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Re: Corrections for air bubble sextants
From: Howard G
Date: 2022 Jul 29, 22:02 +0000

Hi Juan

Good choice, I have used both those sextants as a air force navigator.

I am a bit rusty but typically corrections applied were

Altitude

Parallax

Coriolis

Refraction

And an error if you where shooting through a perspex dome, which we did with the Mk IX.

Ignore altitude and coriolis as you are stationary.

I think marine adjust for dip which doesn't apply.

Parallax and Refraction are highest for low horizon stars, so shoot stars high.

I would think your greatest worry are errors in your sextant and having never used a bubble sextant.

I would just start shooting and calculating and settling your sextants in on high stars.

Once you became proficient and shots start to settle into good readings corrections can then be applied.

The beauty being, you know where you are.

Howard G

Sent from my Galaxy

-------- Original message --------

From: Juanjo Garrido <NoReply_Garrido@fer3.com>

Date: 30/7/22 00:47 (GMT+10:00)

To: Howard George <HHG@raptorbusinessservices.com.au>

Subject: [NavList] Corrections for air bubble sextants

Hello,

Thanks all for contributing to this forum. It is pretty unique and full of interesting people.

I have been always interested in celestial navigation. After reading a little bit, watching some YouTube videos and following this forum, I decided to move on and I got a Kollsman periscopic sextant and a Mk. IX bubble sextant. I went for bubble sextant as I live in Central Europe with no access to big water masses. I know that I could have gone for an artificial horizon and a regular sextant, but I have always been fascinated with aircraft instruments, so I couldn't resists.

My problem now is that I am not sure about doing correct observations. All the tutorials I have found are for regular sextants, and I'm afraid that not all the corrections apply. Or it might be that there are others corrections to be done. Is this assumption correct?

How different is to make an observation with a marine sextant and a bubble sextant? Could you point me to a document/tutorial/article?

Could you help me finding my way?

Thanks in advance.

Juan J. GARRIDO.

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