GSO/rev 12 or ortho 12

[nightfisher]

which would be the better ep for lunar viewing in my long focus scopes....my 12mm gso or a university 12mm ortho

[GazOC]

I use a 12.5mm volcano top UO ortho in my 180mm Mak and it gives great views at a very handy magnification. Never used the GSO though..

[nightfisher]

I use a 12.5mm volcano top UO ortho in my 180mm Mak and it gives great views at a very handy magnification. Never used the GSO though..

Thats interesting, think i would like to add a 12.5 to the ep box if one pops up cheap

[dobbie]

same here 12.5mm volcano top in my 100ed frac best lens iv'e got and i own a bunch of televues.. mmmmm...

[andrew63]

An ortho is always going to show more detail and contrast on moon and planets over a standard plossl - there is a post on here about the BGO ortho at least matching an ethos!

Sure you will notice the difference and they come up all the time used.

andrew

[nightfisher]

right, im on the lookout, might try for an 18mm as well

[hunterknox]

An ortho is always going to show more detail and contrast on moon and planets over a standard plossl

Not sure about that.

I'm a big fan of the GSO plossls. Probably the best value for money eyepieces going. The 15m still has a place in my eyepiece case, sat between Televue and Pentad stuff.

Plossls also have a slightly wider field of view than orthoscopics, which is always usefu, particularlyl if you're using an undriven mount. There's a favourable price difference too.

That said my personal preference would be for the orthoscopic. Plossls tend to give a slightly 'warm' image, whilst orthoscopics give a cooler image which is more to my taste. All subjective, mind you.

By the way, if you're after an orthoscopic in the UK then Glen at Lyra Optics is your man. One of the good guys (and he made my favourite telescope!).

[great_bear]

To be honest, on a long focus scope, theres no difference in planetary views between a 12mm volcano top and a Revelation plossl - I spent many nights comparing using a Mak 180.

I really wouldn't waste any time on it...

[andrew63]

This review my be of interest from cloudy nights - mind you it's very detailed!

6mm Lunar/Planetary Eyepiece Comparison - Review

[nightfisher]

thanks for the link andrew

[great_bear]

Ah, but we're talking about the 12 here - very different beast...

[andrew63]

Fair point! It does though outline some general trends of the ortho design which are valid for others focal lengths.

If you don't have a ortho in your armoury it is a very useful addition.

[nightfisher]

out of curiosity how would a 12.5 ortho perform in my st150 f5 frac, though im not really planning to use one in said scope

[great_bear]

out of curiosity how would a 12.5 ortho perform in my st150 f5 frac

Better than the Revelation Plossl (less astigmatism) - but at only 60x magnification, you'd probably prefer a widefield eyepiece.

[Moonshane]

I much prefer orthos to Plossls but this is partly due to preferring to see the field stop generally and also liking slightly netter eye relief. Plossl eye lenses always seem a bit sunken into the eyepiece to me making the eye relief a bit less accessible than orthos. in my eyes, orthos do give a cleaner more natural look with the expected lots of clarity and detail.

I have a 13mm Ethos and having sold my 12.5mm BGO a while back to fund a mount, I am now re-buying a used 12.5mm BGO. I like them that much.

[Adrian]

Plossl eye lenses always seem a bit sunken into the eyepiece to me making the eye relief a bit less accessible than orthos.

It is possible to solve this problem http://stargazerslounge.com/member-equipment-reviews/160181-antares-15mm-plossl-who-designed.html

Like you, I also don't mind seeing the field stop - I had a quick look throug a 5mm BGO yesterday (£48 second hand at Sussex Astronomy ) and it didn't seem that noticably narrower a field than a plossl (to me).

If it had been a 9, 12.5 or 18mm it would be in my case now. 5mm is just a little too short for that kind of outlay

[nightfisher]

really looking forward to getting one of these University orthos

[Stu]

Sorry to be cheeky Adrian, but I have an 18mm BGO which I'm looking to sell, pm me if you are interested in it :-)

Cheers

Stu

[great_bear]

really looking forward to getting one of these University orthos

You need to be aware that there's a couple of issues with the 12.5mm Volcano Top Ortho (sometimes known as the University Ortho or Circle-T Ortho or Tani Ortho)

1. It has - even for an ortho - a most unusually narrow field of view - measured at only 39 degrees by Mike Hosea on Cloudy Nights. This is narrower than any other focal length in the Volcano Top range.
   
2. It has a slightly misplaced field stop; the edge of the viewing circle is a bit fuzzy, which can be very annoying for some people.
   

From a personal standpoint, I've swung between the Baader Genuine Orthoscopics and the Volcano Tops. There is undeniably something very appealing about the classic design of the Volcano Top, but I now think that - should I re-enter ortho-land in future, I'll be going back to the Baader Genuine Orthoscopics. The Volcano Tops are just very "ordinary" in performance, nice though they are.

Finally, it's worth adding that if you are considering the 12.5mm Baader Genuine Orthos - and intend to use them for binoviewing - you need to make sure they are identical. The field-of-view size changed at some point in history, as have the coatings as well...