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Equipment Discussions >> Binoculars

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AlbertoJ
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Reged: 02/20/08

Loc: Madrid (España)
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594075 - 12/29/12 10:20 AM

Hello again.
I´ve seen a parallelogram mount, Universal Astronomics Unimount Light.
Is this mount big enough to charge steady and without shaking a Docter 40X80 ED binocular? or
Does it need an Universal Astronomics Millennium mount?


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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5594099 - 12/29/12 10:29 AM

The Docters weight near 5 kg, look for the máximum load for each mount

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AlbertoJ
member


Reged: 02/20/08

Loc: Madrid (España)
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594136 - 12/29/12 10:48 AM

Universal Astronomics Unimount Light has a maximum load of 12 Ibs, 5.4 Kg.
But I don´t know how steady Unimount is. I´ve read something about this mount. Look at shaking and dampening times at pages 7, 8 and 9 here:

http://www.cloudynights.com/documents/shootout_bino_mounts.pdf

And besides, Docter is a 40X binocular, not a 16X or 20X.


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Rich V.
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Reged: 01/02/05

Loc: Lake Tahoe area, Nevada, USA
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5594155 - 12/29/12 10:57 AM

Alberto, I use an older Unimount Light for with my WO 22x70s which weigh ~4.5kg which is the mount's max. rating. The mount works but I would prefer the Millennium mount with it. Damping times are a bit slow at maximum load. Having to use 6.8kg of counterweight doesn't help matters.

The Docters are 5kg and the newer light Unimount is rated for 5.5kg now. You would still be at the mount's maximum. It may work but you'll have to be careful not to induce oscillations in the mount while viewing, particularly at 40x. That high mag. makes a big difference over 15x or 20x.

The Millennium mount would be well worth it if you've made the investment in the Docters, IMO. It would certainly be my choice. Your binos will be well within the bottom half of its weight rating. You will then have the extra capacity to assure sufficient damping at 40x. Make sure you get the Ultra Swing Hinge option which is necessary for comfortable reclined viewing. No point setting yourself up for disappoinment!

Rich


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AlbertoJ
member


Reged: 02/20/08

Loc: Madrid (España)
Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5601864 - 01/02/13 08:05 PM

Thanks Rich, I think Millenium mount with Hinge is the best choice to charge a Docter 40x80 ED binocular on.

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ngc 9999
sage


Reged: 08/13/12

Loc: Sunrise, Fl. 26 degrees N
Re: Docter Aspectem 40x80 ED new [Re: AlbertoJ]
      #5601901 - 01/02/13 08:32 PM

Have someone tested the field illuination of the 40x80 ED?

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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: ngc 9999]
      #5609762 - 01/07/13 08:47 AM

I'm back
If someone can indicate me how to measure it I'll give it a try....


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ngc 9999
sage


Reged: 08/13/12

Loc: Sunrise, Fl. 26 degrees N
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5609853 - 01/07/13 10:07 AM

Try to line the edge of the objective with the prism edge or baffle and see how much of the exit pupil is blocked.

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Rich V.
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Loc: Lake Tahoe area, Nevada, USA
Re: Docter Aspectem 40x80 ED new [Re: ngc 9999]
      #5609946 - 01/07/13 10:58 AM

Andres, here's a great example of lining up the objective edge with the rest of the optical system as provided by Michael (GamesForOne). In the case of the Porro prism Docters, one angle is probably fine:

Photo from the "General comments on angled binos" from March 2010

Rich


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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5611081 - 01/07/13 10:42 PM Attachment (19 downloads)

Ok, I'm trying... Taking pictures of the image circle backwards, depending on the distance, makes the circle change its size apparently (the farther it gets bigger, so I took the pictures aproximately at 15 cm from the glass to get a small one). Pictures are from my iPhone, with not too much light and without flash, not too good but good enough... First, an image of the circle just when it starts to clip... I did a rough calculation and found that it has 100% illumination at 50mm of diameter (49.7mm)...

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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611084 - 01/07/13 10:44 PM Attachment (19 downloads)

Then, at the edge, the circle has aproximately 50% of its area illuminated....

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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611087 - 01/07/13 10:45 PM

I'll do this for the 40x150's too, but first I need to know if I'm on the right path...

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Andresin150
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Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611094 - 01/07/13 10:50 PM

FWIW, the test was exactly the same at all edges... And contrary to the image you linked, the circle stayed perfectly round in the inner/vissible part... Why in that image the circle seems clipped towards the center too?

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Rich V.
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Loc: Lake Tahoe area, Nevada, USA
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5611284 - 01/08/13 01:21 AM

Hi, Andres, it looks like your're getting the camera angle right in the second picture. I'm supposing the next aperture seen after the objective edge is the baffle at the first prism face; it's a bit hard to tell.

The linked photo of the 100mm BT shows a small chord cut off by the roof edge of a Schmidt roof prism. Perhaps the prism could have been aligned a bit more precisely to avoid the cutoff. It seems to be common with that particular prism design when used at short focal ratios.

Here's how Glenn LeDrew described this method of assessment of vignette in a thread from several years ago:

Quote:

How to make the sighting when assessing edge-of-field vignetting...

Line up the edge of the objective with the edge of the internal baffle, prism aperture, etc., which intrudes into the eyepiece image the most.

It's that simple. There's nothing ambiguous about it. Even though you are outside the instrument, your sight line necessarily lies on the same path for a ray, traveling from a distant object, which passes through the objective's edge, is refracted and then just clears the most intrusive aperture before reaching the focal surface.

If this ray/sight line is at the same-side edge of the eyepiece image circle (as the Miya Saturn III nearly achieves), the circle of full illumination is as large as the field stop. Yippee!

If this ray/sight line is halfway between the same-side edge and the center of the eyepiece image circle, the circle of full illumination is half as large as the field stop. Nice!

If this ray/sight line appears to intersect the center of the circle of the eyepiece image, the system is fully illuminated on-axis [only]. That's OK!

If this ray/sight line appears to intersect the circle of the eyepiece image beyond the center, the system is not working at full aperture. Boo!

When taking a photo, try to observe these conditions:
- Set focus to infinity, as the eyepiece's image (and field stop) will be collimated by the objective and hence optically lie at infinity.
- Move the camera farther back so as to obtian better focus on the objective's edge.
- Illuminate the objective edge so that it can be readily seen. The camera's flash can help if it's not blocked by the bino's lens shade, etc.




Rich


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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Rich V.]
      #5612488 - 01/08/13 06:42 PM Attachment (15 downloads)

Well, i tried some images with the flash on. It is evident that there is no cutoff, the prisms seem bigger than the eyepiece field stop.

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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5612492 - 01/08/13 06:44 PM Attachment (15 downloads)

If I go farther away to take the photo, the circle begins to grow... I was like 1.5m away....

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Andresin150
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Reged: 08/14/07

Loc: Bogotá - La Calera / Colombia
Re: Docter Aspectem 40x80 ED new [Re: Andresin150]
      #5612500 - 01/08/13 06:47 PM

In the 150's I've observed almost the same behavior, but the circle needs more distance to grow compared with the 80's, maybe because of the difference in the eyepieces Afov?...

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Rich V.
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Loc: Lake Tahoe area, Nevada, USA
Re: Docter Aspectem 40x80 ED [Re: Andresin150]
      #5612525 - 01/08/13 06:58 PM

It's the off axis illumination shot down the optical path from the objective edge like in your second original photo that shows vignette. I wouldn't expect any on-axis problems and don't see any!

I would love to see similar off-axis shots taken through the Fuji 150s. We're looking for the "cats eye" shaped aperture at the eyepiece end of the optical train while sighting along the objective edge. That's what shows the degree of off-axis illumination of the binocular. This is what Glenn's instructions are about.

The off-axis illumination differences between the 25x150 and 40x150 would be most interesting! I'd expect a bit more vignette at 25x than 40x...

Thanks, Andres!

Rich

Edited by Rich V. (01/08/13 07:11 PM)


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