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From: Ken Muldrew (no email)
Date: Tue Mar 14 2006 - 11:21:25 EST
On 13 Mar 2006 at 18:10, wrote:
> I taken steps to take the mirror out of my
> equation by ordering a first surface optical flat mirror from Edmund Comm.
> Opt. 3" X 4" for $22. Hopefully being a 1st surface mirror will fix my
> 'blurry'reflected image and being a optical flat from Edmund should take
> the possible mirror-angle errors out. A couple of quick question before my
> mirror arrives:
> how 'sensitive' is a 1st. surface mirror to (a)placing a light weight
> sensitive level on it.
Are you wondering whether the mirror will bend under the weight of the
level? If so, I don't think that will be a problem. But leave the level in
place when you take your sights as removing the level might take the
mirror out of level.
> and (b)is there a scratch /corrosion resistant
> coating over the aluminization?
Usually there is, but you can call Edmond to find out for sure.
> (c) how was $22 as a price?
Cheaper than Melles-Griot and more expensive than Surplus Shed, but
nothing to worry over. Before the mirror arrives, I think you should use
the accuracy of your spirit level to calculate the error in your altitude
measurement, otherwise you may be surprised with the result.
Ken Muldrew.
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