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    Re: Sextant Shade (filter) Modification Help
    From: Greg Rudzinski
    Date: 2012 Sep 30, 21:00 -0700

    Trials of the solar film Sun shade were done this afternoon at the beach from the waters edge. Conditions were ideal with a sharp horizon and no wind. The Sun presented very well with just the right amount of shading to contrast against the horizon. A set of 5 observations were made using the 7 x 35mm scope. The average intercept was 0.4' with a spread of 0.6'.

    The only unknown to this modification is the durability of the film and silicone adhesive over time. Other than that I will recommend this as a very functional solution for replacing dark Sun shades.

    Greg Rudzinski

    [NavList] Re: Sextant Shade (filter) Modification Help
    From: Greg Rudzinski
    Date: 29 Sep 2012 17:19
    The Tamaya Jupiter's flawed dark Sun index shade has been removed by breaking the filter (ouch!) then removing from the frame. A piece of solar film has been cut to fit and glued to the frame exterior using silicone adhesive. The result is most satisfactory giving me for the first time all four index mirror shade combinations on this particular sextant. Trials are next.

    Greg Rudzinski

    [NavList] Re: Sextant Shade (filter) Modification Help
    From: Greg Rudzinski
    Date: 21 Sep 2012 16:03
    Thanks George and Bill for your reply.

    I tried the boiling water and no luck. The set of four index mirror shades are off the sextant but further disassembly is not going well. An odd nut is holding the works together. Haven't gotten to the Sodd's law part yet but I'm sure that if it can rust into place then it will rust into place ;-) As you say Bill the filter is held into the frame by a brass lip all the way around. I will be trying to bend it back. Not sure I'm up to breaking the glass filter though. That option is not yet on the table.

    Greg Rudzinski

    [NavList] Re: Sextant Shade (filter) Modification Help
    From: Bill Morris
    Date: 21 Sep 2012 14:00
    Greg

    The glass is "swaged" into place. This means that a thin lip of metal has been bent over the bevelled edge of the glass on one side. It is sometimes possible to lift the lip and free the glass by using a sharp point like the tip of a box cutter blade to raise the metal and then running round with the tip of a scriber. This also gives you a fighting chance of having some metal to bend back over the replacement, or you could use super-glue. Or, if the glass really is useless, you have nothing to lose by breaking it and picking out the pieces. It is then much easier to raise the swaged lip. I assume you have tried a variety of solvents to clean the glass and it is sometimes worth trying a very fine polish like rouge moistened with alcohol or even a good quality metal polish.

    All this is much easier to do if you remove the shade from its mounting. You remove the shades bracket from the sextant (one screw) and look carefully at its structure. Usually, there is an adjusting screw one end. Remove this first. At the other end will be the head of the pin around which the shades rotate. The pin is prevented from rotating by a taper-pin through the bracket. Remove this by tapping on the _narrow_ end. Then tap out the pin by putting a short length of 1.5 to 2 mm rod, such as a piece of bicyle spoke into the screw hole and tapping it. If tempted to replace the screw a little and tap it, resist the temptation; it is easily bent. Sometime the pin is prevented from rotating by a grub screw and, Sodd's Law being what it is, it is nearly always rusted in place. Sometimes there is a screw driver slot each end of the pin, just to make life difficult. Look carefully for a grub screw at one end. This is the end that will not turn...

    If stuck, feel free to contact me off list.

    Bill Morris
    Pukenui
    New Zealand
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