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    Re: Big fat sunspot and a solar eclipse
    From: Greg Rudzinski
    Date: 2014 Oct 27, 08:47 -0700

    Francis.

    See these posts on camera CN from the archive. Should keep you busy for a bit.

    http://fer3.com/arc/sort2.aspx?subj=camera+&author=&y=200701&y2=201412

    Camera CN is fairly straight forward for 200mm lens and larger. For 100mm and smaller things get complicated. Practical field of view is limited even with a 50mm lens (24°). The 200mm lens is close to metal sextant accuracy using a 10 MP camera and is a good place to start taking sunset images below 6° in altitude. Then graduate to Moon Jupiter/Venus lunars with the 200mm which will test your manual camera setting skills. The beauty of digital cameras is that an image result is immediately available to adjust ISO, fstop, and shutter speed manually. Automatic zoom digital cameras will disappoint. The Sun will need to be filtered by holding a neutral density filter or polarizer set out in front of the lens covering the Sun yet leaving the horizon unfiltered. Sometimes clouds will assist so that no filtering is needed.

    Greg Rudzinski

    From: Francis Upchurch
    Date: 2014 Oct 27, 11:00 -0000

    Thanks Greg.

    Yes, I think that is the what I need. I found one by Maude, very similar but cheaper. I will look into getting one when I return from this trip.

    Meanwhile, clearly the easiest ,cheapest way is your digital photography and software to work out pixel distances. I’ve never done this, so any advice on how/software etc would be welcome.

    Many thanks to you and Bill for all your advice. I will keep you posted on any progress, or otherwise!

    P.S. Have you done lunars with camera, lens and pixel count to measure LDs?

    If so, what results? Any details of how it is done etc.

    Best wishes

    Francis

       
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