NavList:

   

Reply

I was the one who recommended oil over corn syrup.  The purpose is to
darken the pan to improve reflection, as George and Jim pointed out.
Paint also will darken a pan, and is effective, but oil only in a pan
sloshes out more easily than oil over corn syrup.  The spilled oil is
messy.

Used motor oil is somewhat toxic, which is why I prefer vegetable oil.

Vegetable oil becomes rancid with time.  You can pour off or suck off
rancid oil on top of corn syrup and replace with fresh, and the wife
tends to complain less at the amount of oil being used!  If you keep
the oil out of the sun, the rate at which it becomes rancid is
lessened.

Have not tried tea, but I don't drink it often.  Perhaps coffee for us
Yanks!

Fred

On Feb 19, 2005, at 11:53 PM, Alexandre Eremenko wrote:

> This question was discussed a lot in October 2004,
> and I want to add something.
>
> Recently I made many experiments with Davis art horizon
> sold by Celestaire.
>
> I tried various combination of Caro syrup and oil,
> Caro syrup alone, and oil alone.
> (Caro syrup was recommended on this list).
>
> The best "combination"
> seems to be pure vegetable oil, without any syrup.
> I really don't understand why this sirup was proposed.
> (To make the bottom darker? What for? And if this is
> indeed useful, why not to paint the bottom of the horizon
> vessel black with ordinary paint?
>
> The syrup hardens when the weather is cold (it was 23 F last
> weekend), always has impurities and causes double reflection
> unless the oil layes is extremally thin. Such thin layer of
> oil is usually not enough to smoothen the surface of sirup.
>
> I Have not tried the dark (mahine) oil yet, but why it is
> considered useful to have dark substance in general?
>
> Alex.
>
> P.S. I DO understand why Bauer and others recommend sextant
> mirrors painted black on the back side (to prevent second
> reflection from that back side) but with liquid filled art horizon
> with plastic botom it is different: there is no reflection
> from the bottom.
>

   

Reply