Join for FREE
It only takes a minute!
Zeiss - Always on the lookout for something special – Shop now

Welcome to BirdForum.
BirdForum is the net's largest birding community, dedicated to wild birds and birding, and is absolutely FREE! You are most welcome to register for an account, which allows you to take part in lively discussions in the forum, post your pictures in the gallery and more.

A Brief Review of the Zeiss Harpia 95

Reply
 
Thread Tools Rate Thread
Old Friday 21st September 2018, 16:36   #1
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
A Brief Review of the Zeiss Harpia 95

Last week I had an opportunity to briefly examine a just purchased 95mm Zeiss Harpia. The last time I reviewed a scope (the Zeiss Gavia) I found two days was insufficient for a complete review. This time I had about one hour. The design of the Harpia is so unusual that testing it really demands even more time and energy than a conventional scope. For instance, usually a single star test and a single resolution measurement at high magnification are all that’s needed. That’s not true for the Harpia because the objective’s configuration, focal ratio and aperture change with magnification, so it can be reasonably assumed that aberrations and resolution will not remain constant over its entire magnification range. Unfortunately, I didn’t have enough time or enough control over the test conditions to make the multiple tests at different magnifications needed for this scope, so the results here are barely more than suggestive of areas that need closer examination.

I used the flashlight method to measure clear aperture. That confirmed that the aperture remains constant from 70x down to about 40x (my measurement for the largest clear aperture was about 93mm rather than 95mm). At magnifications below 40x the aperture appears to shrink in a linear fashion until it reaches something between 55 and 60mm at 23x. I can’t be more specific because my test method resulted in the internal obstruction that causes the loss of aperture below 40x to cast a fuzzy shadow rather than a sharp one on my ruler.

Very bad (Hurricane Florence) weather made outdoor testing impossible, so I was only able to star test the scope indoors at about 10m and rather than measuring its resolving power I could only roughly compare its resolution and sharpness at 70x and 40x to a 92mm Astro-physics Stowaway APO (with Baader Hyperion Zoom) using a USAF 1951 glass slide at about 7m. At those distances I expect any scope properly corrected for infinity focus to be somewhat under-corrected, so my experience can only really be applied with much confidence to the Harpia’s close focus performance.

In a 70x star test at 10m I found the Harpia’s spherical and chromatic aberrations to be clearly worse than the reference scope. The Stowaway shows an essentially textbook perfect star test at infinity and is slightly under-corrected at the 10m distance of this test. The Harpia did much better at 10m than the Gavia I tried last year, but it still showed considerable asymmetry between the intra-focal and extra-focal diffraction patterns, with hard rings and an overly bright outer ring outside focus and soft rings with an overly bright central spot inside focus. There was a narrow red fringe of longitudinal chromatic aberration around the focused test star that was pretty minor by spotting scope standards, but still indicated less than true APO performance. There was also some mysterious spiking around the entire periphery of the intra-focal diffraction disk, which resembled the appearance of surface roughness in a star test of a mirror. Other potential defects like coma, pinching, astigmatism and roof edge anomalies were very low or absent. However, unlike “normal” scopes the Harpia’s star test appears to deteriorate as magnification is reduced. Evaluating star tests accurately becomes more difficult at lower magnifications, so I didn’t even attempt it at magnifications below about 40x. The one change I was sure I could see was the gradual development of some astigmatism in this particular Harpia unit as magnification was reduced from 70x to 40x. I’m sure this wasn’t related to my eyesight because astigmatism was completely absent at all magnifications in the Stowaway set up next to the Harpia. This suggests to me that the aberrations and optical defects of the Harpia are indeed not constant with magnification and could grow worse as the optical configuration changes from about f/5.6 at 70x to f/3.2 at 40x.

Using a USAF 1951 glass slide I found the image quality of the Harpia to be a bit soft and gauzy at 70x compared to the Stowaway, with a loss of at least one Element of resolution on the chart. Unfortunately I couldn’t quantify the resolution because I didn’t have a way to measure the exact distance to the chart and besides 70x is a little low for my eyesight acuity to reliably detect the Stowaway’s true resolution. But, since I know the Stowaway’s resolution as about 1.25” using the USAF 1951 I can say that this particular Harpia was no better than 1.40”, probably not quite that good. That was no big surprise given the higher star test aberrations, but unlike every other telescope I’ve seen the Harpia didn’t appear to sharpen up as the magnification was reduced. The image appeared to be no sharper, perhaps even slightly less sharp at 40x, than at 70x. Since the Stowaway follows the usual pattern of appearing sharper as magnification is decreased that made the difference in image quality between the two scopes starker at 40x than at 70x.

Visual comparison to a reference scope of known quality is better than no reference, at all but it still mostly falls into the realm of subjective impressions. I couldn’t do any better than that at 40x because in the time available I couldn’t find a way to firmly attach my 3x Zeiss Tripler to the Harpia eyepiece. The booster would have allowed testing the Harpia’s 40x magnification at 120x, plenty high enough to measure the true resolution and properly evaluate the star test. In the end I suspected from the subjective appearance of the 40x image that higher aberrations at 40x probably degrade the actual instrument resolution at 40x compared to 70x even though the aperture is unchanged. That wouldn’t be a surprise given the f/3.2 effective focal ratio at 40x, but without real measurements I couldn’t confirm it.

One last thing I noticed was that the Harpia’s image was dimmer than the Stowaway’s at all magnifications but particularly, as you might expect, at the lowest power. The Harpia’s actual light transmission was almost certainly lower than the Stowaway’s since, as configured for this test, the Stowaway had only 10 glass to air surfaces and one dielectric mirror reflection vs. the Harpia’s 32 glass to air surfaces and 4 internal prism reflections. But, the increasing difference in image brightness between the two as magnification fell below 40x clearly resulted from the Harpia’s shrinking aperture. The window light I was using was approximately equal to what would frequently be experienced outside on a dark overcast day. Under those lighting conditions the reduced exit pupil of the Harpia at lower magnifications is a definite disadvantage compared to conventional scopes.

That’s pretty much all I could gather from my hour with the Harpia. If I ever get another crack at one on my own turf I would certainly want to star test and measure the clear aperture and resolution over the entire magnification range by placing my 3x booster behind the eyepiece. That’s unlikely to happen with this unit since the owner is not local, so for now I’ll be happy to turn things over to my few colleagues here who are inclined to do the same kind of testing.

Henry Link
henry link is offline  
Reply With Quote
Old Friday 21st September 2018, 20:55   #2
Canip
Registered User

 
Join Date: Jun 2015
Location: Nordschweiz
Posts: 386
Thank you, Henry, for this review, which is very interesting, even considering the caveats you mention.
Would you say that the Harpia‘s performance on the basis of your limited testing was in line with your expectations, or below?
Canip is offline  
Reply With Quote
Old Friday 21st September 2018, 23:00   #3
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
Hi Canip,

So far it's about what i expected. I doubt that Zeiss was even pursuing an optically state of the art scope with the Harpia. The design appears to be built around a user friendly feature set: a constant wide field over a wide zoom range with long eye relief at every magnification. I expect they thought they could then make the optics "just good enough" for the intended market and I wouldn't be surprised if that's what they've done.

Henry

Last edited by henry link : Friday 21st September 2018 at 23:04.
henry link is offline  
Reply With Quote
Old Saturday 22nd September 2018, 11:05   #4
kabsetz
Registered User

 
Join Date: Jun 2004
Location: Finland
Posts: 1,474
Henry,

Thanks for your "brief" review - which, as usual, provides about ten times as much information than most other peoples' lengthy in-depth reviews.

I still have not had a chance to re-visit the Harpia, as stocks have been slow to trickle in. I'll do resolution testing as soon as a production sample becomes available for a few days.

I didn't dig up my aperture checks from a year ago, but from what I recall they were about the same as the results you got.

From what I have heard, one sample of the Harpia that went through a local dealer was very sharp at 70x. It was checked at about 8 m distance on the Edmund Optics glass slide USAF target. Since my ATX 95 is almost as good a reference as you AP Stowaway, I should get pretty reliable results in time.

I'm with you in not necessarily thinking it is a good idea to have lower magnification images compromised, but on the other hand I acknowledge that for a lot of the practical birding people use their scopes for, wide FOV at low magnifications is a real and sizeable benefit. The difference in field between the Harpia and just about any other scope at 20-30x mags is not subtle.

Kimmo
kabsetz is offline  
Reply With Quote
Old Saturday 22nd September 2018, 16:42   #5
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
Thanks Kimmo. I hope you get a chance to do a more thorough review.

70x seems to be where the objective configuration is optimal. I'll be particularly interested in your star tests and resolution measurements from 60x down to 23x.

Henry
henry link is offline  
Reply With Quote
Old Wednesday 26th September 2018, 08:49   #6
Fedster
Registered User

 
Join Date: Sep 2016
Location: Helsinki
Posts: 52
Great review, many thanks! slightly off topic, is there a definitive guide on how to do the star test and how to interpret the results (whether a book or online)?
Fedster is offline  
Reply With Quote
Old Wednesday 26th September 2018, 16:51   #7
Binastro
Registered User

 
Join Date: Aug 2012
Location: S.England
Posts: 3,968
Ilta, Fedster,

There are several books, such as H. Dennis Taylor's classic 1890s? Adjusting and Testing astronomical telescopes. Later editions also.
Or Star Testing Astronomical Telescopes by Harold Richard Suiter.

No doubt someone here will direct you to online guides.

But go along to Ursa, Helsinki.
They probably have something in the library or a keen astronomer could help.

Perhaps go to Kaivopuisto to the Ursa observatory.
Autumn has the best Seeing there.

Terveisin,
B.

Last edited by Binastro : Wednesday 26th September 2018 at 16:57.
Binastro is online now  
Reply With Quote
Old Wednesday 26th September 2018, 16:58   #8
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
Googling something like "star test telescope" will turn up lots of information. The Bible on the subject is Harold Richard Suiter's "Star Testing Astronomical Telescopes", which will likely tell you more than you want to know.

One thing to beware of is examples that use mirrors. Those usually include the effects of a central obstructions, so they look quite different from refractor star tests.


Edit: Thanks for the references, Binastro. You were posting while I was writing

Last edited by henry link : Wednesday 26th September 2018 at 17:00.
henry link is offline  
Reply With Quote
Old Wednesday 26th September 2018, 17:23   #9
Binastro
Registered User

 
Join Date: Aug 2012
Location: S.England
Posts: 3,968
Thanks Henry.
Binastro is online now  
Reply With Quote
Old Wednesday 26th September 2018, 18:33   #10
Fedster
Registered User

 
Join Date: Sep 2016
Location: Helsinki
Posts: 52
Kiitos Binastro, and thanks Henry. Going back to the Zeiss, I am more and more convinced it would not be the ideal scope for low light conditions (I use my scope 50/50 birding/mammal watching, and mammals like low light). What's your take on it? the exit pupils that is stated on the Zeiss website are not encouraging, neither at low mag nor at high mag: here [https://goo.gl/NZ5Sut] the exit pupil for the 95 are a measly 2.50 – 1.34 mm.
Fedster is offline  
Reply With Quote
Old Wednesday 26th September 2018, 20:00   #11
arran
Registered User
 
arran's Avatar

 
Join Date: Jul 2004
Location: Belgium
Posts: 147
Quote:
Originally Posted by Fedster View Post
Kiitos Binastro, and thanks Henry. Going back to the Zeiss, I am more and more convinced it would not be the ideal scope for low light conditions (I use my scope 50/50 birding/mammal watching, and mammals like low light). What's your take on it? the exit pupils that is stated on the Zeiss website are not encouraging, neither at low mag nor at high mag: here [https://goo.gl/NZ5Sut] the exit pupil for the 95 are a measly 2.50 – 1.34 mm.
I have been using the harpia now for 3 weeks quite intensively and compare it several times with the ATx 95 of my brother and we exchange both scopes quite often
What is clear to U.S. till know:
-the harpia is ergonomic superior due to the great working dual focus drive
The feel it gives is very usefull
-the greater FOV is a plus at lower magnification
-the ATx is great on contrast but , especially in darker light, the harpia gives a better resolution, this was confirmed by two unbiased birdwatchers

Both are great of course , but the harpia has a little pro
Now by using both intensively for birdwatching over great lakes is also great for
glass wearers ,as is confirmed by my wife and she sees no difference in comfort between the 2 scopes

Just an honest feedback
arran is offline  
Reply With Quote
Old Wednesday 26th September 2018, 22:14   #12
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
Quote:
Originally Posted by arran View Post
-the ATx is great on contrast but , especially in darker light, the harpia gives a better resolution, this was confirmed by two unbiased birdwatchers
If this observation was made at lower magnifications I think the most likely explanation is that the unbiased observers have higher eyesight aberrations when their pupils are dilated beyond the 2.5mm limit imposed by the Harpia, but it's also possible that the ATX used as a reference might not a very good specimen. One can never assume an expensive scope is as good as it should be until it's star tested.

Last edited by henry link : Wednesday 26th September 2018 at 22:19.
henry link is offline  
Reply With Quote
Old Thursday 27th September 2018, 08:07   #13
Troubador
Moderator
 
Troubador's Avatar

 
Join Date: May 2012
Location: Sheffield
Posts: 8,285
Quote:
Originally Posted by henry link View Post
If this observation was made at lower magnifications I think the most likely explanation is that the unbiased observers have higher eyesight aberrations when their pupils are dilated beyond the 2.5mm limit imposed by the Harpia, but it's also possible that the ATX used as a reference might not a very good specimen. One can never assume an expensive scope is as good as it should be until it's star tested.
Henry
How would higher eyesight aberrations enable the unbiased observers to perceive a better resolution?

Lee
Troubador is online now  
Reply With Quote
Old Thursday 27th September 2018, 08:37   #14
Fedster
Registered User

 
Join Date: Sep 2016
Location: Helsinki
Posts: 52
Quote:
Originally Posted by arran View Post
-the ATx is great on contrast but , especially in darker light, the harpia gives a better resolution, this was confirmed by two unbiased birdwatchers
Just an honest feedback
Just to make sure -- do you mean looking into shadows during the day, or using the scope 30 minutes after sunset?
Fedster is offline  
Reply With Quote
Old Thursday 27th September 2018, 15:03   #15
henry link
Registered User

 
Join Date: Feb 2004
Location: north carolina
Posts: 4,223
Quote:
Originally Posted by Troubador View Post
Henry
How would higher eyesight aberrations enable the unbiased observers to perceive a better resolution?

Lee
I didn't say so, but I doubt that they did see a better measurable resolution (unless the ATX is a very poor unit).

They might have seen a cleaner looking image from the Harpia at 30x magnification and a certain level of low light because their eyesight could be close to diffraction limited at the 2.5mm exit pupil of the Harpia at 30x, but aberration limited at the 3.17mm exit pupil of the ATX at 30x. At 40x under dark overcast conditions I saw just the opposite between the Harpia I tested and a sensibly aberration free reference scope with both scopes operating at full aperture.

Henry
henry link is offline  
Reply With Quote
Old Thursday 27th September 2018, 19:53   #16
arran
Registered User
 
arran's Avatar

 
Join Date: Jul 2004
Location: Belgium
Posts: 147
Quote:
Originally Posted by Fedster View Post
Just to make sure -- do you mean looking into shadows during the day, or using the scope 30 minutes after sunset?
Into shadows and evening light
arran is offline  
Reply With Quote
Old Thursday 27th September 2018, 23:43   #17
DRodrigues
Registered User

 
Join Date: May 2007
Location: Coimbra
Posts: 486
Quote:
Originally Posted by henry link View Post
If this observation was made at lower magnifications I think the most likely explanation is that the unbiased observers have higher eyesight aberrations when their pupils are dilated beyond the 2.5mm limit imposed by the Harpia, but it's also possible that the ATX used as a reference might not a very good specimen. One can never assume an expensive scope is as good as it should be until it's star tested.
Probably just a combination of lower mags and higher AFOVs that suggest this apparent higher resolution... See something similar when comparing my TMB 100º combo with the X95 http://www.pt-ducks.com/cr-telescope..._cr-telescopes - I must include the Swaro 1.7x extender user experience...
Arran, this means that you must compare the Swaro at lower mag with the Harpia at the same mag (30x) and not at it's lower mag (23x) - when light availability is limiting resolution you don't gain resolution by going higher mags... I did and do many hours of duck nasal saddle resighting after sunset...
__________________
David
_____________________

http://www.pt-ducks.com
DRodrigues is offline  
Reply With Quote
Old Saturday 29th September 2018, 16:05   #18
jring
Registered User

 
Join Date: Aug 2015
Location: Germany
Posts: 1,610
Quote:
Originally Posted by Fedster View Post
Great review, many thanks! slightly off topic, is there a definitive guide on how to do the star test and how to interpret the results (whether a book or online)?
Hi,

the definitve guide would be Suiter, the following is also not bad and available online...

https://www.telescope-optics.net/sta..._telescope.htm

Joachim
jring is offline  
Reply With Quote
Old Saturday 29th September 2018, 17:03   #19
jring
Registered User

 
Join Date: Aug 2015
Location: Germany
Posts: 1,610
Hi Henry,

thanks a lot for your "short" test - other authors extensive tests contain less information.
As usual, a spotter will not quite reach up to a very good astro scope... but it's more portable and waterproof.

Joachim
jring is offline  
Reply With Quote
Old Monday 1st October 2018, 18:49   #20
Torview
Registered User
 
Torview's Avatar

 
Join Date: Nov 2011
Location: Dartmoor.
Posts: 2,120
I got to try a Harpia 95 today out in the field in bright conditions, the owner kindly let me look through it.

The biggest wow is clearly the fov, which is impressive, excellent contrast and colour neutrality, the resolution I felt should have been better given the price.

I don`t quite know how I feel about it, the exit pupil was very small at all powers, noticeably so at low power and to me the brightness suffers as a result here, so I`m not sure it will be the best choice on a dull, dark Winter day scanning at its lowest power.

I`d need to spend a lot of time behind one in Winter before I`d take the plunge given the price.
Torview is offline  
Reply With Quote
Old Monday 1st October 2018, 22:47   #21
Torview
Registered User
 
Torview's Avatar

 
Join Date: Nov 2011
Location: Dartmoor.
Posts: 2,120
I forgot to add, I found eye placement a bit finicky in order to avoid blackouts, and a need to refocus every time after changing zoom power.

Last edited by Torview : Tuesday 2nd October 2018 at 06:45. Reason: spelling
Torview is offline  
Reply With Quote
Old Tuesday 2nd October 2018, 10:03   #22
Troubador
Moderator
 
Troubador's Avatar

 
Join Date: May 2012
Location: Sheffield
Posts: 8,285
Quote:
Originally Posted by Torview View Post
I got to try a Harpia 95 today out in the field in bright conditions, the owner kindly let me look through it.

The biggest wow is clearly the fov, which is impressive, excellent contrast and colour neutrality, the resolution I felt should have been better given the price.

I don`t quite know how I feel about it, the exit pupil was very small at all powers, noticeably so at low power and to me the brightness suffers as a result here, so I`m not sure it will be the best choice on a dull, dark Winter day scanning at its lowest power.

I`d need to spend a lot of time behind one in Winter before I`d take the plunge given the price.

John

The EP gets gradually restricted below 40x mag. Above this mag it uses the full 95mm objective and has a normal EP.

Lee
Troubador is online now  
Reply With Quote
Old Tuesday 2nd October 2018, 10:41   #23
Torview
Registered User
 
Torview's Avatar

 
Join Date: Nov 2011
Location: Dartmoor.
Posts: 2,120
Hi Lee,

Trouble for me is this seems like it's the world's most expensive 50mm scope at 23x !

John.
Torview is offline  
Reply With Quote
Old Tuesday 2nd October 2018, 11:10   #24
Vespobuteo
Registered User

 
Join Date: Aug 2013
Location: Utopia
Posts: 1,989
Quote:
Originally Posted by Torview View Post
Hi Lee,

Trouble for me is this seems like it's the world's most expensive 50mm scope at 23x !

John.
I think it's more like 57mm, also your eye pupil will stop down any scope to about that size in daylight.


But, expensive yes, even at 70x mag...

A reasonable edge sharpness and CA control at 23x with that large FOV would probably not be possible without stopping down the scope a bit.

Personally I don't see much visible difference in brightness in most "normal" light conditions between a good 65mm and 80mm+ scope at 25x-30x.

But as you say, in dim late autumn/early winter light the Harpia might not be the optimal scope.

Last edited by Vespobuteo : Tuesday 2nd October 2018 at 11:14.
Vespobuteo is online now  
Reply With Quote
Old Tuesday 2nd October 2018, 11:45   #25
Hauksen
Registered User

 
Join Date: Jun 2017
Location: Germany
Posts: 617
Hi John,

Quote:
Originally Posted by Torview View Post
Trouble for me is this seems like it's the world's most expensive 50mm scope at 23x
Interesting perspective. However, isn't the field of view of the Harpia still larger than that of typical 50 mm scopes at the Harpia's smallest magnification?

I tried to put this into perspective in another thread:

Quote:
Originally Posted by Hauksen View Post
As a Kowa 883 owner, my reference of course is the 25x magnification of the TSN-11WZ, and not the 30x quoted by Dobler. Still, my scope is listed with a 42 m/1000 m field of view at 25x, which is very markedly narrower than the 58.8 m/1000 m listed for the Harpia at 23x. The Harpia also beats the 52 m/1000 m of my Nikon ED50 at 13x, which I always considered a really nice wide field of view.
Regards,

Henning
__________________
3D Printable Objects for Bird Watching: http://www.thingiverse.com/Bikecycli...bird-watching/
Hauksen is online now  
Reply With Quote
Advertisement
Reply


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Stability of the Zeiss harpia arran Zeiss 10 Sunday 26th August 2018 17:57
Zeiss SF - Allbinos review jremmons Zeiss 200 Wednesday 10th August 2016 19:32
Zeiss FL review Zolarcon Zeiss 44 Thursday 24th November 2005 07:59
Zeiss FL review from the USA Curtis Croulet Zeiss 32 Sunday 3rd October 2004 05:56
Alula review of Zeiss FL Ben O Zeiss 24 Wednesday 29th September 2004 22:34



Fatbirder's Top 1000 Birding Websites

Help support BirdForum

Page generated in 0.25556707 seconds with 37 queries
All times are GMT. The time now is 15:41.