Some scribbles from my notebook: the 6mm TV Radian

[AlexB67]

Intro:

Previously on ...

http://stargazerslounge.com/topic/207915-a-little-bit-of-cloud-dodging-the-moon-and-jupiter/?p=2211617

 Report 15/2/2014

 

Saturday night turned out be a rather good night for planetary viewing, at times it was a bit hazy but skies seemed very steady most of the time. Finally, after all the rain, the time was right to give the 6mm radian in the 10 inch skyliner f4.7 Dobsonian a run, and in the process see how it performed against the 6mm UWA from skywatcher. The session was perfectly timed for the GRS transit too, though with an almost full moon, this did not prevent some excellent planetary views.

 

In only a matter of minutes my first impressions of the 6mm radian became apparent, the GRS was deeply coloured, the planet revealed a lot of fine structure on the bands with good contrast, the bands with their own darker tones and distinct colour, versus the more salmon like colour of the red spot. On the whole the colours were noticeably deeper and more saturated to anything I had seen at this magnification to date.

 

I also observed with a UHC for part of the session, at times it made spotting some of the of the finer details a bit easier under a moonlit sky. The UHC filter screwed on very smoothly, for what is quite an old second hand eyepiece, a nice smooth fit and easy turning motion is all that was required on the Radian. Clearly the threading on this eyepiece withstands the arrow of time, no signs of any wear and tear that I could spot. Fitting a filter on some of my other cheaper eyepieces can be much harder work at times, leaving me wonder how long the threads will actually last. !

 

Throughout the session I gave the 6mm UWA and the Radian an about an equal amount of time, but rather than two long sessions I spread it over about 4 each, accounting for a rising planet and any potential variations in seeing. Whilst the radian was very impressive, it also became apparent that conditions were very good indeed, at times the 6mm skywatcher provided some very fine views also, almost as good as I had seen to date, however, on average it could never compete with the radian in terms of contrast and some of the smaller details that could be seen over the whole session.

 

The ability to retain details throughout the FOV proved to be substantially better in the 6mm Radian. The SW UWA, while it offers 66 degrees, begins to degrade half way across the FOV with a noticeable loss in detail and contrast. I'd say half the FOV is useable in a fast Dob such as mine, and only just for best views, there no refocusing that can come to the rescue ruling out field curvature.

The Radian also gives a more clearly defined field stop. In contrast, while the field stop can be comfortably seen in the skywatcher 6mm, it is not as clear and quite as sharply defined. In its defence, it is a 66 degree eyepiece versus the 60 degrees of the Radian and it is a noticeable difference in FOV, even if much the FOV in the SW 6mm in this particular scope is not useable, but you'll likely fair better in scopes with a slower focal ratio.

The radian instajust feature feels a bit like something that may slip rather easily when holding the eyepiece in your hand, however, in pratice when using it, resting against I've found it to be very stable. The instajust is easy to use, you can hold your eye against it, and make adjustment on the fly quite quite easily until you feel comfortable without upsetting the scope/focuser  much. My other eyepieces like The BST starguiders, the maxvisions and pentax are much stiffer in this regard but are less likely to slip . I woudn't say I prefer one over the other, both systems work, thats the most important.

With a comfortable eye relief the radian is very comfortable to use for a long sessions, I observed the whole GRS transit go around without taking a break. I am not sure I could do that with my eyeball glued to an orthoscopic and no eye relief to spare, but who knows, perhaps I'll rise to that challenge one day.

While my processed images in the gimp are not a very good absolute measure of sharpness and colour what was seen, I hope to some degree the serve to demonstrate my point ( in reality it is all that much more crisp ). Top left is the 6mm Radian, Top right is the 6mm skywatcher as a sort of averaged impression over the session. Bottom left shows the Skywatcher 6mm somewhere beyond the half way point off axis, demonstrating it is pretty much unusable, whereas the Radian is a very good for the whole FOV. In practice any detioration is not noticeable in the radian, or at best very hard to see best that I could tell for planetary viewing. More time using this eyepiece will give me a more precise indication using other targets to comment further.

 

While I did not use the 8mm BST for any long time during this session on this occasion, I'll briefly comment on it, but since there is quite a signifcant difference in magnifcaton, it makes a direct comparison difficult. Therre is little doubt the differences do decome more subtle compared to the Radian. The 8mm is a little bit brighter, see the picture bottom right, as you would expect, but the colour depth and impression of contrast is quite similar, though the planet is seen on a smaller scale, thus making the radian more comfortable to use and easier to pick out detials when seeing allows, which certainly was the case on this oaccasion.

 

While the 8mm BST is a noticeably better performer in retaining planetary detail off axis compared to the skywatcher, it cannot compete with the radian. On nights of less good seeing the BST may provide some advantages of course, but I have to test it out as yet, as it happens I was blessed with good conditions in this occasion, so it wasn't limiting the Radian.

 

While deep sky viewing is not the best idea under moonlit skies, I couldn't resist having a brief hop over to the eskimo nebula. An easy find and very near Jupiter, and due to its high surface brightness I've always foud it to take high mangificaton well in a 10 inch Dob. The moon had not yet cleared the roof at this point and this helped somewhat. Considering the moonlit skies the Radian gave a fine view of this target, though I should stress under these conditions there is not much detial to be seen in th first place, having said that, the central star seemed that tiny bit brighter and more clearly defined. In pure bightness terms the SW 6mm UWA did do well here, but due to greater scattering and and lighter background, the nebula was that bit better defined in the Radian, showing superior contrast and a little bit more spread surrounding the central star.

 

Observing report 18/2/2014

 

Observing before a rising moon I had another brief view of the eskimo, with the help of the UHC this has been the best views I've had of this target from my backyard for some time, it went some way towards seeing some extra spread around the nebula normally only seen under better skies for me, though I needed averted vision to see it, with averted vision a notable roughly eliptical spread could be seen. Dispite the light polution, the sky background was remarbly dark. On a straight comparison of brightness the SW 6mm is not that disimilar, but the Radian does offer noticably better contrast against the background, thus allowing more to be seen.

 

A quick hop over to M82 onto the now noticably fading supernova with some medium power viewing, estimated at about 11.2 perhaps, clearly not as obvious as it was a week or more ago. While there, it did not prevent me from popping in the 6mm Radian once again to have a look at M81. Remarkably, though I guess not entirely surprising due its brightness, the galaxy still shone quite brightly above a very dark background at around 200x magnification with some noticeable spread around the core, splendid

 

Concusions:

 

Summing up my thoughts on the two eyepieces, the televue 6mm Radian ( 60 degrees) and the Skywatcher 6mm UWA ( 66 degrees ) : I've tried not to overstate the difference in quality, after all I like cheap and have to be convinced expensive is better , but it is clear there is only one winner. It is just one and my opinion of course, but personally I feel it is not an overstatement to say the differences aren't subtle exactly, but let us not forget that the price difference isn't a subtle one either !

 

I find there is little to fault in the Radian so far, perhaps initial indications are that for a premium eyepiece transmisison is not up there with some of the others, as others have stated elswhere. My initial impression is that I would agree on that point, but it makes up for it with a very dark background and superb contrast in a lot of ways.

 

For planetary viewing a big bright giant like Jupiter it offers a superb rendition of colour though the Radian may not provide the most neatral colour, ( a slight warm tint), I like it as it happens.

 

While an eyepiece like the 8m BST goes a lot more towards making differences more subtle, bearing in mind that a comparison in going from 150x to 200x magnification makes any comparison difficult, I have no hesitation in saying the radian is an eyepiece in a class of its own in this particular comparison.

 

should add that for a similar amount money there will be contenders to rival the Radian, whilst I've never used them, there is enough evidence on the forum and reports elsewhere to suggest this is the case. However, In this case when comparing cheap ( < 30 pounds ) versus what would be almost 200 pounds new, announcing a winner turned out to be straighforward. If I had to make a comparison of something like a vixen, a good orthoscopic, a pentax, or something from the ES range I would have a much harder time no doubt.  

 

Your mileage may vary with the skywatcher 6mm UWA in slower scopes, I expect that in a f/7 instrument or slower you'll probably fair signifcantly better across the FOV where you may find the 66 degrees FOV usable. I can't comment on any chromatic aberration you may expereince in a refracor with this eyepiece since I don't own one, something else to consider when buying this eyepiece.

 

For under 30 pounds I still feel the skywatcher it is a fine eyepiece, given it actually has a generous eyerelief, a must for glasses wearers, and the fact that you have any eyepiece left at all with some performance that still works in an f4.7 Dob to some degree has to be commended.

I Forgot to include my lunar report and I can't wait for some globulars and doubles in the 6mm radian .... another day perhaps.

 

Don't read too much into this as a proper eyepiece review, more as a combined oberving report and initla impression.

If you are thinking of buying a Radian, and since it is old eyepiece in this day and age, you'll find there are plenty more robust and in depth reviews about.

 

If you got this far, thanks for reading  

 

　

　

[michael.h.f.wilkinson]

Excellent report. The Radians are very nice EPs aren't they. The gave me some stunning views, and as you say, the whole FOV is usable.

[Orange Haze]

Brilliant report, thanks so much for posting it. As well as a Maxvision 28mm I have my eye on a Radian for planetary. This review is really helpful.

[alan potts]

Alex,

An excellent report and very nice to hear that you have had some decent weather at last. I think to point you make about transmission is correct but on the other hand I believe these eyepieces are aimed, or should I say were aimed at planetary viewers. Ror the most part this is Saturn and inwards or bright objects where transmisson is not so important. I can't say I see this myself to any great extent but have read many accounts of people that can. I think one ot the reasons is never or rarely having a same focal length eyepiece to compare. I have the 5mm Radian and the Pentax XW and whilst I agree there is a difference, it is not great, but then it is not the same as yours.

Alan

[John]

Really good, thorough and balanced review Alex

I believe the 3mm Radian is the only one you can buy new now. At around £100 or so on the used market they are outstanding eyepieces I feel.

[alan potts]

Myself I believe these Radians are the best S/H value, as I said aimed at planetary views the 60 degree field is plenty and of cousre not everyone wants or needs 100 degree see your feet eyepieces. I do have some nice shoes so it makes sense.

Will you looking to add to the Radian collection Alex?

Alan.

[RT65CB-SWL]

Nice report. The 6mm Radian is one of my favourite eyepieces.

[AlexB67]

Much appreciated guys. Alan as you say the transmission can hardly be called a fault with the planetary bias in mind ( it is what I mainly got it for). I suppose I had to say something otherwise the score would be a 100% pretty much, that is not allowed . I suspect globulars are going to look great in it too, can't wait for that.

Just had another GRS transit earlier, terrific

As for more radians, yes please, or something TV. Perhaps OTT, but at some stage I feel having at least 5,6,7,8mm in that area will be something I'll want to have for planets in the long run., for the 7mm I always had the XW in mind . I think the next eyepiece on my list will be the 14mm TV Delos though, If a second hand pentax XW or XL14mm turns up I'd consider that too. It will depend what turns up on the second hand market in the coming months. If a 5m Radian turned up, or an 8mm it would be hard to resist also. When the cash has been saved and I end up buying nothing second hand in the mean time I suspect the 14mm TV Delos will be next.

Somehow I feel my case will end up being a mix of TV and pentax eyepieces, that said those Maxvisions are cracking eyepieces and were so cheap, and  for the foreseeable future I am in no rush to upgrade those. I  would not mind trying an ortho as well at some stage and some TV plossls too. 

There is a fairly recent new member whose name eludes me, sorry, but he has a great signature

Welcome to SGL, sorry about the wallet

I think it will have to be that way for while,     I can build it up slowly though, overdrafts and bankrupting  will not be tolerated :0)

[rory]

Interesting read Alex. I've not read a bad word about radians .

[michael.h.f.wilkinson]

Interesting read Alex. I've not read a bad word about radians .

Then you haven't read some of the CN posts on Radians. Quite a few rants about "strong color cast", "almost coffee color". Completely overblown. There is a subtle warmth to the view, that's all. It did not bother me, although I did notice it when comparing them to first the Pentax XF8.5 and then the XW 7 and 10. The main reason I replaced the Radians by the latter two was FOV, plus that tiniest smidgen of extra sharpness.

[AlexB67]

The warmth is definitely noticeable, does not bother me personally.  I find the pentax I own is noticeably more neutral, as are the maxvision eyepieces and BSTs, though the BSTs are slightly warmer as well, but not as much as the Radian.

The other criticism I have come across that is common is eye placement, though personally I have not found it to be an issue, but particularly on the moon when something is very bright  when I experimented to see how precise you have to be.  If you have trouble keeping your head still, you'll get some blackouts quite easily if you want them.

[John]

Then you haven't read some of the CN posts on Radians. Quite a few rants about "strong color cast", "almost coffee color". Completely overblown. There is a subtle warmth to the view, that's all. It did not bother me, although I did notice it when comparing them to first the Pentax XF8.5 and then the XW 7 and 10. The main reason I replaced the Radians by the latter two was FOV, plus that tiniest smidgen of extra sharpness.

This is quite true and I think was the reason that it's taken me 10 years to get around to trying Radians. Shows how wrong people can be but I've noticed that about the world of eyepieces - certain types seem to get labeled as "unfashionable" then more folks jump on that bandwagon with a resulting flow of negativity.

I think the Radian is still tainted (poor choice of word !) a bit with this though. The Nagler T6's for example, a few years back, were priced just a fraction more than a Radian (£215 v's £200 I seem to recall) but now a used T6 will fetch £150 quite easily whereas I've seen Radians struggle to sell at £90. 

This situation can lead to some of the best value buys though for the astute purchaser who can see though the "smoke screen"   

[Pig]

Excellent honest report Alex, a great read indeed. I was also very surprised at the effect a UHC filter has on Jupiter

[AlexB67]

Excellent honest report Alex, a great read indeed. I was also very surprised at the effect a UHC filter has on Jupiter

Thanks Shaun,

I don' t use a UHC often for planetary if ever at all, but when the moon is out and that bright nearby I find it can benefit a little to add contrast and darken the whole thing a bit . There were occasions where I tried it and I did not notice much of a difference apart from the colour change in the past. On this occasion the best way I can describe it that as more a case seeing some details a bit easier on the bands sometimes with bit of added contrast.  For most of the session I did not use it though.

UHC can be quite effective when the moon is out  on other targets too ( I find personally anyway).

[Rustysplit]

Excellent report Alex. I use a good range of Radians, and find them to be fantastic to use. Yes the eye placement can be a bit precise at times, but you soon get used to it. I have to say that the colour cast is not something I really notice. I have not used the 6mm, but have the 18,14,12,10,8 and 5mm. I like them all and may one day finish the set with the 6,4 and 3mm, just because. I do not need them as I find they barlow very nicely. A complete set would be a nice thing to have though

[AlexB67]

Just to add a little update. I've viewed quite a few globulars with the Radian and really pleased with the results. M3, M13,M92,M53 all looked stupendous and resolved very well with and xmas tree fest of stars against a very dark background. The cat's eye nebula also looked very impressive over the last couple of sessions.

Mars I had some interesting results, this is a hard object to get surface detail from and I am new to it, I've been repeatedly visiting this target and getting better at it I feel.  I don't know if in part it is the slightly lager image scale, but my pentax XL 10.5mm in the 2x barlow, which is just a SW cheap one, not the deluxe model, gave some vey good results that surprised me somewhat. More time needed and repeated sessions to se what is what, but last night ( early morning )  I had some great views on mars (considering it is quite low in the sky it was very steady).   I must admit I found it hard to split the performance of the XL barlow combo on axis from the radian, though the barlow has tendency to degrade the image somewhat off axis, which the pentax does not do by itself to the same degree, I find it very good by itself without the barlow in that regard.    That said, the pentax / barlow had a certain clarity of colour shades that the radian did not on Mars, very subtle, I am talking tiny differences, but noticeable it seemed all the same. 

And did I forget to mention, I still love that pentax XL 10.5 too, it has been great on deep sky. The clarity and the way it renders stars with great clarity I love, so colourful.  It may not be an ortho, not that I ever compared, but from the way people describe some of these eyepieces and what they see,  to me it comes across as very  ortho like in performance.  Hard to put in words, anyway, awesome, is a good word, galaxies can really pop out in it too, but now I am drifting off-topic from the Radian

[Qualia]

What a great review, Alex and thank you for posting it up. The Radians are some of the finest eyepieces on the market and if that noted warmth is anything similar to what I have found with the TV Plossls as, say, when comparing them to the BG Orthos, then the Radians must surely be outstanding planetary EPs.