15mm superview?

[JJDOBBER79]

Hi there.
I recently bought a 2" 30mm superview from andrews. Best 50 I've ever spent. There is a massive difference from the plossls that came with my scope. Do they only make a 30 and a 42. Something like a 15 or a 17 would be great. I'm not really keen on spending hundreds on a televue (yet)

[mental4astro]

Andrews also has the 15mm Superview. It is just as great value as the 30mm. I've still got both my 30mm and 15mm Superviews.

[brian nordstrom]

:thumbsup: +1 for the 15mm super view .
A year or so back I grabbed one from Andrews for a friend so he could use it in his Meade scope and when it arrived I tried it out and WOAW!! , what a great eyepiece , I had trouble handing it over when the time came , that good and for the price none better in my opinion .
Brian.

[glend]

+1 for the GSO Superview 15mm. I have the 30mm, 20mm, and 15mm Superview and they are great low cost, reasonably wide field eyepieces and hard to go past at their price.

[JJDOBBER79]

Are you guys sure that they do one in a 2". I thought i tried and couldn't find one. I guess I can go for a 1.25. The 30mm is also the first 2" I've used so that probably contributed to how impressed I was with it. I will definitely buy one if I can get it.

[glend]

The 50mm, 42mm, and 30mm are 2" EPs, the rest of the range is 1.25". Check out Andrews Comms website, they are all listed down near the bottom of the Guan Sheng section.

[SkyWatch]

The shorter focal length eyepieces: 20mm, 15mm etc are 1 1/4", because there is no advantage to making a 2" in this focal length. You wont get any more light in because at these focal lengths the field stop is smaller than the maximum aperture of a 1 1/4", let alone a 2" (unless you go for an 82 degree or above apparent field like a Nagler of Ethos: and even these are 1 1/4" for any focal length below 17mm).
So have no fear in buying the 20mm and below Superviews!

[JJDOBBER79]

Thanks for the info. Looks like 1.25 it is.

[bigjoe]

I also have a superview 20mm and 30mm. These eps let in a lot of loverly light.
Its amazing how often I reach for them ahead of some more fancy ones, just to get those extra photons.
Money well,well spent.
Cheers bigjoe.:thumbsup:

[raymo]

I can assure you that my 2" 15mm 80degree is a different ball game from a 1.25". The only time I ever use my 1.25" is if I am imaging and
don't want the aberrations that you get in the outer part of the F.O.V.
of very wide angle eyepieces. It also works well with the 1.5x barlow
that came with my 2" 30mm eyepiece.
raymo

[jjjnettie]

My GSO 1.25" 15mm superview is the most used eyepiece in my collection. :)

[mr bruess]

I also have a superview 20mm. it is very good budget eyepiece.it is sharp to edge in my 90mm meade star navigator but not with my 10 inch dob

[mental4astro]

Mr Bruess note here is a VERY important one here. AND clues are being given by others as to the BEST SCOPE for the SuperView eyepieces.

What am I getting at?

Eyepieces are actually designed to be matched to a particular scope design, be it a Newtonian, refractor, SCT, Mak, etc. This is because the focal 'plane' produced by a scope is actually not a flat one, it is curved - Newtonians produce a concave focal plane; refractors, binos (binos are not simple refractors either) SCT's and Maks produce a convex focal plane. Eyepieces in turn, because they are designed to work with a particular native curved focal plane, they will work brilliantly with one shape and poorly (if not crap!) with the opposite shaped curve.

Remember, this does not mean that there is a fault with the eyepiece. There isn't. Telescope optical geometry is much more complex than we think of at first. It is only when we start trying to take photos that we begin to experience an unevenly focused field in our pictures, or a highly distorted image in our eyepieces do we begin to get our first notions of things not being so simple. Then we begin to resort field flatteners, field correctors, coma correctors (not an immediately related aberration, but ultimately it is a related cousin) to help eliminated these problems.

Add into the mix a staggeringly large variation in f/ratio within any one scope design (Newtonians go from f/3.3 to f/20, refractors f/5 to f/30, etc), and even the radius of the focal length, and then we begin to really get a sense of the complexity in eyepiece/scope matching. And I haven't even added the order of difficulty that different eyepiece designs, focal lengths, coatings, glass types, etc, all add to the mix!!!

All is not lost though, :D

While there are eyepieces that are good only in one scope design and poor in others, there are some that can do very well in one and ok in others, and a few that can do very well in just about all! Some of these are surprisingly inexpensive, like the SuperViews (great in refractors and ok in Newt's). Some are much more expensive (Vixen LVW and TelVue Delos lines). But with ALL of these, there will be variations in performance within their different focal lengths - there has to be, and this is both visible and noticeable with eye strain. Only adding to the complexity here, within the one eyepiece line that is designed for a particular scope, there can be just the single focal length piece that actually does do well in all scope designs!!!

BIG bucks is not guarantee of similar performance of any one eyepiece line doing well in all scopes either. The excellent Pentax XW line is one of the more obvious ones. These are excellent eyepieces, BUT some focal lengths are definitely only for one scope design and not for others.

The biggest problem we have a consumers is the manufacturers do not tell us these things. They fear having their equipment being misinterpreted as 'faulty'. Truth is the complexity of the eyepiece/scope equation is so big, and most people do not have the understanding nor the inclination to want to understand, that the manufacturers find it safer to not say anything. Then we few who are actually interested in optics, get it in the neck with misinformation and spending big $$$ on gear that does not work (match is the better phrase), and we do not understand why, :(

Yes, I like the SuperView line. These are a take on the old Erfle eyepiece design. In a refractor these are very good, good in SCT (these have reflecting components that add their own set of aberrations), and good to ok in Newt's (depending on EP focal length). Just understand that their price is not a true or remotely complete reason for their variation in performance. There's a little more to this...

Mental.

[Akwestland]

Alex (or others),

An interesting read this one. It touches on some niggling thoughts I have been having when it comes to EP's and associated items.

Is there any site/resource that comes close to answering this type of question or is it a case of reading several sites and user reports to create a (hopefully) educated opinion. I hope that this is not a silly question.

Secondly, how do things like filter wheels(for example) affect the overall visual integrity. I assume that this type of item would move the EP further away from the secondary mirror, therefore does that not affect the usable focal length of the EP, or am I missing something?

Cheers,
Andrew.

[mental4astro]

Hi Andrew,

A very good place to start is here:

Telescope Optics (http://www.telescope-optics.net/)

There is also book by the same title, that is referenced in the above site:

http://www.bintel.com.au/Accessories/Books--Charts-and-Software/Telescope-Optics/659/productview.aspx

You might want to have a box of asprin close by... :question:

[Akwestland]

Alex,

Thank you for that, it looks like a comprehensive read, I will aim to wade my way through that site, but not too quickly. I am sure as I go through it it will become apparent that I should have stayed awake in math class at school.

Cheers,
Andrew.