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Mega-mod thread for Zhumell dobs

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1365 replies to this topic

#1351 Sam M

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Posted 29 July 2019 - 01:22 AM

So, is the compression ring actually present and the screws are somehow frozen? 

The compression ring is nothing more than a thin strip of brass fed into a slot. Many people on here have made their own replacement ring, it isn't overly difficult. The material is readily available at craft or hobby shops.

So, the brass ring is in place.  The problem is that one screw is frozen, (broken off), and the other has very little travel, and I fear could be non functional at any moment.  If not the compression ring, then I'm not sure what the part is called that holds the screws that hold the 2" eyepiece in place?  That's what I need to replace.



#1352 SteveG

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Posted 29 July 2019 - 05:36 PM

So, the brass ring is in place.  The problem is that one screw is frozen, (broken off), and the other has very little travel, and I fear could be non functional at any moment.  If not the compression ring, then I'm not sure what the part is called that holds the screws that hold the 2" eyepiece in place?  That's what I need to replace.

It's called a visual back. You can probably get one from any astro store, if not Scopestuff.com.



#1353 Sam M

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Posted 30 July 2019 - 11:00 PM

It's called a visual back. You can probably get one from any astro store, if not Scopestuff.com.

I've always thought the term 'visual back' only referred to SCTs.  Thanks for clearing that up for me.  I've searched a good bit for an OEM part with no luck.  I didn't see one in stock from Scopestuff, but I just emailed them to see if they have anything.  I emailed Agena already, but no luck, and I haven't found anything that looks promising anywhere else.  At this point, I think I'll wait for  a run of cloudy days, and see if I can get the set screws out and tap the hole.  If that fails, I'll probably just replace the focuser.



#1354 Sam M

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Posted 02 August 2019 - 03:11 PM

Scopestuff doesn’t sell it. They informed me that the visual back and drawtube are a solid piece. So that’s what I’m looking for. 



#1355 SteveG

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Posted 05 August 2019 - 05:29 PM

Scopestuff doesn’t sell it. They informed me that the visual back and drawtube are a solid piece. So that’s what I’m looking for. 

That's too bad. I looked at some pictures of my old GSO dob focuser which is the same as yours, and it does appear that the back & draw-tube are 1 piece. Still, I would drill and tap a new hole. I've done this many times using a 1/4-20 tap and then use a nylon set screw. You can then remove the compression ring completely.


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#1356 Maxtrixbass

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Posted 06 September 2019 - 09:28 AM

Many thanks to all for this excellent thread! I have utilized many of the ideas into my z12.

 

I replaced the base top of the dob stand with a circle from Home Depot which may have helped some, but noticed a much bigger difference when I attached 4 velcro squares (smooth side) between the two plates. It stabilizes it and gives a bit more needed dampening to the rotation.

 

Also included: internal flocking, light shield, velcro carry straps, telrad, small grab knob for movement while at the eyepiece, balance weights plus slideable magnetized stack of washers with rubber on bottom (helps between 2" and 1.25" eyepiece changes) , and a leveling platform (most of my yard has slight slope). The feet of the dob base are removed and between it and the leveling platform I use 3 small drum practice pads (they look like the telescope vibration suppression pads) which grab a bit better and reduces vibration time a bit.

 

modded zhumell 2019.jpg

 

note the required clouds that rolled in soon as the modded base was complete..


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#1357 Natdiamond

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Posted 07 September 2019 - 11:39 AM

This is the setup I've been using for several months now on my Z12. The pneumatic tires go over thresholds and up and down stairs & grass very well. It's a $35 Harbor Freight dolly with 8"Pneumatic tires. 2 Ratchet straps around the base. 1 Bungee cord to firmly hold the OTA against it's own base so it doesn't rock back & forth. With these basic modifications to the dolly. The Z12 is Rock Solid when I move it on the dolly!! Meaning when I pull back on the dolly there is no wiggle or empty space. I pull back 1/4" on the dolly and the base lifts off the ground 1/4". Nice and tight.

 

gallery_304134_11821_8956.jpg

 

The 2 brackets (yellow) I made here (below) were for supporting the sides of the base. I noticed with the dolly & 2 straps on the base, it may be putting stress on the sides of the base. Both upwards and downwards. Maybe leading to a weak point down the road. So I cut some matching notches in these 2 top pieces of wood. they are screwed down into a  1" thick piece of wood that was glued & lag bolted to the dolly (lags represented in green).

 

 

gallery_304134_11821_71257.jpg

 

(Below)-I also felt like since the bottom dolly plate was not flush against the bottom of the round bottom plate of the base (since the base has 3 legs to keep it off of the ground), I insert a piece of wood (yellow) manually every time I move it to prevent any flexing of the bottom of the base. If I put the wood on the dolly 1st, the fit is too tight and the wood gets pushed all the way to the back of the dolly's base plate. I want it as far under the scopes base as I can go. So I slide the dolly under the z12, then push the wood in by hand. Or use my foot to tap it in.

 

 

gallery_304134_11821_152048.jpg


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#1358 wdavidsmc

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Posted 09 September 2019 - 04:16 PM

Excellent setup.

I have a question about your setting circle;  what type of "pointer" are you using to show what number your on?



#1359 prototype3a

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Posted 10 October 2019 - 10:53 AM

Somewhere in this thread there is a reference to adding an aperture stop to the Zhumell laser collimator.  I chose to machine a small bushing that I inserted into the front of the laser.  I also noticed while I had it apart that the brass bushing on the back of the laser was a very loose fit and it allowed the laser to have a lot of play so I simply removed it and I'm now careful with my setscrew pressure.  I may make a new bushing but I've also been thinking about drilling and tapping 4 new holes for the adjusting setscrews closer to the back of the laser to allow a bit more precision.

 

In the past, I used to machine VERY small parts and I was actually surprised how tricky this little bushing was to machine despite the part being relatively large.

 

I did, rather foolishly, make it from aluminum.  I may make a new one from 303 stainless steel.


Edited by prototype3a, 10 October 2019 - 10:54 AM.


#1360 prototype3a

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Posted 10 October 2019 - 09:47 PM

Okay.  Maybe I have a picture....

 

DSCF1266


#1361 halx

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Posted 30 October 2019 - 09:26 PM

Excellent setup.

I have a question about your setting circle;  what type of "pointer" are you using to show what number your on?

Clamp with wire to the bottom board. See the first image.

Though, there is a clever way to have a neat pointer fixed permanently in a convenient spot.


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#1362 halx

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Posted 30 October 2019 - 09:36 PM

Somewhere in this thread there is a reference to adding an aperture stop to the Zhumell laser collimator.  I chose to machine a small bushing that I inserted into the front of the laser.  I also noticed while I had it apart that the brass bushing on the back of the laser was a very loose fit and it allowed the laser to have a lot of play so I simply removed it and I'm now careful with my setscrew pressure.  I may make a new bushing but I've also been thinking about drilling and tapping 4 new holes for the adjusting setscrews closer to the back of the laser to allow a bit more precision.

 

In the past, I used to machine VERY small parts and I was actually surprised how tricky this little bushing was to machine despite the part being relatively large.

 

I did, rather foolishly, make it from aluminum.  I may make a new one from 303 stainless steel.

I have removed everything from the pointer inside but the diode pcb. And using the USB power for it. No need in the screw button and it is hard to break the alignment. See in my blog. Also, with the barlowed laser colimation method the larger beam spot is actually beneficial.


Edited by halx, 13 November 2019 - 01:50 PM.


#1363 earlyriser

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Posted 14 November 2019 - 03:47 PM

Many thanks to all for this excellent thread! I have utilized many of the ideas into my z12.

 

I replaced the base top of the dob stand with a circle from Home Depot which may have helped some, but noticed a much bigger difference when I attached 4 velcro squares (smooth side) between the two plates. It stabilizes it and gives a bit more needed dampening to the rotation.

 

Also included: internal flocking, light shield, velcro carry straps, telrad, small grab knob for movement while at the eyepiece, balance weights plus slideable magnetized stack of washers with rubber on bottom (helps between 2" and 1.25" eyepiece changes) , and a leveling platform (most of my yard has slight slope). The feet of the dob base are removed and between it and the leveling platform I use 3 small drum practice pads (they look like the telescope vibration suppression pads) which grab a bit better and reduces vibration time a bit.

 

attachicon.gif modded zhumell 2019.jpg

 

note the required clouds that rolled in soon as the modded base was complete..

Do you have any idea of the weight of the wood circle verses a same size circle cut from 3/4 inch plywood? I figure the plywood will be lighter since it is 1/4 inch thinner. I'm considering building a new mount to cut down on the weight of my AD10, so weight is the main criteria, but buying the pre-made circles would save a lot of work.



#1364 Maxtrixbass

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Posted 14 November 2019 - 04:05 PM

Do you have any idea of the weight of the wood circle verses a same size circle cut from 3/4 inch plywood? I figure the plywood will be lighter since it is 1/4 inch thinner. I'm considering building a new mount to cut down on the weight of my AD10, so weight is the main criteria, but buying the pre-made circles would save a lot of work.

The wood circle I used was thicker than the original piece, but the weight wasn't much different. It actually wasn't plywood, but a pine or spruce "cutting board" looking thing and was stiffer overall probably because of its thickness (again, precut, but unfinished from Lowe's). I don't think one piece by itself would make a huge difference weight-wise unless it was significantly different.



#1365 Natdiamond

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Posted 14 November 2019 - 05:12 PM

Excellent setup.

I have a question about your setting circle;  what type of "pointer" are you using to show what number your on?

I no longer use the setting circles as I've been having success with the EZ push to device & app. But When I was using it, I wrapped a strip of magnetic tape around the bottom base. Then I took a round magnet and a second hand off of a cheap dollar store clock I took apart. Glued the second hand to the magnet and bent it in an "L" shape. So it would stick straight up, then bend over the numbers on the top plate, but not actually touch the top plate of the base or the numbers. And of course I was able to move the magnetic pointer at will.



#1366 halx

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Posted 14 November 2019 - 06:11 PM

If you are using an app for pointing, you don't need a movable hand at all. Having the Az scale on the base board you can make a nice illuminated window in the top board located always conveniently under the eyepiece when you pointing. As there are apps which allow to calibrate the Az Scale after the setup using a single star, so after that the Azimuth value from the app will be always adjusted for your setup orientation. No need to move anything down below or complicate the mechanical construction.




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