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Pentax XW 14mm first light


Pig

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I recently acquired a Pentax XW 14mm and finally got to have a quick look through it last night. I must also add that although the eyepiece is second hand it was still delivered in all of the original packaging:-

  • A plastic bottle screw type container
  • Circular foam inserts inside the bottle to hold the eyepiece securely in place
  • A tailor made corrugated card wrap surrounding the outside of the bottle
  • A lovely tough box to hold it all in
  • Full documentation and instructions on caring for the eyepiece

All this gave me the impression that great care has been taken during the design of this product before I even used it !!! also credit must be given to the seller for keeping all intact.

Next: The performance :laugh: I used my 80mm Skywatcher Esprit Triplet

I didn't have a great deal of time and the conditions were by no means ideal but there were some large enough gaps in the low cloud to get a decent shot and I had waited long enough to use it so I wasn't going to be delayed by conditions any longer.

The area of the sky around Cassiopeia was the clearest even though a little low toward the horizon (23:30pm) but still a perfect area :laugh:

There are an abundance of stars to view around this part of the night sky and the Pentax brought them all out beautifully. The clusters and individual stars I tested were all pinpoint and stayed so when slewing from left to right and top to bottom of the 70 degree FOV

I have read a couple of reviews stating that the eyepiece is prone to a little curvature but this is something I did not experience, even with my little peashooter of a scope

Next I just slewed around the sky picking out clear patches to look at.

Dark backgrounds have always been important to me and the Pentax did not disappoint, in fact it was fantastic. However, the most striking effect was how it brought the colours of the stars out, oranges, blues, white and all shades inbetween could be seen quite clearly, very beautiful indeed.

Summary.

A very well built and comfortable eyepiece to use, the twist up eyecup is fantastic and I experienced no kidney-bean effect or blackouts whatsoever, no matter where I placed my eyeball.

This is my first Pentax XW but I do not think it will be my last.

10 out of 10 from me.

I cant wait to get a qulality100 degree eyepiece to accompany this gem :laugh:

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John,

Thank you. I am very impressed with the eyepiece indeed, 70 Degree Ortho is a very good description :laugh:

Iain,

I think we may have got them from the same chap, I was also going to enquire about the 5mm, but I was to slow and it had gone, I now  know where :grin: I am sure you will be very pleased with it.

Chris,

It is one of those type of purchases that gives you a very pleasant surprise, I am in no doubt I will be joining the 100 degree club in the non to distant future :laugh:   

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Chris,

I did notice and changed it just before your reply. However, I could have left the text alone in the hope he doesn't get on with it and sells it to me :grin:

Rick,

Thank you, I have read this elsewhere and I may well be tempted to hunt down one of the shorter focal lengths as they will be well suited to my shorty refractors :smiley:

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I have had dealing with a few Pentax and never been unset by them , I just wish they made more eyepieces. I had the 14mm a good while ago now and I did think it had field curvature, not bad but there for me, I matched against the 14mm Delos and on this occasion I believe was the only time I went for the TeleVue eyepiece over the Pentax, again though it was like a 100m race when Usane Bolt has a bad leg, very close. Beforehand I think I called 3.5mm 5mm and 7mm against my own black and greens, though the 5mm is mine.

The FC we were talking of may have something to do with different scopes, maybe someone better qualified will tell us. Which ever way you look at it it's a top eyepiece and I like the size of it too, some of the Delos are very tall.

My mornings planting is just floating down the garden, weather!

Alan.

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Alan,

I didn't get any FC with the Delos either although I did with the T31, I put this down to a small aperture and larger than 70 degree FOV. (maybe this is something I need to consider when purchasing a 100 degree eyepiece)

Maybe when conditions are clearer and there are more stars are in the FOV any FC will become more obvious, there were also clouds fleeting by most of the time last night and this may also have been a factor. I am sure I will get some quality time at the eyepiece soon.

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nice review shaun, iain wont be selling it as i have told him how good the 5mm is in the 14" , they are very good shaun love mine on planets and clusters :grin: wait till you get the 100*

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Shuan,

FC or curvature as I understand it it when a slight refocus is require to bring the very edge into sharp focus, I noticed this. I am wondering if it is something that was put right on a later production run and I had an old one, as few seem to mention it, though they are maybe not as popular as they should be. There is also the possibility it shows in some scopes and not others. It is something I was mixed up with before reading something John linked to me about 10 times which I have now lost.

The 31mm suffers from edge distortion which is something else, all Naglers have this to some degree and Panoptics share the fault. I love the 31mm but hate it on the Moon, makes it look like an egg if you put it at the edge. Radians Delos and Ethos seem much better controlled, lord knows how.

Alan

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Congratulations Shaun for a very nice addtion. :smiley:

As to field curvature, there're two parts of it, one from the telescope, one from an eyepiece. A refractor has field curvature of about 1/3 to 40% of its focal length, i.e. the shorter refractor has stronger field curvature, a refractor can have either positvie or negative curvature.

When an eyeiece having the same sign of field curvature as the refractor, the curvature will be enhanced, become more pronounced, conversely, if used in a scope of opposite curvature, the combined result is a much more flat FOV.

Eyepieces with ´wider FOV will surely make the curvature, either from the scope or eyepiece, more visible.

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Thank you Yong, It sounds like  have been a tad lucky and have inadvertently coupled the opposites of the spectrum.

What is the term used for the effect when viewing through a fish eye lens.  IE when you move the scope it appears that the stars are revolving around a central point ?

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The term is distortion. If middle of a straight line curved towards the center like this ) (, it is pincushion distortion; if away from the center, like this ( ), it barrel distortion. both pincushion and barrel distortion are called as Rectilinear distortion (RD).

The opposite of RD is Angular Magnification Distortion(AMD), where the lines are straight in the whole FOV, but lines spacing becomes smaller towards the edge. RD and AMD can't be corrected at the same time with the increased FOV, the wider FOV of an eyepiece, the more distortion will be there (RD or AMD or some kind of combination of both). I'd expected that 31T5 has quite some pincushion distortion as what I can understand Al Nagler's design principle.

BTW, congrations to the Clicklock too, that'll be much safer than any of clamp rings :smiley:

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Cheers for the descriptions Yong all is much clearer now. From your description the T31 was indeed pincushion distortion

I got a rack and pinion focuser in the end instead of the clicklock. My heart nearly fell out of my mouth when I saw it flip over 180 degrees, fortunately the Leica didn't fall out :laugh:

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Shaun. Ha ha, I probably bought the 20mm from the same seller by the sound of it - perhaps we should start a club, ha ha. I already have the 3.5, 5 and 10 and they are excellent planetary eyepieces for many of the reasons you stated. Dickinson and Dyer in The Backyard Astronomers Guide' say that if they could only have one range of eyepieces they would have the XWs in the shorter focal lengths - and it's easy to see why if you try them.

I have tried oodles of eyepieces over the years and in terms of being absolutely with no colour cast I've seen nothing better. If you try eyepieces out in the daytime it's amazing what bad colour casts some eyepieces have - and this doesn't only apply to the cheaper eyepieces by any means. If I dare mention of it, at least some of the Naglers almost have a nicotine look compared with the XWs. (please, no hate mail!!)

Alan is quite correct when he mentions the field curvature of the 31mm Nagler. I remember when I first tried one out on a door frame some way off and it was almost bent double - Ok I'm exaggerating a little! While clearly good old Al has produced some masterpieces of eyepieces, I do think people tend to overlook some of their short comings in some cases because TV is held in such high esteem. Less popular makes sometimes appear to be treated more harshly than others by some reviewers. It pays to compare eyepieces directly, if at all possible, before purchasing.

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Alan,

I was mistaking pincushion for field curvature, I will check again next time I get the chance and correct any points I detailed in my first Light :laugh:

Living is about learning & improving :smiley:

Nick,

Thank you.... I am very impressed with the Pentax, very comfortable and pleasing views :smiley:

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