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Another wide angled EP, but would it be worth it

bomberbaz

By bomberbaz
in Discussions - Eyepieces

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bomberbaz

bomberbaz

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I am looking at options for a wide angle ep for a celestron C8. (Fl2000/f10) I have options of two secondhand ep with televue and meade 5000 and alao new woth a william optics swan 40mm. All the prices are in budget. The other option that i might be prepared to look at is a Vixen nlvw 42mm. The cost is high but so are the specs. It will have a great tfov at 1.5 and i know the views will be superb.

On the scope in question is the difference in views going to be worth shelling out 3 to 4 times more than for the afore memtioned ep from tv, wo ot meade. A C8 scope is quite forgiving on eps as i have noticed so am i just becoming a sucker for the wide angle viewing experience.

Your thoughts will be most welcome.

Steve

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Stargazer_00

Stargazer_00

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As far as I know the vixen 42mm offers the most sky of any eyepiece with its wide afov and focal length combination. In any scope is a winner so I'm told. Don't know anything about the design of it but in an f10 it will deliver more tfov than any other eyepiece

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E621Keith

E621Keith

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Which Televue and Meade S5k are you talking about. If that TV is a Nagler 31 or Panoptic 41 go for the TV. If the S5k is a 30mm UWA go for that grape fruit.

LVW is good, but not that good. If you are offered any of the above eyepieces for 1/3 of the price of a LVW42. Check the seller's reputation and make sure it's not a scam or stolen goods. If the seller is genuine, buy it immediately.

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bomberbaz

bomberbaz

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TV is the plossl 55mm and the Meade 5000 is the ultra wide 40mm. i would have gone for the meade but it would simply be too much weight (about 2lb) for the setup and upset the balance completely. Big shame cos it looks blooming awesome as a peice of kit. The TV Plossl 55mm is a great price and a lovely EP too but I am struggling to convince myself its right.

My conundrum is mag + TFOV, see below

TV 55mm = 36mag 1.36 tfov (great price, down on mag and tfov slightly)

WO 40mm = 50mag 1.4 tfov (great price, great mag and good tfov but not the best ep in quality)

vixen 42mm = 48mag 1.51 tfov (expensive, great mag, excellent tfov and excellent ep)

So you see my conundrum. Inside my head says take the middle option as the scope will forgive the lower quality of the WOptic and it will do all I am looking for, another part says the TV for the quality and good price (about 1/3 price) and my heart says take the expensive vixen one as the best option overall.

Going to have to think about this but why do I get myself into this decision fights, lol :eek:

Steve

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bomberbaz

bomberbaz

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Got me really thinking now Keith. Its mag is 50 but tfov is down to 1.36, cost 135. Thanks for making the decision even easier, hehe.

To help I am going to input the details of the EP's into stelarium and see if this helps me get a better idea of how the magnification and tfov for the ep's compare.

Cheers anyway keith

Steve

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Dunkster

Dunkster

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With the low mags, you've got to be careful of sky glow...well, you haven't got to :eek: but I find it distracting and it almost certainly reduces contrast. In my neck of the woods much below about 70x is starting to get too orangey. Obviously, this will depend on where you are, but they're all quality pieces so far :cool:

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John

John

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I'm just taking a guess here Steve but if the TV 55mm plossl is one of the old "smooth sides" I'd not be so keen on it. The reason is that the eye relief is pretty massive on a plossl of ~50mm focal length and with the older style TV plossls there was no rubber eye cup to help position your eye and keep out stray light - you just have to "hover" your eye around an inch above the eye lens, which is not that easy or relaxing in practice !

If it's one of the newer types with the raised top section and rubber eye cup then the above does not apply and you can ignore my wittering !

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michael.h.f.wilkinson

michael.h.f.wilkinson

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Actually, some of the math is not quite right here. The best way to compute true fields of view is using the field stop size and focal length. Distortion (pincushion) can yield apparent fields of view that are unrealistic when using

TFOV = AFOV/ Magnification

The field stop method works as

TFOV = 2 x arctan( Field Stop Diameter / (2 x Focal Length) )

For a 48mm field stop (as big as they come in 2" mounting) and a 2030mm focal length of the 8" SCT (often longer if a 2" diagonal is used, due to the primary mirror having to move forward to achieve focus), we get

TFOV = 2 x arctan( 48/4060 ) = 1.355 degrees.

That is what the 42mm LVW will get you. The TMB Paragon 40mm I had delivered 1.33 deg FOV with its 46.5mm field stop. The SW Aero is a clone, and should work very nicely indeed. I used the Paragon for years until I got a 31mm T5 "Panzerfaust", after which it languished in the case. The 31T5 gets 1.25 deg TFOV but is more immersive. The Paragon was the comfortable EP I have used bar none, however, easier to use regarding black-out and kidney beaning than the 31T5. Note that the paragon is in principle an orthoscopic EP in that it is virtually free of distortion (less than 1% at the very edge). This means the two methods of computation work out to the same value.

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E621Keith

E621Keith

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http://www.amazon.co...s/dp/B004KW2Y1C Are these the Paragons you are on about Michael?

Burgess Optics TMB Paragon was discontinued a few years ago. However, their production continued and is sold under various brands. Astrotech Titan II is probably closest to the original TMB Paragon. Astrotech is the house brand of Astronomics who appeared to have bought the TMB brands from TMB's estate and is now slapping the TMB stickers on various Chinese made scopes. Original Paragon have the best cosmetic finish, followed by AT's Titan II. SW and TS just sell a generic one. They didn't even bother putting on a brand name or model name on the eyepiece.

Nevertheless you can't go wrong with Aero ED.

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cs1cjc

cs1cjc

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If you are willing to pay for a 40mm Aero then you might also consider the 36mm Baader Aspheric, which is very nice and has a similarly wide field stop (somewhat more than the 31T5).

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cs1cjc

cs1cjc

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The 40mm Paragon/Aero is indeed wider than than the Baader Aspheric 36mm. Field stops as follows:

40mm Paragon/Aero: 47mm (AOK Swiss figure, http://www.aokswiss.ch/d/zub/okulare/kasai/ewo.html)

36mm Baader Hyperion Aspheric: 44.7mm (my measurement)

31mm Tele Vue T5: 42mm (Tele Vue)

30mm ES82: 43mm (Explore Scientific)

But for the weight I would have gone for the ES as I have with other eyepieces.

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bomberbaz

bomberbaz

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I was all but ready to buy the SW Aero but then a cheque for a job i did several weeks ago arrived which i had forgotten about. So after some deliberation ( totalling all of 30 seconds) I have gone and bought a vixen. Cant find a bad review and believe me i have looked. So thanks all but i have been swayed by wide view fever. Anyway, my ep collection but i shall try to give a review once i get a chance to do so.

Thanks again all for your posts, steve

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E621Keith

E621Keith

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I've been tempted to get this as my lowest power EP rather than a 30mm 82 degree offering because this still has a lovely wide view but shows a lot more sky.

Do the LVWs perform well beyond F5?

No, the exit pupil will be too large (8.4mm).

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michael.h.f.wilkinson

michael.h.f.wilkinson

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I found my 40mm Paragon yielded slightly washed out backgrounds even in my F/6 frac. Even if your pupils dilate to 8mm and beyond (it is possible), the result would easily look pale. When I first got my 31T5, I though I would keep on using the 40mm as an "even wider field" EP, but it turned out the darker background in the 31T5 won every time. In 18 months I used the Paragon just once, and that was to let inexperienced observers look through the scope (the 31T5 shows more kidney beaning, the Paragon is dirt easy to look through). I then decided to sell it and put the proceeds towards two XWs which came up secondhand

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