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40mm [or 32mm] pairs for binos?

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#1 iceblaze

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Posted 29 September 2012 - 12:29 AM

Hello,

I am looking at a few pairs of 40mm eyepieces and wanted to get your guys input on which you think would binoview well. I am absolutely getting a kick out of bino viewing with my newly acquired C8 :grin:. Anyway, here are the choices I've found (in order of preference at the moment):

1. GSO 40mm Super Plossl
2. Televue 40mm Plossl
3. Meade series 4000 40mm Plossl
4. Celestron Omni 40mm Plossl
5. Vixen NPL 40mm Plossl

I am leaning towards the Super Plossls based on cost/some reviews I've read on here. However, if the Televue's are really that much better than I can just save for those instead.

So, what say you guys? I really love the Sterling line, but unfortunately their 40mm's are 2" eyepieces.

Thanks!

-James

#2 Astrojensen

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Posted 29 September 2012 - 02:55 AM

Hello James

Be aware that unless your BV has large prisms, the eyepieces will be considerably vignetted, down to 30° - 35° AFOV. This may not be a disadvantage, depending on what you want to observe, but if you like big, wide fields, it can feel pretty cramped. The 35° field will be extremely sharp and bright, so for objects that need maximum exit pupil, rather than large AFOV, to show their best, they will be perfect. I use my own 40mm's when observing galaxy halos and stuff like that.

I use the 40mm TS SuperViews. I think they are plössls, but I am not sure. They are extremely sharp and crisp eyepieces, with adjustable eyeguard, which I consider a very major advantage over the usual 40mm plössls, which often have fixed eyeguards and too long eye relief.

http://www.teleskop-...--46--Feld.html

The picture shows the 32mm's. The 40mm's are longer, but not wider. I recommend them.


Clear skies!
Thomas, Denmark

#3 CarlDD

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Posted 29 September 2012 - 09:54 AM

I use a pair of 40mm TS Super Plossls for H-Alpha Binoviewing, the three magnificacations they give me in the Denk PxS are an ideal range.


The 40mm SP's ( like the 32mm TS SP's ) are sharp and comfortable and since I aquired them, they are now my most used eyepieces for H-Alpha. They are fine for solar whitelight and lunar binoviewing, but for general night time use the 32mm's are better.

To handle the long eye relief I use home made eyeguard exteders from Protostar flock board with winged eyeguards on top. The attached photo gives an idea of the eyerelief.

Best Regards
Carl

Attached Thumbnails

  • 5446594-Pair of 40mm TS SPs.jpg


#4 pftarch

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Posted 29 September 2012 - 11:48 AM

YMMV, but I have a pair of 40mm Black Night Plossls and later I bought a pair of GSO 32mm plossls. Once I got the 32's I pretty much stopped using the 40's. I just liked the combo of FOV and eye relief better with the 32's.

Have you paired up the TV 32 in your sig? (I'm guessing they would offer the same FOV as 40's and I'm guessing that they are nice plossls.)

Peter T.

p.s. Please note that once I got my 28 RKE's I stopped using my 32 mm plossls.

#5 iceblaze

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Posted 29 September 2012 - 12:32 PM

Perhaps the 32mm's may be a better fit, but I have not found one to pair up with my other TV Plossl. I'm afriad my TV Plossl may be an older vintage, so if I were to go with 32's then I would need to purchase a brand new set. I tried 28 RKE's in binos but I didn't like the fact that I had to stand about a half mile away from the binos in order to see the image properly. At the moment I have a pair of 26mm Celestron Taiwan "Halloween" Plossls, and a pair of 17mm Sterling Plossls, both of which are excellent bino pairs. However, in the 8" f/10, I cannot get the entire moon to fit in the 26's. Perhaps the 32's will be just the right balance between FOV, eye relief, and magnification in my 8" f/10 SCT.

Thanks for all the suggestions so far! I'm looking at the TV 32mm or GSO 32's at this time

-James

#6 EdZ

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Posted 29 September 2012 - 12:34 PM

30mm or 32mm plossls will almost always provide nearly 10% larger field of view in a binoviewer than a 40mm plossl. That's because the field stop in the 40mm is so far out towards the end of the chrome sleeve, it ends up closer to the back prism aperture which then becomes the effective field stop, it experiences far more hard (complete fov cutoff) vignette. In fact, a 40mm plossl losses approximately 20% of it's field of view in a 22mm CA binoviewer, but only about 6% of the fov in a 26mm CA (denk) BV. However even in tthe Denk, when used in reducer mode, the 40mm TV plossl losses 12% of its fov, so is reducded to an effective Afov=34°. This doesn't even start to take into account any additional vignette blur darkening. This is the measures of the hard fov cutoff.


Even though 30mm or 32mm plossls will experience some very minor hard fov cutoff, they will still be nearly 20% larger fov than your 26mm plossls.

edz

#7 Astrojensen

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Posted 29 September 2012 - 12:45 PM

The field stops in the 40mm TS SuperViews I use sit well inside the sleeve, at the upper end of it, in fact, the usual position in many eyepieces. That said, they are still vignetted in my Baader Maxbrights.


Clear skies!
Thomas, Denmark

#8 pftarch

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Posted 29 September 2012 - 06:28 PM

Iceblaze,

Do you have the rubber eyeguards with your RKE's? I use mine all the time now and it sort of compensates for the 267 meter eye relief on the 28 RKE's.

Please note that if my math is correct, the FOV with the RKE's will still be smaller than your present 26 plossls, so those 32's are probably still in your future.

Peter T.

#9 EdZ

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Posted 30 September 2012 - 08:25 AM

Please note that if my math is correct, the FOV with the RKE's will still be smaller than your present 26 plossls,



In all cases tested, the 28.7mm RKE, even with some slight hard vignettte, measured a slightly wider field of view than a 26mm plossl.

The field stop in the RKE is 23.3mm. In three different brands of 26mm plossls, the field stop ranged from 21.7mm to 22.3mm. So even comparing to the widest 26mm plossls, the RKE is larger by about 5%. The RKE experienced less than 4% hard cutoff in two different standard binoviewers, and no cutoff in the Denk.

I should note, the 26mm TV plossls have the smallest field stops at 21.7mm. The effective AFOV ot the TV plossls is 48°.

However, I would agree with some other comments regarding the 28.7mm RKE. I found it about the most difficult and frustrating eyepiece I've ever used in a binoviewer, so gave up on trying to use it.

You might go back to considering to pair up your TV26. Mine are old, the smooth sided TV 26 pl. The view is aquired instantly and is held without struggle, and the contrast is better than the RKE or 30mm Ultimas or the 32mm TV plossls. TV 26mm pl is my most used low power pair of eyepieces.

edz

Oopps, just reread, you don't havve 26TVpl, you havve a 32TVpl. There has been very little if any change in design in the TVpl of the years, so you may be fine, except that if you have a smooth sided TV, stick with the smooth sideds.

#10 teskridg

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Posted 01 October 2012 - 05:47 PM

I would recommend the Vixen 30mm NPL Plossls. These are pretty inexpensive and do not vignette in my Earthwin binoviewer. 32mm TV Plossls do vignette in these binoviewers, as do 24mm Panoptics. This is not disabling, but you might find it a little annoying. Also, the total field of view is about the same with 32mm Plossls as with 40mm Plossls, but the 32's will yield a sky view with a darker background because of the smaller exit pupils. I also found the eye relief of the 40mm Plossls long enough to make proper eye placement irritating. Tim

#11 johnthomas

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Posted 01 October 2012 - 06:24 PM

I use some Rini 42's & 30s as my "main" eyepieces with my cheap Celestron chinoviewers. They are fine for me.

1. They are within my budget (about $25 each)

2. I can fit the whole moon in my fov with the 42s despite using a 1.9 corrector. (I use a newt).

3. The eye-relief is long, but that's ok (unless there is a full moon out or a light near me (then I use a hood).

4. They do vignette on account of the narrow field stop of the Celestron binoviewers, but that's OK since their edge performance is less than stellar anyway.

I would buy a longer focal-length set of eyepieces if I could find them in 1.25".


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