Eyepiece choice

[louie_the_fly]

:question: I'm looking to buy a new eyepiece in the 40mm range. I don't want to spend a lot so I was looking at a 40mm (Bintel) Plossl v's a 42mm (Bintel) Superview.

Opinions???

[mental4astro]

There is one main difference between the plossl & SuperView you mention, the former is a 1.25" EP & the latter is 2". Unless you have a 2" diagonal on your SCT you'll be limited to the 1.25".

The difference similar focal length EPs will have in the barrel size is how wide an Aparent Field of View (AFOV) they can go due to the size of the barrel. The wider the barrel the wider the AFOV can be for a long focal length EP. With these two you mention, the plossl's AFOV is a small 43*, the SuperView's is a hefty 68*. This in turn means you'll see a wider patch of sky in the SuperView over the plossl's by some 50%.

The magnification each offers is pretty much the same, the real difference is the AFOV. If you have a 2" focuser, I'd recommend the SuperView. The SuperView's are a very good EP for their price.

For comparison, the Plossl: http://www.bintel.com.au/Eyepieces-and-Barlows/Bintel-/Plossl/Bintel-Plossl-40mm/358/productview.aspx

The SuperView: http://www.bintel.com.au/Eyepieces-and-Barlows/Bintel-/Superview/Bintel-SuperView-42mm/364/productview.aspx

Mental.

[Varangian]

I have the 30mm GSO (Bintel) Superview 68 deg FOV. The 42mm are also 68 deg. Nice ep for the price. I purchased it from Andrews Communications. What is the FOV of the plossl?

[mental4astro]

Did the maths:

40mm plossl, 43* AFOV, gives magnification of 50X in a C8

Field of view (actual amount of sky) is 43 / 50 = 0.86*

42mm SuperView, 68* AFOV, gives magnification of 47.6X

Field of view is 68 / 47.6 = 1.43*

The SuperView shows nearly 2.8 times as much of the sky than the plossl!

[louie_the_fly]

Thanks for the replies and the info. I ended up ordering the 30mm Superview. Currently my largest eyepiece is a 26mm Meade Series 4000 and it seems to be OK for most things. That's why I didn't end up going the 40mm.

Hope I've done the right thing... Will have to wait til it gets here I suppose.

I also ordered a crayford focuser. Christmas has come early. :thumbsup: