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MrBill's new APM Apos....

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#326 JustaBoy

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Posted 14 July 2014 - 12:56 PM

Hi Bill,

It is my belief that the 19mm and 27mm of that series are the eyepieces used in the BA8s.

http://www.united-op...eces/EF_Eyep...

The AFOVs are 53° for the 27mm - 65° for the 19mm - 60° for your 16mms.

Can't prove it though:-)

#327 Mr. Bill

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Posted 14 July 2014 - 02:31 PM

Chuck...

Those are AT Flat Field, no doubt in my mind.

When I bought the semi APOs last year,pairs of 12mm and 19mm unbranded AT Flat Fields were included.

I was so impressed with them, I bought the 16mm from Astronomics.

Interesting that the eps included with the new APOs were vastly inferior SWA 70 degree 20mm with horrible edge distortions. Just do not understand KUO's thinking (or lack thereof.)

:confused:

#328 JustaBoy

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Posted 14 July 2014 - 02:44 PM

"Just do not understand KUO's thinking (or lack thereof.)"

Bill,

In a matter like this, I tend to believe that it's a lack thereof. - Or, they had a bunch and no one wanted them? :-)

Thanks,

#329 Mr. Bill

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Posted 14 July 2014 - 03:23 PM

I believe that there is a disconnect within KUO between the design team and product testing and marketing.

I wonder if there is any field testing by KUO under real life user conditions before release.

Exhibit A....the grossly inadequate mounting bracket supplied with first samples of APM APO delivered to NEAF from KUO.

:p

#330 range88

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Posted 14 July 2014 - 08:49 PM

The swa series perform pretty well in the low end markets here.
I think the reason is they are produced by Kuo and are cheap enough to be included as a freebie. One step up Kuoonly got Uwa series, which are way more expensive.
Nonetheless, Kuo does not suppose a 100 apo buyer will use any eyepiece from them, let alone the swa. So they are just for testing purposes.
And I sold the pair for 70 dollars, that is equal to a price cut.

#331 Mr. Bill

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Posted 14 July 2014 - 08:55 PM

The swa series perform pretty well in the low end markets here.
I think the reason is they are produced by Kuo and are cheap enough to be included as a freebie. One step up Kuoonly got Uwa series, which are way more expensive.
Nonetheless, Kuo does not suppose a 100 apo buyer will use any eyepiece from them, let alone the swa. So they are just for testing purposes.
And I sold the pair for 70 dollars, that is equal to a price cut.


Then don't include any eyepiece with APOs....it just reflects badly on the effort by KUO to produce a superior product....."throw away" eyepieces for a $3000 binocular!

Bad marketing...case in point of my post above .

:mad:

#332 Mr. Bill

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Posted 22 July 2014 - 03:09 PM

Got another decent night in backyard concentrating on M24 and M11 and Aquila regions….beginning to settle in with APO to actually observe rather than testing.

Other than the light leakage issue which I work around with eyepiece choice, I am very pleased with optics….pinpoint stars with very sharp focus; no question where “best focus” is. Interesting that “infinity” focus is different for distant objects. Focus at 200-300 yards is definitely different than objects a mile away. Never noticed that in binoculars before.

Field is dead flat with the right eps….but it puts your eps to the test. The slight amount of field curvature at the edges in the 19 Pans is now apparent. Interestingly, the 24 Pans are flat to the edge of field. Discussion with Al Nagler revealed that even though both are Pans, the optical designs are different.

Contrast is excellent as long as there are no bright stars off axis causing ghosting. When it does happen, I generally can move fov enough to shift the false image from field.

The coatings and glass definitely transmit more light than the semis with greater dynamic range of detail in extended objects such as Milky Way bright/dark nebulae; my main observing interest these days.

Field illumination is uniform across fov in all my eps except in 24 Pans that have a touch of field darkening at edge of fieldstop because of slight vignetting, but not enough to be objectionable.

Eyepiece pairs being used at present are:

24mm Pans
19mm Pans
16mm Astro Tech Flat Fields
14mm Denkmeiers
12mm Astro Tech Flat Fields

#333 JCB

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Posted 22 July 2014 - 07:10 PM

Field illumination is uniform across fov in all my eps except in 24 Pans that have a touch of field darkening at edge of fieldstop because of slight vignetting, but not enough to be objectionable.

Thanks for the report.

Could you post a picture of the vignetted exit pupil at the field edge of the 24 Pan? I would be interested in a picture like the one you took several years ago with another binocular:

http://www.cloudynig... ocular edge...

Jean-Charles

#334 GlennLeDrew

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Posted 22 July 2014 - 07:14 PM

Note that eyepieces have their own surface of best focus, which varies from model to model just as objective field curvature varies. When the objective field curvature matches that of the eyepiece... magic. Just because there is defocus due to field curvature is not necessarily the fault of the eyepiece.

#335 JustaBoy

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Posted 22 July 2014 - 07:19 PM

:waytogo:

Right you are, Glenn; FC is a product of both the objective and the eyepiece and if you get lucky in their combination - Magic!

But, this tends to not usually be the case:-(

#336 Mr. Bill

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Posted 22 July 2014 - 08:57 PM

Note that eyepieces have their own surface of best focus, which varies from model to model just as objective field curvature varies. When the objective field curvature matches that of the eyepiece... magic. Just because there is defocus due to field curvature is not necessarily the fault of the eyepiece.


Now I go back with Oberwerk BT and semi...see same field curvature in 19 Pans, only less noticeable because of softer images on axis.

#337 Mr. Bill

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Posted 27 July 2014 - 01:45 AM

Just got pairs of 21mm and 23mm prism rear aperture baffles from APM....note shoulder that fits into existing 25mm baffle.

Only problem is that they would have to be glued in place which obviously means a permanent installation. No going back on that.

Not sure the cure is better than the disease... :p

Present fix of using screw in baffles in eps at least is reversible.

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#338 Stellarfire

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Posted 27 July 2014 - 03:15 AM

Only problem is that they would have to be glued in place which obviously means a permanent installation. No going back on that.


Hmmm..., how about a double-sided tape, exactly cut to ring shape? It would be removable. Maybe worth a try?

Stephan

#339 GlennLeDrew

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Posted 27 July 2014 - 05:07 AM

Better yet, just a couple small pieces of double-sided tape; easier to remove the stop when desired.

#340 Mr. Bill

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Posted 27 July 2014 - 01:07 PM

Better yet, just a couple small pieces of double-sided tape; easier to remove the stop when desired.


Easier said than done....you would have to pry it up by inserting a tool between the optical window behind the rear aperture and the added baffle.

I know that the 23mm baffle would probably not be very effective in blocking off axis light as I have tried the 17.3mm Delos which almost bottoms out against the existing 25mm baffle and has a 22.5mm aperture stop at the bottom of the ep, and it still shows lots of ghosting.

The 20mm screw in baffles on the eps do a good job but definitely vignette the 19mm and especially the 24mm Pans.

I still think that the real problem is undersized final prisms given the current position of the focal plane...If the design was increased to f/6- f/6.5 with the same prisms (less steep light cone) and focal plane position, I have a suspicion that this problem with off axis ghosting would be eliminated or at least greatly reduced.

The desire to accommodate many eps by pushing the focal plane farther back also contributes to the issue.Perhaps moving the objectives forward with the current optics would mitigate the problem if not eliminate it, but would eliminate many eps with field stops above the barrel shoulder from reaching infinity focus.

Think I'll just use as is for now....

#341 GlennLeDrew

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Posted 27 July 2014 - 02:33 PM

I suspect the geometry would hardly be changed simply by moving the objectives some 15-20mm farther forward. The prism system will still 'see' the objective as occupying nearly the same angular diameter, and more so for the rear parts of the system.

On those annular stops, one could file a small notch on the outer edge for the insertion of a pointed tool for prising it out. It should be possible to make it small enough that no light shine through it?

If they can be employed, they should be better than eyepiece rings which lie nearer to the focus...

#342 Mr. Bill

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Posted 27 July 2014 - 11:42 PM

On those annular stops, one could file a small notch on the outer edge for the insertion of a pointed tool for prising it out. It should be possible to make it small enough that no light shine through it?

If they can be employed, they should be better than eyepiece rings which lie nearer to the focus...


That's a thought....OTOH, I'm not sure I want to stop them down after all. This kinda puts "my feet to the fire." :confused:

It means that the 24mm Pans would be REALLY vignetted and I enjoy the views at 23x, 2.95 degree RFOV, and 4.4mm ep in spite of the ghosting. Get a really dark, transparent night and the starclouds POP. :shocked:

#343 Mr. Bill

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Posted 28 July 2014 - 10:13 AM

I suspect the geometry would hardly be changed simply by moving the objectives some 15-20mm farther forward. The prism system will still 'see' the objective as occupying nearly the same angular diameter, and more so for the rear parts of the system.


I was thinking of the front prism aperture seeing a smaller on axis light cone. Maybe the false pupils would be further out from exit pupil (fieldstop.)

#344 EricP

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Posted 28 July 2014 - 01:47 PM

It'd be nice if they incorporated a Denkmeier style power (or filter) switch, so you could simply slide them into place when needed.

#345 Mr. Bill

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Posted 28 July 2014 - 01:57 PM

How about an adjustable iris shutter?

:question:

#346 EricP

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Posted 28 July 2014 - 02:08 PM

Even better!

#347 Mr. Bill

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Posted 29 July 2014 - 11:31 AM

Plan B....

Took these (two sets) and removed filter glass.

Super glued the 21mm and 23mm aperture stops supplied by APM to the filter cells...these are stackable so I could put aperture stops within 1/8 inch of optical window when ep focused. This simulated what the aperture stops would do if mounted into the APO.

As expected when used on the 19mm Pans, the 23mm aperture stop did virtually nothing to improve the ghosting and the 21mm showed noticable improvement, but still lots of off axis light. Also seemed to improve contrast, but could that be as a result of adding another knife edge baffle rather than the stopping down?

This was done using my town streetlight test....

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#348 GlennLeDrew

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Posted 29 July 2014 - 02:45 PM

Bill,
Contrast improved by adding a baffle, rather than stopping down? If you added a baffle of the same diameter as the prism aperture, there would be no real improvement. It's the stopping down which made the difference, and so we can say the restrictors do work to at least some extent.

#349 Mr. Bill

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Posted 29 July 2014 - 02:57 PM

Well, it appears that stopping down either end doesn't make a real significant improvement in eliminating the false pupils.

Remember, some time ago (and many pages ago in this thread) I masked the aperture from 90mm, 80mm, 70mm without a dramatic improvement.

My conclusion is that the problem lies in the prisms....

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#350 GlennLeDrew

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Posted 29 July 2014 - 06:14 PM

Ah, yes, that is indeed suggestive of the subtended angle of the objective being not the only problem. But if stopping down like this did realize *some* reduction in the false, clipped pupil, objective angular size as 'seen' from the prism(s) is nontheless a factor.

It would be most interesting to compare the innards in detail with another bino such as the Miauchi Saturn...






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