Pentax 7mm XW and 7mm Nagler.

[alan potts]

Pentax XW 7mm and Televue 7mm Nagler

I would like to extend thanks to my friend Dani who is the Meade Dealer in Bulgaria for the loan of the 7mm Pentax XW eyepiece.

Also putting in a guest appearances were the very fine 7mm Baader BGO and the 6mm Televue Delos, used only to augment the report and to help show the reader that a small increase in magnification can deliver where even two fine eyepieces seem not to be able to. This is of course no reflection upon the eyepieces as conditions and simple lack of magnification are most probably the reason almost all of the time.

Pentax 7mm XW

I solid looking eyepiece that comes packed in a rather nice box with a bullet case, the latter being something that I think other high-end eyepiece manufacturers could do as well for the cost of one. I know most of use have some form of eyepiece case but myself I rarely take them out side as I always know what I need and select accordingly, and put them into my photographers waistcoat. The bullet case is in my opinion a nice touch that set these apart from others but it is of course the optical quality that we are spending the hard earned cash on. The eyepiece has a twist up eye-guard that seemed stuck on this particular eyepiece, as it was not mine I did not want to turn it too hard in case of an accident. Eye-relief on the Pentax XW range is also user friendly for glasses wearers at a very nice 20mm though without the eye-guard in the raised position I did find it blacked out a great deal, this is only a matter of getting used to it though. It also offers a field of view that is 70 degrees, 12 degrees less than the T6 but looks more, anyone could be forgiven for thinking these were two eyepieces with different magnifications such is the optical illusion. 

The eyepiece weighs in at 400grams on my Argos specials that have served the kitchen well enough now for about twenty years and is fairly large when place along side the Televue offering of the same focal length, I can’t see this being an issue for a Dobsonian user. All in all a solid looking package that we have come to expect from the likes of Pentax and as many would agree, sad that they did not see fit to market more eyepieces for our hobby.

Televue 7mm Nagler.

]

No real shocks here when it comes to packing, the T 6 range of Televue eyepieces all seem to come in the same type of box with caps and a plastic bag, lets not for get the powered by Televue sticker of which I have a fair collection. The boxing and presentation of the Pentax looks and is much better though is of little importance. The eyepiece is small when place besides the Pentax and weighs in at 240grams so it would fall below the 500gram limit for our courier service here and I would save a few quid if selling it in the UK, again of little importance. The eye-guard system on all of the T 6 range is the same with a firm rubber rim that can be folded down though I never have, I found it easier to use than the Pentax though I am sure this is only due to the fact that I am familiar with Televue range and do not need to wear glasses when observing. With the eye-relief of 12mm I would doubt if anyone wearing such would be able to see all of the 82 degree field of view, I could not with my reading glasses on which is the best test I can come up with with.

[attachment=111770:IMG_0006.JPG]

Just to show there is life outside ofthe UK

Scopes.

I am just using the two scopes for this report, I did want to use the GSO 150 with its 1370mm focal length but I do not have it at the moment. It is in fact up for sale in Sofia as I would like to get a sizeable Dobsonian. However I feel the chances of selling it here are about as good as winning the Americas Cup in a rowing boat so maybe it will make a return later in the year.

I am using the 115mm APO and the 190mm Maksutov Newtonian, the former giving a magnification of X115 and the latter X142, I am rather assuming that both eyepieces are the same focal length, with these two manufacturers one would expect that to be the case.

Targets.

I have to say this is one of the first times where the weather has made the target selection more so than me. The observations were taken from 14 hours scope time 5 weeks apart with a 16 day gap in the middle where cloud watch was the only thing on offer.

Targets were.

The Moon,

Messier 57

Jupiter

IC 348

Mirach’s ghost

Messier 1, the crab nebula

Messier 42, the great Orion nebula.

Venus.

Skywatcher 190mm M/N. Collimation checked.

Venus,

The planet now is getting very low in the sky but I can still just see it before it slips below the hillside which is about two miles away, I think last night was about the last chance I have as walnut trees were also getting in the way. It was nice to glimpse the very thin crescent which is only about 2.5% and getting thinner before the planet gets too close to the sun to be seen or the hill gets in the way. The other factor here is also the fact that the planet is fairly low in the sky and atmospheric turbulence plays a part in just how well it can be seen. Earlier in the month of December the planet was showing about 22% phase and was much better placed for observations. I like to use the very bright objects like Venus to check out light scatter, though I also use bright stars.

I have to say that I could not see any difference between these two eyepiece for light scatter though placing the planet at the very edge of the Pentax I feel there was a touch of chromatic aberration that I could not see in the Nagler. Both eyepieces showed just a touch of atmospheric aberration as the planet fell lower in the sky, though nothing to get upset about.

This was much the same story for 4 nights at the weather was allowing me about 30 minutes every night before a double helping of clouds reared its ugly head. It is very annoying when it has been so clear all day and this happens, for it to happen once is fair enough but 4 nights in succession is rather strange.

Messier 57.

This is not best placed now but was a reasonable target when I started the review. I wanted to see how well it stood out with there being about a 10% in the sky. This is not the end of observations for us eyepiece lovers though I am sure it would put a stop to any astro-photography, people who do this must have the Moon very low on their wish list. Spending a reasonable amount of time on this smoke-like ring and swapping back and forth many times which is not made easy by the significant difference in the focus positions. I thought the nebula stood out just a fraction better with the Pentax, but believe me there was a very little in it, this is not an easy object to focus on and I relied on near by stars a great deal.

Mirachs Ghost.

This is an object I have never seen before, well not knowingly, it was only a question that was raised by another member on site a few weeks back that made me research the meaning of it.

I am not sure if X 142 is the best power for this object but that is all I have to work with, faint fuzzy objects have never really appealed to me but accept that many site members drive miles to get sky to see them, so must love them.

The goto of the HEQ 5 pro landed Mirach smack bang in the middle of the field of view of the 7mm Nagler, which must have been a first. There, bold a brass was the galaxy NGC 404 which was easy to see in the good optics of the Skywatcher, something of a surprise with there being a Moon on both nights and the galaxy is only of the 10^th magnitude, however the object was very high in the sky and conditions were fairly good. I have to say there was no difference in the sharpness of Mirach, showing nice diffraction rings with both eyepieces and no scatter difference either and there was no winner on this target that my eyes could detect.

IC 348.

This is the very first time I have ever looked for anything from the IC list of clusters and I do not have a clue what it stands for, other than maybe something “clusters”, insignificant maybe. Skymap tells me it has a brightness of magnitude 7.3 and there are 20 stars therein. Well I have to say that sitting counting the stars was not easy as some of them are very faint but I believe I got to 14 stars with each eyepiece. I did try the 6mm Delos on the same cluster and thought I could see another one but I could not be sure. The extra magnification (X167) did I feel make it just a little better in the scope, though this is not a heart stopping object by any stretch of the imagination. I do not believe there was any real difference in the view afford to me by either eyepiece though I did prefer the Nagler on this target, how nice it would be to have a selection of the same focal lengths to view different subjects, one can dream.

Messier 1, the crab nebula.

Not the most exciting object in the night sky but I was again just trying to see if one eyepiece was better than the other on faint objects. It would appear to me from a distance that the Pentax is favoured by galaxy hunters over other eyepieces and I wanted to explore this avenue. After spending a good deal of time looking at a faint grey patch of gas and finding it ever harder to focus with cold hands I have to conclude that the Pentax seems to have an edge here but not one you could shout about, it was very marginal. If looking for faint objects is your forte then with the two eyepieces being much the same price the Pentax would make sense. I brought the BGO 7mm into play here and I could see no difference between the two in terms of brightness or sharpness, when you consider the XW 7mm has more than twice the elements it really is some eyepiece.

        

The Moon.

I put a great deal of time into the moon on this review, I was able to view the Moon in early December and the last few nights, when the clouds allowed me. I did find something strange, the goto on the mount controls the clouds which is something that I could not find in the instructions. Two nights back I was looking at the moon which was in and out of haze, called it a day and slewed to Jupiter, when the scope got there the Moon was as clear as bell and Jupiter was in haze, neat trick.

First night on the Moon and a few nights backI was looking at a thin crescent showing about 7-8% of the total surface. I focused my efforts around the three craters Vendelinus, Petavius and Langrenus which I have to say show fantastic detail, Petavius seems to have some type of rill or crack in it, I thought it was shadow from the rim of the crater at first then realized it would have to be very high to cause this effect and checking the map showed I was completely wrong. I could see no difference in sharpness but did notice the Pentax offered a flatter field of view, though I did not find the slight pin-cushion of the Nagler off putting, I did in fact prefer the Naglers rendition of things and there may have even been a touch more contrast to boot.

I redirected my attentions to the group of craters named Atwood. Bilharz and Naonobu, a stranger name I have yet to come across. There is the remains of what looks like an old crater very near by but I could find no name for this feature, even at X142 with the Moon getting lower seeing was drifting a little in and out. I found that the view from the Nagler was a little easier to focus on with my eyes than that from the Pentax, I would not call this as significant and it could have been solely down to conditions but the same craters were observed a month apart on three nights.

In general I was liking the Nagler more than the Pentax for the Moon which is something that I never thought I would say, still I would not throw the Pentax away based on that.

I placed the very tip of the Moon at the very edge of each eyepiece, using the area of the Moon where craters Amundsen and Shackleton are situated. It was really staggering to see how much detail you could see in a fairly fast scope using only the very edge of the field of very, these two really are sharp to the edge though again I could see a little chromatic aberration in the last 2-3% with the Pentax that I could not pick up in the Nagler. The one thing that needs to be said here is that all the Naglers do show this bright blue ring all the way around the field edge when looking at something like the Moon, I do not mind it myself but could understand that some would prefer it not being there.

Jupiter.

The magnification of X142 is a little below what I would like for Jupiter but it is not a million miles away. I have to say I would have liked the planet a little higher in the sky as it is not in the best place for me, if the house is not in the way then a walnut tree is. I guessed scope placement very well to allow me a 45 minute window before being treed out. Jupiter looked superb which was a bit of as surprise, I could see four belts and polar shading with both eyepieces though no Great Red Spot, I am sure it has gone on holiday as I never seem to see it. I feel the planet did benefit from the extra power of the 6mm Delos, it was just more pleasing on the eye, but I could not see any extra detail in the belts, neither did the BGO show any extra but it may have had slightly better contrast. If you are looking for a planetary eyepiece of sheer quality the Pentax is going to be on any ones shortlist but I have been very impress with just what a good all rounder the Nagler is.

APO 115mm.

Mirachs Ghost.

Finding this was no problem as the goto did get close even with the 7mm Nagler in the focuser and the lower magnification permitting an even wider field of view. With the scope more or less pointing straight up I was having to sit on a couple of bricks which were far from comfortable, still I would rather do this than have to re-align the scope later on. There was a small crescent Moon which was 4 days old, so there was some light pollution coming from that source, I was not full of optimism looking for a 10^th magnitude patch in the sky with a scope who’s limit will be about 12^th magnitude. This was born out as I could not see NGC 404 at first but could see it later when the Moon had dropped much lower in the sky and the constellation of Andromeda was still well placed for me. It was difficult to see though and was no way as obvious as it was in the larger 190mm scope, when looking for faint fuzzy patches of light, size matters. There was nothing between the two eyepieces as far as I could see though I did feel the wider view of the Nagler was my favourite. With the scope being F 7 both eyepieces were razor sharp to the very edge as the both were at the faster F 5.26. I did however think that the Pentax was giving a slightly tighter point of light on Mirach, not all of the time but just now and then.

Moon.

Using a few nights observations on the moon from around first quarter to just over three quarters, I looked at and learned a few new names of some new craters. It is rather nice to have the luxury of an old laptop from my days at work which has Virtual Moon loaded, it helps compliment the viewing experience when you can put a name to a given crater there and then. A good atlas will do the exact same thing and would be my first choice if I only had one, with the laptop being now 13 years old it is a little slow but still working fine after all this time, they don’t seem to make things that well now.

Starting around Manilius and the wide vista of Mare Serenitatis I was again placing various features at the very edge of the field of view with both eyepieces and I have to say was astounded by the quality of both. We often talk of on axis and off axis sharpness of an ocular, well as far as I can see the two are one and the same with these. Just the slight aberration from the Pentax and the blue ring from the Nagler, which was not so obvious as the whole moon fits the field at this power even for the 70 degree eyepiece.

Moving on few nights, Copernicus comes into view with its dazzling rays stretching out in all directions,  always a stunning sight in any scope. Dropping down or up the Moon depending on your scope Longomontanus is a lovely site with all the craterlets that have bombarded the area since. At no time did I see any one eyepiece out perform the other, these are both top draw in every sense.

Just over three quarter is about as late as I ever leave the Moon for observations, I do not see a great deal in view the Moon when full. Using the laptop I manage to locate and bag the small Heraclides 4, a 3klm wide crater. Now the interesting thing is that the Virtual Moon information was telling me I would need a 200mm reflector to see this but I could see it with something a fair bit smaller, I do not think I have made a mistake but it is not as if there is only one crater on the Moon and getting lost is not difficult.

Jupiter.

Better placed the night before last and with a scope that is easier to move I tried out X114 on the planet, not something that I would do normally. It was really sharp and the belts stood out amasingly well, almost as good as in the large M/N 190mm. I could clearly see the two equatorial belts and one either side of these as well as some polar shading. I believe that the Nagler was just a touch richer than the Pentax with regards to contrast, the latter seems to give a whiter and slightly bright image, though I am talking about feelings here more than black and white stone cold evidence. I turned to scope around to Alberio earlier in the night and again here I just feel there was a bit more richness of colour in the two components. That said I have to say that for an out and out planetary eyepiece the Pentax is excellent and in my books as good as the Delos though I was not doing a side by side test of these two, maybe that is something for later in the year.

Messier 42, the great Orion nebula.

Orion had cleared the walnut tree as looking at this object is no fun through the twigs I thought I would include it the report. This was only based on one night and the conditions were not that wonderful, though they did get better as time went by.

Both the Nagler and the XW showed a vast expanse of nebulosity even with the Moon still low in the sky and slowly setting below the hills. I could see nothing in either rendition of the gaseous field that would cause me to say one was better than the other, so turned my attention to the trapezium. I was trying to hunt down ‘E’ and ‘F’ components of the little group, something I had done before with the same scope and Nagler eyepiece. I am sad to say that after over an hour I was not able to crack this at X114 but was able to do with the 6mm Delos giving an enhanced magnification of X134. At the lower power I had the feeling the Pentax was trying very hard to show me the ‘E’ part of the puzzle but I never saw it clean and for me to claim a double there has to be a gap. This was only the conditions as the water content of the air has been very English of late with humidity up around 85% every night, we are normally better off with 35% humidity at this time of year.

Venus,

I must have got my last view of Venus last night for this orbit as one of the walnuts and hills come into play, it seems to accelerate as it gets closer to conjunction and whether that is; inferior, exterior, superior or interior, I don’t know, knowing my luck none of them. All joking aside the tiny sliver of Venus shimmering away in the rising heat from the land was hardly a good enough image to assess any eyepiece by but very nice to have had a scope on again, maybe for the last time before we see it in the morning sky.

Conclusion.

I think it is fair to say that both of these have been around for some time, neither being the new kid on the block, having said that they have been not over shadowed by much newer offerings.

I can’t say I would call a winner here and maybe that I am not good enough to do this in any case, both are remarkable eyepieces from two of the best manufactures on the market. Many say, and I agree, it is very sad that Pentax did not see fit to make more eyepieces and what could they as a Company have done if they turned their attentions to astronomy as opposed to finder scopes, maybe we will never know. Before I started this I thought, based on site reports from people that own them, the Nagler would left wanting in many departments, owning one I am very pleased to say it was not. Any differences between these two were very marginal at best and could have even been a combination of my imagination and conditions. I believe that anyone that is bent towards planetary or deep space objects viewing would be hard pressed to better the Pentax XW as many times even the BGO did not improve the situations before me. On the other hand for a person that likes quality and a wider field of view the Nagler is up there with even the more exotic offerings from Televue costing a good deal more if we consider Ethos, it held up very well against the newer Delos 6mm, regarded by many as the best range on the market. If I were to have another chance to set up my eyepieces again I would not favour one over the other and I do not believe a mistake was made going down black and green avenue, however with having a few scopes |I think I may well be able to make a very strong case to have both.

.

Hope you enjoyed this as much as I did.

.                     

[John]

Another great review Alan 

I did a similar comparison a few years back between the Nagler T6 9mm and the Pentax XW 10mm and, rather to my surprise at the time, I found the Pentax just edged the contest showing less light scatter and very slightly better light transmission. I think it was observing the faint moon of Saturn, Enceladus and the elusive disk markings that just tipped the balance in favour of the Pentax.

That result ultimately sparked my move from the T6 Naglers to Ethos and Pentax XW's.

The T6's are excellent though, by any standards. 

[jetstream]

Excellent report Alan.I picked up on "like to get a sizeable Dobsonian" ......can't wait to read the report on it!Off topic here,but I can't help but ask.....which dob are you considering?

[alan potts]

John,

I think I will have to learn your skill at making a summery of things, I think the' Pentax just edged it 'sums things up nicely though I would say both have their strong points and it didn't turn out as I first thought it might, still one should never pre-judge. Those few words would have saved me 2 hours but would not have looked as good.

Gerry,

I was thinking of a 12 inch Meade as Dani has one he wants rid of, but I really want a 16 inch but I am not sure I want to grow old on my own. The dob would be less demanding though.

Alan. 

[swamp thing]

Another nice review Alan. These are really great reads. Thanks for taking the time to write them

ps Get the 16"

[alan potts]

Steve,

 I really wanted an 18 inch Sumerian with the high quality mirror he offers and a goto system, but I got a bad case of Televue eyepiece syndrome. I just think a Dobsonian is the missing link.

Alan

[John]

John,

I think I will have to learn your skill at making a summery of things, I think the' Pentax just edged it 'sums things up nicely though I would say both have their strong points and it didn't turn out as I first thought it might, still one should never pre-judge. Those few words would have saved me 2 hours but would not have looked as good.

Your report was comprehensive and balanced Alan and shows the time and care that you put in to comparing equipment. It was also very readable which is even better.

There is a lot of interest in eyepieces and I think in depth comparison reports such as yours are really valuable in helping folks make spending decisions (or decide not to spend, in some cases !) or at least to decide where their aspirations might lie in the future.

While the results are important so is seeing your "workings out"

[Damo636]

Another cracking read Alan, thanks for taking the time and effort to compile it  

[alan potts]

Just as an aside to the work I normally put in with mainly top line eyepieces, I am seeing if I can borrow some lesser TMB ( not the originals) type eyepieces from my friend to match up against the likes of short Delos and Radian. I think I can get a 6mm and a 9mm so far, so it may be interesting for me alone to see how they match up against the mighty. I am going to try and get it moving in February.

Alan.

[Stu]

A very entertaining and informative read as normal Alan, thank you. Nice to see my old ep being put to good use :-)

The idea of showing the (presumably greater) differences with less expensive eyepieces is a great plan and I'm sure would be very helpful for many.

The idea of being able to observe anything other than cloud, or stars that are not dancing around as the scope is blown around in a gale seems very remote here at the moment :-(

Cheers,

Stu

[YKSE]

Great work, Alan, an enjoyable read as always.

[AlexB67]

Great read,  another great novel by Alan Potts.  

That 7mm XW is very much an eyepiece I'd like to have and will be surprised if it does not end up in one of my cases in future. I can only go by my predecessor XL 10.5mm,  but it offers a level of transmission and colour rendition on stars I adore.  More than anything, it gave me a taste of an eyepiece that has such a consistent performance across the whole range of the FOV, something I really like about it as well, in my f4.7 Dob that quality shows, it has all my other eyepieces beaten in the off axis department as much as it may be the oldest as well. I should add when saying that it is a bit futile to compare a 20 and 28 mm Maxvision, my next most expensive eyepieces after the pentax XL 10.5mm.  Suffice it to say when it comes to taking in all that FOV, bar the last few percent it is the only eyepiece I've use to date where I feel it is the case there are virtually no aberrations left, bar a few of my good old coma friends turning up near the edges to say hello. :0)

On the naglers, I don't think a nagler would be for me potentially given the shorter eye relief and not really crying out for that 82 degree FOV as a need either.  I would still love to try one out one day to make sure what I am missing and see if I still feel that way when I do.   

[Stu]

Yep, the 7XW is a lovely ep. I now have a nice mix of Delos and XW at the short focal lengths, not a lot to choose between them and I enjoy having different types to keep some variety.

I do worry about Alan having to sit on a pile of bricks though ;-). Perhaps time for an observing chair? Or even a review of different seating options :-)

Stu

[alan potts]

Alex,

If you put eye-relief to one side, I once said to Dani the guy I refer to in the review " what the hell does anyone want with an 82 degree field of view", that was my general feeling of the time, about 5 years ago. Now , too many Naglers and a slack handfull of Ethos's I should maybe eat a large slice of humble pie.

But from your point of view needing eye-relief, XL's XW's, Delos and Radians will deliver in bucket loads, the longer Panoptics are also exceptional eyepieces with plenty of ER. 

Alan   

[alan potts]

Stu,

I was sitting on the concrete but it was a bit too low, I agree a chair is a great idea but bricks are very cheap and flexible. Most times I sit on an old chair and adjust the height with a brick of two but when using the M/N you can't avoid standing, no luxuries here.

Alan

[faulksy]

very nice report alan, i will be looking for something in that focal length soon, i quite like the nagler due to the larger fov, which would be easyer with the dob, thanks for putting this together alan

[alan potts]

Faulksy,

The pleasure was mine, I think I could well have made the suggestion that the Nagler would favour those with a Dobsonian but 70 degrees is not a small field of view. It is funny I read the review twice before posting it and could not see any mistakes; spelling, grammer and end of words missing etc, I have just scolled down it an picked up three, ghosts in the machine.

If you did not want to spend so much the old 6.7mm Meade UWA is a good second string, I had both of these together and whilst not as good as the Nagler it is by no means poor, just depends how fast that VX 14 of yours is.

[Pig]

Alan,

I really do love reading your reviews they always have a good mix of scopes, targets and objects.

Very funny in places, I laughed out loud about 3 times causing he Mrs to look at me like I have few screws loose   I think the " I " in IC stands for Index and not insignificant  but your description is better.

[John]

The eye lens of the Pentax XW's is massive, about 3x the diameter of the the Nagler's, and I find this gives the eyepiece an immersiveness which makes it subjectively feel like it has a wider field than 70 degrees. Even when I switch from the Ethos 6mm to the XW 5mm, it does not feel claustrophobic at all.

 The 60 degrees of the Radians does feel like a more significant drop in FoV on the other hand although still quite practical even with a dob

[BillP]

Great review Alan.  Detailed and balanced!  For most of the top tier eyepieces it is always trench warfare and a battle of inches.  But some of us live for those inches    I had a number of the 82s (Meade, Explore, TeleVue), but have finally settled in with the XWs and feel at peace finally!

[YKSE]

Great review Alan.  Detailed and balanced!  For most of the top tier eyepieces it is always trench warfare and a battle of inches.  But some of us live for those inches    I had a number of the 82s (Meade, Explore, TeleVue), but have finally settled in with the XWs and feel at peace finally!

Would you care to share your thoughts about the subtle differences between these top EPs (Ethos/Delos/Naglers/Radian/ES100/ES82/MeadeUWA/Pentax XW etc)? And deciding edge(s) of your choice of Pentax?

[alan potts]

John,

I think you would like the Delos as apart from it being about as good as it gets the eye-lens is also about the same size at the XW's, or at leat the ones I have had in my hands. There seems to me to be a different type of viewing experience with the Delos when compared with the Pentax, it is difficult to put into words but I believe it has something to do with the location of the eye-lens itself. I hope you can get to view one or two at SGL 9  then you will see what I mean. The only thing I have against either of these two eyepiece ranges is they don't come free with Suger-puffs, if they did I may well weigh more.

Alan