A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2018 Aug 18, 22:00 -0700
I was hanging a sign at work the other day when a co-worker and I got into a discussion about levels. I told him that I had recently inherited a builder's level. (A very nice Keuffel & Esser, by the way.) He then told me that he had a transit he was trying to sell. I asked "How much?" and he replied "Fifty dollars." I told him I'd buy it as I am interested in precision instruments in general. Of course, I also wanted to try out some celestial observations with it, but I've learned that most people simply aren't interested in hearing all about that.
A few days later he brought it to work and I took it home. It's a David White 8307 and, aside from being extremely dusty, appeared to be in very good condition. Luckily, it fit the threads on the tripod which came with the builder's level. I set it up and proceeded to try and level it. And that's when I found out that it was completely out of whack. No matter how carefully I leveled it in two directions (90° apart), it was way out when turned 180°. So, against my better judgement, I decided to try and adjust it myself. Now, keep in mind that I know little to nothing about transits, especially how to adjust them. But, I figured I had little to lose and I don't know of anyone locally who could do it right, anyway.
Well, I must have done something right, because now the instrument levels almost perfectly. Or so I believe. I'm not 100% sure the telescope is parallel to the level, but the bubble stays centered when I turn the instrument now. I intend to do a "two peg test" with both the level and transit sometime in the near future. (Whenever I can convince my wife to be my rod ... lady.) Until then, I decided to shoot Polaris to see how accurately I could measure its altitude. The transit is a "five minute instrument", which means that the verniers only read to five minutes. But, I've found that I can interpolate rather easily, especially with a magnifying glass. Following are the results of a few attempts. I don't know what kind of accuracy I should expect with this instrument, but I was very satisfied with the results so far. Especially considering who adjusted it. ;)
David White 8307 Transit
Polaris Test Sights
2018, Aug. 17 09:38:00 UTC
2018, Aug. 18 07:52:03 UTC
2018, Aug 18 08:04:59 UTC
2018, Aug. 18 08:24:00 UTC