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vineyard

A night of comparing some EPs

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Hello,

Finally had some clear skies here last night, so spent a v nice 2.5 hrs taking various EPs for a run.  Some v interesting findings for me (different ppl have different eyes & scopes so I'm sure ppl will disagree with some of the below!).

Firstly, a huge thank you to @heliumstarfor sending out his lovely 13T6 to try out.  The backdrop to this was that I recently started using a supercharged BV by @denis0007dland enjoyed the immersiveness so much that it made me wonder what Naglers would be like with a BV.

Anyway, the kit used was: TV102iis (both monocular and then also BV'd), EPs: 2xTV40mm plossls (one an old smoothie), 2xZeiss 10x/20 aspherics, 18.2mm & 13mm Delites, 13T6 & 12T2.  I also during the night added an Astronomik UV/IR filter (and then also stuck on an old Lumicon O-III filter for some nebulae).  Most of the viewing was on the Pleiades, & then M42, & then Castor.  Most of the comparison was of the Delites to the Naglers.

Here are my main findings:

1.  As I'd noticed on prior occasions too, the plossls have massive ER and the exit pupil is such that the light polluted sky can appear grey at times.  But they capture the stars clearly & sharply.  A great finder EP!

2.  The Zeiss EPs were the absolute stars of the night.  Big ER although not as much as the Plossls (I'm going to add eyecups) - the combination of FOV, the sharpness across the field, & the transmission was stunning.  Just wonderful EPs - I get what the fuss is about (and I'm v lucky to have sourced them from a microscope dealer who perhaps didn't realise what they're capable of!).  I haven't had a chance to try them on the moon yet with this BV, but I. really. cannot. wait. :)  If you're thinking about them, definitely take them for a spin although from what I can tell from Google you need to be careful w provenance (Denis also cautions on that).

3.  The 13T6 vs the 12T2.  The T6 probably wins on balance - its smaller & lighter, with bigger lens surface (making it seem easier to look through).  But the old T2 actually still has a v nice feeling to it - you have to get stuck in and swivel the eyes around and wherever you look there are stars.  It also felt darker than the T6.  (I will probably still end up parting with it as it can't really be BV'd, although I'm not yet sure about that decision - sentimentality...).

4.  The DTs vs the 13T6.  This was probably the most interesting comparison for me.  Long story short: I actually ended up preferring the DTs, and in particular I think the EP that nails the 13T6 is the 18.2DT.

On a focal head-to-head between the 13T6 vs 13DT, the T6 probably shades it b/c of the FOV.  But w both DTs I found that the focus had a cleaner snap & thus easier to find than the T6.  The stars also seemed sharper & almost larger (!) in the DTs, and the sky darker (although in fairness the T6 was v v close) - others will know better than me whether that's b/c of different transmission or different contrast.  The DTs definitely seemed sharper right across to the edge of the field - stars remaining pinpoint right up to the moment they disappeared.  Whereas with the T6, there distinctly seemed to be some v slight tails on the stars right at the very edge of the field (I kept checking on this) - has anyone else noticed anything like this?

At various times I had both 13s in the BV so that I could compare instantaneously, and then also had the 13T6 and the 18.2DT in at the same time.  That's when I was most pleasantly surprised by the 18.2DT.  It had the same FOV as the 13T6 (actually slightly larger), which together with the better snap, contrast & sharpness, actually made it a better EP for me.  Comfort wise, the DTs were v comfortable - the cup mechanism is better than the old Radian instajust, and for extended viewing I could already tell that the DTs would be more comfortable than the T6s.  (The shorter ER on the T6 doesn't bother me - it's more that to get the FOV in the T6 you have to reach with your eyeball a bit more in a given direction whereas for example the 18.2DT presented the same FOV more comfortably).  Yes the magnification on the 13T6 was more than that with the 18.2DT (68x vs 48x on my scope) but tbh that didn't make a huge difference to me.

So I wonder whether the 18.2DT actually nails the 13T6.  It's a v v good EP.

Don't get me wrong, the 13T6 is still an amazing EP - but I think it gets hit in a pincer attack by the DTs.  For the FOV the 18.2DT wins, and if you want the same magnification the 13DT delivers that better snap, contrast & pinpoint sharpness, with a better sense of zeroing in on what you want to examine more closely.  Splitting Castor was restfully easy.

I started the night hoping the 13T6 was going to blow me away, and excited about using it in a BV.  And it really is a v good EP - I can see why it must have been so exciting when it first came out.  But in all fairness I'm having to rethink my own particular configuration based on how well the DT tag team seemed to work.  I haven't tried Delos or Ethos so can't compare those - but those are all heavier EPs (and beyond budget) too.  For the shorter focal lengths, my aim is to somehow compare 7DT vs 9DT - to see whether it's worth getting dedicated EPs or whether 2.5x powermates may be the best thing to go for in the soon-to-conclude Televue sale :)

Anyway, this has gone on far too long.  I'm still v much a newbie so I'm sure I'm overlooking important considerations or use cases!  And thank you again @heliumstar for the test-run (& @denis0007dlfor the BV).

Happy Christmas all,

Vin

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Thanks for that comprehensive write up Vin. I think that eyepiece preference for binoviewing can be even more personal than single EP viewing. But I don’t think you can get much better than the eyepieces you’ve been testing. I love the 18.2 Delites too, along with pairs of TV Plossls and Fujiyama orthos. Haven’t tried any of the Zeiss microscope eyepieces yet - but SGL member Stu swears by them. Sounds like you may have picked up a bargain there. 

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On 31/12/2019 at 19:04, Highburymark said:

Thanks for that comprehensive write up Vin. I think that eyepiece preference for binoviewing can be even more personal than single EP viewing. But I don’t think you can get much better than the eyepieces you’ve been testing. I love the 18.2 Delites too, along with pairs of TV Plossls and Fujiyama orthos. Haven’t tried any of the Zeiss microscope eyepieces yet - but SGL member Stu swears by them. Sounds like you may have picked up a bargain there. 

Thanks Highburymark.  Agreed I can't grumble too much - these are nice choices to have :)  I've managed to pair my 18.2DL up now w a 2nd hand purchase (before the TV prices went up again it seems...) - just waiting for it to arrive along with a gap in the clouds.  I've heard all about the Fujiyamas but never had a chance to try one (so far).  I'm yet to test the Zeiss BV'd on the moon (when I figure any defects at the edge will be most easily discernible?) but I'm keeping my fingers crossed.  HNY!

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5 hours ago, vineyard said:

I'm yet to test the Zeiss BV'd on the moon (when I figure any defects at the edge will be most easily discernible?)

I've found the Trapezium in Orion to be the best test of edge performance.  It's fairly easy to discern if they lose any fidelity as they approach the edge.  The moon, being an extended object, is a bit more difficult.  Sure, edge color is easy to discern, but field curvature and astigmatism are much less readily apparent.  Try looking for very fine details, both high and low contrast, on a relatively featureless mare and see if they are less distinct at the edge.

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The Delite design has a very small spot size all the way to the field stop, so you should see somewhat sharper stars near the edge in the Delites.

The true test, though, would be to see how the stars compare with the Nagler T6 when the star is in 10° from the edge, i.e. 30° off axis instead of 40° off axis.

My recollection is that, compared this way, the two eyepieces are more similar except for the eye relief.

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Hi Vin, very interesting reading, I doubt if I would change, for me the 13T6 is as clear and sharp as I can appreciate with these old eyes, however, the 13 LVW gives it a good run for the money, my original ep in this range.

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