BillP
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Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Jon Isaacs]
#5417311 - 09/12/12 01:30 PM
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Although I was working with the assumption of using an Ortho similar to the Vixen 2" 40mm...still, using the the very modest 25mm Ortho all these scopes generate sufficient TFOV for the entire Veil (not a great list but certainly feasible):
- Orion FunScope 76mm Tabletop Reflector Telescope
- Stellarvue SV50 ED APO
- Stellarvue 80mm Finderscope (and the smaller ones that many use as small scopes)
If we consider other Orthos, like the 2" 40mm Vixen (32mm FS), then field opens up quite a bit including:
- Takahashi FSQ-85ED
- Takahashi FCL-90
- TV 85
- TV 76 APO
- TV 60
- Astrotech AT65EDQ 65mm f/6.5 ED quadruplet
If we consider the 28mm Flat Top UO Ortho than a few scopes from the second list make it to the first. Again, the core point I expressed was that it was certainly feasible for these magnificent small AFOV eyepieces to be able to produce sufficent TFOV to see the entire Veil without any need to go wide-field. And as a matter of fact, IMHO the 28mm Ortho mentioned puts up a rather *spectacular* view!!
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Jon Isaacs
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Reged: 06/16/04
Loc: San Diego and Boulevard, CA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5417435 - 09/12/12 02:40 PM
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Although I was working with the assumption of using an Ortho similar to the Vixen 2" 40mm...still, using the the very modest 25mm Ortho all these scopes generate sufficient TFOV for the entire Veil (not a great list but certainly feasible):
- Orion FunScope 76mm Tabletop Reflector Telescope
- Stellarvue SV50 ED APO
- Stellarvue 80mm Finderscope (and the smaller ones that many use as small scopes)
Indeed.
That's the point, the telescope choice is governed by the eyepiece. These are all very fast and suffer from serious off-axis aberrations that are exacerbated in a 25mm Ortho. I know what sort of quality a 25mm ortho provides in these scopes, I have the eyepiece(s) and I have the scopes or very similar scopes. They don't match up well.
The very properties that make a 25mm Circle T Ortho so special in a comparatively slow scope are lost and overwhelmed by the various aberrations in the eyepiece and the scopes.
Yeah, you can get a 3 degree TFoV with that 25mm Circle T but it's going to be messy and underwhelming.
So, to my eye, a decent 24mm Widefield the Meade Series 5000 SWA offers the possibility of observing the entire Veil in a much more detailed and pleasing manner because it does not limit my choice of telescopes so severely.
Jon
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Jon Isaacs]
#5417559 - 09/12/12 03:53 PM
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The very properties that make a 25mm Circle T Ortho so special in a comparatively slow scope are lost and overwhelmed by the various aberrations in the eyepiece and the scopes.
But not always the case. You can reference my 24-26mm Review and see that is a fast f/4.7 Dob with Paracorr, the 24 Pan and Circle-T Ortho you mention were both beautiful right to their field stops (figure 10). I rated it low for clusters, but only because dim compared to fully multicoated contenders. All in all though excellent in my fas dob!
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KWB
Postmaster
Reged: 09/30/06
Loc: Westminster,Co Elev.5400 feet
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5417660 - 09/12/12 04:51 PM
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To me the case to be made is whatever I enjoy using as to eyepieces definately depends on the telescope,AND the chosen target. No hard and fast rules here as to what an individual observer may find suitable. Many different strokes for many different folks,as in what works for me may not work for you.
I'll state this once more,with my F/10 refractors for planetary and double star work,my orthos are worth their weight in gold AFAIC. I don't have a tracking mount on any scope I own and could care less about owning one or the TFOV capability of this type eyepiece. I also can manually track at 300X with my dobsonian with relative ease. Not that I would recommend this combination to the new observer but FWIW,this ain't my first rodeo.
For viewing M6,M7,M45,etc., and such similar objects,an 80mm F/7.5 refractor used with an eyepiece like the 22T4 Nagler under my suburban sky gives me an exit pupil of 3mm and eyepiece TFOV capability of about 3.0°. For me that is about optimum and the type telescope/eyepiece combination I prefer to use. For objects in between,you can fill in the blanks as to what I or any other observer could use as to a telescope/eyepiece combination.
YMMV is the best way to think about eyepiece useage. I believe in letting Jesse rob the train however he see's fit. One persons eye for beauty could be anothers eyesore. The bottom line is depending on one circumstances and one's preference,yes,there can be a better eyepiece than a 25mm Ortho. IMO there is no way to substantiate the thread title question/statement for all observers for all purposes.
See subjective opinion. 
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: KWB]
#5417677 - 09/12/12 04:56 PM
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One persons eye for beauty coud be anothers eyesore.
That is a great quote!! 
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Jon Isaacs
Postmaster
Reged: 06/16/04
Loc: San Diego and Boulevard, CA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5418116 - 09/12/12 09:24 PM
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Quote:
Quote:
The very properties that make a 25mm Circle T Ortho so special in a comparatively slow scope are lost and overwhelmed by the various aberrations in the eyepiece and the scopes.
But not always the case. You can reference my 24-26mm Review and see that is a fast f/4.7 Dob with Paracorr, the 24 Pan and Circle-T Ortho you mention were both beautiful right to their field stops (figure 10). I rated it low for clusters, but only because dim compared to fully multicoated contenders. All in all though excellent in my fas dob!
With a Paracorr, your Dob is F/5.4, the scopes you were pointing to were F/4 and under. The fundamental point is that to get the same TFoV as the 24mm Pan you would have to either reduce the aperture or the focal ratio.
Really, the reality is that if you want wide true fields of view, eyepieces with wide apparent fields of view provide the best views for a given aperture or just over all.
These things we are batting back and forth, the Veil in the 25mm Circle T Ortho or the Veil in the 24mm Panoptic.. the 24mm Panoptic + NP-101 provides a 2.86 degree TFOV, not 3 degrees but enough to be sharp-sharp right to the edge and certainly a far more detailed view, a far more aesthetically pleasing view than the Veil in a First Scope 76 or an 80mm F/3.75 finder.
Jon
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Jon Isaacs]
#5418205 - 09/12/12 10:04 PM
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Again...aesthetics and other things are off-topic from my point. All I was contending was that one can achieve the TFOVs necessary with a 42 deg AFOV Ortho. I was not contending it had to be a 25mm. But if you want that constraint then I can still manage it in several scopes. What are aesthetically best in each beholder's eye and so forth is something that is not an absolute. Lots of observers live for challenges and prefer the smallest apertures possible. So anyway, can't bring those other constraints into the point I was making as it takes the point off-topic. Again, the point is, perfectly feasible to attain 3 deg TFOV with an Ortho (i.e., ABBE) design...and no arguing that *fact*. 
To recap the posts...initial point was:
"If you want to see the entire Veil - or most of it - with relatively good correction, a larger AFOV is not only a very nice characteristic of an eyepiece but an essential one."
And my retort:
"Won't any telescope-eyepiece combination that produces about 3 degrees TFOV do that? As example, no 2" wide field will out perform (in terms of TFOV) a 55mm Plossl. Similarly no 1.25" wide field, even the Ethos, will catch more TFOV than a 32mm Plossl. Your 2" 40mm Vixen Ortho in my 80mm APO will give me 3.6 deg TFOV! [to see the Veil] "
I really don't think there is anything to argue here!! An ABBE Ortho has no issue seeing the entire Veil...period!! All the other points you are trying to make, are not in the original point-counterpoint so really a different thing all together if you want to start adding FL of EP constraints or aperture and focal ratio constraints, etc, etc. Bottom line...An ABBE Ortho has no issue catching the entire Veil and more. All you have to do is mate it with the proper scope.
ps - my Paracorr I have measured multiple times, drift, bench, etc. It is exactly 1.1x so my f/4.7 becomes f/5.2 and not f/5.4.
Edited by BillP (09/12/12 10:17 PM)
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5419816 - 09/13/12 07:34 PM
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FWIW, when I put my Vixen 2" Ortho 40 in my 10" f/4.8 Dob, I get a 1.5 degree TFOV. That shows barely half of the Veil. My 5" f/5 Dob teamed with the Ortho 40 yields 2.4 degrees. It shows me most of the Veil. But the exit pupil is about 8mm in both those scopes; not good, IME & IMO, for a Newt. The Ortho 40 in my ST80 gives 4.5 degrees TFOV and will display the entire Veil with a nice border. This is a refractor, so a big 8mm exit pupil doesn't really matter except for loss of some light by my 7mm iris.
Actually I haven't tried the Ortho 40 in my ST80 yet. The Veil looked pretty good even through my old Meade QX 36 in that little scope. But I don't like the view through my 10" and 5" Dobs with the Ortho 40. If I stack it with a Paracorr, that will clean up much of the coma, but the FOV is still not exacly sharp to the edge, to put it mildly. I much prefer viewing the Veil with the ES 82 30mm, with or without a Paracorr.
Mike
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Jon Isaacs
Postmaster
Reged: 06/16/04
Loc: San Diego and Boulevard, CA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5420440 - 09/14/12 05:54 AM
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Bottom line...An ABBE Ortho has no issue catching the entire Veil and more. All you have to do is mate it with the proper scope.
This thread is about the 25mm ortho, in particular the 25mm Circle T ortho. Note the title, "Is there a better eyepiece than a 25mm Ortho?"
My point is simply that for some/many purposes there are better 25mm eyepieces than a 25mm Ortho.
Jon
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Jon Isaacs]
#5420553 - 09/14/12 08:34 AM
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Jon,
Quote:
My point is simply that for some/many purposes there are better 25mm eyepieces than a 25mm Ortho.
Mike
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Jon Isaacs]
#5420951 - 09/14/12 01:24 PM
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Quote:
Quote:
Bottom line...An ABBE Ortho has no issue catching the entire Veil and more. All you have to do is mate it with the proper scope.
This thread is about the 25mm ortho, in particular the 25mm Circle T ortho. Note the title, "Is there a better eyepiece than a 25mm Ortho?"
Yes that is indeed the thread title. Unfortunately that is yet another out of scope constraint relative to the sub-discussion I presented to Mike in my post #5413174. So recommend you take a closer look at that as it is clearly not limiting the sub-discussion started between me and Mike to the 25mm focal length. So once more...staying on sub-topic...indisputable fact = no problem getting 3 degrees TFOV with a ABBE Ortho and wide field eyepieces are absolutely not "essential" to attaining 3 degrees of TFOV. I think this sums it up for the original sub-topic
Now, moving to the main title..is there a better EP than a 25mm Orthos? The answer to that is of course yes and no. Yes any eyepiece can be better than another depending on the target and circumstances. And the answer is also no of course if the observer likes the asethetics that a 25mm Ortho is giving them over all other eyepieces for a particular target and circumstance. So clearly there is a domain where it certainly can have no equal. As I recall, there was this little shootout I did with a mix of narrow and wide field eyepieces in the 25mm range and sure enough, in some circumstances the 25 ABBE had not even a close rival...and in other circumstances the wide fields presented aspects that made them be the better choice. 
So I agree very much on your point that there are some/many circumstances where a 25mm Orthos is not the better choice. But that point necessarily implies that there are also some/many circumstances where a 25mm Orthos *is* the better choice! And of course YMMV as always. ubetcha:
ps - i think it is a well established fact on this forum that *better* means little becuase it means so much...like when you see "all natural" on a food container, it's unregulated and meaningless. So 25mm Orthos are All Natural as well 
Edited by BillP (09/14/12 01:37 PM)
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5421003 - 09/14/12 01:51 PM
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Bill,
Many of us can't stay on topic, and now you expect us to stay on sub-topic? You might as well try to herd cats. Cats are smart, but they tend to be independent and somewhat uncooperative. 
By the way, I did have a cat that I trained to sit up and beg, "speak" and come when I whistled for him, but I think he was an exceptional cat.
Mike
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Sarkikos]
#5421013 - 09/14/12 02:00 PM Attachment (16 downloads)
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Many of use can't stay on topic, and now you expect us to stay on sub-topic? You might as well try to herd cats.
Point taken. Don't know about herding but can teach them to observe! Want her to sketch what she sees as the next step. 
Edited by BillP (09/14/12 02:02 PM)
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Sarkikos
Postmaster
Reged: 12/18/07
Loc: Suburban Maryland, USA
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5421023 - 09/14/12 02:03 PM
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Now that's a smart cat! Maybe you can train her to scratch - er, sketch - the Mice? 
The Mice Galaxies
Mike
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: Sarkikos]
#5421056 - 09/14/12 02:27 PM
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Sadly not...when one finds its way in the house she shows a little interest then walks away. She prefers observing things that don't look like mice! Now birs really catch her attention
Edited by BillP (09/14/12 02:28 PM)
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desertlens
sage
Reged: 12/06/10
Loc: 36°N 105°W
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5421115 - 09/14/12 03:17 PM
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I have to agree that there's something special about a 25mm Ortho. I'm using a UO VT frequently and it provides that floating image plane experience so often mentioned with the 28mm RKE.
Some time ago, I acquired a Stellarvue SV60 finder hoping it would be an option for binocular class magnifications. BillP mentioned these above. I was disappointed in the performance of my widefield EPs in this finder. Knowing full well that Orthos were not known for their performance at short ƒ-ratios (This finder is ƒ3.75.), I half-heartedly mounted the 25mm VT and lo and behold a lovely 9x image that beat out any binocular view I'd experienced. The 18 and 12.5 were equally nice. The 18 and 25 required a bit of an outward cheat with parfocalizing rings in order to focus. I use a Baader M&SG filter to tame the background at these exit pupils. Just for grins I mounted the 25mm with an O-III filter and enjoyed a very nice 5 degree view of the entire Veil nebula.
A very nice EP at a modest price... one of my favorites.
Edited by desertlens (09/14/12 03:28 PM)
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BillP
Postmaster
Reged: 11/26/06
Loc: Vienna, VA
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Re: Is there a better EP than a 25mm Ortho?
[Re: desertlens]
#5421143 - 09/14/12 03:41 PM
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I've often thought of picking up a SV60. Looks like a nice product. Great to hear the ABBEs work so well in it
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desertlens
sage
Reged: 12/06/10
Loc: 36°N 105°W
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Re: Is there a better EP than a 25mm Ortho?
[Re: BillP]
#5421189 - 09/14/12 04:07 PM
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Bill, I'm told that the SV50 is sharper but I can't honestly complain about what I'm seeing. Just FYI, due to its longer barrel design the 18mm BGO comes to focus without the cheat... also an excellent image. I do wish there was a 25mm in this line.
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Richard Low
professor emeritus
Reged: 11/27/05
Loc: Singapore
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Re: Is there a better EP than a 25mm Ortho?
[Re: desertlens]
#5421696 - 09/14/12 10:36 PM
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In my SV60, the XW 14mm performed quite well, sharp almost to the very edge. The XW 14mm didn't perform as well in my SV80 though. My Circle-T VT Ortho 25mm always perform well in any of my finders.
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