View Full Version here: : Pick your Nagler
Well I have decided that for visual observations I really would like to up my game, so I am going to get rid of all my eye pieces and bite the bullet and buy a full set of Naglers.....
If you had a choice, which 4 would you buy? and why.
These will be used in all my scopes ie Megrez 80 , CPC11 , LB16 , LB12 etc etc
Above is the list of Naglers that are on the Bintel Website.........pick your best 4 choices
07-01-2007, 08:46 AM
I picked the 3 type 4 naglers based on my preference for eye relief. No point spending all that cash on an expensive wide field if you don't have enough eye relief to comfortably enjoy it. For focal lengths shorter or longer than 12mm to 22mm, Pentax XW is a better choice.
07-01-2007, 08:55 AM
My reasoning is much like Tony's, although if I was thinking of binoviewers I would have to include two 13mm T6s. (I can dream, can't I?)
07-01-2007, 09:03 AM
Im with casstony. If I had a budget to purchase four premium eyepieces, they wouldnt all be naglers :whistle:
07-01-2007, 09:33 AM
We have only one Nagler the 17 type 4 as a mid range focal length it performs perfectly in our 12" and like you Harb we're thinking of getting a 16" at a later date.
Whether it's Nebulae, Clusters or Galaxies this wide field EP is a gem
Considering your scopes my pick would be the 9mm, 12mm, the great 17mm and the beautiful 31mm.
But I'd also consider the Pentax range too.
Thanks for the input everyone.
I hadn't really thought about Pentax..................silly I supose, but I just assumed that the naglers would be better.
That makes things a little bit more complicated.......
I really would like to keep with the widest field posible.
07-01-2007, 04:31 PM
Thats the power of marketing ;)
Also, widest field does not always = the best :whistle:
07-01-2007, 05:30 PM
I agree with Geoff. The 7 and 10mm XWs have really grown on me and I would not be happy to swap them for T6s. The 30mm XW is pretty awesome too. I'm not Pentax fanatic, just go for what's best at every focal length. One of the last two EPs I bought was a Nagler 20mm T5. Very happy with it.
Exactly my thoughts, I just want to buy 4 of the very best eye pieces available.............not worried to much about brands.
08-01-2007, 09:42 AM
... and don't sell all your other EPs. It's good to have a set of decent but relatively inexpensive EPs you can let other people use without having to babysit them.
Now thats a good idea!!!
I think I will keep my 12" LB after the new 16" arrives for the same thing!
08-01-2007, 06:51 PM
Only have one ..13 t6 ( no eyerelief issues ).like it lots .. its a little cheaper at bintel for a while ..good luck .
. and take your time .
I have 31mm,13mm,2.5. 4times powermate, 2.5times powermate, and the 2times powermate. Love then all and will never sell then Phil.
08-01-2007, 10:03 PM
I have lots and lots of eyepieces :).
Including some of the best from the Pentax range and the Televue Naglers and Panoptics. I use them in a 10"/F5 dob and an 18"/F4.5 dob.
If I could only have 4 eyepieces, cost no issue, it would be the following.
31mm T5 Nagler
17mm Nagler T4
10mm Pentax XW
7mm Pentax XW
In the shorter focal lengths ie. 7mm and 10mm, the Pentax XW's are superior to Naglers. The 30mm Pentax XW is also a very good match to the 31mm Nagler. The Nagler has a larger TFOV, the Pentax has superior contrast and light transmission and goes a little deeper on dim objects. However, at this focal length I believe the aim is to maximise the TFOV. If you want to pop faint fuzzies you should be using a higher powered eyepiece with about a 2mm exit pupil IMO.
Thanks John.............exactly what I wanted , a list of what you would consider the best choice............
Thanks heaps for that.....great.
09-01-2007, 01:50 PM
Thanks to the info provided to us by John B and others on the forum some months ago our EP purchases were
27mm Panoptic ( Couldn't afford a Nagler at the time :whistle: )
17mm Nagler T4
10mm Pentax XW
7mm Pentax XW
They are all great EP's and we will never part with any of them. The four we have when used in our 12" Dob cover every aspect of our observing Lunar, Planets, and DSO'S .
Barb & David
10-01-2007, 12:11 AM
Sorry to be late to he party...
I made a set of Nagler only choices but as others have already stated if you want the best you should include some Pentax pieces as well (I've got a few ofboh brands)...I've got the 7 and 10 Pentax XW and they are top shelf...I also have a T6 11 Nagler...while the 10 XW does have an edge on the T6 in many areas I also like the view through the 11mm T6 a lot...the different brands do give a different look...both are fine and quite enjoyable.
11-01-2008, 06:54 PM
My next purchase is going to be the 31T5.
I have done quite a bit of reading comparing its performance with the 35 Panoptic, and from what I understand, the 31 Nagler has noticeably better brightness and contrast side by side. I have also thought about the 30 Pentax XW, but with my longest focal length EP, I want the widest FOV, even though the Pentax has better throughput and light contrast still.
I have recently acquired a 9mm Nagler and it is a sheer joy to use when the seeing is steady enough. I don't have any problems with shorter ER, but for those who wear glasses when observing, this might be an issue with the 9, which, like all T6's, is about 12mm ER.
I have heard many people rave about the 20T2, which is not available from Bintel. I understand that from those currently available, the 17T4 has effectively taken over that mantle as the most highly regarded, mid-focal length Nagler EP. Had I not just recently acquired a 13 Ethos, I would have voted for 17T4. But having that area covered now, I voted for a 20T5.
11-01-2008, 08:32 PM
Where do you get your Pentax lenses from?
12-01-2008, 06:38 AM
Frontier Optics (Central Coast NSW) stock Pentax EP's. Daniel, the operator of the business, could not be more helpful to deal with.
12-01-2008, 10:40 AM
I think people can count themselves very fortunate to have any of these eyepieces. Nagler Pentax or any high end ones.
But for this exercise and I have used all the Naglers mentioned, bar the 16mm.
I liked the 31 for it's huge field. The 20mm Is a super eyepiece.
Also I liked the 11mm and 5 mm Nags. But there all about the same in the smaller focal lengths.
Depends on your scope and focal length of your scope.
My friend uses a NP101 and uses the 2.5 mm and 3.5 mm often. He loves them and that's all that matters.
Enjoy whatever EP you have.:D
13-01-2008, 09:31 AM
I see Claudio at AEC also lists Pentax eyepieces on the Takahashi LE page of their website.
I have the 31,17 and 13mm Naglers and think they are great. I've not yet tried the Pentax eyepieces.
13-01-2008, 12:09 PM
In my 3000mm FL scope I use the 7XW, 10XW, Ethos, 20XW and 30XW most. Basically the 30XW lives in my focuser on DSO nights (gives circa 40' field) and then I go shorter if I need more mag.
The 31mm Nagler is a good alternative to the 30XW though, in comparisons I like the XW more for optically quality but the Nagler does have a wider and more immersive field.
25-01-2008, 12:47 AM
Rod, just a thought about the 31mm T5 with your 'scope.
At f/5, the 31mm T5 will give you x82.6 magnification with a field just on 1 degree -- _but_ the exit-pupil will be just on 6.1mm. A bit on the marginal side I'd reckon unless you've got "teenage eyes".
I've got a 26mm T5 instead (mainly for that reason) but, had I tried the William Optics 28mm UWAN before I purchased the 26mm T5, I would have bought the UWAN. It is a wonderful eyepiece (equally good as the Nagler I think) with the same apparent field as a Nagler design, appears to be just as sharp and contasty but somewhat cheaper and would have provided a slightly larger true field.
They also make a 16mm UWAN, but I don't think it is as good as the 16mm T2 or T5 (I've got the T2).
Matter for you, but seriously consider the 28mm UWAN before you outlay the cash on that 31mm T5 -- slightly smaller true field I know, but, the 5.5mm exit-pupil makes it a bit more comfortable to fit it all in your iris and a lot more comfortable on the credit-card.
My favourite Naglers? Well, they're not on the list to vote for. I think I've looked through all the Naglers except the very short fl T6's (ie 5mm and under), the 22mm T4 and the 20mm T5.
I have a very old (art-deco style) 9mm T1. No grip-ring, no pooncy rubber eye-cup. It was one of the first Naglers ever in Australia (I got it second-hand -- it is a circle N made in Japan). It is sensationally sharp and contrasty -- just a tad better than the more recent designs I reckon. Velvety black field, does kidney-bean a bit though, until you get the hang of it.
The real killer is the 20mm T2 -- IMHO the best Nagler of all that has just one drawback: mass. The 20mm T2 is very, very large and heavy. Light not only bends going through it, it also bends around it ;-)). It wasn't nicknamed the "holy hand-grenade" for nothing. But wow, what a view! It was discontinued a few years back when the (much lighter and optically simpler) 20mm T5 came out.
Long term, the 20mm T2 could become a collectors item -- like the 11mm T1 which has enjoyed "cult-status" for several years (people speak of it in hushed and hurried tones). They are pretty rare birds and attract very big 2nd-hand prices (like $400-$450 USD). I've looked through one and it was excellent but I don't think it was any better than my 9mm T1 which is the same design.
If you really want to spend big, look out for the 30mm Leitz with an 88 deg AFOV. You would be paying about $2000- AUD though!
25-01-2008, 06:10 AM
Thanks for your thoughtfulness, Les, in making those suggestions.
At that focal length, I will be using a Paracorr which whatever Ep I get. As I understand it, the effect of the Paracorr is to transform the 31 Nagler into having an actual focal length of about 26.35mm. I am assuming the exit pupil is similarly adjusted, and would end up being about 5.2mm? :shrug:
I have used RB's 31 Nagler in the Mary Rose, and the view was stupendous. But I will certainly look out to try a 28mm UWAN before parting with my cash. I seem to remember trying Joe's at Kulnura one time, and while it performed well in his SCT, at the faster focal ratio of my scope, it deteriorated very badly at the fringes (not just coma).
As I still have many years of observing ahead of me, I don't mind shelling out a bit more for my EP's. Spending $800 on a 31 Nagler ends up costing me 40 cents per week over the next 40 years. :)
25-01-2008, 06:15 AM
One specific point about the Type 6s: they're great if you're using both eyes. The eye relief is adequate for bino-ing (provided you don't wear glasses), and the fact they are so light and compact is a huge benefit. You can get them very close together if children are using the scope, for example (way down to 43mm spacing, which is enough for anyone human). And no balance problems.
I have a pair of 11mm T6s which are more or less permanently attached to the bino, except on those special occasions when a second Ethos happens along. :D:D
26-01-2008, 09:31 PM
Hi Rod & All,
"As I understand it, the effect of the Paracorr is to transform the 31 Nagler into having an actual focal length of about 26.35mm. I am assuming the exit pupil is similarly adjusted, and would end up being about 5.2mm?"
Well Rod if you're using the Paracorr, you'll be sweet. As I understand it, the Paracorr operates effectively as a x1.15 barlow and as a result it will effectively operate like a 26.95mm Nagler and accordingly produce a reduced exit pupil. :thumbsup:
I had a chance to compare the 28mm UWAN and my 26mm T5 side-by-side mid-last year in my 'scope (which is f/4.9 ~ yours is f/5 by the photos, yes?) and I was very impressed with the UWAN as were two others who also looked. I could not see much degredation near the edges of the field -- hardly (if any) more than the 26mm T5 Nagler and it was equally dark and contrasty. Coatings look good and construction was of high quality. I seem to remember not being overly impressed by the eyecup on the UWAN, but I never use 'em anyway -- mine are always folded down out of the way.
On the same night I also compared the 16mm UWAN to my trusty 16mm T2, but thought the Nagler was ahead ~ not by a much but the three of us all thought the ol' Nagler was more contrasty, had better edge-of-field definition and possibly showed a very marginally wider field than the UWAN.
Best wishes to all for Ausralia Day,
27-01-2008, 03:11 AM
I use a 31mm Nagler in my 18"/F4.5 Obsession with and without a Paracorr. I am also at least 10 yrs older than Rod, who is but a pup. I am 48. Although he "ALMOST" has less hair than me already :poke:
Without parracor the exit pupil is 6.88mm
With parracor the exit pupil is 6.00mm
I also have a 27mm Televue Panoptic which gives the following exit pupils:
Without paracorr the exit pupil is 6.00mm
With paracorr the exit pupil is 5.2mm.
I have spent quite a bit of time comparing the exit pupil/contrast/background sky brightness issues under a number of different scenarios and sky conditions. Ultimately I don't have a problem with the 31mm Nagler under any circumstances with the exception of almost city sky conditions. Even then it is still very useable. Under rural and dark skies the 31mm Nagler works very well for me without the paracorr at F4.5 for a 6.88mm exit pupil. Although, I usually do use the paracorr as it cleans up the EOF nicely. It is worth adding the following. I haven't smoked in almost 10 years, drink very little alcohol, take no medications on an ongoing basis and I am in very good health. These things can have an enormous effect on ones ability for their pupil to fully dilate. Take it as an absolute given that someone who smokes, drinks alcohol, or is in a poor state of health, will not have anywhere near the pupil dilation of someone who abstains and is in good health. On top of these external influences everyones physiological composition and abilities are different and their pupil dilation abilities vary. Age is also a significant factor. The older you are the less pupil dilation you will have. Rod observes regularly with me under reasonable sky conditions, he doesn't smoke and drinks very little. He will be fine with a 31mm Nagler in his F5 scope, for a 6.2mm exit pupil. With a paracorr which he has, it's a no brainer.
27-01-2008, 10:02 AM
Having compared the 35Pan and the 31Nagler side by side this appears to be correct. I was surprised that the 31 is so much better. The TFOV is marginally wider, and the contrast and sharpness really stands out.
But then the 35Pan is a $US380 eyepiece and the 31N is $US640, so this is what you would expect.
The 31 Nagler is probably one of the best in that range, alongside the 17T4.
27-01-2008, 12:58 PM
Hi Rod, John & All,
Re the issues raised by John and exit pupil.
John, you might well be correct that either or both yourself and/or Rod can dilate to approaching 6.5mm given a dark environment but taking into account your age(s) is not particularly likely. 6.5mm is generally "teenage-territory".
Of course the only way to know for certain is to measure it -- and I believe based on what I've read elsewhere it is possible to do this. The procedure of course will re-enforce in your respective families a belief that you are completely nuts.
Start with a rainy or cloudy evening and get a camera (digital is best for instant results) with a flash, tripod and a suitable rule/measure and a mirror. Set the camera/mirror/rule set up so you can take a close-up photo of your face in good focus in the mirror with the rule/scale close to your eye and in focus -- in complete darkness. Make sure the red-eye reduction (pre-flash flash) is off. Get it all set up exactly right and then shut and the door and any blinds to the room turn the lights off and ... dilate.
After 10 mins your iris will be fully open. You won't be fully (chemically) dark adapted but it won't matter. Take the photo in complete darkness and compare the iris diameter to the rule/scale.
I haven't tried this myself but I'm told it works -- though it will likely be several attempts to take a useful pic. You will look like a complete dill in all of the attempts.
Playing devils advocate, lets assume for a moment that you can physically dilate to about 6.5mm. Is it desirable then to use all of that? I reckon not. Optical aberrations are most likely to be found in the outermost edges or a lens and that includes your eyes.
Will you be able to tell when your iris is vignetting the light cone just by looking through the 'scope/eyepiece? No -- you won't have (can't have) any benchmark to compare it with.
Will it make _that_ much difference in the end? Again no, not a great deal of difference. If the exit pupil is 6.1mm (assuming 20" f/5 with 31mm T5) and you can only dilate to 5.9mm you are loosing 2/3rds of 5/8ths of ... not a lot. Remember I said in my original comment that " the exit-pupil will be just on 6.1mm. _A bit on the marginal side_ I'd reckon"
But I've equally seen a lot of folks using 35mm and 41mm Panoptics and 40mm and 55mm Plossls to achieve that "Ultimate wide-field" in 'scopes that will make for 7 and 8mm exit-pupils -- sure its wide, but you may as well place an aperture stop over the front of the 'scope! Not marginal at all. You are throwing away between 15 and 30% of your light-gathering power!
27-01-2008, 04:30 PM
I am not sure that using an exit pupil of 7mm or greater (as I use with my lowest power) is such a felony.
I find that the longer focal length eyepieces with consequent greater exit pupils will provide a much wider TFOV. Although you cannot "take it all in at once" you can move your eye around the field to take in any objects of interest.
27-01-2008, 04:36 PM
That doesn't sound simple.
Some years ago S&T magazine sold a pupil gauge where you could measure your dark adapted dilation using a simple template. This was based on a make your own pupil gauge article publised in TM magazine even more years ago.
According to this template, my fully dilated pupil extends to 6mm, sometimes less. If anyone is interested you may PM me and I will see if I can locate the article.
As to the accuracy of the respective measures, I have no data.
27-01-2008, 07:44 PM
Hi Argonavis & All,
"I am not sure that using an exit pupil of 7mm or greater (as I use with my lowest power) is such a felony.
I find that the longer focal length eyepieces with consequent greater exit pupils will provide a much wider TFOV. Although you cannot "take it all in at once" you can move your eye around the field to take in any objects of interest."
Well, no, you can't actually -- it doesn't work that way. The exit pupil is the diameter of the beam produced by a telescope/eyepiece combination, that comes out of the eyepiece. It is found (approximated) by dividing the aperture in mm, by the magnification used. Alternately you can divide the fl of the eyepiece by the f/ ratio of the 'scope. The simple fact is, if the diameter of your fully dilated iris is less than the diameter of the exit pupil then your iris will vignette the beam coming out of the eyepiece before it gets to the retina, thereby acting like an aperture-stop.
For example, if a person hypothetically has a fully dilated iris of 6mm (common in the 35 to 50 age-group), and the exit-pupil employed is 8mm diameter, then your iris will be blockiing some of the light gathered by the 'scope. It won't matter how much you move your eye around, you can't fully fit an 8mm beam into a 6mm iris. As foghorn-leghorn was fond of saying "Son, yer can argue with me, but yer can't argue with figures".
But is it a felony?
But you have to realise that to get that wider field at lower magnification, you _are_ effectively trading-off light-gathering power. There is no free lunch.
Accordingly, the biggest exit-pupil _I choose to use_ with my 18" is 5.5mm. I know my iris won't be vignetting the light-path, nor will I be using the extreme outer reaches of my cornea where aberrations are most likely to be found.
My earlier (attempted) sarcasm :P regarding the ease with which you can measure your full dilation seems to have slipped under the radar. It isn't easy at all to measure at home (but it can be done). Therefore I proceed on the assumption that I have just less than average and then subtract a fudge-factor -- hence my self-imposed limit of 5.5mm.
28-01-2008, 09:23 AM
Just to clarify, Les, let's take the example of an EP-telescope combination which produces an exit pupil of 8mm, the scope has an aperture of 20 inches, and a sample observer has a 6mm iris dilation.
By my reckoning, the area of a 6mm light path is about 56% of an 8mm lightpath. Are you saying that 44% of the light gathered by the scope is effectively lost, such that the scope's effective aperture in this instance is being reduced by the same factor? (In this case, by my calculations, the 20 inch mirror is effectively reduced to a 15 inch mirror).
28-01-2008, 10:50 AM
Hi Rod & All,
Yep, the maths look good to me and so far as I understand it, that has been the established lore since I was a boy (and beyond).
If the 'scope is producing an 8mm diameter beam then there is no way it can fit into a into a 6mm hole (your iris) no matter how you do the maths. Similarly, you can't fit a 5/8ths bolt into a 1/2" nut -- it just won't go.
You may ask then why do the manufacturers make eyepieces like the 41Pan?
Of course in a "slow" system, for example an f/10 C-11, the magnification is x68 and the exit pupil for that scope/eyepiece is not much over 4mm -- very comfortable.
Put that 41mm Pan into your 'scope (which has a fairly similar fl to the C-11) and you get a pretty similar magnification of x61, but the exit pupil jumps to a massive 8.2mm and some of the light gathered by the 'scope will be effectively lost as there is no way you can get all of it inside your eye as it emerges from the eyepiece.
I have seen instances of people (no names, no pack-drill -- over 10 years ago) using a 10" f/4.5 with a 50mm plossl at x25. Fantastically wide field -- 2 degrees but, the exit pupil was 10mm!
In your case as I said, the 6.1mm exit-pupil the 31mm T5 produces in the 20" f/5 probably won't quite "exceed the limit" -- but it is pushing close to the boundary that your average 30-something oberver's dilation can achieve. I don't (can't) dispute that both yourself and John might well be able to dialate to 6.5mm (or even further), but if you can, you will be a bit above average certainly.
I'm 46 yo, and I proceed on the assumption that 6mm (or fractionally over that) is my limit. The 31mm T5 in my 'scope would have produced nearly 6.4mm of exit pupil. That is the main reason I didn't buy it. The 26mm T5 produces a smalller field certainly (57 arc-mins -vs- 68 arc-mins) but the exit pupil is 5.4mm -vs- 6.4mm.
The 28mm UWAN (had I known of it, I'd have bought it) would have been the best comprimise of all (for me) -- x79, 63 arc-mins of field and a 5.7mm exit pupil -- and much cheaper!
28-01-2008, 10:58 AM
It is in fact quite easy to measure your pupil dilation at home, or at least somewhere that you are properly dark adapted.
Take a set of tools of known diameter which increase in diameter in set known increments. I in fact use a set of metric "Twist drills" that increase in .5 mm increments. You could also use for instance, a set of "allen keys".
Get yourself "dark adapted". Look at a star of about 2nd or 3rd magnitude. Get one of the drills. Start at say 8mm and hold the drill at arms length and introduce it between the star and your eye. If it blocks out all of the light from the star, your pupil dilation is smaller than the diameter of the drill. Continue the process with progressively smaller sized drills. When you come to the first drill that allows you to glimpse the starlight around its edges, you know your pupil dilation exceeds the diameter of that drill and lies between that drill and the previous larger sized drill.
My own pupil dilation lies between 6mm and 6.5mm as you correctly predicted.
Everything you have mentioned about "lost aperture and wasted light" and "ones own eye aberrations manifesting at larger exit pupils" is 100% correct. Not disputing any of it. However, the practical reality of the situation is that it doesn't really matter it is all academic.
When I use a 31mm Nagler in my F4.5 scope, I am not doing so to make critical observations of targets on the verge of visibility. I am using that eyepiece solely to maximise the FOV an an extended target or an extended starfield. If I wanted to critically observe the target in intricate detail or indeed observe threshhold targets on the verge of visibility, I wouldn't be doing it with a 31mm Nagler in an 18"/F4.5 scope. I will be using one of my higher powered Pentax XW's, in the 5mm to 20mm range. The Pentax XW's have marginally better contrast and light throughput as compared to the equivalent focal length Naglers and the contrast gain is further improved by using increased magnification. Indeed if I wanted to maximise optical performance at the 30mm focal length end, I would be using a 30mm Pentax XW and not a 31mm Nagler. That isn't the goal however at this end of things, it's all about field of view. It is also worth making mention of the fact that the optical effects of those issues you raise, are clearly less significant when observing from truly dark skies.
It is also worth noting that I am not talking about going ridiculously overboard with oversized exit pupils. I am talking about an exit pupil less than 10% over sized as compared to the observers own pupil dilation. Clearly, 7.5mm and 8mm exit pupils for people over 40 years of age are taking things past the extreme and are useless IMO.
28-01-2008, 12:16 PM
For many, many practical purposes, you are right. Looking at very bright high-surface-brightness thngs like M42 or Eta Carinae (NGC 3372) or Omega Centauri (NGC 5139) etc etc it won't make any practical difference at all, except that you are bringing the outer edges of your cornea into play -- relevant, but not critical at low-power :thumbsup:
Remember I said earlier:
"Will it make _that_ much difference in the end? Again no, not a great deal of difference. If the exit pupil is 6.1mm (assuming 20" f/5 with 31mm T5) and you can only dilate to 5.9mm you are loosing 2/3rds of 5/8ths of ... not a lot.
But, I think even a seemingly small variation (lets say, 0.4mm) would make a _small_ practical difference when looking at an extremely faint but extremely large object (like the California Nebula NGC 1499 or the Witches Head Nebula IC 2118, or outlying segments and wisps of the Vela SNR -- yum!) -- particularly when it might be a threshold object at a particular aperture.
As you note, the over-the-top exit-pupils are, well, over-the-top!:thumbsup:
For fine detail/ close things again you are certainly correct about using a higher power.:thumbsup:
Which brings me back to the reason why I made my original comment. I think 6.2mm is starting to get into the "marginal" territory as an exit pupil. In fact, with Rod's 'scope assuming a 504mm aperture (reduced 4mm by bevel on mirror) at f/5 and the 31mm gives 6.25mm exit pupil -- certainly I think in the "marginal" territory. If it were more than 0.5mm over maximum dilation I'd say "clearly too big". From my brief experience with it in my 18" f/4.9, the 28mm UWAN is a very, very good eyepiece and would, for the purposes of this exercise reduce three things:
(1) The true field (slightly -- a few arc-mins) -- undesirable but we are not talking about too much.
(2) The exit pupil (slightly) to take it away from "marginal" to perfectly comfortable. Desirable but not critical for many purposes.
(3) Price (markedly) -- Very desirable.
In the end, it is up to the preference of the individual. Whichever way you go Rod, I certainly hope it provides many, many years of very enjoyable observing!:D
14-08-2010, 11:43 AM
I've had 5 Naglers for a while now and they are all excellent.
22, 17, 12, 9 and 7. The 17mm T4 is the pick of them, a real gem.
I don't see much need to go wider than 22, but a UWAN 28
would be on the list. I find the main limiting factor is not the
quality of the EP's, but the atmosphere.
09-09-2010, 05:23 PM
I don't get much chance to do comparisons but I own two of the eps discussed here. I've had a 20mm T2 for a couple of years and it's great. I mean I love it. Pinpoint stars, good colour, contrast, edge performance, comforable 'feel'. I'd never sell it.
I've had a 28mm UWAN for a couple of months and so far I'm happy with it. It's a big step up from my previous wide-field ep (30mm 1rpd) and I haven't seen it next to naglers so I can't say too much. My feeling though is that it's very good. At f/8 it's essentially perfect to the edge, indicating (I believe) that the ep is well corrected. At f/5 there is a bit of unobtusive coma but in the 40cm f/4.5 I came away thinking that I need a paracorr. On my budget I can't imagine getting rid of it soon.
09-09-2010, 07:49 PM
i think you could easily check the size of a dark adapted pupil with a red torch and an opticians P.D. rule (pupilliary distance)
i have used this rule every day of my life for thirty years being a dispensing optician
you could easily measure it to a tolerance of at least a quarter of a millimetre no fanct tools required and extremely accurate
during daylight hours on occasions during spectacle "marking up" i have noticed some pupils dilated more than others
this may be the same at full dark adaption and you could then observe with the largest pupil
on another similar subject i myself used to observe with my right eye only until recently when an subsequent eye test revealed that my right eyes astigmatism has increased from a half dioptre to a full dioptre
so what did i do? i observe now with my left eye which is only a quarter diotre of astigmatism! blacker skys and more pinpoint stars
the brain admittedly decided it was all wrong but it got over it!
12-01-2012, 04:44 PM
I just recieved my very first TV eyepeice, a TV Nagler 31mm Type 5 (Thanks Tony!).
I am eager to test how this will perform with my Mewlon 300. However as I look out the window I see clouds rolling in :-(
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