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Equipment Discussions >> Eyepieces

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astro_baby
scholastic sledgehammer


Reged: 06/17/08

Loc: United Kingdom
Re: University Abbe Orthoscopics new [Re: kepheus]
      #4841309 - 10/03/11 12:47 PM

The last two I bought cam in those boxes. They are the same as normal boxes but with a metal foil sticker. It does look cute though.

Tell you what I'll trade the box for a 7mm...hows that


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Zad
super member


Reged: 01/05/08

Re: University Abbe Orthoscopics new [Re: jrbarnett]
      #4842223 - 10/03/11 08:19 PM

Hi Jim,

I am considering getting the ES 127 ED scope for some planetary work (Mars is coming). Since this scope is f/7.5, do you think a 4mm UO volcano top would be an effective planetary eyepiece? I don't wear glasses, and this will be GEM mounted with tracking. I was thinking about the 4mm because that would bring me to 238x (near the limits of a 5" scope).

I have several ES 82 Deg. Waterproof eyepieces for my 10" Dob including the 4.7mm. Which brings up another question - am I going to get more detail on Mars from the bigger appeture of the 10" dob (Sky-Watcher USA) or the ES 127 with an ortho eyepiece due to better contrast?

Decisions decisions....

Thanks!


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: University Abbe Orthoscopics new [Re: Zad]
      #4842496 - 10/03/11 10:59 PM

"Since this scope is f/7.5, do you think a 4mm UO volcano top would be an effective planetary eyepiece?"

Yes. However, the difference between Orthos and quality ultra-wides isn't monumental, but is instead subtle. I don't think you'd be giving up that much using the ES 82s rather than adding some Orthos.

Now the 10" Dob vs. 5" triplet is an interesting question. On a steady night, with the 10-incher cooled and perfectly collimated, it should easily outdo the refractor on Mars. However, on a less steady night, or with the Dob not cooled or slightly miscollimated, the 5-incher would likely bet the better performer. Also, the fact that the refractor will be on a tracking mount cuts in its favor on planets. I see substantially more detail when (a) seated and (b) the planet remains centered.

I love refractors, but mainly because they tend to perform well out of the box, with little care and feeding.

Regards,

Jim


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ibase
Vendor Affiliate
*****

Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: University Abbe Orthoscopics new [Re: jrbarnett]
      #4842786 - 10/04/11 03:18 AM

Quite intrigued that a 5" refractor would perform better than a Dob w/ double the former's aperture in a less steady night. What's involved in this gravity-defying act? Thanks.

Best,


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Mike Hosea
Postmaster
*****

Reged: 09/24/03

Loc: "Metrowest" Boston
Re: University Abbe Orthoscopics new [Re: skypilgrim]
      #4843382 - 10/04/11 12:01 PM

Quote:


But I have to wonder what they were thinking when they switched to those @$#%# undercuts?





BTW, anybody who doesn't like the undercut on the 12.5mm and shorter UO Abbe (classics) can use the black anodized aluminum 1.25" barrels from Surplus Shed. You can use them on the 18mm and 25mm, too, I expect, but you'd probably want to move the field stops over, which would be more work and might be hard to do if they're not easily loosened.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: University Abbe Orthoscopics new [Re: ibase]
      #4843455 - 10/04/11 12:36 PM

Larger and faster scopes are more affected by poor seeing than smaller. Neil and Vlad's work on the topic is instructive.

http://www.cloudynights.com/item.php?item_id=2529

http://www.telescope-optics.net/induced.htm#environment

Also, adding aperture isn't a panacea for ills affecting a particular system. A poor quality or poor condition 8" scope wouldn't be any better than a similarly impaired 16" scope.

So I'd call it hardly "gravity-defying" but rather I would liken it to an understanding that the convention of a flat Earth is wrong.

Regards,

Jim


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astro_baby
scholastic sledgehammer


Reged: 06/17/08

Loc: United Kingdom
Re: University Abbe Orthoscopics new [Re: jrbarnett]
      #4843732 - 10/04/11 03:08 PM

Jim,

Thats interesting because I was flamed one time ona nother board for suggeting my 100mm Achro could whup my 200mm F5 Newt on planets and lunar.

On deep sky the newt will win but the 100mm is not actually that far behind.

People told me it was impossible and must be shockingly bad collimation on the newt (which isnt so) or the newt must have terrible mirrors (doubt it myself).

I have long suspected it was down to the newts susceptibility to poor seeing which your post confirms.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4843816 - 10/04/11 03:59 PM

While not generally accepted yet, your results certainly mirror my own field testing.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3911979/page/0/view/collapsed/sb/5/o/all/fpart/1

Neil and Vlad have further studied the phenomenon and, in my opinion, have provided a very well explained theory as to why that would be the case.

As they say, she who flames last flames hottest. You have every right to feel smug.

- Jim


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sixela
Postmaster
*****

Reged: 12/23/04

Loc: Boechout, Belgium
Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4843927 - 10/04/11 05:41 PM

Quote:

Jim,
That[']s interesting because I was flamed one time on another board for sugge[s]ting my 100mm Achro could whup [sic] my 200mm F5 Newt on planets and lunar.




I was flamed on this board for suggesting something similar as well (by someone living in Florida who couldn't believe anyone would look at planets with less than 600x magnification!).

The devil's in the detail. For that 100mm to likely beat the 200mm because of seeing D>3*r0 should hold for the 200mm, which means the Fried parameter should be hovering around 70mm or so. That corresponds to roughly 2.1 arcsecond seeing.

So yes, if the seeing was that bad then it's not only possible but likely.

If it was a night with better seeing than that, though, then something is amiss with the Newt, but it's not easy to conquer the thermal gremlins on them: even the fact that you're personally very close to the tube opening on a Newt but at the back on a refractor is sometimes enough to give "bad seeing" if the wind direction isn't favourable! Not to mention cooling mirrors to ambient temperatures is a constant battle (if you don't engage in that battle then you're almost guaranteed "bad seeing " very close to the primary).

we had some excellent nights recently (where 350x-450x was basically the minimum you'd be using on Jupiter, with peaks to 710x to see detail on Ganymede!), and on my Dob just moving your arm to the focuser would have visible effects on the image. I had to wear lots of clothing and hold my arms behind my back to get the very best images...

Here, it's indeed not that interesting to look at planets in 2 arcsecond seeing, given there are enough nights in which the seeing is a lot better, so the smaller scope (a 130mm) only gets preferred if there's something special to see (Saturn very close to opposition, some Jovian satellite transits) and the seeing happens to be abysmal.

There are enough nights of better seeing even here to make it worthwhile to have roughly 250mm of good quality aperture, but you'll certainly get better images some of the nights with a 130mm APO.


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ibase
Vendor Affiliate
*****

Reged: 03/20/08

Loc: Manila, Philippines 121*E 14*N
Re: University Abbe Orthoscopics new [Re: jrbarnett]
      #4844037 - 10/04/11 06:56 PM

Quote:

Larger and faster scopes are more affected by poor seeing than smaller. Neil and Vlad's work on the topic is instructive.

http://www.cloudynights.com/item.php?item_id=2529

http://www.telescope-optics.net/induced.htm#environment

Also, adding aperture isn't a panacea for ills affecting a particular system. A poor quality or poor condition 8" scope wouldn't be any better than a similarly impaired 16" scope.

So I'd call it hardly "gravity-defying" but rather I would liken it to an understanding that the convention of a flat Earth is wrong.

Regards,

Jim




Jim thanks for the note, and those are indeed instructive links! Was half-expecting that you'd allude to using a Brandon to pull off the gravity-defying act.

Best,


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deSitter
Still in Old School


Reged: 12/09/04

Re: University Abbe Orthoscopics new [Re: jrbarnett]
      #4844990 - 10/05/11 11:05 AM

Quote:

How much you wanna spend and do you want/need decent eye relief?

Here's my "Ortho" collection, by the way:



My faves are the Pentax SMCs.

- Jim




You are not well

-drl


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deSitter
Still in Old School


Reged: 12/09/04

Re: University Abbe Orthoscopics new [Re: deSitter]
      #4845010 - 10/05/11 11:19 AM

My standard comment about Orthos involves the completely flat exit pupil (in optical language, no spherical aberration of the exit pupil). You can put your eye anywhere in the exit pupil and the view is the same. For looking at planets, you don't even need the whole 40 degree field, just the central 10 or 20 degrees, so you can use the short ones for high power viewing at some comfortable distance from the eye lens. Even Plossls will not allow this, and widefields demand that the eye be in a specific place in the exit pupil. This adds up to complete eye comfort and no dropout effects from a moving head. Being forced to fix one's head in one place to use a widefield adds up to muscle strain that diminishes one's ability to see fine details. This is particularly important with Newtonians where one may be standing up and the head wavering to and fro (the older I get, the harder it is to stand stock still).

The other consequence is a field stop that appears to be effectively at infinity. This gives deep sky objects an objective and crystalline appearance, and the telescope seems to melt away. This is what I most love about Orthos. The telescope disappears and one is in direct touch with the field of view, like looking out a window.

So Orthos are all about eye comfort and a strong "clinical" view, despite the short eye relief in the shorter focal lengths. The UO Orthos are all winners!

-drl


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astro_baby
scholastic sledgehammer


Reged: 06/17/08

Loc: United Kingdom
Re: University Abbe Orthoscopics new [Re: deSitter]
      #4845712 - 10/05/11 05:44 PM

Off topics on the aperture issue.....

Seeing conditions where I live are seldom great. Even when the upper air is stable there are huge thermals created by a large airport nearby and a town.

I have long suspected that the achros abillity to outperform the newt is down to some kind of cell disruption which the newt with its bigger aperture is more unsettled by.

Jim the articles about apo versus achro seem to hold true in my experience as well. Ie the achro does have CA but tha aside its ability to extract detail is not significantly worse than an APO.

i ran my TAL 100RS against a Meade 5000 102 which wa being offerec to me cheap a few months back. I decided to pass on the .Meade as it was more bucks and to be honest I couls see little difference in views apart from the CA which while present is not obtrusive and can be controlled with filters sufficient fir my needs.

Its been really fascinating to have some of this confirmed, especially after some of the brickbats I took. Thanks for posting those very enlightening articles.


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mike bacanin
Carpal Tunnel
*****

Reged: 03/19/07

Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4845767 - 10/05/11 06:20 PM

I live in UK, with generally quite poor seeing, which only improves after midnight. My current C8, has very nice optics, but frustratingly, is hampered by the seeing. That said, its potential is obvious in those split second moments of great clarity.
The absolute best scope which seemed to always work well was the Tak FS128.I think it was a perfect scope for my seeing.

Mike


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great_bear
scholastic sledgehammer


Reged: 07/05/09

Loc: Walthamstow, London, UK
Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4846985 - 10/06/11 11:26 AM

Quote:

The last two I bought cam in those boxes. They are the same as normal boxes but with a metal foil sticker.




Howcome you're buying UOs when you live in the UK?
Isn't it cheaper just to buy the unbranded Circle-Ts from Glen at Lyra?


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astro_baby
scholastic sledgehammer


Reged: 06/17/08

Loc: United Kingdom
Re: University Abbe Orthoscopics new [Re: great_bear]
      #4847247 - 10/06/11 01:39 PM

Well to be honest I never knew Glen was selling them until after I bought the first two - by then I wanted them all to look the same ( I have moderately severe OCD ) . But I also had in mind resale value.

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t.r.
Post Laureate
*****

Reged: 02/14/08

Loc: Upstate NY
Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4847305 - 10/06/11 02:06 PM

Quote:

by then I wanted them all to look the same ( I have moderately severe OCD ) . But I also had in mind resale value.



I think we all suffer from it to some degree!


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: University Abbe Orthoscopics new [Re: deSitter]
      #4848215 - 10/07/11 12:12 AM

Quote:

My standard comment about Orthos involves the completely flat exit pupil (in optical language, no spherical aberration of the exit pupil). You can put your eye anywhere in the exit pupil and the view is the same. For looking at planets, you don't even need the whole 40 degree field, just the central 10 or 20 degrees, so you can use the short ones for high power viewing at some comfortable distance from the eye lens. Even Plossls will not allow this, and widefields demand that the eye be in a specific place in the exit pupil. This adds up to complete eye comfort and no dropout effects from a moving head. Being forced to fix one's head in one place to use a widefield adds up to muscle strain that diminishes one's ability to see fine details. This is particularly important with Newtonians where one may be standing up and the head wavering to and fro (the older I get, the harder it is to stand stock still).

The other consequence is a field stop that appears to be effectively at infinity. This gives deep sky objects an objective and crystalline appearance, and the telescope seems to melt away. This is what I most love about Orthos. The telescope disappears and one is in direct touch with the field of view, like looking out a window.

So Orthos are all about eye comfort and a strong "clinical" view, despite the short eye relief in the shorter focal lengths. The UO Orthos are all winners!

-drl




Excellent post. I agree 100%. And i do enjoy comfortable eye relief even with my 4mm abbe just because i keep that ten or twenty degrees centered on the planet. I love my orthos. I only regret i cant get a 3.5mm UO ABBE.

Pete


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great_bear
scholastic sledgehammer


Reged: 07/05/09

Loc: Walthamstow, London, UK
Re: University Abbe Orthoscopics new [Re: astro_baby]
      #4848311 - 10/07/11 02:22 AM

Quote:

I wanted them all to look the same




Well that's fair enough really - even I express a shudder when a forum poster says: "Here's my set of orthos" and puts up a photo showing a mixture of UO and unbranded Circle-Ts!!

I think to myself - that's not a set, that's an assortment!


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deSitter
Still in Old School


Reged: 12/09/04

Re: University Abbe Orthoscopics [Re: great_bear]
      #4856727 - 10/11/11 10:33 PM

I'll bet jbarnett, the eyepiece hooligan, has a complete set of 6mm Orthos!

-drl


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