How good are Radians?

[acey]

All my eyepieces are Televue Plossls and I was thinking of getting myself a Radian.

The Radian doesn't come off too well here:

6mm Lunar/Planetary Eyepiece Comparison - Review

but the emphasis there is on lunar/planetary, and the reviewer does describe the Radian as a "great jack of all trades and my preferred wider field eyepiece". That sounds fine for me as I'd be using it for deep-sky. However according to this review:

12mm Radian and 12mm Pentax XF - Review

the Radian "is not recommended at all for galaxy observers" because of its poorer contrast compared with the Pentax.

It leaves me wondering if the only thing I'd be paying for is a wider field of view - which is of less importance to me than seeing fine details in DSOs (i.e. optimum light transmission and contrast). Maybe I'm better off sticking with what I've got, or getting an ortho?

Andrew

[Ben Ritchie]

Personally i've always considered the Radians the weakest of the Televue line-up. Some time ago I got to try out a pair of Radians alongside B/TMB planetaries of the same focal length and wasn't particularly impressed, the fit and finish was better with the TV eyepieces as the B/TMBs are relatively basic but optically the two were rather similar on-axis on lunar/planetary and double stars, didn't try DSOs from what I remember - would need to dig out my notes to be sure. At f/5 the Radians were better corrected at the edge, but the B/TMBs weren't bad. There certainly didn't seem to be enough in the Radian to justify the (much) higher price.

[acey]

Thanks for that. I had a quick look and it seems the B/TMB planetaries are no longer available so it might be one to look out for secondhand.

[Ben Ritchie]

I think (but i'm not certain!) that the TS planetary HR eyepieces are the same as the B/TMBs

Eyepieces @ Modern Astronomy

if not, the B/TMBs turn up used for around £40-45 quite regularly and are very easy to sell, so well worth picking up one to see what you think. Potentially a lot cheaper than Radians unless you're using a fast Dob.

[acey]

Ah, well I am using a fast dob - 12" F5.

Saw these on Ebay - are they the same thing?

Eyepiece Planetary 1,25", premium Qu, designed by TMB on eBay, also, Telescopes, Binoculars Telescopes, Photography (end time 13-May-09 07:38:18 BST)

[Ben Ritchie]

By "fast" I meant more f/4 than f/5, but it depends on your preferences - if you want well-corrected to the edge then the B/TMBs aren't going to cut it even at f/5. I didn't mind too much, but I'd suspect they'd be suffering at f/4.

The ebay ones look the same, I think there are a number of variants around (possibly the cause of the demise of the B/TMB version of the eyepiece?)

[steve51450]

TMB Eyepieces

try this link as i find we are ripped off in the uk for burgess tmb's $40

even with the postage if you get a few you will still save loads.

i have a full set from 2.5mm to 9mm and as Ben say's for the money you can't beat them

on axis they are superb, with great eye relief and a 58 degree field of view, a fantastic planetary ep all round. The 9mm i use for deep sky like globs etc

[John]

Interestingly, the Radian is the only Tele Vue eyepiece design that I've never tried. I have tried TMB Planetaries / TS Planetary HR's and they are very good - at least down to F/6. Personally I've found the Nagler T6's to work extremely well for medium and higher power viewing - even compared back to back with good Orthos they give very little away in peformance (nothing that I could detect in fact) and the wide FoV is very nice in my un-driven scopes !.

John

[ollypenrice]

I have a 10mm Radian and like it. Because many people use my kit I have to bear in mind spectacle wearers and here the LER of the Radian is great, especially with the eye relief guide. Just for my own use I think I'd have gone for a 9mm Nagler. The Radian has a very clean, flat field without 'pin cushion' effect and in the f=2M 20 inch Dob the view of M13 is INCREDIBLE!!!! On a very good, dark, contrasty night it is great on M51 as well. Having said all that, it is probably the tamest of my TeleVue EPs on 'Wow Factor.' I do use it on the planets but I'm not enough of a planetary observer to say anything useful.

Olly

[ottUp]

I am very fond of my radians - they are used mainly for planetary work as my high-mag EPs, but I do use the 10mm as a medium power EP for deep sky too.

It's true that it is not as contrasty as my Pentax XW eyepieces, but the Pentaxi also cost twice as much. The Radians are better for bright planets than the Pentaxi, by the way, because of fewer internal reflections.

One of the reasons I like radians so much is that I do a lot of public outreach "sidewalk" astronomy, where moon and planets are common targets. The long eye-relief of the radians means I can focus with my glasses on, which means I am focused for the corrected vision of my visitors. And the click-stop eye guard makes adjusting for glasses/no-glasses visitors simple.

They are an older design but, I think, still very functional. Probably my most used EPs.

- Richard