The Wide Field quest (Rambling)

[Macavity]

Mostly a "thinking out loud" thread, but comments welcome! Perhaps like many of you, I have a certain love of wide-field views? And, when it comes to eyepieces, I try to accommodate BOTH my MAK 127 (f=1500mm) and ST102 (f=500mm F5!) refractor.

With my MAK, the initial barrier of 32mm / 50 Deg Plossle-dom has already(!) been broken with an the addition of (Thanks to a Jim E idea!) the Telescope-Service 35mm T2 to 2" adapter diagonal. Basically it increases a (supposed!) vignetting limit of 27mm MAK "exit hole" and 1.25" diagonal to allow for the use of some 2" eyepieces. In practice, it's a much sturdier (T2 Screw-On) support for Baader Hyperions (in 2" mode). The Hyperions then cover range of : 3.5-21mm and we have to look for something a bit "longer" to (maybe!) expolit the potential of maximum field.

As a first experiment, with the MAK setup, I stuck in a MoonFish type "Widescan" 32mm / 70 Deg e.p. This seemed to suffer "hard" vignetting, just below the calculated TFOV of ~1.5 Deg. With this in mind, I then bought a 30mm / 60 Deg Standard 2" Vixen Lanthanum. This gives a nice, clean 1.2 Deg and is light enough to compliment the Hyperion range, without balance adjustment! Conclusion: (a) I suspect, despite "common wisdom" it is worthwhile TRYING to extend the Visual TFOV of small MAKs, e.g. with 2" adaptors - You never know what you may find. ( Vixen 2" Lanths are also Cool!

Now, as everyone is doubtless clamouring to tell me (LOL) the MAK is not really a wide-field 'scope! So, returning to my ST102. At F5, the MoonFish e.p suffers (predicatably) from edge astigmatism. For me, this does not preclude it being a useful wide-field eyepiece. The Vixen Lanth is a (IMO) "a cut above" it, but needs JUST a tad more in-focus to work on an ST102 <sigh>. Aside: Maybe I can find some shorter path 2" diagonal - Or SAW a bit off the end of my ST102 (LOL). As a "grab & go idea", I have decided to TRY OUT the new lightweight Antares W70 34mm / 74 Deg - Or is that 68 Deg? <Grin> eyepiece. This is supposed to be "better than a (typical?) "SuperView" - That we will see...

Perhaps older / wiser heads are now shaking (with laughter). Or perhaps in the "fast(er)" scope there is no REAL alternative to the Panoptic 35? (Sadly, I cannot afford / justify a Nagler in an ST102). Another vague interest is the Vixen LVW 42mm 70 Deg. In a ST102, an incredible 6 Deg - Or maybe that would turn our typical British skies to (slightly orange tinged) milk...

[geppetto]

Will be interested as to the outcome of this.

My new (second hand) St102 is crying out for just such an

eyepiece for widefield grab and go

[John]

I recently bought a Super Wide Angle 38mm 70 degree 2 inch eyepiece which turns out to be the same as the Rigel 38mm that Ian King sells for £50 and the Orion Q70 38mm which go for about £70 I think. I paid a bit less than either of those for my "no name" version .

It performs very well and comes to focus in my ED80 with a 2inch mirror diagonal fitted, which is more than I can say for my Wide Scan III eyepieces which need about 5mm more inward travel than the ED800 can give with the 2 inch digonal fitted . They work OK with a 1.25 inch diagonal though.

The SWA 38mm gives a true field of view of nearly 4.5 degrees with the ED80 and the star images are pretty good until the last 10% or so of the field when they get a bit "seagull-like".

For what I paid for it I reckon the SWA 38mm performs very well, just as well as the Orion Optiluxe 40mm (62 deg FoV) which it has now replaced. At a 70 degree FoV the 38mm is just about as wide as you can get in the 2 inch format. I reckon I would have to spend a lot of money to get significantly better performance.

John

[GazOC]

Mac,

For your Lanth/ 102 problem, try to get a cheap prism diagonal rather than a mirror, they are a TAD shorter optically.

Gaz

[Macavity]

John, interesting info on your own eyepieces. I guess if I can amass a number of my "cheapies", I can trade them in for one "better" one. (joking). Frankly, e.g. I had some hopes for the "Scopos" e.p's, which seemed destined to augment the Hyperion range. But, much as their Stratii(?) predecessors, they seem to have "disappeared" again. Sadly too, the (much lighter!) 30mm Scopos didn't get exactly rave reviews. And, at 1kg+, the 35mm seemed a bit too 'eavy loike!

Ta Gaz, my thoughts of tube surgery on the ST102 have remined just that -There should indeed be better solutions! Meanwhile, the 30mm Lanth can give fine service in the MAK 127, where there is plenty of in-focus! For the ST102, I had e.g. already redrilled the EQ3 to relocate the tube rings on 10cm centres to allow balance with a Hyperion swinging on the end - But it still needs some additional "nose" weight. The slightly lighter Antares 34mm might help the "grab and go" concept a bit. But again, we'll have to see what that edge performance is really like...

Finally, confirmation of some things regarding lowest power limits for reflectors and refractors, in an article by Mr. Nagler. Guess I had kind-of surmised this myself, and NO "granny teaching" is implied! But I did find the stuff about "7mm", reflector "black spot" (a.k.a. secondary shadow), and the idea of "no" real low power limit for refractors, quite instructive.

[Macavity]

A few thoughts on the Antares W70 34mm / 74 Deg. (N.B. "ad-hoc", rather than a serious review!) First off, despite courier effort (smashed bullet case), the e.p arrived in one piece. First impressions are of a v.nice contruction and lightness of weight. During daylight, I tried to measure some physical parameters for the e.p. esp. re. the ST102. Using a variety of "devious" means, I compared it to a Vixen Lanthanum 30mm / 60Deg and Moonfish Widescan 32mm / 70Deg. In the ST102, the Vixen gave a TFOV ~3.6 Deg and the Moonfish W/S ~4.7 Deg. I'm pretty sure the Vixen AFOV is 60 Deg. I suspect the Moonfish is more than quoted - maybe 75 Deg? In comparision, the Antares seems to give a TFOV around 4.2 Deg.

Try as I might, I could not confirm the 74 Deg AFOV for the Antares. I suggest, like it's W70 bret'rin, it's more ~68 Deg? This seems to tally (vaguely) with the Antares TFOV. I've NOT star tested the Antares. I sense it may be a bit "sharper at the edges" than my particular "Moonfish". OTOH, the Antares' edges are that bit closer than the Moonfish! Despite it's (probable) 34mm, the Antares does not give a TFOV much bigger than ~4 Deg - Certainly not the (vaguely hoped) 5 Deg. In conclusion: Fair Enough. Pretty, v.Light - Quite a bit short on AFOV? Little to distinguish it from the other 30-35mm / £50-60 herd...

As someone of middlin' "Hyperion Budget" (I have found few to better 'em) my 20-40mm range remains a bit un(full)filled! For the moment, a £107 Vixen Lanth 30mm 60 Deg still remains pick of (my) bunch. It may be a bit short on AFOV, but Vixen's quoted data match measurements! (LOL). I sense I might have to move upmarket (£200) to better it? Maybe a Pan 35mm, Vixen LVW 2" 42mm / 70 Deg, (eventually) a Vixen LVW 22mm instead of the "slightly dodgy" Hyperion 21mm? We can dream...

As a postscript: I wonder if someone would (dare to!) say a few words about the Panoptic 35? I've heared them described as the "Poor man's Nagler" (Some poor man? LOL!). Also e.g. "Bit short on eye relief", "Pincushion distortion", "Sea-sickness inducing" ... Otherwise: "The best in it's price range"! Just wondering, from the perspective of one reluctant to spend more than £200 (S/H) on ONE eyepiece - Is the PAN still about the best there is?

[GordonCopestake]

I can't comment on the 35mm Pan having never owned one, but the 24mm pan (largest TFOV in a 1.25" barrel) is a FANTASTIC eyepiece. Everyone (who can afford the £140 second hand price) should own one.

[Macavity]

(Belated) thanks Gordon. I strongly suspect that is so. After much pondering, I shall probably await funds for a 35mm Pan - Much as I have developed an irrational(!) wariness re. the "Nagler" word from another place. (LOL) Generally, I am taking more note of the Field Stop size - It's interesting both to look at the quoted values and measure those in my posession. After all, it's the 46mm (or so) of 2" eyepieces, that's ultimately going to dictate any maximum potential TFOV. I do sense the price dictates how well these are going to perform in a fast scope though. Ultimately, one can worry too much. I think I've identified that most of my observing limitations stem rather from "hostile natives" and street lighting...