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Hi Professor,

Heath made a nice sextant; I have two (2) similar sextants: a ~1910 Heath 3 ring, vernier and 1975 Heath 3 ring, micrometer.  The later was used in 1991 and 1995 during the Marion–Bermuda Cruising Yacht Race (see pics).  Anyway, here are my answers to your questions:

Question 1:
>The ring where the primary scope screws in is angled upwards about 45 to 50 degrees. I'm told this should point at the horizon mirror, which BTW is missing.
>I'm letting a little WD 40 soak in

Answer 1:
I agree it needs to be realigned.  I inspected my 1910 Heath 3 ring, vernier sextant (similar to your 1944 Model 802) and it does not want to move; also, I was leary of forcing it.  The WD-40 might work but it stands for "Water Displacement, 40th formula" and I suggest you use a more applicable product: Kroil Penetrant:
https://www.kroil.com/product/kroil-original-penetrant/8-oz-drip-kl081/

Question 2:
>horizon mirror...The index mirror is missing as well and I'd like to replace them.
>where I can get replacement mirrors

Answer 2:
Buy a used Heath 3 ring sextant (1940's) for parts e.g. eBay, etc.  

Finally, I recommend you reach out to Ridge White and ask him your questions:
Ridge White, President
62 Washington Street
Marblehead, MA 01945
+1 (503) 359-7467
https://www.robertwhite.com/

Ridge's father sold me the 1975 Heath 3 ring, micrometer sextant and he has recently serviced my three (3) sextants - great guy!

Have fun!

--
Ian Gifford 42° 38' N, 71° 24' W

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