rlmxracer
super member
Reged: 11/09/11
Loc: Motocross Mecca , CA
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Re: Mega-mod thread for Zhumell dobs
[Re: simpleisbetter]
#5600690 - 01/02/13 02:41 AM
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rlmxracer, checkout ScopeStuff for the rail and balance kit you're looking for - Dob counterbalance kits
Thanks I have seen those kits. That will be my next project. Is there a source for the Zhumell alt bearings? I'd like to get rid of my tension spring set up if possible.
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: kfiscus]
#5600797 - 01/02/13 07:35 AM
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Ken,
I've never heard of anyone attaching felt or ProtoStar on the outside of the OTA around the focuser. Do you really experience much glare from the outside surface of the OTA? If you're at a green/blue site, why would you see any glare from the OTA's surface? Glare from what? Now possibly there might be a need in more light polluted areas.
This problem has been completely below my radar. 
Mike
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: rlmxracer]
#5600802 - 01/02/13 07:41 AM
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rlmxracer,
Quote:
Quote:
rlmxracer, checkout ScopeStuff for the rail and balance kit you're looking for - Dob counterbalance kits
Thanks I have seen those kits. That will be my next project. Is there a source for the Zhumell alt bearings? I'd like to get rid of my tension spring set up if possible.
One thing that has always steered me away from rail and balance kits, is that the optimal place to position a counterbalance for a Dob is at the lower end on the underside of the OTA. Unfortunately that is also the most inconvenient place if you have to reach down and around to adjust the position of a weight.
Mike
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kfiscus
professor emeritus
Reged: 07/09/12
Loc: Albert Lea, MN, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: Sarkikos]
#5601579 - 01/02/13 04:55 PM
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When doing outreach or gazing from a site nearer than my good site. I sometimes use a boat landing and passing cars' headlights are obnoxious. (I really should buy or have my wife make me an observing hood.)
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rlmxracer
super member
Reged: 11/09/11
Loc: Motocross Mecca , CA
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Re: Mega-mod thread for Zhumell dobs
[Re: Sarkikos]
#5601694 - 01/02/13 06:13 PM
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Quote:
rlmxracer,
Quote:
Quote:
rlmxracer, checkout ScopeStuff for the rail and balance kit you're looking for - Dob counterbalance kits
Thanks I have seen those kits. That will be my next project. Is there a source for the Zhumell alt bearings? I'd like to get rid of my tension spring set up if possible.
One thing that has always steered me away from rail and balance kits, is that the optimal place to position a counterbalance for a Dob is at the lower end on the underside of the OTA. Unfortunately that is also the most inconvenient place if you have to reach down and around to adjust the position of a weight.
Mike
Right now I am using a velvet pouch filled with a few magnets, nuts and bolts that I can slide up and down as needed. I am hoping to find someone parting out their Zhumell to ge a set of the adjustable alt bearings. I will eventially make a new lighter mount out of birch so I could set it up for the Zhumell alt bearings.
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Tim J K
super member
Reged: 05/19/09
Loc: Iowa
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Re: Mega-mod thread for Zhumell dobs
[Re: rlmxracer]
#5602029 - 01/02/13 10:00 PM
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rlmxracer,
Opticsmart.com carries the side bearing clutch assembly. Look on their web site under the "Telescope Accessories" tab and click on "Other parts and accessories".
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rlmxracer
super member
Reged: 11/09/11
Loc: Motocross Mecca , CA
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Re: Mega-mod thread for Zhumell dobs
[Re: Tim J K]
#5602039 - 01/02/13 10:03 PM
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rlmxracer,
Opticsmart.com carries the side bearing clutch assembly. Look on their web site under the "Telescope Accessories" tab and click on "Other parts and accessories".
Great, I did poke around Omarts site but did'nt find them.
Ouch I just checked and their $60 each and they don't come with the part that mounts to the tube.
Edited by rlmxracer (01/02/13 10:07 PM)
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kfiscus
professor emeritus
Reged: 07/09/12
Loc: Albert Lea, MN, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: Sarkikos]
#5602218 - 01/03/13 12:15 AM
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Last week I posted a thread "Anybody ever flock the EXTERIOR of their scopes?" and had several replies of "yes".
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: kfiscus]
#5602439 - 01/03/13 07:14 AM
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Never heard of it. But I might do it myself. 
Mike
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Gastrol
scholastic sledgehammer
Reged: 11/04/11
Loc: los angeles
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Re: Mega-mod thread for Zhumell dobs
[Re: Sarkikos]
#5602915 - 01/03/13 12:35 PM
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Quote:
One thing that has always steered me away from rail and balance kits, is that the optimal place to position a counterbalance for a Dob is at the lower end on the underside of the OTA. Unfortunately that is also the most inconvenient place if you have to reach down and around to adjust the position of a weight.
Mike
I think the major issue is the clearance problem with the front face board of the mount when pointing the scope near zenith.
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: Gastrol]
#5602964 - 01/03/13 01:00 PM
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Gastrol,
Yes. The front of my 10" Dob mount has a big cut-away section that allows my counterweight to slip through. For the 8", there is more clearance between the OTA and the front of the supplied Zhumell Dob base, so a cutout is not necessary.
My counterweights are packets of lead in sports packs that are strapped around the OTA. They are longer around the circumference of the OTA - which makes sense for a counterweight that will not be shifted up and down the tube - and are only a couple inches thick.
For the 10", I've set up a counterweight near the bottom end of the OTA on the underside. That is for longitudinal balance. A second, smaller counterweight near the top end of the OTA opposite the finder/focuser/Telrad is for lateral balance. I have set up these two weights so that the 10" scope is perfectly balanced horizontally or vertically for when my heaviest eyepiece is in the focuser.
This is important because my 10" Dob base does not have altitude detention springs or any other method of detention. When I replace the heaviest eyepiece with lighter ones, I just attach a small magnetic weight or two on the OTA near the focuser to make up for the loss in weight. Perfect balance everytime and smooth motion in azimuth and altitude!
Mike
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: Sarkikos]
#5602979 - 01/03/13 01:08 PM
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Gastrol,
The bottom line is if the counterweight is flat enough and you don't need to move it or change it, it should be near the bottom of the OTA on the underside. That's another reason why lead shot is a good material. It takes up less space than iron (denser) and can be more easily packed into a flatter area.
Actually, ideally even that lower weight should be on the side of the OTA opposite the focuser/finder/Telrad for best balance when the OTA is horizontal or vertical. But then there might not be enough room between the OTA and the side of the Dob mount. Having the weight on the underside of the OTA - when the OTA is horizontal - approximates the ideal position much better than having it on top of the OTA.
Mike
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petrus45
member
Reged: 01/31/11
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Re: Mega-mod thread for Zhumell dobs
[Re: Tim L]
#5757056 - 03/25/13 09:30 PM
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I used allen-wrench screws, which have a barrel on the end that can be tightened with the fingers. These can be found cheap at the local hardware store.
This is brilliant. Less than a dollar for 3 screws versus $25 and up for the high end screws. I found M4-0.7 x 30 mm Metric Socket Head Cap Screw (3-Pack) at the hardware store and they are working great.
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N7XW
sage
Reged: 05/04/07
Loc: Westport, WA
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Re: Mega-mod thread for Zhumell dobs
[Re: petrus45]
#5757417 - 03/26/13 02:28 AM
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Good info. Thanks for sharing.
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Scanning4Comets
Markus
Reged: 12/26/04
Loc: Deep Space!
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Re: Mega-mod thread for Zhumell dobs
[Re: N7XW]
#5757679 - 03/26/13 08:31 AM
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Quote:
One thing that has always steered me away from rail and balance kits, is that the optimal place to position a counterbalance for a Dob is at the lower end on the underside of the OTA. Unfortunately that is also the most inconvenient place if you have to reach down and around to adjust the position of a weight.
Mike
Yup.
I have a round magnet permanently duct taped to the underside of my OTA, (at the mirror end ), on the opposite the focuser as well. It hasn't moved in almost 2 years that it has been there.
I also have tension handles which also helps a lot if I need to lock the OTA in place.
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Mega-mod thread for Zhumell dobs
[Re: Scanning4Comets]
#5757735 - 03/26/13 09:08 AM
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Yes, the way you are balancing the scope is the way that makes the most sense.
The old school method of balancing a Dob is to throw a magnetic weight on the back of the OTA, and shift it up and down the tube depending on the position of the telescope. An updated version of this - which looks better but makes no more sense - is to shift a weight back and forth on a rod attached to the OTA. Certainly not the best method nor the most rational one if you stop and visualize how a lever on a fulcrum can be balanced most efficiently.
My Z8 has spring tension on the altitude bearings. My 10" Dob has none. I can achieve smoother movement with the 10", but I have to be more careful balancing the scope.
Mike
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