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Harpia Extender

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Old Wednesday 26th December 2018, 05:48   #1
Bsimmons
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Harpia Extender

I've been really interested in the Harpia 95, but am wondering if there are any future plans to release an extender for it.

I currently use a Kowa 883 and, though its not practical for my purposes often, I really like the option of the 1.6x under the right conditions.

Does anybody have information on this?

Thanks
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Old Wednesday 26th December 2018, 11:27   #2
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Hi,

the Harpia will not need an extender, just another eyepiece. With the Harpia the zoom is inside the body (basically a telephoto zoom lens) and the EP is a fixed mag wide angle EP. So a shorter EP will give higher magnification

I don't think there is an adapter or alternate EP available yet from Zeiss, but since they made astro adapters for their other scopes, there is hope... otoh it might not happen since then a lot of peple might skimp on the premium priced stock EP which makes a Nagler look cheap.

But then there might be other companies stepping in... Baader - what about an adapter for Morpheus series on Harpia?

Joachim
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Old Wednesday 26th December 2018, 19:08   #3
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Hi Bsimmins,

Increasing the magnification across the zoom range of the Harpia, whether with an extender or a shorter FL eyepiece, might not be such a good idea. Even at 70x, where the optical performance is optimal, the one I tested was at its visible resolution limit for most people's eyesight acuity. Anything higher would have been empty magnification. Also, the most optically compromised part of the zoom range in the Harpia design (23-60x) would likely not fare well at all if its magnification range were increased by 1.6x to something like 37-96x.

23x increased to 37x would certainly look dim even in bright daylight compared to a conventional 95mm scope since the exit pupil would be only 1.55mm, and 40x increased to 64x would have its already high aberrations magnified to the point that even the most casual observers might begin to notice.

If you have a good 883 specimen I think you already own a scope that's optically superior to the Harpia .

Henry

Last edited by henry link : Wednesday 26th December 2018 at 19:57.
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Old Wednesday 26th December 2018, 22:25   #4
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I don't agree with Henry. I used the Harpia today, my wife used the 95 Swaro. I could not see, that the Harpia is at the "resolution limit". (My glasses are new and fine).

I fully agree with Joachim. Another eyepiece will do the best.

I do not have any information from Zeiss, if there is any in development or even in planning. I do have information from Zeiss, that an eyepiece with shorter focal length will be able for the Zoom. In other words: The zoom is able to deliver more information at higher magnification according to Zeiss.
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Old Wednesday 26th December 2018, 23:12   #5
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We'll need properly done measurements to know exactly what the resolving power of even one sample of the Harpia is. However, using the USAF 1951 chart I was clearly able to see that the unit I tested could not resolve line pairs as well at 70x as a diffraction limited scope of slightly less aperture set up next to it and also set at 70x. From that I could deduce that the best possible line pair resolving power for that Harpia would be about 1.4", but it almost certainly was not quite that good. A person with about 20/16 eyesight acuity should be able to see the 1.4" line pairs at 70x. Any higher magnification than that would be "empty" for that observer because the Harpia can't resolve any of the smaller line pairs on the chart no matter how high the magnification. Those with lower acuity would need higher magnification just to resolve that same set of line pairs and those with higher acuity would need less magnification.

Last edited by henry link : Thursday 27th December 2018 at 02:00.
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Old Thursday 27th December 2018, 00:45   #6
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Hi Henry,

Quote:
Originally Posted by henry link View Post
Any higher magnification would be "empty" Those with lower acuity would need higher magnification to resolve the same line pairs through the Harpia and those with higher acuity would need less magnification.
Thanks a lot for the explanation! So "empty magnification" is the proper technical term?

The German "Blindvergrößerung" ('blind magnification') describes the exact same concept, but so far I've been unable to find an English translation ... seems you just provided my missing puzzle piece! :-)

Regards,

Henning
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Old Thursday 27th December 2018, 13:12   #7
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We'll need properly done measurements to know exactly what the resolving power of even one sample of the Harpia is. However, using the USAF 1951 chart I was clearly able to see that the unit I tested could not resolve line pairs as well at 70x as a diffraction limited scope of slightly less aperture set up next to it and also set at 70x. From that I could deduce that the best possible line pair resolving power for that Harpia would be about 1.4", but it almost certainly was not quite that good. A person with about 20/16 eyesight acuity should be able to see the 1.4" line pairs at 70x. Any higher magnification than that would be "empty" for that observer because the Harpia can't resolve any of the smaller line pairs on the chart no matter how high the magnification. Those with lower acuity would need higher magnification just to resolve that same set of line pairs and those with higher acuity would need less magnification.

Henry

I have never used a boosted scope but I am wondering if boosting a Harpia in this way would make its native resolution more easily discernable at 'pre-boosted' distances and also make this detail visible at much longer distances. Always assuming the boosting EP was of sufficient quaility.

Lee
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Old Thursday 27th December 2018, 16:51   #8
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In my experience increasing the magnification beyond the point where full detail is seen is of considerable benefit.
It makes the detection of hidden detail more likely.
Just barely using the minimum full detail magnification does give a brighter image, but does not reveal all there is to be seen.

With a test chart, one knows what is there.
This is an entirely different observation to detecting hidden unknown detail.

This is from my observations as a planetary observer.
With my 317mm Dall Kirkham my normal magnification was 265x.
But this was increased to 400x to detect the fine detail.
It was only beyond 700x that I would call it empty magnification.
Of course with fine Seeing. But the scope could not show more above 700x.

Paul Doherty, who could see Jupiter's moons without optical aid, used 190x on his 305mm Newtonian.
Probably more for fine detail.
So someone with exceptional sight needs less magnification and sees more because of the brighter image.

In short, I would not use the term 'Empty magnification' at just beyond the minimum magnification needed to see all the detail, but at considerably higher magnifications.

Also empty magnification applies in my opinion to the quality of the telescope.
With the Pentax 100mm f/12 refractor 300x was certainly not empty magnification.

Rev Dawes used over 400x on his fine 6.5 inch approx. refractor on Jupiter, Jupiter's moons, and Mars in his published drawings.
He would not have called this empty magnification.

With the Harpia it seems to be that the quality of the optics is not great, especially if above 70x is considered empty magnification.
I would expect to be able to use 200x with a 93mm aperture Harpia if it was any good.
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Old Thursday 27th December 2018, 17:05   #9
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Originally Posted by Bsimmons View Post
I've been really interested in the Harpia 95, but am wondering if there are any future plans to release an extender for it.

I currently use a Kowa 883 and, though its not practical for my purposes often, I really like the option of the 1.6x under the right conditions.

Does anybody have information on this?

Thanks
Only Zeiss know about this.

But considering the large zoom range in the Harpia it would do with only 1.4 "extra mag" in the eye piece for a range of 30-98x. Perhaps a bit more useful than 40-96x in the Kowa it might seem, especially considering the difference in FOV. Things like DOF and loss of light might also be a bit better.

I know a few birders that bought the extender (for Kowa and Swaro) but they mostly seem to wine about the downsides with it. Not sure what they expected though. TC:s have their limitations from technical reasons obviously. Shake from wind and atmospherical disturbance is other parameters that might be difficult to control at those high magnifications.

Also CA becomes more visible, especially in the Swaro 95mm, that already is lagging the Kowa in that department.

Last edited by Vespobuteo : Thursday 27th December 2018 at 18:04.
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Old Thursday 27th December 2018, 20:28   #10
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Originally Posted by Vespobuteo View Post
.... Shake from wind and atmospherical disturbance is other parameters that might be difficult to control at those high magnifications. ....
Good point! I'm using the 95 Harpai solely with my Berlebach Report, which weighs app 3 kg + head (my wife has the carbon tripod for the 95 Swaro). Even the Berlebach is on its limits, if I want to get the last details from the greatest magnification. (it is much better than the FLM Carbon, and much heavier)

With about 100 magnification I would recommend a Berlebach Uni, which weighs about 9 kg + head.
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Old Thursday 27th December 2018, 22:29   #11
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Quote:
Originally Posted by Binastro View Post
In my experience increasing the magnification beyond the point where full detail is seen is of considerable benefit.
It makes the detection of hidden detail more likely.
Just barely using the minimum full detail magnification does give a brighter image, but does not reveal all there is to be seen.

With a test chart, one knows what is there.
This is an entirely different observation to detecting hidden unknown detail.

This is from my observations as a planetary observer.
With my 317mm Dall Kirkham my normal magnification was 265x.
But this was increased to 400x to detect the fine detail.
It was only beyond 700x that I would call it empty magnification.
Of course with fine Seeing. But the scope could not show more above 700x.

Paul Doherty, who could see Jupiter's moons without optical aid, used 190x on his 305mm Newtonian.
Probably more for fine detail.
So someone with exceptional sight needs less magnification and sees more because of the brighter image.

In short, I would not use the term 'Empty magnification' at just beyond the minimum magnification needed to see all the detail, but at considerably higher magnifications.

Also empty magnification applies in my opinion to the quality of the telescope.
With the Pentax 100mm f/12 refractor 300x was certainly not empty magnification.

Rev Dawes used over 400x on his fine 6.5 inch approx. refractor on Jupiter, Jupiter's moons, and Mars in his published drawings.
He would not have called this empty magnification.

With the Harpia it seems to be that the quality of the optics is not great, especially if above 70x is considered empty magnification.
I would expect to be able to use 200x with a 93mm aperture Harpia if it was any good.
Hi Binastro,

Keep in mind that I'm choosing to limit my resolution target to high contrast line pairs viewed under daylight conditions so that I can make repeatable comparisons. I think that's much easier for the eye to resolve than low contrast astronomical targets, which is why empty magnification comes so much sooner. Even so, I agree that for very high quality optics under those conditions an exit pupil of 0.8-0.7mm does make the smallest resolved line pairs on the USAF 1951 easier to for me to see with an eyesight acuity of around 20/15, mostly because the bars on that target are relatively short.

In the case of the 95mm Harpia at 70x what convinced me that I was looking at its daylight line pair resolution limit was the fact that a 92mm scope set up next to it was resolving line pairs at least one Element or at least 12% smaller. I say "at least" because the next smaller Element was too small for my eyesight acuity at 70x even if it had been resolved by the 92mm scope.

Henry
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Old Thursday 27th December 2018, 23:20   #12
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Thanks Henry.

Yes it is true that night time planetary observations are quite different to bright daylight observations.

I could resolve Mizar with the Canon 10x30 IS at 14.4 arcseconds unequal double, but realise that in daylight with ball bearing stars I could probably do better.
I was quite surprised how close daylight artificial stars can be with daytime acuity.

I think though that I'd give 5 to 1 odds that if I sneaked in a doctored USAF 1951 chart to an expert at testing, the changes I made would not be seen at the normal testing resolution magnification, but might be spotted at 60% higher magnification, or if I told the tester what I had done.
To detect or discover hidden detail is mighty difficult and needs higher magnification.
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Old Thursday 27th December 2018, 23:22   #13
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Henry

I have never used a boosted scope but I am wondering if boosting a Harpia in this way would make its native resolution more easily discernable at 'pre-boosted' distances and also make this detail visible at much longer distances. Always assuming the boosting EP was of sufficient quaility.

Lee
Hi Lee,

I'm not sure I'm following you here. A conventional telescope's "native resolution" doesn't really change with magnification or distance, but the Harpia design doesn't have a single "native resolution". We know without even measuring that its resolution is increasingly limited from reduced aperture at magnifications below 40. As I said in post #5 it's also very likely that it has reduced resolution compared to the 70x setting for all magnifications below 60x caused by aberrations from increasingly low focal ratios. Boosting these lower magnifications with a shorter FL eyepiece or an eyepiece/Barlow combination by a factor of perhaps 1.5-2x should allow the true resolving power across the zoom range to be accurately measured. I think any decent eyepiece or Barlow would be plenty good enough not to be the limiting factor.

Henry

Last edited by henry link : Friday 28th December 2018 at 04:07.
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Old Thursday 27th December 2018, 23:45   #14
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...

But considering the large zoom range in the Harpia it would do with only 1.4 "extra mag" in the eye piece for a range of 30-98x. Perhaps a bit more useful than 40-96x in the Kowa it might seem, especially considering the difference in FOV. Things like DOF and loss of light might also be a bit better.

...
Swaro was clever commercially and produced an 1.7x extender that results on 43-102x with the X85. This means that the X85 goes higher mags than the Kowa 88 and that makes a difference, at similar image quality! I don't know why the Kowa 88 is usually compared to the X95 instead of the X85...

Bottom line, if Zeiss will release a higher mag e.p. it will have to produce >= 1.7x higher mags, to be comparable to the Swaro... I'm very happy with my Swaro extender but Zeiss can achieve better results with a new ep instead of an extender, although should be more expensive.

I'm curious why no owner of Harpia tested an astro ep to see if reaches focus ...
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Old Friday 28th December 2018, 07:51   #15
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Hi Lee,

I'm not sure I'm following you here. A conventional telescope's "native resolution" doesn't really change with magnification or distance, but the Harpia design doesn't have a single "native resolution". We know without even measuring that its resolution is increasingly limited from reduced aperture at magnifications below 40. As I said in post #5 it's also very likely that it has reduced resolution compared to the 70x setting for all magnifications below 60x caused by aberrations from increasingly low focal ratios. Boosting these lower magnifications with a shorter FL eyepiece or an eyepiece/Barlow combination by a factor of perhaps 1.5-2x should allow the true resolving power across the zoom range to be accurately measured. I think any decent eyepiece or Barlow would be plenty good enough not to be the limiting factor.

Henry
Thanks Henry and I clearly didn't express myself well with my question so I will have another try.

I understand your contention that increasing magnification with a different eyepiece would not reveal more detail but I am wondering if it would make the detail it can resolve easier to see and then I 'extended' this question to ask whether boosting the magnification would enable this level of detail to be seen at greater distances. If the answer is yes to both, then such a boost would have practical birding benefits.

Lee

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Old Friday 28th December 2018, 10:07   #16
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Swaro was clever commercially and produced an 1.7x extender that results on 43-102x with the X85. This means that the X85 goes higher mags than the Kowa 88 and that makes a difference, at similar image quality! I don't know why the Kowa 88 is usually compared to the X95 instead of the X85...

Bottom line, if Zeiss will release a higher mag e.p. it will have to produce >= 1.7x higher mags, to be comparable to the Swaro... I'm very happy with my Swaro extender but Zeiss can achieve better results with a new ep instead of an extender, although should be more expensive.

I'm curious why no owner of Harpia tested an astro ep to see if reaches focus ...
96x vs 102x or seems pretty close to me. Quality of the tripod might be more important at those mags? To me 60-70x is more than plenty but I can understand that extenders can be useful in some cases. And also it might help some people with not that sharp eye sight.

I guess people tend to compare the biggest available scope from each manufacturer?
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Old Friday 28th December 2018, 10:46   #17
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I am wondering if it would make the detail it can resolve easier to see and then I 'extended' this question to ask whether boosting the magnification would enable this level of detail to be seen at greater distances. If the answer is yes to both, then such a boost would have practical birding benefits.

Lee
I might not answer your question but to me "boosting" (with an extender/teleconverter) does not make sense other than if the resulting magnification is higher than the scope's maximum magnification with the original eye piece.

Otherhwise it's better to use the zoom function in the eye piece/body. In the Harpia, I guess boosting with an 1.4x booster, below 50x magnification, would be a bit pointless. And for any significant optical benefit you would probably have to be close to the max magnification of the scope. Obviously you might want to zoom out to find target easier etc. at lower mag and a bigger FOV then would be useful.

Technically/optically a shorter eye piece sounds like a better solution than a booster. But most likely more expensive. I guess Zeiss could go for either alternative, but I don't think Zeiss will follow the main stream and make a booster.

An EP that gives 33x-100x mag with significantly larger FOV than competition, and with less downsides of a booster, I suspect is a bit tempting for some, at least on paper. Personally I would probably prefer 23-70x and a larger FOV at low mag.
C'mon Zeiss! You can do it!

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Old Friday 28th December 2018, 13:55   #18
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I might not answer your question but to me "boosting" (with an extender/teleconverter) does not make sense other than if the resulting magnification is higher than the scope's maximum magnification with the original eye piece.

Otherhwise it's better to use the zoom function in the eye piece/body. In the Harpia, I guess boosting with an 1.4x booster, below 50x magnification, would be a bit pointless. And for any significant optical benefit you would probably have to be close to the max magnification of the scope. Obviously you might want to zoom out to find target easier etc. at lower mag and a bigger FOV then would be useful.

Technically/optically a shorter eye piece sounds like a better solution than a booster. But most likely more expensive. I guess Zeiss could go for either alternative, but I don't think Zeiss will follow the main stream and make a booster.

An EP that gives 33x-100x mag with significantly larger FOV than competition, and with less downsides of a booster, I suspect is a bit tempting for some, at least on paper. Personally I would probably prefer 23-70x and a larger FOV at low mag.
C'mon Zeiss! You can do it!
Thanks for this VB.
I can see from your reply that 'boosting' = extender/teleconverter when I only meant to refer to an increase of magnification with a different eyepiece, so I have edited my post to reflect this otherwise I will have Henry scratching his head again.

Personally I would not want to go beyond 70x and like you I would stick to 23-70x and that terrific field of view.

Lee
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Old Friday 28th December 2018, 14:43   #19
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Thanks Henry and I clearly didn't express myself well with my question so I will have another try.

I understand your contention that boosting magnification would not reveal more detail but I am wondering if it would make the detail it can resolve easier to see and then I 'extended' this question to ask whether boosting the magnification would enable this level of detail to be seen at greater distances. If the answer is yes to both, then such a boost would have practical birding benefits.

Lee
Yes, there would be some practical benefit to boosting the size of the smallest resolved details for those with below average acuity, but that will come at the price of degraded brightness and sharpness at lower magnifications, a disadvantage unique to the Harpia design.
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Old Friday 28th December 2018, 14:56   #20
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Yes, there would be some practical benefit to boosting the size of the smallest resolved details for those with below average acuity, but that will come at the price of degraded brightness and sharpness at lower magnifications, a disadvantage unique to the Harpia design.
Thanks for this Henry.

And would those with normal acuity be able to see these smallest resolved details revealed by maximum magnification at longer distances with such an eyepiece?

Lee
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Old Friday 28th December 2018, 19:19   #21
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Nothing much would be gained at any distance from boosting the size of the smallest resolved details beyond 70x for someone like me with eyesight acuity of 20/15, which is about average. I could already see 12% smaller line pairs at 70x through the 92mm reference scope set up next to the Harpia.
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Old Friday 28th December 2018, 20:13   #22
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Nothing much would be gained at any distance from boosting the size of the smallest resolved details beyond 70x for someone like me with eyesight acuity of 20/15, which is about average. I could already see 12% smaller line pairs at 70x through the 92mm reference scope set up next to the Harpia.
Hi Henry

If by "Nothing much would be gained at any distance" you mean extra detail, I wasnt refering to extra detail. I understand that you are saying no extra detail would be gained.

What I was wondering was whether the detail resolved by the standard eyepiece at maximum magnification, would be visible at greater distances than with the standard eyepiece, if there was a magnification increase.

Forgive me if you feel you have answered this but from my side it is still not clear that you have. For example your reference to seeing smaller line pairs through the other scope doesn't seem connected to my question about additional distance.

Lee

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Old Friday 28th December 2018, 22:37   #23
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I'm not sure why we can't seem to connect about this. Maybe somebody else can join in.

Does it help to say that on the USAF 1951 size and distance are interchangeable? There's no difference between changing from one set of line pairs to the next 12% smaller size and just moving the larger set 12% farther away.

To put it another way imagine that a scope resolves 20 line pairs per mm on the USAF 1951 at 10 meters. If the distance to the target is doubled to 20 meters the same scope will resolve only 10 line pairs per mm on the same target. No amount of increased magnification will extend the 20 lp/mm resolvable at 10 meters to any longer distance than 10 meters.

Are we getting anywhere?

Henry
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Old Saturday 29th December 2018, 09:10   #24
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Yes Henry this made it absolutely clear:

No amount of increased magnification will extend the 20 lp/mm resolvable at 10 meters to any longer distance than 10 meters.

Thank you for sticking with me on this.

Lee
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