Quote:
Originally Posted by Merlin66
Certainly worth trialing. The published results show low efficiency but used as an objective prism, may still be OK. Look forward to seeing some results.
BTW Paton-Hawksley do a "standard" range of transmission gratings for about the same price.....
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The cokin "filter" is very poor for spectroscopy (It is designed to give a little rainbow effect on photographs and as so most of the light goes stright through (only 5% into a useful spectrum) The "Jeulin" grating immediately below on Christian Buil's webs page is 8 times more efficient and is in fact the one manufactured by Paton Hawksley that the Star Analyser was developed from. As you say they can be bought cheaply from PH
http://www.patonhawksley.co.uk/nuffield.html
(model TE218b)
note the other l/mm gratings on this page are not particularly efficient unfortunately)
As you might expect, they are not as efficient or consistent in quality as the Star Analyser but they are much better than the Cokin filter and is what I used to start with.
Cheers
Robin
www.threehillsobservatory.co.uk