balance it’s almost sticky in my MyT whereas any imbalanced position causes movement. My question has to do with it means to say “balanced”.

I’ve been recently experimenting with using a Powermate (1.2lbs), QHY247c (1lb), and diagonal (1.25) pounds, so about 4 pounds max all on one end of the scope. Using a 10lb counterweight I’m able to get some kind of a weird balance with the counterweight at one end and the scope on the other on the RA (polar) axis and then on the declination it is worse – no matter what I do by adding weights at the top, etc. I’m not able to get the best balance like I used to (on both axes). I’ve had the same problem with a 20lb counterweight (which is now moved up high).

My problem is that while I can get the horizonal/vertical balance but any movement towards one side or the other causes further movement. I can either get the horizontal or vertical balancing (on either axes, i.e., I can balance horizontally and vertically in RA/polar axis at 90 and 180 degrees relative to the ground plane and likewise on the dec I can balance parallel to the ground plane or at 90 degrees) but I can’t get to say 45 degrees (at an angle relative to the ground) and then it tends to move in one direction or the other. I struggled with this for a couple of hours (though. I was very tired) but the moment I removed the diagonal and used only the camera connected to the powermate straight through, it balanced like usual . The diagonal obviously creates this L shape that seems to cause this weird balancing behaviour with the camera sticking out on the top the scope at the end of the L where the long arm of the L is the RA/polar axis and the middle of the L is the dec axis and the small arm of the L is the camera.

I was using the diagonal to make sure I could reach focus visually and switch with the camera since once you start to magnify it’s harder to find objects and you don’t know if you can achieve focus WITHOUT the diagonal. So it’s mostly for trial and error purposes and getting the distance right since I found my 2″ extenders (without diagonal) only after the clouds came in but I was surprised with this behaviour. Is this normal?

Also as part of the moving counterweights, etc. I tend to lock the mount (with the little pull out knobs) in an imbalanced state for a few minutes – I assume this is okay?

Thanks!

–Ram

[JayTee]

Sometimes.

IMO you have two options: 1) you can add weight to the front of the OTA moving the balance point back toward the center of the Vixen bar, or
2) you can replace the Vixen bar with a much longer one so you have room to slide the OTA to a position where everything is in balance.

I've used both of these methods with some degree of success.

Cheers,
JT

[ram]

Thanks JT. Okay, good to know it's not something I was doing wrong. I did try to put weights at the front and I can make the front heavier and have balance at 180 and 90 but not at other angles. It creates this weird [___] shape when I do that which still just goes heavy one side or the other. I also have a longer dovetail (losmandy) but you said "some degree" so I'm wondering if the L shape of the diagonal would still problematic.

I am able to do it with a straight through connection and fortunately I have 2" extenders and then the balance is good (the clouds rolled in as I was about to check the centering) but I was wondering why I was having issues with a heavy L shape or [___] shape.

And I guess a key question is, suppose I have this weird balance, is it bad for the mount to use it like that? Probably right? Especially at positions that are far from the 90 or 180 (i.e., at 45) then it would be putting weight on the gears.

--Ram

PS: I sent you a PM about your observatory, did you receive it? It doesn't show up in my "Sent messages" but it shows up in my "Outbox" so I am not sure if it was sent or not.

[JayTee]

I just spent an hour trying to balance an asymmetric load (my side-by-side setup) on my CEM60. The best that I can do is to average the imbalance for each quadrant of the sky. Sometimes everything is a little bit scope heavy and other times it's a little bit counterweight heavy depending upon where I'm pointing. There is no perfect solution. So the discrepancies on one side I try to make a equal to the discrepancies on the other side.

Cheers,
JT

[ram]

Thanks - yeah, if it happens in the future I will deal with it I guess but for now I solved it with a straight through setup (fortunately I was able to find these Tak 2" extenders that came with the FC100DF so it worked out fine.

BTW, did you see my PS about the PM I sent you about your observatory? There's no hurry to respond in case you're collating info but I wanted to make sure it did get sent. It's not in my sent messages folder but in a place called the Outbox. Thanks.

--Ram