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Mega-mod thread for Zhumell dobs

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#351 Sarkikos

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Posted 06 June 2013 - 01:51 PM

The easiest way I've found to add counterweights to a Dob, is with a fanny pack / sports pack filled with sealed plastic baggies of lead shot. Strap it below the OTA, close to the bottom end. If necessary to make sure the pack won't slip down the tube, place opposing Velcro strips on the back of the pack and on the OTA. I doubt very much if there is any easier, simpler, more compact and more logical way to add a counterweight to a Dob OTA.

Yes there is actually. I have a round magnet opposite my focuser, but on the mirror end of my OTA. I used duct tape to keep it on the lower OTA and it has been there for three years now. Simple, but effective!


Very good. That's the equivalent of the primary counterweight I have toward the bottom of my OTA. That's where it should go. :waytogo:

The weight shouldn't go on the back of the OTA to be shifted up and down the tube every time you reposition. :foreheadslap: I stopped doing that many years ago and haven't gone back.

But try just that one weight if you have a 70mm finder, Telrad, dew shield and maybe a binoviewer or filter wheel or heavy ES eyepiece in the focuser. Then you might also need a counterweight directly opposite the finder, etc. to compensate for that cluster of stuff. Otherwise when you point the OTA toward zenith, the scope might move in the direction of the finder, etc. And then if you take your big heavy ES eyepiece or etc. out of the focuser, you'll have to compensate for the loss of that weight. That's where the magnetic weight right by the focuser comes into play.

Well, all this works and gives me smooth, fluid motion of the Dob mount without altitude detention springs or other gizmos.

Mike

#352 kfiscus

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Posted 06 June 2013 - 11:44 PM

I rotated my spider 45 degrees to accommodate my Astrocrumb (original style) filter slide. I tightened each of the vanes until it looked like the tube would start to pucker. Several of the Z12s I've bought had the vanes WAY tight and had 4 dimples to prove it.

#353 kfiscus

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Posted 09 June 2013 - 08:01 PM

Practically instant response from the proprietor and equally fast shipping at payment. :jump:

#354 kfiscus

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Posted 12 June 2013 - 09:10 PM

Yabbut...31,000 hits and going on 400 posts. Can't get no moderator love! Compare these numbers to the other threads.

#355 Herr General

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Posted 30 June 2013 - 10:24 PM

Just bought a Z12 used yesterday (thanks Nick, if you're reading this!) and had fun reading through this thread. I have a few questions though, as someone who's new to big dobs.

1) What's the best way to move it around? Someone suggested a hand cart of some sort, but I'm not sure where to find one- hardware store maybe? I have practically nonexistent muscles as a skinny college kid so it's extremely difficult to move the OTA around alone.

2) Mine didn't come with a collimation laser, but I have a little collimation cap that came with my Orion 6". I did some preliminary collimation when I got it, but is it worth it to invest in a laser?

3) I haven't used a finder scope before, so I suppose I should ask this as well- does it make enough of a difference when it's not "correct" orientation that I should invest in a right-angle finder? I'm already looking into getting a Telrad- I've used those before and they're very useful.

#356 kfiscus

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Posted 01 July 2013 - 03:16 AM

Welcome to one of the best threads on one of the best forums on CN. I have a Z12.
1) I use a Strap-A-Handle (gotten at Staples) to help maneuver the OTA. I take the dust cover off the front and have one hand there while the other holds the Strap-A-Handle. It takes some practice to get it right. I don't use a 2-wheeler. They can be quite bumpy with their solid tires.
2) You'll be okay using the collimation cap as you get started. Lots of people HATE the laser collimators that come with dob kits. Read up on the various popular collimation tools and put out feelers for other scope owners near you that might let you try their tools out. I've just bought the very popular TuBlug and am awaiting its arrival later this week.
3) There are many opinions on the correct suite of finders. I firmly believe in using a straight 9x50 and a Telrad in combo. Hearing you say that you've used a Telrad and liked it tells me that you have it together. Many like the convenient angle of a Right Angle Correct Image (RACI) finder. I can't stand 'em. I use the both-eyes-open method with my finders to know where I'm pointing.

#357 kfiscus

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Posted 04 July 2013 - 01:02 PM

I'd run out of ideas for posts to keep this thread active, and then...
My astrobuddy and I were out with my Z12 having a grand ol' time when my focuser suddenly got a hitch in its giddyup. I couldn't turn the main focus shaft while the fine focus seemed okay.
Here's what happened. The small "grub" screw (hex key set screw) right by the fine focus knob had worked itself inward until it fell into the tiny void inside the shaft housing. It was happy there until I'd turn the knob and a straight pin in the shaft would come by and lock up or grind past the offending wanderer. I got everything apart, inspected, and back together. I put a microdrop of superglue on the hole's threads before returning the screw to its home. I'd recommend that you check your focuser and do the same. The hole in the housing may be too loose. Good luck.

#358 plaidmelon

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Posted 20 July 2013 - 05:19 PM

Great ideas here.
Bought my Z10 used with no mods. So far I've disassembled and adjusted, flocked, added a knob and installed setting circle w/ digital inclinometer. All of these have made a noticeable difference in viewing ease and pleasure. Seems like I need some counterweights, so that will be next.

Is there anything else the more experienced Z-owners deem to be a must-do?

#359 newtoskies

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Posted 21 July 2013 - 11:02 AM

I have an XT6 and am considering either buying a new Z8 (can't afford the Z10) or a used XT8. I know with the XT8 I would want/need to upgrade a lot on the scope just to get it at stock Z8.
I know the best jump up would be the Z10 from a 6" but as I said, don't have the extra funds unless I get one used. How big a difference is it from a 6" to an 8" dob? I really love those Z dobs and now with all the mods posted here a Z will/would be a killer scope to last a life time.

#360 St Pete Keith

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Posted 21 July 2013 - 03:28 PM

I guess you could call this a fully modded Zhumell...

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#361 St Pete Keith

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Posted 21 July 2013 - 03:30 PM

Almost complete...

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#362 AstroTatDad

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Posted 21 July 2013 - 04:20 PM

Almost complete...


Well HOLY BLEEP!! look at that!!! Man I wished I had tools and patients to do something like this. I would like to get a Z12 and make it a truss. That is looking good, what else do you still need to do?

#363 St Pete Keith

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Posted 22 July 2013 - 05:37 AM

The base is next, need to make it a bit more stable. Should be done in a week or so.

#364 petrus45

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Posted 27 July 2013 - 09:58 PM

I see you're also not a big fan of the standard Telrad mount. All the empty pockets underneath don't leave much in the way of taping surface ... altho I do see they make handy places to put ceramic magnets! <G> Plan B for me, yet again. I just got done filling the base with bondo. Put a couple layers of wax paper on the OTA, then pressed the wet plastic into place so it's a perfect match for the Z8 tube. I got some peel 'n stick magnet tape that I'll cover the entire base with for now. Eventually, when I find the perfect sweet spot for the Telrad, I'll tap a couple holes and mount it permanently with screws and 3m tape. I got it roughed out right now. Skin coat, paint so the tape sticks, and I'm good to go. Still haven't figured out the best place to mount it ...


Brilliant solution for affixing strip magnets to the bottom of the Telrad! I happened to have some left over Bondo from patching up the rust on the old van, and used it for the Telrad base. The Bondo is easy to work with and dries pretty light. Once those magnets are glued on with some Super 77, it snaps onto the Z10 with no gaps - fits like a glove.

#365 kfiscus

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Posted 01 August 2013 - 10:54 PM

Clever use for the empty pockets inside the base. Instantly installed and removed = no mistake holes in tube.

#366 kfiscus

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Posted 10 August 2013 - 09:08 AM

Me with my finished (?) Mega-modded Z12 at the 2013 Nebraska Star Party. This is the main scope in my signature. Note carbon-based go to.

Photo by Bob Runyan.

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#367 bleep

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Posted 02 September 2013 - 12:13 PM

Here is what I did to my AD10. As soon as I unboxed it I took it all apart and flocked the tube. I cut the flocking paper into square tiles which made the job way easier for me. I only use 4 eyepieces so the bigger eyepiece holder works perfect. I keep the 2" twist lock adapter on the 1.25" eyepieces and not have to worry about switching the adapter back and forth. I used a hole saw to cut a notch out for the setting circle and a little nail for the pointer. Double sided taped a small bubble level on the base and use a magnetic digital inclinometer on the tube. I switched the positions of the Telrad and RACI cause every time I looked into the finder I was breathing on and fogging up the Telrad. This way works much better for me. I replaced the focuser tension screw with a hex screw because I kept tightening and loosening the wrong one when viewing. Heavier springs were added to the primary and a milk jug washer to the secondary. Finally i added a strip of moleskin to the other side of the bearings holders on the base. There was a little bit of play and I had to put the object on the top half of the the view to let it drop into the center. This made it a little tighter and now I can center the object much better. Next is to figure a holder for the Nexus 7. Here's a couple pics of what I've done so far.

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#368 bleep

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Posted 02 September 2013 - 12:17 PM

more pics

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#369 bleep

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Posted 02 September 2013 - 12:19 PM

Finally

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#370 Billytk

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Posted 02 September 2013 - 01:50 PM

Where did you get the hex screw for the focuser and what size is it?

#371 tag1260

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Posted 02 September 2013 - 02:27 PM

Any hobby shop with RC cars and airplanes (my other debt inducing hobby) should have the screws in metric. Take the original along to match the size.

#372 bleep

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Posted 02 September 2013 - 11:41 PM

I got the hex screw at Lowes. I took the original in with me and used the display they have to size it. its an M4-.7x10mm but I had to grind it down a little so it wouldn't stick out so far.

#373 sslcm56

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Posted 03 September 2013 - 12:39 AM

Has anybody tried to install boundary layer fans on their AD/Z scope? I was wondering if it would be worth it. Beside I am scared to cut into the side of my scope. Would I really need to cut holes on the opposite side of the tube for exhaust?

#374 MrJones

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Posted 03 September 2013 - 11:36 AM

I've certainly thought about it! My idea is one hole (on the "top") and one fan wired to the stock fan. I don't see any need for exhaust with that giant hole at the top :) and I would actually like to avoid any more ways for dust to get on the mirror. So it's either that or redo the bottom with a baffle and more fans.

#375 sslcm56

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Posted 03 September 2013 - 11:49 AM

I've certainly thought about it! My idea is one hole (on the "top") and one fan wired to the stock fan. I don't see any need for exhaust with that giant hole at the top :) and I would actually like to avoid any more ways for dust to get on the mirror. So it's either that or redo the bottom with a baffle and more fans.



There is a thread that talks about thermal management with links to several articles by Brian somebody. He has a boundary layer fan and says that you should have exhaust holes equal to the area of the fan blowing on the mirror. I'm with you tho I don't want more holes than necessary in the tube. I do want to baffle the bottom also. I just think it would be a great help.






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