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Equipment Discussions >> Reflectors

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Tim L
Carpal Tunnel
*****

Reged: 12/17/08

Loc: Missouri
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #3893984 - 06/29/10 09:49 PM

In the interest of helping a beginner who has never used a finderscope before:

I'm not sure if the info is in the Zhumell instruction manual (which many report is missing, anyway), but focusing the finderscope is very easy to do.

There is a ribbed locking ring just below the objective lens (where the company name and info is printed). Loosen this ring, and then rotate the objective portion of the finderscope until the image is in focus in the eyepiece. Re-tighten the locking ring. That's all there is to it, though it's a bit different than your binoculars.

If you wear glasses, decide whether you will use the finder with or without your glasses most frequently, and set the focus accordingly.

Not really a "mod," but I hope helpful nonetheless.
Clear skies!


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Tim L
Carpal Tunnel
*****

Reged: 12/17/08

Loc: Missouri
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #3894002 - 06/29/10 09:56 PM

Here's another for new Z owners:

Several have posted having problems bringing their 30mm eyepiece that comes with the scope into proper focus. The common complaint is that there is not enough "out-focus" travel. This is most often heard about the Z8 model.

There's a simple fix for this. On the front of the focuser are two thumbscrews. The upper screw controls tension for the crayford focuser. But the lower screw is a focus lock, useful for astrophotography, but not much needed on a dob used for visual.

The problem is, that lower screw keeps the focuser drawtube from extending all the way. The solution is to loosen the screw several turns (or remove it if you wish), which will let your focuser extend an additional 1/4" and bring your 2" eyepiece to focus.

Clear skies!


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d.sireci51
Arachnoid
*****

Reged: 11/19/09

Loc: The Tholian Web [S. Wisconsin]
Re: Mega-mod thread for Zhumell dobs new [Re: Jason D]
      #4119332 - 10/16/10 01:03 AM

O.K. Heres an Idea that I doubt anyones considered yet? Its especially for you Zhumell users that have incorperated the added use of a Hand truck or dolly to haul your scope in and out of the garage/house for observing.
As everyone knows the Zhumell tube has a knurled lock seam down the length of the tube.
I have expressed before that if the tube is bounced around or accidently jared, this seam could slip and put your tube out of square! Along with other problems one would all of a sudden wonder what happened to my collimation?
A simple thing can be done to help insure from this problem.
After you've disassembled your scope for flocking, and before you flock. With the tube laying on its side, the seam at the bottom, Take some Locktite on the inside of the tube and apply a reasonable amount on this seam. Before you stand the tube up, be sure the Locktite has hardined. Another good idea would be to place the tube on some plastic just in case some Locktite leaks thru. I also checked for this every 10-15 minutes. If some does come thru WD40 on a rag will remove the Locktite if its not totally dryed.
Clear and dark skies, D.Sireci


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sailor70623
Post Laureate
*****

Reged: 01/12/08

Loc: Ok.
Re: Mega-mod thread for Zhumell dobs new [Re: d.sireci51]
      #4119339 - 10/16/10 01:09 AM

A strip of fiberglass tape and some epoxy resin would work even better.

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d.sireci51
Arachnoid
*****

Reged: 11/19/09

Loc: The Tholian Web [S. Wisconsin]
Re: Mega-mod thread for Zhumell dobs new [Re: sailor70623]
      #4119375 - 10/16/10 01:40 AM

Good idea Sailor, You need something that will leak into the knurling to lock it into place.

Clear and dark skies, D.sireci


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Donnie
scholastic sledgehammer
*****

Reged: 03/15/04

Loc: Western Ky
Re: Mega-mod thread for Zhumell dobs new [Re: d.sireci51]
      #4149159 - 10/28/10 09:09 PM

Great thread Tim, and great additions by everyone else as well.

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okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4150907 - 10/29/10 04:45 PM

Quote:

One more very simple mod I should mention with the laser--put a piece of scotch tape around the barrel to help it fit a little more snugly in the focuser.




If you can get your hands on some, aluminum tape works well for this. I keep a roll in my field case because it comes in handy for all kinds of quick shimming applications. Be careful when using aluminum tape because it can cut like a razor blade if mishandled.


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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4151488 - 10/29/10 10:12 PM

Excellent, excellent thread!

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NewAstronomer
Post Laureate
*****

Reged: 09/03/04

Loc: Northeast, PA U.S.A
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4152543 - 10/30/10 01:37 PM

Unless it was posted and I missed it, the next big mod you want for these scopes (at least for my pre-Zhumell GSO 10" f/5 Dob) was a scopestuff kit Ebony Star laminate bearing with virgin teflon (PTFE) pads.

http://www.scopestuff.com/ss_ldxx.htm

Many recommend a car wax paste applied and buffed out on the laminate strip to help with stiction. I haven't done this yet and keep Jupiter in the FOV at around 300x easy enough.


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Mary B
Vendor - Echo Astronomy and Electronics
*****

Reged: 05/21/10

Loc: Minnesota
Re: Mega-mod thread for Zhumell dobs new [Re: NewAstronomer]
      #4152600 - 10/30/10 02:10 PM

The current Zhumells use a roller bearing sandwiched between 2 steel plates.

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Enig
sage


Reged: 06/24/09

Loc: NW GA, U.S.A.
Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
      #4159836 - 11/02/10 11:01 PM

Quote:

Improve your laser
  • Collimate your laser.
  • Add an aperture stop to your laser.




  • Got this done tonight. I had previously collimated the laser, but I really wanted to squeeze that beam into a tighter dot, so I did the mod exactly as shown in the thread you linked, then re-collimated to a tighter tolerance. All of this had *exactly* the results described... and then my batteries were depleted, so I will be forced into going to Wal Mart, tomorrow I suppose. I think I'll get a goodly supply (maybe three sets) to insure that it will be a decent while before it happens again, and maybe when I get down to one set left I can wait till my wife is going and get her to get them while *she's* there!

    Anyway, thanks *very* much for these helpful instructions, everyone involved! I think my next upgrade from this thread will be the Rigel QuikFinder... I too like the idea of it being able to fit between the focuser and finder, and I also like the built in pulse, and the higher profile which should require less neck / head contortion, no?


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    Sarkikos
    Postmaster
    *****

    Reged: 12/18/07

    Loc: Scotophobe Maryland, USA
    Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
          #4159847 - 11/02/10 11:06 PM

    Tim,

    Yep, you've put the counterweight in the right place. That way you'll balance the scope horizontally and vertically. Putting the weight along the top of the OTA is not the best solution. I use a sports pack (fanny pack) containing lead weights. I strap the sports pack around the OTA.

    Mike


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    Tim L
    Carpal Tunnel
    *****

    Reged: 12/17/08

    Loc: Missouri
    Re: Mega-mod thread for Zhumell dobs new [Re: Enig]
          #4159904 - 11/02/10 11:40 PM

    Quote:

    I think my next upgrade from this thread will be the Rigel QuikFinder... I too like the idea of it being able to fit between the focuser and finder, and I also like the built in pulse, and the higher profile which should require less neck / head contortion, no?




    Hey Enig,

    I think it's only a fraction of an inch taller than a Telrad in actuality, so there are still some contortions needed if viewing near zenith. But, I do like the small footprint that lets it tuck in close to the finder / focuser.

    During the blazing summer heat, my double-sided tape loosened in the garage, and the Rigel fell off once. No damage done, but I'm taking it off after each use now.

    Glad the laser mod worked for you. I burned up a set of batteries when I first collimated it as well, but now a set lasts a good long time, and collimation of the laser, if needed, is much quicker.

    Clear skies!


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    Enig
    sage


    Reged: 06/24/09

    Loc: NW GA, U.S.A.
    Re: Mega-mod thread for Zhumell dobs new [Re: Tim L]
          #4159909 - 11/02/10 11:44 PM

    Quote:

    I'm taking it off after each use now.






    Does that not put the fear of the dreaded tab breakage issue into you?


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    Tim L
    Carpal Tunnel
    *****

    Reged: 12/17/08

    Loc: Missouri
    Re: Mega-mod thread for Zhumell dobs new [Re: Enig]
          #4159927 - 11/02/10 11:55 PM

    Not since I've seen Rigel offer to fix broken tabs for free!

    I do try to be very careful when removing it, however. I suppose the smart thing to do would be to just replace the tape.


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    VikingRaider
    sage


    Reged: 01/29/08

    Loc: Mukwonago, Wisconsin
    Re: Mega-mod thread for Zhumell dobs [Re: Tim L]
          #4161294 - 11/03/10 05:04 PM

    I'll throw in my hat here...I've used a lot of these tips on my new Z8 (well, new as in July...) especially the ones about focusing with the Crayford (those little thumbscrews on the bottom had me stymied for a few days) and the finderscope focusing trick.

    I've since added a Telrad in between the focuser and the RA finder, but a little futher back down the tube. I find there's no real problem sighting on the Telrad, because the tube is so long to begin with it doesn't feel awkward. I took some black nylon "zip-ties" I had picked up at Home Depot for another project and put 5 together, head to tail to make on big one. They're the standard 12" or so variety.

    This I threaded betwen the base and the Telrad itself. One at the front and one at the rear and tighten. The Telrad doesn't move AT ALL and there's no harm to the paint's finish on the OTA. I decided to do it this way because in the middle of the summer my garage can get pretty hot when it's 110 outside. In fact, it was hot enough to melt the glue on the four little felt pads that are around the edge of the OTA cover. A dab of superglue on each fixed that.

    Also, speaking of the cover, I drilled a small hole and bought a wooden ball from an arts and crafts store, of a size comfortable to my hand. It was flat on one side and had a pre-drilled hole. This I painted about 3 times with dollar store paint, let dry and attached to the cover with a screw and some wood glue in the ball. Now my cover has a convenient and very secure grip to pull the cover off without groping for the edge in the dark.

    Also, I like the way the Orion scopes had a little knob on the front of the OTA by the opening to allow for easier positioning of the OTA during your viewing session. I felt real nervous about drilling a hole in the OTA so I used some more of the zip-ties (I guess they're technically called cable ties) and cut a piece of 1" black PVC in half. Next, I bought a clearance cabint knob from the Depot for .59 (already black!) and drilled a hole in the slice of pipe. Attach the "handle" to the OTA with cable ties and I now have a very secure handle for moving the OTA around while viewing without getting fingerprints all over the tube (or sticking my fingers around the lip of the opening).

    Next up, flocking!


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    Enig
    sage


    Reged: 06/24/09

    Loc: NW GA, U.S.A.
    Re: Mega-mod thread for Zhumell dobs [Re: VikingRaider]
          #4161601 - 11/03/10 07:36 PM

    Quote:

    four little felt pads that are around the edge of the OTA cover.




    ??? There are felt pads on yours? Curious... mine is just a plastic disc with little "bumps" around the edge that just sorta friction fits... evidently they've made some sort of change. A pic would be great, also of where you have mounted your Telrad and your wooden OTA lid handle!

    Laser Batteries

    Went to Wal Mart to get replacements... they are $5 and some change for 3 of them... *but*, if yours is like mine, up in one of the checkout lane impulse items they have little laser pointer keychains for about $2.40 that have a set of three inside them, *plus* an extra set of three in the package... I bought three lights for $7 and change which provided 6 sets of batteries (total of 18).


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    VikingRaider
    sage


    Reged: 01/29/08

    Loc: Mukwonago, Wisconsin
    Re: Mega-mod thread for Zhumell dobs [Re: Enig]
          #4165846 - 11/05/10 04:09 PM Attachment (118 downloads)

    Quote:

    ??? There are felt pads on yours? Curious... mine is just a plastic disc with little "bumps" around the edge that just sorta friction fits... evidently they've made some sort of change. A pic would be great, also of where you have mounted your Telrad and your wooden OTA lid handle!





    Sure thing. I'll have to do it as attachments one at a time though. Okay:

    "felt.jpg" this is a picture of the little square patch of felt that was glued at 4 spots around the inside rim of the "lid".



    Edited by VikingRaider (11/05/10 04:10 PM)


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    VikingRaider
    sage


    Reged: 01/29/08

    Loc: Mukwonago, Wisconsin
    Re: Mega-mod thread for Zhumell dobs [Re: VikingRaider]
          #4165852 - 11/05/10 04:11 PM Attachment (137 downloads)

    This is a picture of the underside of the lid, showing a few of the pads I reglued, and the screw and some washers holding the handle on the other side.

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    VikingRaider
    sage


    Reged: 01/29/08

    Loc: Mukwonago, Wisconsin
    Re: Mega-mod thread for Zhumell dobs [Re: VikingRaider]
          #4165856 - 11/05/10 04:12 PM Attachment (150 downloads)

    This is a shot of the ball I painted and attached to the outside of the lid. Makes putting that lid on REAL easy now. The washers have the added benefit of giving the lid just a bit of weight---just enough to keep it in place when I'm observing and a slight breeze blows up (which is pretty often where I live...no trees or anything to block that ever present Texas wind).

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