Author Topic: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?  (Read 48 times)

calbeyrefrows

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I've recently acquired a classic eq-mounted Meade 6" f/5 reflector and am loaning my prior nexstar slt130 (operated as guide alt-az because motors no-worky) to great friends who are interested in astronomy but don't have a telescope.  On my old range I had the red-dot finder along with an AT Titan 32mm which were really helpful for scanning the skies and searching DSO.  On the new scope I have a barely functioning 6x30 directly finder and a 25mm Meade plossl (or even kellner?  or other?  Not sure... it is one of 2 EPs that came originally bundled with the extent in the late 80s.) .  Star hopping is not as pleasurable using the new range and I am shopping for a few updated parts to enhance the performance with this new setup.  I am planning to acquire an 8x50 RACI and maybe a cheap red-dot pointer, but I would also like to obtain an EP that will give me max or near max TFOV (so 2 a hair)  I am always working on a strict budget.

The obvious choice is a 32mm Plossl, and I will likely get one, but I am also considering shorter FL, wider AFOV choices.  I truly liked the 70* AFOV of my Titan in spite of the fact that things got a little soft at the borders.  I am also considering the fact that I really do 95% of my observing out of my driveway at a red, bordering on white zone using a horrendous streetlight shining straight on me.  There's hardly any opportunity for me to become really dark-adapted when I am viewing from home, so I am thinking the 6ish mm exit pupil from a 32mm EP will probably be squandering aperture the majority of the time anyway.

And so, I am considering an ES 24mm 68*, but it is stretching my budget and they are rarely available.  Hyperion 24mm, however, it is even more expensive and doesn't get the maximum favorable press.  Then you will find the 60* EPs.  Maybe a 25mm Starguider/HD-60?  Are there other budget choices available that I might not be aware of?  Any suggestions/advice considering my equipment and observing conditions?  Thanks!



Zachary Tenk

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #1 on: December 27, 2017, 10:28:01 AM »
TV Panoptic 24mm and ES68 24mm are the generally recommended lower focal length options to a 32mm Plossl. They are well corrected high performance ep's that will likely outperform the others you reference.
But the Astro-Tech Paradigm Dual ED/Agena Starguider Dual ED ep's are very good values through they have considerable more narrow AFOV's.
You might wait until you get your RDF up and running. I fond them very effective on widefield scopes and yours may solve your problem.

falkwinsliche

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #2 on: January 04, 2018, 04:29:48 AM »
Still stretching your budget, but after getting the 32mm plossl, consider the 20mm ES68....excellent eyepiece, probably still in stock somewheres with a bit of looking, and could probably find a used one.

biocaunico

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #3 on: January 08, 2018, 05:36:58 AM »
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I would get a TV 32mm plossl. It will handle the f5 focal ratio better. Excellent examples come up in the classifieds frequently.
-Rob
Why do you think a Plössl gets better if it's from TeleVue?

cesconali

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #4 on: January 11, 2018, 11:56:59 AM »
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I would get a TV 32mm plossl. It will handle the f5 focal ratio better. Excellent examples come up in the classifieds frequently.
-Rob
Why do you think a Plössl gets better if it's from TeleVue?
Well, what I understand is that they take more care with some things like baffling and blacking that leads to better contrast than cheap plossls, but I'm sure televue isn't the only brand that makes good ones.

Are there any available for under $100 (preferably well under and preferably available new) that stand out as better than others?

Akida Holland

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #5 on: January 12, 2018, 12:24:58 AM »
If on a strict budget, then consider a 32mm GSO plossl. Even more affordable used.
http://agenaastro.co...ASABEgKTP_D_BwE

Marvin Alexander

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #6 on: January 13, 2018, 09:36:27 AM »
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I would get a TV 32mm plossl. It will handle the f5 focal ratio better. Excellent examples come up in the classifieds frequently.
-Rob
Why do you think a Plössl gets better if it's from TeleVue?
Because ALL Televue plossls are corrected down to F4 , if theres something going on in the eyepiece , its 'your ' eyes normally at f5 in a 6inch. . The ES 24-68 for widest fov at a 5mm exit pupil , My astigmatismis pretty bad at 5mm exit pupil and light pollution is more obvious ,  so I use the Meade 20mm-68, ES same glass , different wrapper

ryepittimy

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #7 on: January 20, 2018, 03:29:23 PM »
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Quote

Quote
I would get a TV 32mm plossl. It will handle the f5 focal ratio better. Excellent examples come up in the classifieds frequently.
-Rob
Why do you think a Plössl gets better if it's from TeleVue?
Because ALL Televue plossls are corrected down to F4 , if theres something going on in the eyepiece , its 'your ' eyes normally at f5 in a 6inch. . The ES 24-68 for widest fov at a 5mm exit pupil , My astigmatismis pretty bad at 5mm exit pupil and light pollution is more obvious ,  so I use the Meade 20mm-68, ES same glass , different wrapper
Are televue plossls a true plossl design or are they "plossls?" I know a lot of eps marketed as plossls aren't really. Seems like the optical design would be the thing that would determine how well-corrected it is at fast apertures.

David Varnavas

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #8 on: January 25, 2018, 02:26:11 PM »
My thinking:

If you purchase the ES 24 mm 68 degree, you'll never fell the need to upgrade to a "better" eyepiece. There are, arguably , better eyepieces but you have to look mighty hard to see the differences even with a practiced eye.

Dark skies, one can make a case for the 32 mm Plossl with its 6.4 mm exit pupil but from a red zone, the greater magnification and dimmer background sky is the winner.

Jon

Matt Christopherson

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #9 on: January 25, 2018, 08:41:28 PM »
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Still stretching your budget, but after getting the 32mm plossl, consider the 20mm ES68....excellent eyepiece, probably still in stock somewheres with a bit of looking, and could probably find a used one.

The Explore Scientific 20mm 68° would be an excellent choice.
A 4mm exit pupil, so nice and bright.
Adequate 38x magnification for a frequently-used low power.
22.8mm field stop would yield a 1-3/4° field, adequate for even very large DSOs.
And, it's one of the 3 best in their 68° series, IMO.
I know the 24mm is short in supply, but I think nearly every retailer has the 20mm still.
Remember, they go up in price August 1st.

Chuck Klem

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #10 on: February 09, 2018, 02:50:06 AM »
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The 24 mm provides a 2.07 degree TFoV.. I would not claim that's adequate for very look are DSOs but it just about the limit of what one can do with a 6 inch F/5.. The 20 mm is a nice eyepiece but if you make that choice, you'll probably want to get the 24 mm at some point.

Jon

xgamodrakmu

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #11 on: February 09, 2018, 02:56:29 AM »
Well, I was assuming as a companion to a 32mm Plössl.
No 32mm Plössl, then the 24mm for sure.

Steven Tolbert

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Re: Recommendations for a max TFOV EP for 6" f/5 reflector 1.25" barrel?
« Reply #12 on: February 09, 2018, 11:16:24 AM »
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Quote

Quote
I would get a TV 32mm plossl. It will handle the f5 focal ratio better. Excellent examples come up in the classifieds frequently.
-Rob
Why do you think a Plössl gets better if it's from TeleVue?
Because ALL Televue plossls are corrected down to F4 , if theres something going on in the eyepiece , its 'your ' eyes normally at f5 in a 6inch. . The ES 24-68 for widest fov at a 5mm exit pupil , My astigmatismis pretty bad at 5mm exit pupil and light pollution is more obvious ,  so I use the Meade 20mm-68, ES same glass , different wrapper
TeleVue does not claim that their Plössls were corrected down to F/4. TeleVue makes outstanding eyepieces, but please don't make them better than they really are. At F/6 the TeleVue Plössls have noticeable off-axis aberrations - at F/5 it gets worse.

My recommendation: wait and save money for the ES24/68°