Circle T Ortho?

[paul mc c]

How close are these to BGO in quality.

Paul

[nightfisher]

close, depends on your taste in ep`s i have a nice 12.5 circle T volcano top, i also like my BGO 18mm, the BGO`s are probably better in the smaller focal lengths

[dweller25]

Very close .....

The BGO costs 30% more than the circle T but is maybe 5% better..... it has slightly more contrast.

Personally I find the volcano top orthos more comfortable to use than the flat top BGO's

[John]

I agree with the above assessments. Small improvements in the BGO except for ergonomics. Sometimes small improvements matter though .... they can make that subtle, "on the limit" detail just a little bit easier to see

Generally, it's during the periods of excellent seeing that these differences are a little more noticeable I've found.

[paul mc c]

I just picked up a 6mm for a good price,giving the rare times you can use a 6mm i cant go wrong i suppose.

Paul

[4lefts]

has anyone tried the circle-ts in a pst? i'm on the look out for one nice ep to use with mine. how about the bgos?

[John]

I found the PST not too fussy about eyepieces - it seemed to work well with everything from a cheap plossl to an Ethos. I reckon orthos would work fine.

[Damo636]

Does the Circle T and the BGO have the same afov? I may be wrong but i think i read somewhere that the BGO has a slightly wider afov.

[AndyH]

I'd take manufacturers published afov's with a pinch of salt.

I've measured the field stops on most of my eyepieces and with some exceptions(eg:Tal's), the true fov is often considerably lower than the published afov.

Take the good ole volcano topped orthos(edit: these calculations were not done by me, but were published on an excel eyepiece file available on 'cloudy nights')

FL/published afov/calculated fov

4mm : 41 / 42

5mm : 43 / 38

6mm : 43 / 40

7mm : 42 / 38

9mm : 42 / 42

12.5mm : 44 / 39

18mm : 46 / 41

25mm : 47 / 40

Have yet to read anywhere this calculation done with either U.O. or Baader flat-tops. Would be interesting to find out.

It's relatively easily done if you have an accurate set of calipers.

Andy.