Pentax - Naglers shootout

[PlanetMan]

Austrastromer (John)

As the resident expert of Pentax XWs I would be very grateful to hear and be appreciative if you could share your thoughts on the specific merits of the Pentax XW 30mm versus the 31mm Nagler?

[casstony]

I recall John expressing a preference for the 31 Nagler at this focal length to maximise FOV. Having owned both the Nagler and 30mm ES 82 degree eyepieces, I'd suggest you look at the ES since it's almost as good as the Nagler for nearly one third of the price.

[ausastronomer (John Bambury)]

Originally Posted by PlanetMan

Austrastromer (John)

As the resident expert of Pentax XWs I would be very grateful to hear and be appreciative if you could share your thoughts on the specific merits of the Pentax XW 30mm versus the 31mm Nagler?

Tony is 100% correct.

With the scopes I own ranging from a 10"/F5 newtonian to an 18"/F4.5 newtonian, a ~30mm eyepiece is essentially a low power widefield eyepiece and about as long a focal length eyepiece as I like to use, based on fairly fast F-ratio scopes and liking to keep the exit pupil < 7mm or thereabouts.

The strong points of the 31mm Nagler are widest FOV at this focal length (outside of the 30mm 88 deg Leitz, which is very expensive) and sharp to the EOF in fast f-ratio scopes. The strong points of the 30mm Pentax XW are slightly higher contrast, light throughput and on axis sharpness. However for my purposes these are less important criteria than maximising FOV at the longer focal length end of things. If one of my scopes was a 16"/F20 Classical Cassegrian having a focal length of 8.1 metres, things would be entirely different. In such a scope the ~30mm eyepiece would give 270X and generally be used for high power observations where light transmission, on axis sharpness and contrast are more important considerations than FOV IMO. In addition the cooler colour tone of the 30mm XW would be an important consideration as it would see use for lunar/planetary viewing as well, in such a scope. The 30mm XW is smaller and lighter than the 31mm Nagler, by a reasonable amount. The 31mm Nagler can unbalance a lot of dobsonian scopes under 14" aperture, that are undriven. The 30mm XW can also exhbit some field curvature with some scopes and some observers. The 31mm Nagler on the other hand will give a flat field view right across the FOV in just about any telescope. I own the 31mm Nagler and have never really wanted to change it for a 30mm Pentax XW, notwithstanding the 30mm XW ticks a lot of boxes.

I haven't used any of the Explore Scientific 82 degree eyepieces so I can't comment on those from first hand experience. The feedback I have seen indicates they perform to a different standard in different focal lengths, some very good, some not to the standard of the premium eyepieces, but reasonable for the price. I don't know which are good and which are not so good. What you need to remember is that "some" of these "cheaper" eyepieces perform very well in long focal length and focal ratio scopes like SCT's, but their performance deteriorates by comparison to the premium eyepieces, in faster F-Ratio telescopes, like newtonians.

I did use a prototype of the Explore Scientific 14mm 100 degree eyepiece before it hit the streets for sale and was very impressed with it. It was very good optically, pretty close to my 13mm ETHOS when used in the 18"/F4.5 Obsession, at a lot lower price than the 13mm ETHOS. However you can't assume that because one eyepiece from company "A" is good, then all eyepieces from company "A" are good.

If you plan to use the eyepiece for lower power widefield astronomical views and your scope(s) handle the size and weight of the 31mm Nagler it is IMO the best choice at this focal length.

Hmmmm I never thought I would see the day where I recommended a Nagler over a Pentax XW

Cheers,
John B

[casstony]

I'd like to add that I've used the ES30mm in a 16" Lightbridge and, while I was too busy enjoying the views to examine the edge of field, the eyepiece performed quite nicely in general.

Certain ES eyepieces are so close in performance to Televue that there's no point spending 3x the cash. Televue must be feeling the pinch and I'm looking forward to their 30% discount sale () to pick up a Delos or two.

ES quality control is definitely not as good as Televue and I won't risk any further overseas purchases now that there are competitive local suppliers.

[David Niven (David Niven)]

I wish there are more ES dealers but it seems, there is only one VTI Optics in Melbourne that is actually selling.
The others being thrown around are just mere promises till the day they actually have any items to sell.
I could be wrong and stands to be corrected!
Hope VTI will build up their product range and I would prefers to buy from an Authorized Distributor then just any ordinary retailers, that's for sure.

[Suzy]

Originally Posted by ausastronomer

Hi Suzy,

I think some of your following comments, which I have quoted, indicate that the individual observers physiology has a lot to do with things as well as the eyepiece itself



Could not agree more. I have problems with blackouts on a a lot of the type 1 Naglers and the 16mm T2 Nagler. I find the 35mm Panoptic (which others have no issues with) absolutely horrendous.



One of the easiest eyepieces to use from a comfort viewpoint that I have used, outside my Pentax XW's. My 17mm Nagler T4 sees a lot of focuser time, as it hits the sweetspot in the 18" for a lot of DSO's. It does need a paracorr to give a good view across the entire FOV in a fast newtonian but works beautifully when combined with a paracorr. As does the 22mm Nagler T4.



Never had a problem with this one either.



Here's where it comes down to the individual user. This is my absolute favourite high power eyepiece for lunar/planetary in both my 18" (300X) and my 14" (230X) and I have never experienced a blackout or kidney bean with it, and I have owned it for 10 years



I know you spent your very hard earned dollars on the 14mm Denkmeier based on my recommendation, a year or more ago. Me recommending the 14mm Denk was pretty funny in itself on the basis that I own a 12mm UO HD ortho, 12mm Nagler T4, a 13mm ETHOS, a 14mm Pentax XW and don't own a 14mm Denk I also know that you initially had some reservations with the 14mm Denk. Am I correct in assuming that on the basis you still own and use the 14mm Denk, you are happy with it? While I don't own the 14mm Denk I rate it as optically the best eyepiece around this focal length outside the 12.5mm Docter and the 12mm Nikon NAV HW which are a serious amount of coin, and a major waste of $$$$ on my old burned out retinas.



Of equal importance to eye placement is the ability to keep your head/eye still while you observe. If you move your head around like "Noddy the Clown" you will have a lot of difficulty with a lot of eyepieces. The ability to "find" the exit pupil and then hold your head still is of critical importance.

Cheers,
John B

Crickey John, when I saw my post being chopped into quotes, I felt the sweat trickling off my otherwise chilly body. And then I read on, Phew...!

Interesting point you made on the XW7

Regarding the Denkenemier 14mm...
When or when will I finally get around to putting my review of it on that thread- note to self- asap! I get a few pm's asking about it from people who've seen the thread and want to buy one.

I love it!!!!!
The stars aren't as pin point as my XW or LVW- could it be the astigmatism it's picking up from my eyes that my other eyepieces don't?- I don't know. But that's okay- because everything else about it I absolutely love!!!! Nice black background- amazing contrast! It seems to have a slightly darker background than my XW10mm. It has a shallow cup and with that 20 degree eye relief, it means you can see the entire fov without having to get that close into the ep. Comfort wise, personally, I rate this even more comfy than the XW (in itself a very comfy ep). Seems to suffer the effects of dew a lot quicker than my XW's or LVW though- I wonder if this is because it has a very short eye cup .
You steered me (yet again!) very well John in pointing me towards this ep.
Oh, I nearly forget- the advertised fov is supposed to be 65deg- I would say it leans more towards 68 deg.

After saying all that, I just realised this would make a good review for that thread, so I've copied & pasted from here to there.
Help Choosing a Premium 14mm Eye Piece.

[moonunit (Joe)]

Bought a 26mm Nagler based on this thread, it superceded my original GSO 26mm, I had first light last night and it blew me away, could not believe the clarity, no blurring towards the edge of the eyepiece, cost me a weeks wages but it has given my 10" dob a much longer life.

[Larryp (Laurie)]

I have a 26mm Nagler too-absolutely superb!

[Tom Hancock (Tom)]

My most used ep is the Pentax XF8.5
Fantastic performer and one that will stays by my side as long as my eyes are capable.