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Old Sunday 29th October 2017, 22:29   #1
Stephen Mark
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Two 1.6 extenders

I need to know if anyone has used two of the extenders for birding. One worked fine in Indiana were most of the birds are within 100 yards but in North Carolina especially going to the ocean the distances can be much farther so I thought two might be an answer.
Steve
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Old Sunday 29th October 2017, 22:40   #2
jring
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Quote:
Originally Posted by Stephen Mark View Post
I need to know if anyone has used two of the extenders for birding. One worked fine in Indiana were most of the birds are within 100 yards but in North Carolina especially going to the ocean the distances can be much farther so I thought two might be an answer.
Steve
http://www.lifeinfourthirds.co.uk/ko...he-boundaries/

Regards,

Joachim
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Old Monday 30th October 2017, 12:33   #3
Stephen Mark
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Joachim thank you that's exactly what I needed Its pretty amazing that sharpness holds up at that magnification. I hate to think what a camera lens would cost at that range and I doubt that any lens company could stabilize that much zoom.
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Old Monday 30th October 2017, 15:20   #4
Binastro
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Firstly 153.6x is not significant. I would call it 150x or 155x unless measured.

The Nikon P900 might be similar and stabilized. Although ultimately the 88mm Kowa aperture will be better than the front lens aperture of the P900.

With the Skywatcher 90mm Maksutov looking at a crow on a chimney pot at 120m, I think I saw considerably more detail visually at either 190x or a more reasonable 125x. The crow's eye was amazing.

I frequently used 120mm and 150mm aperture astro scopes terrestrially at one mile in the daytime, or 4.7 miles at night at 250x at 3 a.m. with excellent results.
200 yards is not far.
At long distance only the atmosphere is the problem. One needs stable temperatures and early morning or late afternoon.
A temperate climate is best.
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Old Monday 30th October 2017, 16:09   #5
henry link
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Originally Posted by Stephen Mark View Post
Joachim thank you that's exactly what I needed Its pretty amazing that sharpness holds up at that magnification.
Steve
Keep in mind that the photos exaggerate the sharpness and brightness you would see at the eyepiece.

The phone camera has adjusted the exposure so that the 153X image is just as bright as the 60x and 96x images. Your eye can't do that.

Also, the size of the image viewed on a computer is reduced by an unknown factor compared to its apparent size at the eyepiece. For me the photo subtends about 25 when viewed on the computer screen. If we assume the eyepiece field stop is just off the corners of the photo frame that would mean the diagonal corners need to subtend about 75 to match the apparent image size at the eyepiece, so the photo needs to be about three times larger. As it is the photo shows "sharpness" as it might appear at about 50x.

Frankly, even with a cherry sample of this scope I doubt that under long range daylight conditions you will ever detect any smaller detail by increasing the magnification beyond 96x.

Last edited by henry link : Monday 30th October 2017 at 16:28.
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Old Monday 30th October 2017, 16:25   #6
jring
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Hi,

the linked images were shot with an iphone and reduced to 800x600 for web - unless we get to see full resolution files at 4032x3024, pixel peeping is a moot point.

But it has to be said, that this will be not what you will see visually - the image with an exit pupil of 0.5mm will be fairly dark even in bright sunshine - the camera compensates for that.

Joachim
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Old Tuesday 31st October 2017, 13:09   #7
henry link
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Hi,

the linked images were shot with an iphone and reduced to 800x600 for web - unless we get to see full resolution files at 4032x3024, pixel peeping is a moot point.

Joachim
Hi Joachim,

Yes, what I should have said was that by the time the linked image is enlarged enough on the monitor to match the apparent size at the eyepiece it is too pixelated to be of any use in predicting visual sharpness.

The reviewer could easily have digiscoped a standard resolution chart and made a crop of the relevant area, including a bit less than 800x600 of the original file. That would have shown us the true resolution of the scope/phone combination and, when viewed at the proper apparent size, something closer to the visual sharpness at 153x.

Henry
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Old Tuesday 7th November 2017, 10:20   #8
yves0071
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HI,
Indeed, I tried with 2 extenders.... and finally sold one.
I found it quite difficult to use on my 883 due to focussing point of view reason.
Having one in place it is not so easy to manage the focus (limited range) but still manageable. With 2 extenders, it is even more difficult and becomes not friendly!.
Also, starting with a 64x magnification with a smaller field of view, it is quite difficult to find the target and it is not something enjoyable to use.

I also found that the image definition (eye view) with 2 is too much deteriorated particularly at long distance.
I am still happy with one :) (and sold the second ne to a BF member)
Regards
Yves
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