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Vertical Circle Adjustment

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(@frank-willis)
Posts: 800
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Question. When doing multiple shots direct and reverse, assume the software tells you that the vertical circle index variation is 16 seconds. Does that mean that when the instrment is level it could be off by about half that or 8 seconds?

 
Posted : September 18, 2010 4:23 pm
(@plumb-bill)
Posts: 1597
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Assuming you have an instrument with a working and well adjusted tilt compensator and are making accurate sightings and you have a better than 10" gun and you can read run-on sentences - you will need to run the collimator calibration routine, assuming it has one. 😉

 
Posted : September 18, 2010 5:19 pm
(@jim-frame)
Posts: 7277
 

> Does that mean that when the instrument is level it could be off by about half that or 8 seconds?

Sounds like it to me. Example: You turn to a distinct target and read 90°00'00" direct and 270°00'16" inverted. Assuming that all of the error is in the vertical index setting (i.e, the horizontal axis bearings aren't sloppy, the circle is correctly divided and the sensors are working as designed), that means that when the gun reads 90°00'00" it's actually pointing 89°59'52".

 
Posted : September 18, 2010 9:17 pm
(@peter-ehlert)
Posts: 2951
 

Lots of good advise!

My old school way is to first disable the electronic compensator and see how the actual "machine" is adjusted.
Of the several I have tried it was often way too far out for me so I adjusted the cross hairs to get warm and fuzzy, then went on to re-enable the the electronic compensator and checked it again.
I understand those 'black box' electronic compensator fixes do have their limits to how much error they will take out, and we all know that error messages are often misleading.

To adjust the "machine" is rather simple, you can do it.
I needed to learn that skill on a T1 "back in the day" after tumbling down a few hill sides and the "shop" was days away (and no paycheck while they did what I could do). Better to practice on an old open wheel transit where you can visualize what is really happening.

While you are at it, you can check your Hz plate too!

 
Posted : September 19, 2010 7:22 am