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domstar

In praise of the lowly Plossl

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Under spectacularly transparent winter skies, I tried out my 10mm Vixen NPL in my ED100 refractor. I was blown away. I was hunting doubles around Orion because the moon was full and the stars were pinpoint sharp. It gave sharper views than my 10mm BCO and I found that surprising. I like(d) my BCO and maybe the inferior views were because it's used more and despite (or because of) the fact I cleaned it over Christmas.

At 90x magnification in my scope it split Rigel with the companion well away from the glare. Although Alnitak had no black sky between the two large stars, it was as close as could be and the two stars could be seen as different colours. Beta Monocerotis was easily split. The views were so good I even spent a while trying for the pup in Sirius. I wasn't successful although I convinced myself I was close to it (is it even possible at 90x in a 4 inch? I'd appreciate some advice). 

Anyway, I understand that the conditions were unusual. It's also true that I haven't tried it on the moon yet and my BCO is very strong there as would be eyepieces with a larger field of view than 50 degrees. But for 34 pounds new (I unexpectedly won an auction for just over a tenner) I'd be surprised to see it beaten significantly on doubles in my scope. It's true I don't wear glasses but I really think it's a high performing eyepiece and when I go for an 8mm I'm tempted to try another one in place of the Starguider, which I had expected to get.

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I have always found Plossls to be really sharp. I had three Vixen-made Plossls originally with my C8, and all were sharp. The only shortcomings were limited FOV (still fine for many targets) and eye relief at both the short and the long end. My 10mm was VERY uncomfortable for me with my glasses, and the 36 mm left me hovering some distance from the EP (which didn't have a rubber eye cup or anything). I got my sons a cheap 20mm Plossl for use with their small Dob, and it is a really good performer.

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Hi Domstar, very good report.  Would you mind sending some of those clear skies over here?

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Interesting report. Slightly surprising because I found the Baader Classic 10mm one the very best eyepieces of any design that I've owned and used. I can't say that I've used a Vixen NPL 10mm though so I'll have to find one of those and try it someday.

Thanks for posting your findings :smiley:

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Thanks John. I'm wondering if it's because the Vixen was unused and, despite cleaning the BCO, there is enough dirt/grease/dust to make the stars just less than round. I wish I had the vocabulary. I'll try again tonight with both, numb fingers allowing.

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The reason for the humble Plossl giving sharp definition is because it is actually a type of orthoscopic eyepiece - not conforming exactly to the original ortho, but still orthoscopic in being free from the same aberrations that the Abbe ortho is free from.

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So last night I did part two. I even had a quick look through my Skywatcher 10mm. All three performed well but the Vixen just squeezed past the BCO. There's almost a tiny spike with the BCO which gives my stars an angle, if that makes sense. I'm thinking grease on the eyepiece maybe?

Here's what I learnt-1 This was not supposed to be an eyepiece review but more of a 'wow I'm surprised at my new eyepiece' thread. Take my finding with a pinch of salt.

2 Interesting but maybe not totally fair to check out a new eyepiece under unusually favourable conditions.

3 Wow, I'm surprised at my new eyepiece.

4 We all love stargazing so much we'd like to give it some money, but the lowly plossl can be quite a performer and not necessarily a stepping-stone to greater things.

5 The Vixen seems to be really good as maybe other eyepieces are too.

6 Transparency is king.

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1 hour ago, domstar said:

...2 Interesting but maybe not totally fair to check out a new eyepiece under unusually favourable conditions...

I've found that optical performance differences become a little more apparent when the seeing conditions are really good. Sometimes it has only been under such conditions that a difference has shown itself.

I've also found that observing targets that are pushing the limits of the optics, the conditions and the observer helps to show up differences in ultimate optical performance that otherwise remain unnoticed.

 

 

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1 hour ago, John said:

I've also found that observing targets that are pushing the limits of the optics, the conditions and the observer helps to show up differences in ultimate optical performance that otherwise remain unnoticed.

Well I mentioned on another thread that I'd almost certainly found the F star in the Trapezium and I confirmed it last night with a 20mm Starrguider and 2.5x Baader Barlow, which I'm really pleased about. Thanks for the other Orion tips- they were great. (and thanks for your tact on both threads).

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On 21/01/2019 at 11:29, John said:

Slightly surprising because I found the Baader Classic 10mm one the very best eyepieces of any design that I've owned and used

Me too John, while I don't have your extensive experience I can say that the 10mm BCO is one of my best eyepieces.

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It could very well be that Vixen has specified a higher level of polish for their NPL line than most manufacturers specify for their budget or "super" Plossls.  That could easily account for the greater clarity you're seeing.  The NPL line is possibly more comparable to the older Baader Genuine Orthos rather than the newer Baader Classic Orthos.

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