10 replies to this topic

[revans]

I bought a WO binoviewer last fall but hadn't got around to using it very often.  I used them on my C5 and the view was nice, but recently I put them on my C9.25 and this provided a brighter image, which was at least as good as I was getting from my 127mm binocular telescope. 

 

Rick

[denis0007dl]

Hi Rick,

what 127mm binocular telescope you have exactly?

WO binoviewer was my first, never forgotten binoviewer, where my binoviewer passion and love started, and extended.

Kind regards,
Denis

[junomike]

Not surprised.  l'd expect even a C8 + BV's would out power the 127mm Binoscope

[revans]

Hi Rick,

what 127mm binocular telescope you have exactly?

WO binoviewer was my first, never forgotten binoviewer, where my binoviewer passion and love started, and extended.

Kind regards,
Denis

It is an Oberwerk BT-127 XL SD.  Oberwerk makes binoculars and binocular telescopes in Ohio, US.  Recently, I think some of their products are sold at the big NY retailer, B&H photo also.  

 

Rick

[Eddgie]

I bought a WO binoviewer last fall but hadn't got around to using it very often.  I used them on my C5 and the view was nice, but recently I put them on my C9.25 and this provided a brighter image, which was at least as good as I was getting from my 127mm binocular telescope. 

 

Rick

You may not have realized it, but unless you use a Barlow or a GPC, there is really no configuration using a standard visual back that will give full aperture when using a binoviewer with the C5.  Even with the T2 diagonal unless you are using the 10mm visual back, the aperture is reduced to 118mm

 

Using a standard 1.25" diagonal and visual back is is reduced to something like 96mm. 

 

Also, when you reduce the aperture, since the secondary does not get smaller, the percentage of the secondary obstruction becomes quite large. 

 

For your C9.25, despending on your configurations, you could also be losing some aperture, but since you have so much more than the C5 to start with, you are still going to get a much brighter view. Keeping the light path short on a C9.25 is important though but there are configurations that give full aperture. 

Edited by Eddgie, 05 March 2024 - 10:11 AM.

[lizzyrose]

I bought a WO binoviewer last fall but hadn't got around to using it very often.  I used them on my C5 and the view was nice, but recently I put them on my C9.25 and this provided a brighter image, which was at least as good as I was getting from my 127mm binocular telescope. 

 

Rick

Did you have to use a GPC or barlow with the 9.25?

[revans]

Did you have to use a GPC or barlow with the 9.25?

The WO binoviewer achieves focus without any barlow by just slipping it into the telescope back.  But I don't know how much aperture I'm losing... I hadn't given that any thought and probably I should. Not sure exactly how to know.

 

Rick

[JKSnyder]

Never tried a BV before, but last September I picked up an Oberwerk bino telescope - BT 100 - 45 from an estate auction at low price. I had always dismissed binoculars before, but, the views of Andromeda, Perseus clusters, and Orion nebula were fantastic. Invested in reasonable quality eyepieces to have matching pairs.

 

Then I started thinking about BVs. But I was skeptical about them because my eyes have maybe 4 diopters of difference. Consequently, I cannot bring both eyes to sharp focus on many binoculars. This is not a problem with the Oberwerk BT due to its wide range of focus. I Read many CN posts, but could not find specs on any BVs regarding how many diopters of difference they can accommodate. So I did what any reasonable, impulsive, astro junkie would do...

 

Just ordered the WO binoviewer kit through High Point. Regular shipping to Virginia. I plan to use the BV on my C8 and my 16 dob.

[betacygni]

Never tried a BV before, but last September I picked up an Oberwerk bino telescope - BT 100 - 45 from an estate auction at low price. I had always dismissed binoculars before, but, the views of Andromeda, Perseus clusters, and Orion nebula were fantastic. Invested in reasonable quality eyepieces to have matching pairs.

Then I started thinking about BVs. But I was skeptical about them because my eyes have maybe 4 diopters of difference. Consequently, I cannot bring both eyes to sharp focus on many binoculars. This is not a problem with the Oberwerk BT due to its wide range of focus. I Read many CN posts, but could not find specs on any BVs regarding how many diopters of difference they can accommodate. So I did what any reasonable, impulsive, astro junkie would do...

Just ordered the WO binoviewer kit through High Point. Regular shipping to Virginia. I plan to use the BV on my C8 and my 16 dob.

It’s not particularly convenient, but you can pull out the eyepiece slightly on one side of the binoviewer to accommodate any diopter difference you wish. This is actually how the Televue Binovues work by design.

[planedriver]

The WO binoviewer achieves focus without any barlow by just slipping it into the telescope back. But I don't know how much aperture I'm losing... I hadn't given that any thought and probably I should. Not sure exactly how to know.

Rick

These smallish aperture SCTs or Maks are not really bino-friendly even if you can achive focus easily. I have a 127 Mak and even the 2.67 APM barlow ( which is operating at 2.67x when used with a bino) is still not enough to fully recover the designed focuser/mirror position.
This means you need very good seeing conditions to use the binoviewer - in my case I use the Baader 2.25 barlow (supplied with the Baader Zooms) to achive designed focal length focuser position with the barlow working at around 4x.

[betacygni]

These smallish aperture SCTs or Maks are not really bino-friendly even if you can achive focus easily. I have a 127 Mak and even the 2.67 APM barlow ( which is operating at 2.67x when used with a bino) is still not enough to fully recover the designed focuser/mirror position.
This means you need very good seeing conditions to use the binoviewer - in my case I use the Baader 2.25 barlow (supplied with the Baader Zooms) to achive designed focal length focuser position with the barlow working at around 4x.

You should be able to get a barlow working at around 2x to achieve parfocal positioning. The discontinued binovue 2x amplifier does this, and while I’ve not tried it personally, the 2.5x Televue powermate I suspect would be fairly close as well (it gives 2x in binoviewers).