About Visual AstronomyCustom Telescope ModsTips & TricksNewsObservationsRSS FeedContact

Saturday, January 5, 2008

Zhumell Mod: Balance your OTA


Now that you've got that big aperture Dobsonian and all the accessories to go with it, does it still balance in its base? This was the problem I encountered once I attached my Telrad to the OTA. I realized that with the extra weight of the Telrad and my biggest eyepiece, the OTA wouldn't stay still if I put the telescope under 45 degrees altitude. This is a problem, but fortunately, one easily dealt with. Of course, one could just get stiffer altitude springs, or use Scope-Gripps, but that just works around the problem. I decided to actually fix it by adding a counterweight to the rear of the OTA. This is how I made my counterweight:

  1. Remove everything from the scope that did not come preinstalled. This included removing the Telrad from its base and no eyepiece in the focuser for me. Take these items (use your heaviest eyepiece for this) and weigh them. I used a kitchen scale. If you can't use a scale, my Telrad and 32mm wide-field eyepiece were approximately 1.25 pounds. Your mileage may vary.

  2. Okay, now we know that we need to balance out 1.25 pounds. Problem is, the business end of the OTA is longer than the mirror cell end, so it won't simply be 1.25 pounds of counterweight. To figure out how much weight you need, use this formula: Multiply the weight of these accessories by the length from the altitude bearing center to the tip of the OTA. This is the amount of torque that these accessories exert, and we need to counter this. Divide this torque number by the length from the center of the altitude bearing to the mirror cell. This will give you the weight you need to counterbalance your telescope. Mine came out to 2.34 pounds with a Telrad and big eyepiece on a 10" Zhumell.

  3. I went to Wal-Mart and got this running pack and a 2 pound dumbbell. I figured that was close enough to the 2.34 pounds I needed. The nice thing about this pack is that it has a hole for iPod headphones. This works great, because it lets you put the battery pack for your cooling fan in there, too. Just feed the wire out the hole, and plug it in to the port on the mirror cell.


  4. Then just strap the pack around the end of the OTA, making sure it is good and snug, and you're ready to observe without the OTA sagging near horizon!


Disclaimer: I cannot take any responsibility for any damages, to you or to your property, occuring before, during, or after performing this telescope mod or resulting from any advice taken from this website. Do so at your own risk.

Clear skies!

13 comments:

Diamond Dave said...

Pretty good idea. Might just be cheaper than adding magnetic conterweights. Thanks...

David

Sean Welton said...

Yeah, I tried the magnets trick, and while its nice that they're so easy to adjust, it seemed like it would scratch the paint up a bit on the OTA. So I decided to come up with this to prevent scratches and still allow some adjustability.

Sean

July 29, 2008 at 8:19 AM

Bruce Barbour said...

Searched through dozens of sites re balancing but this one solved my problem. As a former runner, I had the required belt and with 2 1/4 pounds of lead shot, it worked perfectly!! Oh, this was for a 10" Skywatcher collapsible Dob.

张栋 said...

nba jerseys
pandora jewelry
cheap uggs, http://www.uggboot.com.co
mcm handbags
kobe bryants shoes
rolex watches uk
michael kors outlet
ralph lauren uk, http://www.ralphlauren-outletonline.co.uk/
babyliss pro
roshe run men
foamposite gold
christian louboutin sale
stuart weitzman boots
coach outlet, http://www.coachoutletstoreonline.in.net/
michael kors outlet, http://michaelkors.outletonlinestores.us.com/
louis vuitton outlet
polo ralph lauren outlet
chanel handbags
instyler ionic styler
replica watches
oakley outlet
iphone 6 plus cases
oakley,occhiali oakley,oakley italia,oakley occhiali,oakley sunglasses
air force 1 shoes
gucci,borse gucci,gucci sito ufficiale,gucci outlet
michael kors outlet, http://www.michaelkorsoutletonlinestores.us.com/
nike free uk
washington redskins jerseys
oakley sunglasses
new orleans saints jerseys

dong dong23 said...

mont blanc pens
christian louboutin outlet
true religion outlet
jordan shoes
basketball shoes
coach outlet
coach outlet store online
adidas shoes
kobe 11
ray ban
jordan 3 infrared
louis vuitton handbags
michael kors outlet
gucci shoes
vans shoes
beats wireless headphones
coach outlet store online
nike running shoes
michael kors outlet
louis vuitton outlet
coach outlet
toms shoes
lebron james shoes 2015
kate spade handbags
tory burch sale
kate spade
oakley sunglasses wholesale
ray ban sunglasses outlet
michael kors purses
tods shoes
supra shoes
coach outlet
cheap toms shoes
oakley sunglasses
louis vuitton outlet
toms shoes
marc jacobs
louis vuitton outlet
louis vuitton
louis vuitton outlet stores
20164.9wengdongdong

Yuanyuan Lin said...

7.14lllllyuan"hollister shirts"
"true religion canada"
"true religion outlet"
"beats by dre"
"nike tn pas cher"
"ray ban sunglasses"
"tory burch outlet"
"mulberry handbags"
"prada outlet"
"michael kors outlet"
"tiffany outlet"
"louis vuitton neverfull"
"louis vuitton handbags"
"giuseppe zanotti shoes"
"nike uk store"
"michael kors wholesale"
"tiffany jewelry"
"michael kors outlet"
"ralph lauren pas cher"
"mulberry bags"
"nike air force 1"
"police sunglasses for men"
"gucci outlet online"
"ray ban sunglasses"
"jordan shoes"
"asics,asics israel,asics shoes,asics running shoes,asics israel,asics gel,asics running,asics gel nimbus,asics gel kayano"
"cheap jordan shoes"
"basketball shoes"
"fitflops sale"
"prada outlet online"
"ralph lauren polo"
"nike air max 90"
"omega outlet"
"lacoste shirts"
"longchamp outlet"
7.14

Zheng junxai5 said...

zhengjx20160715
nike store
michael kors handbags
toms shoes
coach outlet online
tory burch outlet online
kobe shoes 11
nike sb dunks
oakley sunglasses
celine bags
jordan retro 13
jordan 11
ray ban outlet
louis vuitton outlet
christian louboutin shoes
nike blazers shoes
cheap jordans
louis vuitton outlet
michael kors outlet clearance
retro 11
cheap toms shoes
kate spade
replica rolex watches
adidas stan smith
jordan shoes
coach factory outlet online
coach factory outlet
kd 7 shoes
ralph lauren polo
adidas outlet store
michael kors outlet
michael kors purses
kate spade outlet
coach outlet store online clearances
louis vuitton purses
lebron james shoes 13
nike roshe run
celine bags
louis vuitton outlet stores
coach outlet store online clearances
ray ban sunglasses

Rudy Lay said...

Super website with a great sharing and amazing stories is ur web.. please keep doing what u do now.. thanks to you.
Togel Online Singapore

Togel Online Hongkong

Bandar Togel Singapore

Bandar Togel

Togel Online Terpercaya

Bandar Togel Online Terpercaya

Togel Online

Agen Togel Online Terpercaya

Agen Togel Online

agen togel

agen togel indonesia

togel sgp

daftar togel online

Togel Online terbesar

bandar Togel Online

Rudy Lay said...

Super website with a great sharing and amazing stories is ur web.. please keep doing what u do now.. thanks to you.
Agen Bola Resmi

Bandar bola

Agen Bola Terpercaya

Agen Bola Terbesar

Agen Bola online

Judi bola

Berita Bola

Agen Sbobet

Agen Ibcbet

Rudy Lay said...

Super website with a great sharing and amazing stories is ur web.. please keep doing what u do now.. thanks to you.
Togel Online Singapore
Togel Online Hongkong
Bandar Togel Singapore
Bandar Togel
Togel Online Terpercaya
Bandar Togel Online Terpercaya
Togel Online
Agen Togel Online Terpercaya
Agen Togel Online
agen togel
agen togel indonesia
togel sgp
daftar togel online
Togel Online terbesar
bandar Togel Online

Rudy Lay said...

Your post helpful sanagta where I like it
Togel Online Singapore
Togel Online Hongkong
Bandar Togel Singapore
Bandar Togel
Togel Online Terpercaya
Bandar Togel Online Terpercaya
Togel Online
Agen Togel Online Terpercaya
Agen Togel Online
agen togel

chenlina said...

ray ban canada
louis vuitton outlet stores
ralph lauren uk
louis vuitton outlet
coach outlet
ray ban sunglasses
hollister outlet
michael kors bags
adidas yeezy
oakley sunglasses
chenlina20170307

alice asd said...

michael kors outlet
longchamp
cheap snapbacks
true religion outlet
hugo boss
cheap mlb jerseys
ugg boots
philadelphia eagles jerseys
cheap jordan shoes
kate spade outlet

Post a Comment