20mm T5 vs 22mm T4 Naglers

[swamp thing]

Had a chance to put my 20mm T5 up against faulksy's 22mm T4 this weekend.

Sorry no pics, I forgot to take em, I reckon most of us know what they look like though anyway.

Conditions were pretty good with excellent, steady seeing, and good transparency, the only slight issue was it wasn't as dark as it could be because of the time of year. However I did my best to try and split them.

I used my 20" f/4 Dob this has the SIPS Paracorr system fitted, that takes it to f/4.5 but I think that's fast enough for most people.

The 22mm gives me 105x, a 0.77 degree field with 4.8mm exit pupil. The 20mm gives 115x, a 0.68 degree field and 4.3mm exit pupil, so both are pretty close.

First off the 22mm is heavy at 1.5lbs and feels it in the hand compared to the 20mm which weighs in 1/2lbs lighter. If balance is an issue with your scope this may be a problem. My 20" scope has no trouble coping with huge heavy eyepieces so this was a non issue for me, perhaps if I'd used my 10" it would be.

The 22mm has a large eye lens and long (19mm) eye relief. This makes it ideal for observers using specs. The 20mm has a smaller eye lens and tighter (12mm) eye relief. I'll discuss what this actually means in use later.

The 20mm has a volcano top and soft rubber eyecup that guides your eye into precisely the correct position every time you use the eyepiece. The 22mm comes with TV 'intajust', an adjustable eye guard, which helps to space your eye correctly from the eye lens. It also comes with a pupil guide one may use to help position ones eye correctly. The 'intajust' eye guard gets mixed reviews with some disliking it whilst others find it very nice. I fall into the latter group and find once one knows how many 'clicks' to set, using the eyepiece becomes second nature. I've never needed the pupil guide, finding correct eye position is something my eyes naturally do.

As these are both aimed at mid to low power eyepieces I saw little point in looking at planets with them, as the moon was almost a non entity this weekend I went straight to deep sky to compare them.

First up was some of the fainter NGC galaxies in the dippers bowl to check light transmission. Here I couldn't split them, both were giving as good results as one another. Both were picking out numerous small galaxies. So nice were the views through the 20" it reminded me of the Virgo cluster with a 10" scope literally galaxies everywhere.

Contrast and sharpness through both is exceptional and colour correction to my eyes is identical. I'd read about field curvature being a problem with T4's but it really was a non issue that I could discern.

I tried a couple of globs M13 & M92. Here again I couldn't split them. Optically to my eyes they aren't different. Both are cracking eyepieces that I would highly recommend. The extra FOV in the 22mm gives it a small edge when coupled with my 20" scope, but if I want a bigger field I'll swap down to my 31T5 anyway, so it's a non issue really.

Now had I been using my 10" scope the extra FOV may have been of real benefit, but it's weight might not have been so it could be a catch 22 job.

Now I have read that the 22mm is more 'immersive' can't say I found that myself. Both lose you in their giant fields of view, both take you on that 'space walk' that you've read about. Both offer such good correction I can't split them like so many others before me. Coupled with a large aperture scope both are amazing.

In use there is only the issue of eye placement.

Now if one gets the 'intajust' in completely the wrong position it is possible for the 22mm to suffer from kidney beaning and blackouts. I should add, I'm used to using Naglers and had to consciously try to make this happen before it did. The big eye lens does allow you to ness up your pupil position and get back outs if you try at it. The 20mm T5 I can't get to kidney bean or blackout at all, no matter how hard I try. The volcano top puts your eye in exactly the right position every time. Meaning its a simpler eyepiece to use.

Although as I've said for me it's a non issue I do have these problems when I've used Pentax eyepieces so I know it can be a problem for some, and worth considering.

So which would I recommend.

The 20mm T5, purely because it's an easier eyepiece to get on with, and it's weight will be less of a concern with most scopes. However I'd pick the 22mm T4 as I prefer the big eye lens and extra eye relief

Either way whoever buys either is gonna love em.

[Moonshane]

What a superbly written review Steve. I bet we could have guessed the 'pretty much the same' conclusion but the eye positioning was something I was not aware of for these two specifically. As you say, you really cannot go wrong with this sort of quality and meeting up and sharing other's gear is a superb way to try before you buy (or don't buy).

I borrowed a 20mm T5 for a short time a while ago and it really was excellent. The view reminded me of a Radian on steroids in some ways with a sharp flat (but much larger) field and pinpointy stars.

[swamp thing]

Cheers Shane.

I had a more shocking moment this weekend too.

I had my scope pointed at the veil nebula with my 31mm T5 and O-III filter in place, when a younger observer came up for a look. She looked through the eyepiece and said "it's red"

It floored me. I've never seen colour in the veil. Too old I guess

[DirkSteele]

Great write up of a fantastic compare and contrast.  As you write, whether you have the 20mm T5 or the 22mm T4, you will likely be one happy observer.

[michael.h.f.wilkinson]

Great review. I love the three T4s I have, as well as the 31T5, and got on famously with Olly's 26T5. If eye relief were no objection, I would probably have gone for the 20T5, but as it does matter for me, the 22T4 was the one (my first Nagler, in fact). Regarding instadjust: I like it, and have found that if I extend the eye cup a few clicks above my favoured position, people without glasses have no trouble with blackouts. This holds true for many other EPs with the same system. My new(ish) Radian 14mm blacks out badly with the eye cup in the lowest position (even for me). A few clicks up, there are no problems.

[YKSE]

Excellent write up on these two top EPs

[John]

Great review Steve 

I've owned them both and agree 100% with your findings. Two great eyepieces from a great company 

[faulksy]

nice report steve and spot on

[alan potts]

Conditions were pretty good with excellent, steady seeing, and good transparency!!!!!!!

Hard man to please Steve, only pretty good. All Joking aside very nice report on two fine 2 inch eyepieces. I have never had the two together but I reckon there is nothing optically between them it's all down to design and eye-relief and based on that I would probably go for the 22mm even though I bought the other one which one could never call a mistake.

Alan.