Force 4 Practice Bubble Horizon for Sextant

Practice Bubble Horizon for Sextant

At long last, here is a way to effectively practice taking sights without having a natural (sea) horizon, and without spending hundreds of dollars for a Professional Bubble Horizon. With this, you can use the same sextant you will take to sea, and use it in a normal manner to take sights from your backyard. It differs from the more expensive professional bubble horizon in that it is not as accurate, is unlighted, and has less light gathering.

How it works

The scope is of zero-magnification, and is mounted on the sextant in place of the regular telescope as shown above. An ordinary spirit level is reflected by a mirror to appear upright in the opaque left side of the scope. The right side admits a view of the outside world as reflected by the sextant's index mirror (when using a whole horizon mirror, a horizontal view is also seen superimposed). The right side is divided by a horizontal hairline. The sextant is held such that the bubble appears alongside the hairline (as shown), and the celestial body is brought down to the hairline by movement of the micrometer drum. A reading is then taken and the time noted in the normal manner. The problem of focusing simultaneously on both the celestial body and the much nearer bubble is solved by using a slit aperture in the eyepiece. This acts like a lens to keep the bubble in focus without altering the image of the celestial body.

Capabilities

The scope is unlighted which prevents its use after dark. The bubble is exposed to ambient light, which is adequate for use during daytime, and the normal star observing period (twilight) when both stars and outside features are discernible. A sextant installation correction (SIC) is initially determined, and is applied to subsequent observations. The slit aperture slightly reduces the eye's natural light gathering to the extent that faint stars may be more difficult to ascertain. Test results with the Practice Bubble Horizon show repeatable observations to an accuracy of 2 minutes of arc under ideal conditions. Although this is quite good, and rivals that of many more expensive bubble horizons; its accuracy cannot be relied upon for all lighting conditions. Accordingly, we recommend this product for practice purposes only, and not for serious navigation.

The Practice Bubble Horizon fits the following modern metal sextants:

• Astra IIIB
• Astra III Professional
• Cassens & Plath
• C. Plath
• Tamaya (full sized)

This item is currently not available to purchase.

Royal Mail Service Update: Please be aware when choosing Royal Mail as your preferred delivery method, your delivery time may be impacted by ongoing strikes and may take up to 20 working days. If your order is time critical we suggest choosing a courier or Next Day Service

 

Our Mail Order team ship chandlery, yacht parts and sailing clothing around the world. We use the best value couriers available, and we will endeavour to get your products to you as quickly and as cost effectively as possible.

International Orders: Due to delays we have had to suspend our international delivery options. 

UK Standard Delivery

• UK Mainland 0 - 2Kg (small jiffy) £3.95 Royal Mail Service. Despatch within 3- 5 working days, delivery in 7-10 working days for orders under £50.00
• UK Mainland up to 25Kg £5.95 Courier service with signature. Despatch within 3- 5 working days, delivery in 7-10 working days
• UK Mainland 25Kg+ Price on request
• UK Mainland Next Day 0 - 25Kg £9.95 Courier service with signature, orders must be placed before midday
• Northern Ireland, Highlands & Islands 0 - 2Kg (small jiffy) £3.95 Royal Mail Service. Despatch within 3- 5 working days, delivery in 5-7 working days for orders under £50.00
• Northern Ireland, Highlands & Islands 1 - 25Kg £10.95 Courier service with signature. Despatch within 3- 5 working days, delivery in 7-10 working days
• Northern Ireland, Highlands & Islands 25Kg+ Price on request
• Channel Islands 0 - 2Kg (small jiffy) £5.95 Royal Mail Service Despatch within 3- 5 working days, delivery in 5-7 working days for orders under £50.00
• Channel Islands 1 - 25Kg £13.50 Courier service with signature. Despatch within 3- 5 working days, delivery in 5-7 working days
• Channel Islands 25Kg+ Price on request

UK Exceptional Delivery

• UK Mainland; Antifoul & paints £5.95
• UK Mainland; Inflatable dinghy £10.00
• UK Mainland; Liferafts £17.50
• UK Mainland; Flares £49.95
• Northern Ireland, Highlands & Islands; Antifoul & paints £9.95
• Northern Ireland, Highlands & Islands; Inflatable dinghy price on request
• Northern Ireland, Highlands & Islands; Liferafts price on request
• Northern Ireland, Highlands & Islands; Flares not available to ship at this time
• Channel Islands; Antifoul & paints £13.50
• Channel Islands; Inflatable dinghy price on request Channel Islands; Flares not available to ship at this time

For further delivery information click here.

Standard Returns

If you are not entirely happy with your purchase, we will exchange or refund your goods in full, provided that the items are returned within 14 days of receipt.*

Please check the condition of goods on arrival - we are unable to accept goods damaged during shipping after 14 days.

Returned goods must be packaged securely, with all original packaging undamaged and in a saleable condition i.e. shoe boxes must be in the same condition as when received.

Goods must be unused and security seals intact.*

If you would like to return goods because they were ordered incorrectly or if clothing does not fit, return postage will be at your expense. If you would like us to replace the goods with another size or colour, we will charge carriage on the replacement.

Please be aware that some navigational and safety products may be dated, and as such a full refund may in some cases not be possible. If you are purchasing dated navigational charts we suggest you contact us for more information.

Faulty Goods

If you receive your goods and believe them to be faulty, please contact us straight away with a brief description of the problem. If we require you to return the product for a replacement, we will send you a pre-paid Royal Mail label for delivery back to us. Unfortuantely we cannot send the courier back to collect the items.

Returning goods to Force 4 is easy!

1. Please contact us by ringing 0345 1300 710 or email on [email protected]. This way we'll be able to determine whether you would like to return the product for a refund or whether you'd like to exchange the product. We are unable to process the return of faulty goods that we're not expecting.
2. We'll then give you a returns number. This returns number will need to be clearly marked on the outside of your parcel so it can be identified on arrival. Please note, failure to mark a returns reference number on the outside of your parcel may result in a delay in processing your return.
3. Don't forget your proof of postage, just in case!
4. Once we receive the item we'll be able to proceed with a refund or an exchange.

*this excludes faulty goods with manufacturers defects. If goods are found to be faulty during use, after the returns period, please just give us a ring on 0345 1300 710 and we'll be happy to help.

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