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Thread: Balancing a CEM60

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    Default Balancing a CEM60



    Hi all. Just joined the forum and have my first question of many. I have a CEM60 and wondering if it requires a compensation balance to counteract gear backlash. Should I balance the RA east heavy (heavier on the telescope side) when imaging to the west and heavier on the counterweight side when imaging to the east? Does the DEC axis require any balance adjustment?
    Alex
    Scope: ES 152mm f4.8 Mak-Newt & Motorized Moonlite Focuser Mount: iOptron CEM60 on tri-pier Cameras: QHY163m, Nikon D5300, ZWO asi120mm, asi120mc Accessories: Baader LRGB Oiii Sii, Astrodon 5nm Ha, IDAS LPS-D1, Orion 60mm Guidescope, Polemaster Software Photoshop, StarTools, SGP, BYNikon, PHD2, DSS, Astrotortilla


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    Default Re: Balancing a CEM60

    Quote Originally Posted by ic_1101 View Post
    Hi all. Just joined the forum and have my first question of many. I have a CEM60 and wondering if it requires a compensation balance to counteract gear backlash. Should I balance the RA east heavy (heavier on the telescope side) when imaging to the west and heavier on the counterweight side when imaging to the east? Does the DEC axis require any balance adjustment?
    I'm not sure about the others, but I don't bother with mine. Same for RA and DEC
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    Roger
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    Default Re: Balancing a CEM60

    Balancing "East" heavy here in the North worked well on my Zmount when using it to image with but that's not quite the same mount as the CEM60. There are a few owners of the mount on here. I'm surprised they have not chimed in. Hopefully they have clear skies and are busy using them.
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    Default

    I balance east heavy in RA and camera end heavy in DEC. With my WO 71mm on I don't readjust counterweight after meridian flip. I am able to achieve 0.35-0.45 total RMS over hours of imaging. With a little heavier scope like my 8" RC I may readjust after flip.


    -Brad
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    Default Re: Balancing a CEM60

    I have been balancing mirror heavy in DEC which I guess is the same as camera heavy on a refractor. For RA when I imaged east I balanced scope heavy and counterweight heavy when imaging west. So the consensous is if you balance counterweight heavy (thats east heavy when imaging west) it should be ok no matter if you image East or West?
    Alex
    Scope: ES 152mm f4.8 Mak-Newt & Motorized Moonlite Focuser Mount: iOptron CEM60 on tri-pier Cameras: QHY163m, Nikon D5300, ZWO asi120mm, asi120mc Accessories: Baader LRGB Oiii Sii, Astrodon 5nm Ha, IDAS LPS-D1, Orion 60mm Guidescope, Polemaster Software Photoshop, StarTools, SGP, BYNikon, PHD2, DSS, Astrotortilla


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    Default Re: Balancing a CEM60

    Quote Originally Posted by ic_1101 View Post
    I have been balancing mirror heavy in DEC which I guess is the same as camera heavy on a refractor. For RA when I imaged east I balanced scope heavy and counterweight heavy when imaging west. So the consensous is if you balance counterweight heavy (thats east heavy when imaging west) it should be ok no matter if you image East or West?
    When balancing Dec, it doesn't matter which end is heavy, since Dec isn't supposed to be moving anyway if everything is perfect.

    You have the directions wrong. Imaging west, the scope is on the east side of the mount and the counterweights are on the west. So you would want the scope (east) side heavy. That keeps the gears lifting consistently as the mount tracks.

    If the balance is the opposite way, i.e. west-heavy, which you would get after a meridian flip, the gears are lowering the weight. You are counting on friction being low enough that the weight can descend smoothly.

    If friction is high, as it is in Synta mounts with their legendarily thick grease, and you are west-heavy, friction could hang up the mount, causing the mount not to track for a bit until the gears had taken up the backlash and started pushing. On such a mount, you would want to always balance east-heavy, and you would need to re-balance after a meridian flip. However, the CEM60 has very low friction in comparison, so this is not a problem. I just balance my CEM60 east-heavy and don't touch it after a flip.
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    DSO AP: Orion 200mm f/4 Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on HEQ5 pro; C-90 on wedge; 20x80 binos; Etc: Canon 350D; Various EPs, etc. Obs: 8' Exploradome; iOptron CEM60 (pier);
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    Default Re: Balancing a CEM60

    Ioptron recommends balancing east heavy.
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    Default Re: Balancing a CEM60

    You are absolutely right Kathy and thats the way I do it as well. I think im just getting myself in a knot with all this eastheavy westheavy scope and counterweight heavy.
    Right now when I image West I have my scope (east) side heavy. Can I leave it like that when I image East as well?
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    Alex
    Scope: ES 152mm f4.8 Mak-Newt & Motorized Moonlite Focuser Mount: iOptron CEM60 on tri-pier Cameras: QHY163m, Nikon D5300, ZWO asi120mm, asi120mc Accessories: Baader LRGB Oiii Sii, Astrodon 5nm Ha, IDAS LPS-D1, Orion 60mm Guidescope, Polemaster Software Photoshop, StarTools, SGP, BYNikon, PHD2, DSS, Astrotortilla


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    Default Re: Balancing a CEM60

    Quote Originally Posted by ic_1101 View Post
    You are absolutely right Kathy and thats the way I do it as well. I think im just getting myself in a knot with all this eastheavy westheavy scope and counterweight heavy.
    Right now when I image West I have my scope (east) side heavy. Can I leave it like that when I image East as well?
    This topic has always tied me in a knot as well. Somewhere I thought I saw a couple illustrations detailing the balancing position of the CEM60 in DEC with the scope in a level position. I can't recall which direction the telescope end was pointing, but in the field I've been making the telescope end slightly heavier than the camera end while the mount was pointing north. I picked east since I usually align in that direction and most targets are located there. I don't have much range because of vision obstructions, the west is blocked by my house while the north is blocked by a neighbor's fast growing tree. However, I can still see Polaris though.

    Since I can't find those two photos I mentioned I have to start over with this process and my first question to get me on track is what is the proper starting position of the mount and OTA? Would it be in your standard zero position with the telescope and mount pointing north towards Polaris? From there should I level DEC to be in the horizontal position to start with, I'm really confused now! But, acccording to Kathy, I can ignore DEC balancing and simply move on to balancing the mount in RA.

    At this point I really get confused. I figure the mount should still be in the zero position with the telescope and mount pointing at Polaris, correct? If I ignore DEC adjustments and Kathy stated she has her CEM60 always in the east side heavy orientation, even after a meridian flip. I can't get it through my head how do you make the OTA east side heavy when it's in the zero position? What entails making the scope east side heavy, does the fact the CEM60 mount being configured more biased in weight towards the rear of the set-up, does that add to it being east side heavy to begin with? Or, to better understand the physical positions of the mount and telescope, if you are going to image something in the eastern sky and your initial star alignment routine usually takes in eastern sky stars, should you turn the OTA either by disengaging the worm gear (manually move the mount) or use the hand pad to slew the OTA so it points east and is horizontal now? When the the telescope is in this position I can grasp adjusting DEC to be objective side heavy, but I never could get the hang of adjusting the counterweights in RA to be east or west side heavy. When the telescope is pointed east, after I balanced it in DEC and locked the worm gear, I could never accurately adjust the counterweights to get the telescope to fall east or west side heavy. It always had a bias to fall to the west side, but of course I was probably doing this under the wrong circumstances to begin with.

    Man, I'm I screwed up and it doesn't help the iOptron instructions were so vague in this topic to begin with. I'm amazed I've been able to pull off alignment routines and create star models all this time, however, that took a long time to figure out workarounds and it's still not perfect. If anyone can understand what I'm trying to say and describe what I should be doing instead, I would be grateful and that is an understatement! It also doesn't help I underwent hand surgery today and I'm a little on the loopy side right now from being on pain medication. I'm not supposed to be typing right now, but this thread set the groundwork for me to jump in, no way was I going to ignore it.

    It would also be helpful if someone could supplement any instructions with a simple line drawing, just to illustrate the positions and relationship between the telescope and mount.
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    Default Re: Balancing a CEM60

    Forget the zero position. That is only one of several starting positions for the goto system. It is not relevant for balancing. (Well, mostly not relevant.)

    You can't ignore Dec. It must be balanced too. In fact, it must be balanced in two dimensions. Starting in the zero position, rotate the OTA 90 degrees in Dec. It is now pointing either east or west (it doesn't matter which), and the counterweight is down. Slide the dovetail forward or back in the saddle until the scope balances. Then move it a little bit one way or the other - this is your backlash compensation.

    Now move the OTA back to the zero position. Release the Dec gear switch. Ideally, the scope will not drop to either side. Usually, though, it will, due to asymmetrical loads like guide scopes, finders, or Newtonian focusers. You need to rotate the OTA in the rings until Dec will balance in this position. It may not end up in the most convenient orientation for viewing, but you are doing this for AP.

    Now that Dec is balanced, you need to balance RA. Lock the Dec gear switch and unlock RA. Rotate the mount in RA until the counterweight arm is horizontal. It is going to make more sense if you set it up in the direction you are going to be imaging. So if you will be imaging east of the meridian, swing the scope to the west and the counterweights to the east. Or the opposite way if you plan to be imaging west of the meridian. Adjust the counterweight until the rig balances in this position. Now adjust the counterweight a little more so that the east side (either the scope or the counterweight, depending which way you will be pointing) is slightly heavier.

    I don't keep the east side heavy after a meridian flip. I balance to be east side heavy before the meridian, which is counterweights heavy. At the flip, I do not readjust the balance. So the counterweights are still heavy after the flip, even though they are now on the west side. This is the "wrong" way according to most sources. But the CEM60's friction is low enough that you can get away with it.
    Last edited by KathyNS; 09-29-2017 at 02:06 AM.

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    DSO AP: Orion 200mm f/4 Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on HEQ5 pro; C-90 on wedge; 20x80 binos; Etc: Canon 350D; Various EPs, etc. Obs: 8' Exploradome; iOptron CEM60 (pier);
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