Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Binoviewers

This topic has been archived. This means that you cannot reply to this topic.
9 replies to this topic

#1 Rich N

Rich N

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,624
  • Joined: 22 Sep 2004

Posted 28 April 2005 - 05:53 PM

..... binoviewer. :-)

Rich



this discussion was CUT out of the Binocular Mirror Platform thread.

edz

#2 craig_oz_land

craig_oz_land

    Ranger 4

  • -----
  • Posts: 345
  • Joined: 21 Jan 2004

Posted 28 April 2005 - 07:22 PM

A little bit more on the pros and cons of a mirror and the binoviewer (bv).

The aiming of the mirror is a significant con. A laser pointer could be used to overcome this problem.

The bv scope combination looks good but there is a bit more difficulty in not stretching out the focal length due to the amount of extra path length required by the bv.

TMB Optical was one of the more notable manufacturers to design their refractors with removable extension tubes to allow bv'ing without focal length extenders.

Having said that, I do remember somebody saying that their bv's worked better at slower f ratios. Was that you Rich?

Found out it was Silvio on the "Binoviewers and Prism Diagonals" thread in Binoviewers

Now, if a can persuade Takahashi in doing a one off shortened tube for my 102.

Regards.

#3 Joe Ogiba

Joe Ogiba

    Fly Me to the Moon

  • *****
  • Posts: 7,250
  • Joined: 14 Feb 2002

Posted 28 April 2005 - 08:08 PM

Craig, system binoviewers like my dual arm Denk II work well with most any scope since my OCS magnification can be as low as .5x (Starsweeper) on my C9.25 and Apex 127 and as high as 6x (dual-arm 2x + 3x multiplier cell). I use low power 20mm Pentax XW's,20mm Widescan III's (84°) or 16mm Nagler T5's then adjust the power with the .5x Starsweeper or multiplier cells. I have even lower power eyepiece sets up to 40mm but I like a wide AFOV. If you want wide angle 36-40mm eyepieces in a binoviewer then the 2" Seibert binoviewers will do the trick.
If you want more info on binoviewers then see Binoviewers .

Joe

#4 Rich N

Rich N

    Fly Me to the Moon

  • *****
  • topic starter
  • Posts: 5,624
  • Joined: 22 Sep 2004

Posted 29 April 2005 - 11:35 AM

A little bit more on the pros and cons of a mirror and the binoviewer (bv).

The aiming of the mirror is a significant con. A laser pointer could be used to overcome this problem.

The bv scope combination looks good but there is a bit more difficulty in not stretching out the focal length due to the amount of extra path length required by the bv.

TMB Optical was one of the more notable manufacturers to design their refractors with removable extension tubes to allow bv'ing without focal length extenders.

Having said that, I do remember somebody saying that their bv's worked better at slower f ratios. Was that you Rich?

Found out it was Silvio on the "Binoviewers and Prism Diagonals" thread in Binoviewers

Now, if a can persuade Takahashi in doing a one off shortened tube for my 102.

Regards.


Hi Craig,

Sorry to be slow getting back to you.

I don't think I've said binoviewers perform better with slow optical systems. But, it seems slow optical systems make life easier for virtually any eyepiece or binoviewer.

I use an AP/Zeiss/Baader binoviewer. It works very well with my fast refractors.

I love binoculars. Binoculars with 45 deg or 90 deg angled eyepieces are a big help in reducing neck problems. When using regular binoculars I use a chair I can slide down in and rest my neck. It would be really nice if the chair would pivot (horizontal movement) but I don't have that.

I'm working on getting a refractor with good aperture and a relatively short focal length so that I can easily get into the 30x power range.

I can use my AP/Zeiss/Baader binoviewer with my Tak FC-100 f/8.

All the best,
Rich

#5 craig_oz_land

craig_oz_land

    Ranger 4

  • -----
  • Posts: 345
  • Joined: 21 Jan 2004

Posted 30 April 2005 - 06:50 PM

Hi Joe,

The 0.5x mode will not work on a standard FS-102. Denk informed me it is an SCT only package.

Cheers, Craig.

#6 Joe Ogiba

Joe Ogiba

    Fly Me to the Moon

  • *****
  • Posts: 7,250
  • Joined: 14 Feb 2002

Posted 30 April 2005 - 08:48 PM

Craig, with my Meade 102ED APO I can use the .5x mode on my dual arm Denk II and a 2x multiplier cell screwed into a 2" diagonal and get an unvignetted image with my 20mm Pentax XP's that would have a power of about 1.4x with the combo. The .5x mode with just a 2" nosepiece on the Denk II is for my C9.25 or Apex 127 (5" Cat) for an unvignetted view with my 20mm Pentax XW's. With my 20mm Widescan III's (84°) I pull out both arms for 1x and an unvignetted view with the SCT and Cat.
I use Denk II dual arm SCT package on all my scopes (except the Pentax PF-80-ED spotting scope) in combination with 2x or 3x multiplier cell's and for my refractors I also have the low power s cell that screws into a 2" diagonal. There is an even lower power SR cell for Televue 2" diagonal but since I also have WO diagonals I only have the s cell.
For daytime closeup use in my backyard I can use the .5x mode with no vignetting even with my 20mm Widesan III's (84°) with my WO Megrez 80mm F6 Fluorite triplet or 120mm F5 achromat and unvignetted view with my 20mm Pentax XW's (70°) with the 102 F9 APO or 150mm F8 CR150.
In a way they are right about not being able to use .5x power in a normal tube refractor without using one of the screw-in cells to reach infinity focus.
If you go to Denkmeier Optical and under SCT Package you will see this:
"Multiple Use
For use in a Refractor: Use the 2X Multiplier cell threaded into the filter side of a 2" star diagonal as an amplifying lens for high power. Thread the Star*Sweeper™ cell onto the 2" hollow nose piece of the binoviewer and the 2X Multiplier cell onto the filter side of a 2" star diagonal to reach focus at low power."
So with the right arm pushed in with the dual arm PowerX Switch .5x = starsweeper cell.

The bottom line is the lowest (infinity focus) power you can get with a normal tube refractor and a binoviewer is between 1-1.5x. To go under 1x and reach infinity focus with a refractor you need a short tube like the TV 102i with 5" shorter tube .

Joe

#7 craig_oz_land

craig_oz_land

    Ranger 4

  • -----
  • Posts: 345
  • Joined: 21 Jan 2004

Posted 01 May 2005 - 01:45 AM

Joe,
Thanks for that thorough rundown.

I may have been too specific with my question when I contacted Denk.

That makes sense to juggle the focal extender and reducer to give a more favourable focus range and keep the focal length about the same.

I want to get low power bright views so I may go for a TMB or similar OTA that is better equipped for bv'ing.

Apologies for drifting off the thread.

Cheers, Craig.

#8 Joe Ogiba

Joe Ogiba

    Fly Me to the Moon

  • *****
  • Posts: 7,250
  • Joined: 14 Feb 2002

Posted 01 May 2005 - 10:44 AM

I want to get low power bright views so I may go for a TMB or similar OTA that is better equipped for bv'ing.


Craig, this TMB would work well with a binoviewer.
"The Sky & Telescope review pointed out about the extension tube that, “unique among refractors, the TMB focuser is designed to accommodate a binocular viewer. Because of their long internal light path through a series of prisms, most binocular viewers require a focuser to be racked in several inches from the normal position, a distance far greater than most focusers provide. But the TMB focuser has a 4-inch-long extension tube that, when removed, allows any binocular viewer to reach focus without any additional optics (usually a Barlow lens) to compensate for the longer light path. Thus, with the TMB scope I was able to enjoy the widest field possible with a binocular viewer, for truly spectacular panoramic and almost three-dimensional views.” Because of the removable extension tube, the total back focus from focuser to image plane is an exceptionally long 220m. The shortest possible tube length is 340 mm with the extension tube removed, while the standard tube length during visual observing is 675 mm. The focuser itself has 70mmm of travel available, so that any focal length eyepiece can be accommodated."


Joe

#9 craig_oz_land

craig_oz_land

    Ranger 4

  • -----
  • Posts: 345
  • Joined: 21 Jan 2004

Posted 02 May 2005 - 01:09 AM

Thanks Joe.

I was thinking of a 130F6. Might be time to sell my Taks 22x60s for a BVer.

Cheers, Craig.

#10 Joe Ogiba

Joe Ogiba

    Fly Me to the Moon

  • *****
  • Posts: 7,250
  • Joined: 14 Feb 2002

Posted 02 May 2005 - 08:08 AM

Craig,

The 130 F6 would be my pick also if I could come up with the money (about $6000 USD).

Joe


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics