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    Re: Measure the Sun's diameter
    From: Frank Reed
    Date: 2013 Jan 7, 11:05 -0800

    I forgot another bit of advice. Nine years ago, in one of my first posts on lunars, I described holding the sextant with both hands and adjusting the micrometer separately, as follows:
    "I usually do the lunars observations themselves with both hands on the sextant frame since the angle at which you have to hold the sextant is often awkward --and even painful after a few minutes. Holding he instrument stably is critical. To make this work, I would alternate between adjusting the sextant angle, making small adjustments of the micrometer, with the actual process of looking through the sextant. The lunar distance changes so slowly that you don't really need to keep a hand on the micrometer while observing (as is essential with altitude observations)."

    This was a rather long post which I rather enjoyed re-reading just now. I recommend it! ;) You can read it here:

    My comment above about tweaking the micrometer and then looking through the sextant with both hands on the frame applies even more so to the measurement of the diameter of the Sun since it doesn't change for days. This process is much less stressful than ordinary altitude observations. You're not chasing a rapidly moving body, trying to swing the arc, and trying to make sure you've got the horizon in proper view (not hidden by a swell, as it may be from the deck of a smaller vessel). In this respect, lunars are actually EASIER observations than common altitude observations. You don't have to worry about the horizon, and there's much less rush involved.


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