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George Huxtable wrote:
> Nicolas may find this useful; a part page from the catalogue of Edmunds 
> Optics Ltd, the British end of the US firm.
>
> Their address is - Tudor House, Lysander Close, York YO10 4XB, UK
>
> phone +44 1904 691469, fax +44 1904 691569
> email- uksales@edmundoptics.co.uk
> website www.edmundoptics.co.uk
>
> It shows two versions; one with precision of deviation angle 90º +/- 
> 1arc-min, and the other to 3 arc-min. Prices are in UK £.
>
> Or he may find it cheaper to cannibalize a defunct pentaprism camera, if the 
> size is right.
>   
And Geoffrey Kolbe wrote:
> Nicolàs wrote [NavList 9905]
>
>
>   
>> "Yes, we still have those prisms" was the reply, but at €747,- not
>> really a part one would just buy to complete an old instrument. Now I am
>> thinking of getting myself a separate prism (if that can be obtained for
>> less than that) and build myself the fitting that is needed to attach it
>> to the sextant frame.
>>     
>
>
> The size of the prism cutout in the box (shown on 
> your website) would presumably give you the 
> dimensions you need for the prism. I assume the 
> prism itself would fit in the cut-out and the 
> bracket to attach it to the sextant would be on top.
>
> I think €747 is a bit over the top. This looks 
> more like the market price for such prisms.
>
> http://www.cvilaser.com/Catalog/Pages/Template1.aspx?pcid=1664&filter=0
>
> So, for something closer to €100, you should be 
> able to make yourself a replacement.
>
> Geoffrey Kolbe
Thank you George and Geoffrey for these links. I think the 1 arc minute 
version George pointed out to would be the best option of the three and 
the 25mm versions would be, at GBP70,-, a good affordable alternative 
indeed. In the meanwhile I found a picture of an original pentagon prism 
on an even earlier C.Plath as you can find attached. It seems that the 
fitting is closed on all sides apart the two 90 degree faces and that it 
has one beam that allows it to be attached to the holes of the horizon 
shades on the sextant's frame. The prism is held in place by two angled 
strips with three screws each and from this side it seems not to have 
any adjustment screws. Furthermore it seems that one had to remove the 
horizon mirror completely in order to be able to use the pentagon prism 
as both would have been equal in height (32mm). Of course I would 
appreciate further details and pictures if any of you had such available 
(maybe from a catalogue?).

Nicolàs


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