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40mm eyepiece

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#1 starnutty

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Posted 16 June 2013 - 04:24 PM

Hi guys was going to purchase a 40mm eyepiece for my scope. I take it this would only be used for deep sky work and not planetary. For example would this lens be ideal for viewing the beehive cluster or Plaides. If not which lens would be ideal.

Thanks
Ben :grin:

#2 petert913

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Posted 16 June 2013 - 04:34 PM

The strange thing I notice about 40mm eyepieces on the market (in 1.25" size) is their narrow field of view. Most are only around 45 deg. You can get a good 32mm with 65-80deg FOV. So, in my opinion, low mag is only good if you get wide field to go with it. Maybe a wide-angle 32mm is better.

#3 RogueGazer

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Posted 16 June 2013 - 05:55 PM

If you are able to use a 2" EP and are thinking plossl I would recommend the 40mm Sterling from Smart Astronomy. It has an AFOV of 55° and will set you back $80. It really is a good deal.

#4 Jon Isaacs

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Posted 16 June 2013 - 06:04 PM

Hi guys was going to purchase a 40mm eyepiece for my scope. I take it this would only be used for deep sky work and not planetary. For example would this lens be ideal for viewing the beehive cluster or Plaides. If not which lens would be ideal.

Thanks
Ben :grin:


Ben:

What telescope will you be using, does it have a 1.25 inch or a 2 inch focuser?

If it's a fast scope, 40mm is probably too long and you want to look in the 30mm-35mm range. If the focuser is 1.25 inch, you won't gain field of view over a 32mm Plossl or a 24mm SWA.

Jon

#5 ibase

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Posted 16 June 2013 - 06:19 PM

Here are some longer focal length eyepieces, inc. 40mm's at right:

Posted Image
R-L: GSO Superview 42mm, TMB Paragon 40mm, Siebert Optics Observatory Series 36mm, Proxima 31mm, UW-80 30mm, TV Panoptic 27mm

The 70-deg Paragon shown above is a good 40mm, discontinued (but obtainable at the used marts) but there are new versions available. Depending on scope used, maxes the available true field width on a 2" eyepiece and will readily fit the 2 open clusters mentioned with field to spare for good surrounding context.

Another good one is the Meade SWA68 Series 5000 40mm, 68-deg. AFOV, the stoutest EP in the stall:

Posted Image
L-R: Meade SWA 40mm, Celestron Axiom LX 23mm, 25mm plossl

The SWA40 is discontinued, but said to be optically same are the current Explore Scientific 68ES40mm's.

Best,

#6 ibase

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Posted 16 June 2013 - 06:37 PM

Oh, don't forget the Series 3000 Meade 40mm plossl, it's a classic for a 40mm 1-1/4", very fine performer.

Posted Image
Meade 40mm plossl

Best,

#7 junomike

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Posted 16 June 2013 - 07:26 PM

Hernando, Which do you find better between the Paragon and Meade 40mm SWA (5000)?
(edges and overall feel in slow/fast scope)

Mike

#8 ibase

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Posted 16 June 2013 - 07:50 PM

Mike, haven't done an A-B comparison (will do it when the skies clear up, been rainy here, and post impressions) and I reckon it will be close if not a wash, but find it more often reaching out for the Paragon 40mm, very good for scanning or as a finder; when used on my F/5.9 refractor scope, it displays virtually no pincushioning, a plus for many and so too for terrestrials. It does have some softness near the end of the field but better on slower scopes like the 8" SCT F/10. Images are bright, sharp and crisp, eye relief is good, a little lateral color, but no blackouts or kidney-beaning. It helps a lot that the Paragon 40mm has become some sort of a classic among many which contributes to its aura of desirability. (Bought mine for $135 in the used mart.)

Posted Image
40mm's: Meade 3K 40mm, Meade 5K SWA 40mm, TMB Paragon 40mm, GSO Superview 42mm

Best,

#9 rockethead26

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Posted 16 June 2013 - 08:30 PM

Ben,

Without knowing information about the telescope that you will be using with a 40mm eyepiece, it's hard to make a recommendation.

I went through the research last year for my 120mm f/7.5 refractor and ended up buying the TMB Paragon 40mm. It provides 23x, a 3° field and a very comfortable exit pupil of 5.3mm in my scope. It is a very nice eyepiece and provides truly outstanding wide field views.

If your scope is similar, I highly recommend it.

#10 bremms

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Posted 16 June 2013 - 10:10 PM

a 40mm EP is wasted in a 1.25 barrel. Maximum field is about 42-43 degrees. Just get a nice 32mm 50degree Plossl. same true field and more magnification. I have a Parks gold 30mm GS-5 (Orion Ultrascopic, Baader Eudioscopic, original Celestron Ultima). Very good EP. Good as the 32mm TV Plossl.

#11 derangedhermit

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Posted 16 June 2013 - 11:17 PM

The strange thing I notice about 40mm eyepieces on the market (in 1.25" size) is their narrow field of view. Most are only around 45 deg. You can get a good 32mm with 65-80deg FOV. So, in my opinion, low mag is only good if you get wide field to go with it. Maybe a wide-angle 32mm is better.

With a 1.25" eyepiece, at 40mm focal length, 42-43 degrees apparent field of view is as wide as will fit in the 1.25" barrel. 32mm 1.25" eyepieces can go to about 50 degrees AFOV. 24mm 1.25" eyepieces can go to about 68 degrees.

Eyepieces with a 2" barrel can have wider fields of view.

The OP needs to tell us what telescope he has before useful suggestions can be given.

#12 dennilfloss

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Posted 17 June 2013 - 03:09 AM

Speaking of 40mm eyepieces, has any of you guys ever looked through this one? Wondering if it's decent quality for the price. One of the reviews says it's not good for fast scopes.

http://agenaastro.co...n-eyepiece.html

#13 starnutty

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Posted 17 June 2013 - 05:23 AM

Hi for people that are. Asking I am using a celestron 114 LCM answer has a 1.25 inch focuser. Would based on my scope and focuser size is a 40mm lens ideal

Thanks
Ben

#14 Jon Isaacs

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Posted 17 June 2013 - 06:20 AM

Hi for people that are. Asking I am using a celestron 114 LCM answer has a 1.25 inch focuser. Would based on my scope and focuser size is a 40mm lens ideal

Thanks
Ben


Ben:

A 32mm Plossl is generally chosen over a 40mm Plossl because they both provide the maximum True Field of View possible with a 1.25 inch eyepiece but the 32mm provides a larger Apparent Field of View and greater magnification, both are most often advantages.

Jon

#15 GlennLeDrew

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Posted 17 June 2013 - 06:26 AM

This model scope has a 1,000mm f.l., at f8.8. Obviously of the Jones-Bird construction. The exit pupil provided by a 40mm eyepiece would be a useful 4.5mm, resulting in fairly high image surface brightness, helpful for the observation of fainter nebulae. But as noted, in terms of true field, this will be no larger than provided by some shorter focal length eyepieces, and the necessarily narrow apparent field can seem claustrophobic. Moreover, a shorter f.l. eyepiece will reveal somewhat fainter stars due to the darker sky glow that the smaller exit pupil renders.

#16 Sarkikos

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Posted 17 June 2013 - 06:55 AM

For 1.25", I like the Meade 3000 Plossl 40mm. For 2", I like the AT Titan-II ED 40mm. Nice views in both. But the Meade 3k has only about a 38 degree AFOV, while the Titan-II has 68 degrees. I keep the Meade at home for scopes with 1.25" focusers. I take the Titan-II to the dark site.

Mike

#17 ibase

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Posted 17 June 2013 - 08:28 AM

Since the OP had revealed the need for a 1-1/4" EP, here are some 32mm options:

Posted Image
R-L: Celestron 32mm plossl, Baader Classic 32mm plossl, TeleVue 32mm plossl, RKE 28mm.

The best (and most pricey) would be the TV, and the BCO & Celestron (or GSO) are viable options for budget considerations. The RKE 28mm is a wild-card, a runaway favorite of many for its floating projection effect.

Best,

#18 starnutty

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Posted 17 June 2013 - 09:46 AM

Thanks for all your comments guys they've been really helpful I think I might settle for a 32mm lens

#19 starnutty

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Posted 17 June 2013 - 09:49 AM

I found this one I have used this make before and they are very good. Would this better then the 40mm

http://www.amazon.co...0858IF1A/ref...

#20 Jon Isaacs

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Posted 17 June 2013 - 10:04 AM

I found this one I have used this make before and they are very good. Would this better then the 40mm

http://www.amazon.co...0858IF1A/ref...


Hi:

Not all 32mm Plossls are created equally and in this case, that is my concern. We speak as if all 32mm Plossls have the same true field of view but in reality, most are very similar but some, particularly less expensive models, have an undersized field stop and this limits the AFOV and the TFoV.

Looking at the other items this particular seller offers, I suspect that this particular 32mm Plossl probably has a restricted field of view in comparison to most others.

Jon

#21 starnutty

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Posted 17 June 2013 - 10:39 AM

Hi Jon thanks for that the trouble is I only have a very limited budget. what other eyepiece would you recommend

#22 faackanders2

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Posted 18 June 2013 - 07:23 PM

Hi guys was going to purchase a 40mm eyepiece for my scope. I take it this would only be used for deep sky work and not planetary. For example would this lens be ideal for viewing the beehive cluster or Plaides. If not which lens would be ideal.

Thanks
Ben :grin:


Get 40mm 70AFOV 2" Eyepiece (University Optics) or 41mm 68 AFOV Panoptic. Do NOT get 40mm 1.25" eyepiece, since 1.25" are only good to about 24mm panoptic or 18mm 82 AFOV Meade 5000.

#23 faackanders2

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Posted 18 June 2013 - 07:27 PM

Hi for people that are. Asking I am using a celestron 114 LCM answer has a 1.25 inch focuser. Would based on my scope and focuser size is a 40mm lens ideal

Thanks
Ben


40mm 68-70 AFOV require 2" focuser to maximize TFOV.

#24 BillP

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Posted 18 June 2013 - 09:12 PM

I would think the GSO would get high marks from most. Antares or Sky Watcher also get good reviews.

#25 Jon Isaacs

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Posted 19 June 2013 - 04:32 AM

I would think the GSO would get high marks from most. Antares or Sky Watcher also get good reviews.


Bill:

I have a 32mm Celestron Plossl that I purchased new in 1996, it's black with the orange lettering, made is Taiwan, I believe it's a GSO and it's been a good one for me.

I believe that Starnutty is in England, any ideas who carries GSO Plossls in England?

Jon






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