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» Online Classroom   »   » Public Discussion of Cel Nav   » scopes on sextants, will this work?

Author Topic: scopes on sextants, will this work?

 - posted December 04, 2017 11:31 AM      Profile for navi           Edit/Delete Post 
This topic is on sextant scopes.

Since only one picture can be added at a time this will start with 3 posts.

This is the scope the sextant came with (Roger Poulain, Seine France).

It works well under good light conditions, but the horizon is hard to see for star sights.

Next will be a picture of my special adaption...

From: Chi

 - posted December 04, 2017 11:33 AM      Profile for navi           Edit/Delete Post 
This is a 4x40 from a binocular(Chicago made old but functional)that I dismounted and then addedd a bracket to.

Next will be the last post with the question in it.

From: Chi

 - posted December 04, 2017 11:39 AM      Profile for navi           Edit/Delete Post 
So here is the "new" scope with bracket made out of an old 4x40 binocular.

It seems I got it inline with the frame and the center of the scope is about centered of the mirror (left-right direction), and about at the center of the horizon mirror (up-down direction. But I have no fancy equipmnet to check if it is EXACTLY centered.

Wen I measure something (like moons diameer) I get the same value using both scopes.

The "new" 4x40 is clearly brighter than the 6x30.
What strikes me is that a 4 magnification leaves the body very small. (Buying a 2000 USD German sextant only getting 4x40 seems limiting.)

Do you think this homne made things will work, i.e, the precision will be the same?

From: Chi
Capt Steve Miller

 - posted December 04, 2017 01:55 PM      Profile for Capt Steve Miller           Edit/Delete Post 
There is no reason that the scope as described will notwork.
The horizon will not increase in brightness regardless of the magnification used with the scope.
A bigger object would be a bit better for measuring, but there really is not that much difference between a 4x40 and 6x30.

From: Starpath
David Burch

 - posted December 05, 2017 08:24 AM      Profile for David Burch           Edit/Delete Post 
Just an added comment. 4x40 is the standard telescope used internationally for daily work, all bodies, for very many decades. The higher power monoculars are used for sun or moon only and for checking the index correction.

It does improve sun and moon sights and the IC measurements, but is not crucial to good work. It is not useful for stars, in fact makes them harder, less light -gathering (30/40)^2 and too much magnification.

From: Starpath, Seattle, WA

 - posted December 06, 2017 05:19 PM      Profile for navi           Edit/Delete Post 
Yes I have noted that the 6 magnification is difficult for star sights, that was the reason to fit the 4 magnitude scope.

I have noticed that the 4 magnitude sits a but low compared to the other scope, it still works but having it higher will center the images better.

From: Chi

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