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    My New Toy
    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
    Hs: 37°45.0'
    R: -0°1.3'
    Ho: 37°43.7'
    Hc: 37°42.6'
    δ: +0°1.1'

    2018, Aug. 18  07:52:03 UTC
    Hs: 37°35.0'
    R: -0°1.3'
    Ho: 37°33.7'
    Hc: 37°35.6'
    δ: -0°1.9'

    2018, Aug 18  08:04:59 UTC
    Hs: 37°37.0'
    R: -0°1.3'
    Ho: 37°35.7'
    Hc: 37°36.9'
    δ: -0°01.2'

    2018, Aug. 18  08:24:00 UTC
    Hs: 37°38.5'
    R: -0°01.3'
    Ho: 37°37.2'
    Hc: 37°38.6'
    δ: -0°01.4'

       
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