250mm dobsonian dimension.

[wormix]

Good evening all,

 

I have an Orion IntelliScope 250 OTA that I need to build a mount for. To start with I was just going to copy an existing mount and to ensure I’m in the right ballpark would anyone be able to tell me what height off the base the Alt pivot is?

 

As it’s a synta tube it should be the same on a skyliner 

 

cheers

[pjsmith_6198]

The Alt pivot should be located on the OTA's center off mass.    So measure from the midpoint of alt bearings to the end of the tube.  Then add a couple of inches in case you add a RACI finder and or heavy EP's in the future so you can re-balance the scope.     Do you have  azimuth bearings?

I have a Z10 which I re-built the mount based off the Stellafane.org design here https://stellafane.org/tm/dob/mount/index.html   because I added a 60mm finder , a telrad, and used heavy EP's.   I couldn't adjust the altitude bearings enough to balance the scope.    I found the large bearings worked better than the stock bearings.   But if you have working alt bearings and don't have extra stuff on the front end you can just copy the existing mount design as long as you have the azimuth bearings.

 

Phil

 

 

[NGC 1502]

7 hours ago, wormix said:

I have an Orion IntelliScope 250 OTA that I need to build a mount for. To start with I was just going to copy an existing mount and to ensure I’m in the right ballpark would anyone be able to tell me what height off the base the Alt pivot is?

 

The previous post has good advice, allow a couple of inches/ 50mm clearance between the lower end of the tube and the mount base board, or greater if you’d like a higher eyepiece position.

Worst case you can always add weights to the tube for balance.

Good luck with the build, Ed.

Edited December 4, 2019 by NGC 1502
Correction