Kain Posted June 27, 2006 Share Posted June 27, 2006 I have been offered a brand new 40mm plossl for £8 off a mate who bought it then realised he had already got one lol.Are they worth it?It will probably be more useful on the 10inch rather than the 4.5..What do you think?Kain Link to comment Share on other sites More sharing options...
Albireo380 Posted June 27, 2006 Share Posted June 27, 2006 I guess that the quality of the Eyepiece will depend on who made it. Is there a name on it, or is no one owning up to it? Having said that, for £8 - does it really matter? Buy it, give it a try and if it is no good, then it has only cost you the equivalent of 3 pints of beer Tom Link to comment Share on other sites More sharing options...
Kain Posted June 27, 2006 Author Share Posted June 27, 2006 It's Antres or something like that!(probably made a complete fool out of myself by getting the name wrong lol)Kain Link to comment Share on other sites More sharing options...
Ambermile Posted June 27, 2006 Share Posted June 27, 2006 Having said that, for £8 - does it really matter? Buy it, give it a try and if it is no good, then it has only cost you the equivalent of 3 pints of beer TomOr eight cans of Grolsch :occasion5:Get it - you're not going to lose and it's only the higher-powered EP's you have to watch out for in faster scopes.Arthur Link to comment Share on other sites More sharing options...
Kain Posted June 27, 2006 Author Share Posted June 27, 2006 Ok fair enough!Oh and I only Drink Stella and Fosters Kain Link to comment Share on other sites More sharing options...
Ambermile Posted June 27, 2006 Share Posted June 27, 2006 Saturdays and Sundays? In that order?Arthur Link to comment Share on other sites More sharing options...
Kain Posted June 27, 2006 Author Share Posted June 27, 2006 Something like that yeah Kain Link to comment Share on other sites More sharing options...
GordonCopestake Posted June 27, 2006 Share Posted June 27, 2006 a 40mm eyepiece will give you very low magnification and very wide field views, a good addition to any collection. Some people use them instead of finder scopes heh Link to comment Share on other sites More sharing options...
John Posted June 27, 2006 Share Posted June 27, 2006 Hi Kain,Sounds like it may be an Antares plossl eyepiece in which case it's probably good - Antares stuff is usually very competatively priced but works well. John,North Somerset Link to comment Share on other sites More sharing options...
ric_capucho Posted June 28, 2006 Share Posted June 28, 2006 There's something about the plossl design that means that afov of a 1.25" plossl starts to decrease inherently above 32mm. We've never offered plossls, so I never got to the bottom of it, but it's there.Check out the Celestron/Meade/Tele Vue plossls, and you'll see that the 'standard' afov of about 50deg for the plossl range suddenly drops down to 43deg for the 40mm version.I tested against the Televue eyepiece calculator (on their website) and came up with the following: For a 200mm f/10 SCT, the 40mm gives yer 50x and 0.8deg tfov, while the 32mm gives yer 62.5x and 0.8deg tfov. With a f/6.8 80mm refractor, yer get 13.8x and 2.8deg tfov with the 40mm, and 17.2x and 2.8deg tfov with the 32mm. Erm, the tfov's are the same, so yer better off with the slightly higher magnification of the 32mm 'cos it gives yer a darker background.Of course, a cut price 40mm is also worth having, so if it's a half-decent brand, and it's been looked after, then bite his hand off.Ric Link to comment Share on other sites More sharing options...
GazOC Posted June 28, 2006 Share Posted June 28, 2006 Ric, is it that is pointless making a 40mm 52 deg eyepiece in 1.25" format? The 40 deg still gives the same TFOV as a 52 deg, your still at the limit of what 1.25" can show.Gaz Link to comment Share on other sites More sharing options...
John Posted June 28, 2006 Share Posted June 28, 2006 I think it's because the limiting factor to the field of view of an eyepiece is the diameter of the field stop, which is in turn limited by the internal diameter of the eyepiece barrel. So the widest field stop a 31.7mm eyepiece can have is about 28mm (basically the diameter of the inside of the barrel) which with a 40mm focal length equates to around 43 degrees FoV. This is also why 2 inch eyepeices can have wider fields of view.Vixen used to make a 45mm plossl in the 31.7mm fitting but the FoV was limited to around 36 degrees - that really was like looking down a narrow tube. Someone please correct me if I've got this wrong.John,North Somerset Link to comment Share on other sites More sharing options...
GazOC Posted June 28, 2006 Share Posted June 28, 2006 Thats what I said!! Link to comment Share on other sites More sharing options...
John Posted June 28, 2006 Share Posted June 28, 2006 Gaz,Yes you did - and you did it more concisely ! - I think it was Churchill who once wrote "..sorry for the long letter, I did not have time to write a short one...".Regardless of all that - £8 for a 40mm plossl has got to be worth a shout.John,North Somerset Link to comment Share on other sites More sharing options...
GazOC Posted June 28, 2006 Share Posted June 28, 2006 Regardless of all that - £8 for a 40mm plossl has got to be worth a shout.Defineatly, it still gives you the same TFOV as the 32mm. Link to comment Share on other sites More sharing options...
ric_capucho Posted June 29, 2006 Share Posted June 29, 2006 Oooooo, buy the damn thing. Yer can always sell it on Ebay later. :-)Ric Link to comment Share on other sites More sharing options...
GordonCopestake Posted June 29, 2006 Share Posted June 29, 2006 You'de probably be in profit if you sold it on ebay heheYou could go into business selling them at that price! Link to comment Share on other sites More sharing options...
iancandler Posted June 29, 2006 Share Posted June 29, 2006 yeah the anatres isnt that bad an eyepiece.. I have one myself. grab it at that price. Link to comment Share on other sites More sharing options...
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