HELP 155mm triplet f/1.9 for a super fast refractor??

victorpei (Victor) · #1 07-11-2010, 03:30 AM

Hey all,

I saw a lens package, which is a 155m triplet f/1.9, together with a 85mm doublet which is said can bring the f number up to 3.25.

I dont know much about refractor. I find the normal f value is about 7-10, so 3.25 is much lower than that. Don't know what does that mean. My question is

1) Is it possible to build a superfast refrator with this lenses package?
2) How to build a refractor with 2 set of lenses, a simply digram will help a lot.

Thank you with your time and help, and, of course clear sky!
Victor

robz (Robert) · #2 10-11-2010, 01:17 PM

Quote:

Originally Posted by victorpei

Hey all,

I saw a lens package, which is a 155m triplet f/1.9, together with a 85mm doublet which is said can bring the f number up to 3.25.

I dont know much about refractor. I find the normal f value is about 7-10, so 3.25 is much lower than that. Don't know what does that mean. My question is

1) Is it possible to build a superfast refrator with this lenses package?
2) How to build a refractor with 2 set of lenses, a simply digram will help a lot.

Thank you with your time and help, and, of course clear sky!
Victor

Victor, this guy has had that lens on Ebay for ages and can't sell it.
I'd say that it's only good for starting camp fires without matches