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Re: Practice Bubble vs. Professional Bubble
From: Robert Eno
Date: 2012 Aug 7, 18:55 -0400

Two bits' from the cheap seats.

I can more or less echoing Paul Saffo's observations.

I have not tried the practice bubble horizon offered by Celestaire, so I cannot comment on it.

I used to own one of the professional bubble attachments manufactured by Cassens and Plath. It did not meet my expectations so I returned it to Cassens and Plath for a refund.

I've tried the two latter versions of the C.Plath Bubble attachment mentioned by Paul Saffo and while they are both passable, I would not pay big money for them. With the "middle" version, at least you could adjust the intensity of the bubble chamber lamp; a feature which was absent from their last line of bubble attachments. This is one of the sad things about the once great C.Plath firm: they started cutting corners and seemed to go downhill from there.

So......drum roll please: Based on my own experience, the older style C.Plath bubble attachment with the adjustable bubble is the best marine sextant bubble attachment that I have ever used. My own experience suggests that being able to adjust the size of the bubble is crucial if one is to realize any accuracy in bubble attachment observations. Another great feature of the old C.Plath bubble attachment is that you could use it in daytime without the need for an electric lamp. I had a machinist turn an aluminum cap for me that replaces the light cap on the unit. I obtained a microscope mirror and mounted it on the cap. In this way, I can reflect sunlight right into the bubble chamber. The major drawback of the C.Plath unit is that it is of limited use for lesser magnitude stars because even at the dimmest setting, the bubble chamber light washes out the dimmer stars.

If we are talking aircraft bubble sextants, I believe that the RAE MK IXA series of British Aircraft sextants were the best and the most accurate bubble sextants ever made. Again, this is based on my own experiences.

Robert

----- Original Message -----

From: Paul Saffo

To: NavList@fer3.com

Sent: Tuesday, August 07, 2012 12:42 PM

Subject: [NavList] Re: Practice Bubble vs. Professional Bubble

David,
You have a third option -- an aircraft bubble horizon converted for use on a sextant. Cost typically runs $200 to $400 and they show up on eBay from time to time. I got mine from a member of this list who does an esp nice conversion.

I found the practice bubbles nearly useless.

I have three other AHs. Here is my opinion:
-- the converted aircraft bubble: best choice. It is affordable and is terrific for both day and night sights.
-- the last version Plath Bubble horizon. Fine for night, but very difficult for day sights because the lighting level isn't adjustable.
-- the middle version Plath bubble: it terrific for both day and night sights. It has an adjustable internal light powered from the sextant. It is my favorite AH.

I also have a 1941 continuo-style Tamaya Sextant with integral bubble horizon. It is a fascinating device, but awkward to use. After messing around with it for a few hours, it became obvious why so few of this style AH was made. A pain to use on dry land; I can't imagine trying to use it in a plane.

Finally, I don't have the earliest Plath AH (am still hoping to get one), but suspect it is the best option as it apparently has both an adjustable light and an adjustable bubble.

I am happy to send photos if you like, Feel free to contact me directly if you want to have a phone call about any of this.

best
-p

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