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Mega-mod thread for Zhumell dobs

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1545 replies to this topic

#1526 Crankyanken

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Posted 18 November 2020 - 01:09 PM



Does anyone know what drill size hole is needed for the milk jug washers to fit around the center screw holding the secondary?

I’d like to try it without removing the secondary mirror altogether by cutting a slit across one radius of the washers.

For an AD8 (same as Z8 I assume)

I went to ACE and got two nylon washers, 44mm OD, 16mm ID, 1.5mm in thickness. I cut them just like you suggested at about 5mm, and simply rotate the cuts away from the three thumbscrews.

 

50618058822_1fb85a357d_z.jpg


Edited by Crankyanken, 18 November 2020 - 01:16 PM.

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#1527 SteveG

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Posted 18 November 2020 - 02:33 PM

I went to ACE and got two nylon washers, 44mm OD, 16mm ID, 1.5mm in thickness. I cut them just like you suggested at about 5mm, and simply rotate the cuts away from the three thumbscrews.

 

50618058822_1fb85a357d_z.jpg

You only need to cut a single slit. Removing that section isn’t necessary.



#1528 Crankyanken

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Posted 18 November 2020 - 03:07 PM

You only need to cut a single slit. Removing that section isn’t necessary.

Very true, I just didn't want to try and force it through since this is my first scope.  With the two cuts they drop right in, and I didn't have to worry about jacking something up even if I probably wouldn't in the process. 



#1529 CowTipton

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Posted 08 December 2020 - 02:57 PM

My AD8 so far:

 

-Wixey alt gauge (attaches magnetically to top of OTA)

-Added 3M velcro tape (soft loop material) to other side of the base where the bearings slot in.  There was way too much play in that space.  Super annoying when making alt adjustments.  Very stable now.

 

IMG 2518
 

-Az setting circle on top plate of base, 4 white tape markers on bottom plate 90 degrees apart.  I typically pick two bright stars or planets for alignment.

-Homemade leveling platform as my driveway is sloped.  Wood frame and square with leveling feet from Rockler.

 

IMG 2523
 

-Thumbscrews for secondary collimation.

-Plastic furniture leg caps cupping the end of the thumbscrews.  I intend to shave these down a tad and color them black with a sharpie.

 

IMG 2519

 

-purple shower cap to keep the spiders out of the primary end

 

IMG 2521

 

 

 

Still to do:

-flock OTA opposite the focuser (no way I'm doing the whole thing)

-Mount a holder for the fan's battery pack.  Currently I just slide it onto the base.  Unless I'm viewing near the zenith it's not in the way.

-light shroud for the end of the OTA to help reduce some of the house and street light intrusion.

 

Any other recommendations?



#1530 Lukes1040

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Posted 08 December 2020 - 06:07 PM

Picked up this idea from Dakota Starry Nights on YouTube. Helps dial in the correct angle without having to have the base perfectly level. 

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  • 1CC69530-4F83-4A0E-AE51-1C6446840869.jpeg

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#1531 Traveller128

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Posted 13 December 2020 - 12:27 PM

Picked up this idea from Dakota Starry Nights on YouTube. Helps dial in the correct angle without having to have the base perfectly level. 

Why not just put a small bubble level on the tube, then hit "zero" on the angle finder?  



#1532 sunrag

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Posted 14 December 2020 - 10:29 AM

Anyone found a shower cap to cover the mirror end of a 12" Dob? I find that the even a large size shower cap won't fit on my AD12.


Edited by sunrag, 14 December 2020 - 10:29 AM.


#1533 Lukes1040

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Posted 14 December 2020 - 10:44 AM

Why not just put a small bubble level on the tube, then hit "zero" on the angle finder?


My method allows me to have fewer items in my kit. I do not like to have a bunch of different parts and pieces that could be lost/broken while out observing. For example, I used to use a barlowed laser for collimation which required a laser, Barlow, and a mirror so that I could actually see the ring on the bottom of the Barlow. Now I use a single astrosystems barlowed laser system, which is basically one piece of equipment.

Also, I would think getting aligned on a star to a tenth of a degree is going to be more accurate than a bubble level.

#1534 Woj2007

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Posted 14 December 2020 - 10:54 AM

Anyone found a shower cap to cover the mirror end of a 12" Dob? I find that the even a large size shower cap won't fit on my AD12.

This one is large and flexible enough. I use it on the mirror side:

https://www.teleskop...--aperture.html


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#1535 Traveller128

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Posted 14 December 2020 - 02:01 PM

Also, I would think getting aligned on a star to a tenth of a degree is going to be more accurate than a bubble level.

I have a small carpentry spirit level attached to the tube (about 2" long metal framed one, weighs about an ounce), and the angle finder is tenth of a degree accurate when locating things using a setting circle and Sky Safari.  .1 degree in altitude is the max it's ever been off.  I have two different angle finders, one is magnetic (higher end one, use it for building cars) and a non-magnetic that I can just double side tape to the tube.  The non-magnetic one was the one I was using for a long time, but I have to remove it from the tube if I ever want to modify, so I went back to the magnetic.  


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#1536 Lukes1040

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Posted 14 December 2020 - 03:11 PM

I have a small carpentry spirit level attached to the tube (about 2" long metal framed one, weighs about an ounce), and the angle finder is tenth of a degree accurate when locating things using a setting circle and Sky Safari. .1 degree in altitude is the max it's ever been off. I have two different angle finders, one is magnetic (higher end one, use it for building cars) and a non-magnetic that I can just double side tape to the tube. The non-magnetic one was the one I was using for a long time, but I have to remove it from the tube if I ever want to modify, so I went back to the magnetic.


Mine is magnetic. I like the ability to move it around, or take it off the scope for travel.

Just for completeness, I think I spent $3 on this mod and that was for magnet tape. The base and angle holder plate are made from a paint stick cut to length, and I had some nuts and bolts laying around. Also, I have done the spring upgrade on my mirror cell, and these springs in the mod are from the original mirror cell springs. I had some free time and wanted to tinker.

#1537 Crankyanken

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Posted 16 January 2021 - 05:50 PM

I think I am having more fun modifying the Dob than I am looking through it!  Conditions have been terrible, so I did some fun mods with all the down time I have had. 

 

I shifted the dovetail for the RACI over a full inch so I could figure out a way to mount the Telrad, but where I wanted to mount it put the long nose of the Telrad well past the end of the OTA.   I liked the viewing position, it made it quite easy to use, it did not interfere with the RACI viewer at all, however, it was not very aesthetic. 

 

50741299797_ff080e5f54_c.jpg

 

My only real option was to cut off the bulk and cut down the mount itself since it will only be attached on the rear legs.  I drilled two holes into the tube to place the mount, overall the mount width was about an inch. The batteries do not get in the way of the 1x view at all, but it would be nice to get a closed battery case to hide the batteries, but I can mount them to the side if they get annoying - who doesn't love velcro?  I used a left-over pool cue bumper to stabilize the Telrad against the end of the OTA tube rim using more velcro. Overall I think this looks MUCH better than the overhanging Telrad, and it doesn't use up so much space in the case, which is a nice bonus.

 

50740461478_e7dd31f98b_c.jpg

 

50740460948_df4814672b_c.jpg

 

For fan power, I purchased a USB cable so I could utilize a rechargeable battery pack instead of having to buy AA's, which I wrapped around the fan and put a smidge of hook velcro on the same side of the USB to keep it from dangling when not in use.  More velcro to hold the battery pack against the OTA, plus it adds a bit of weight for balancing.

 

50710372643_8c30e0622d_c.jpg

 

Since my neighbors love their floodlights so much, I decided to install a setting circle so it will be easier to locate stars that I cannot see.  I had a few red spokes from the last wheelset I built, so I figured I would use them as pointers on the Dob base.  I made up a setting circle and glued it to the base, then notched out the upper base, and installed two red wheel spokes.  The thought behind the second 90* spoke is so I can mark true North against my 0* indicator at the three spots in my yard I can view from.  Hopefully this will make setup even quicker when I can put the base at my markings without having to find True North, since my visibility of the North is practically nil. 

 

50842732947_4a18d1c3b9_c.jpg

 

50841923818_f42b390e60_c.jpg

 

All that is left is to wait for the digital angle gauge to show so I can get proper altitude.  I can't wait to try it all out!


Edited by Crankyanken, 16 January 2021 - 05:53 PM.

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#1538 FoxIslandHiker

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Posted 17 January 2021 - 06:49 PM

Cranky:

 

Good looking work.  Thanks for posting photos.  Very helpful.  I am also working on similar mods.  

 

Why did you pick a Telerad and not a Rigel Quikfinder?  Rigel Quikfinders has the advantage of fitting between the RACI and focuser without modification.

 

I have not seen an azimuth circle that looks quite like yours.  Where did you get the template?  Is it something you can share?

 

How did you seal the "wound" after you cut the V opening in your base?  Anything more than just black paint?



#1539 rlmxracer

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Posted 17 January 2021 - 08:20 PM

I have searched this thread for mods anyone has made to their 10” (or 8”) mirror cells. All the mods I’ve found were for 12” mirrors which have a much different mirror cell. I’ve done a lot of reading on Lockwood‘s site but most of the information there is geared towards giant mirrors. I don’t know how much of that design philosophy would improve a smaller mirror or if it even matters on mirrors below 12 inches. I just got a new mirror for my scope and was looking at it thinking if there’s any improvements that can be made now is the time. Thanks in advance.


Edited by rlmxracer, 18 January 2021 - 11:03 AM.


#1540 sunrag

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Posted 18 January 2021 - 10:07 AM

I am looking for ideas to install rubber feet to the bottom of a Z8, so that i can standup Z8 when it is not on the dob base.

The AD12 (and Z12) has an extra set of 3 holes tapped for M8 threads that i used to screw in 1” dia rubber feet. No extra holes are present in Z8. I don’t want to take out the locking mirror screws and use them. Thanks.



#1541 BradFran

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Posted 18 January 2021 - 10:50 AM

If you put stiffer springs in the mirror cell, then you won't need the locking screws and can use those holes to attach rubber feet. The locking screws should be M6.


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#1542 vicm

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Posted 18 January 2021 - 11:34 AM

What are the size of the screws to replace the ones on the secondary mirror?  I want to get ones that have the "twist" top but was thinking I could get them cheap at Lowes or HD rather than paying more.  Sorry if this has been covered before.



#1543 BradFran

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Posted 18 January 2021 - 11:43 AM

The three adjustment screws on the secondary holder should be M4. I replaced mine (GSO 10") with 30mm long metal thumb screws similar to Bob's Knobs. I couldn't find ones with rounded tips, that would be even better to avoid biting into the metal.


Edited by BradFran, 18 January 2021 - 11:44 AM.

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#1544 vicm

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Posted 18 January 2021 - 11:44 AM

The three adjustment screws on the secondary holder should be M4. I replaced mine (GSO 10") with 30mm long metal thumb screws similar to Bob's Knobs. I couldn't find ones with rounded tips, that would be even better to avoid biting into the metal.

Thanks!!! I also have a Z10.


Edited by vicm, 18 January 2021 - 11:45 AM.


#1545 FoxIslandHiker

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Posted 18 January 2021 - 12:12 PM

For the primary mirror adjustment knobs, I bought a package of springs from Home Depot for about $5.  It has 4 each of 20 +/- different size springs.  One size is the same as those that come with my AD10 on the primary adjustment knobs but significantly stiffer.  In this photo, on the left, is one of the original springs and on the right are the three I used as replacements.  Now I still have a variety of springs for other uses in the future.  (Bob wants $17 for these three springs.)

 

Springs.jpg

 

With these stiffer springs, the locking knobs are not needed.  I cranked the adjustment knobs down and then back off to get collimation.  Much easier to collimate without having to mess with the locking knobs.

 

For the secondary I used M4 x 40 socket head screws that I got from Ace.  I first tried M4 x 30.  They would work but were a little short.  The M4 x 40 are easier to use.


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#1546 Crankyanken

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Posted 19 January 2021 - 11:15 AM

Cranky:

 

Good looking work.  Thanks for posting photos.  Very helpful.  I am also working on similar mods.  

 

Why did you pick a Telerad and not a Rigel Quikfinder?  Rigel Quikfinders has the advantage of fitting between the RACI and focuser without modification.

 

I have not seen an azimuth circle that looks quite like yours.  Where did you get the template?  Is it something you can share?

 

How did you seal the "wound" after you cut the V opening in your base?  Anything more than just black paint?

Thanks!  I picked the Telrad primarily due to light pollution in my backyard so I can star hop around.  I have a 15' area where I have some shadow, but it only goes E and W, with hills and trees.  To view anything S, I am out exposed to several flood lights and streetlights which makes seeing stars a much harder in that part of the yard.   I may not use it as much now with the latest azimuth upgrade, but I think being able to star hop is worthwhile tool to have.

 

I would be happy to email you the PDF file, but I have already made another one since my viewing window is kind of large.  You can also make up your own HERE.  There are lots of options, allowing you to make it how you would like it.  The Z8 is 19 1/8" diameter and I used a slow tack adhesive spray to mount it to the base after cutting it out with curved scissors.  $15 for Staples to print and laminate the circle.

 

As far as sealing the wound, I have lots of matte black latex paint laying around, so I just gave it a few coats.  It's very rare humidity gets over 15-20%, and the same for the house, so I don't worry about moisture penetration as much.  Matter of fact, it is so dry here that I have never used a dryer in the 26 years I have lived here. 


Edited by Crankyanken, 19 January 2021 - 11:16 AM.

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