Posts Made By: Donald Durbin

Ron,

Are you talking about the new Celestron binoviewers?

Looking through the EP holders on a Burgess you can see the edges of the prism. They actually clip about 1 mm or more of the viewing circle.


The new Celestron and the Burgess are made in the same factory in China.

Don

David,

You can measure magnification by using a single eyepiece focused on a yardstick an appropriate distance away. Then use the same eyepiece in the binoviewer with the corrector.

If you have a refractor you may find that you can focus on a terrestrial object (Like a yardstick) by going straight into the focuser without an adapter. You can then add the adapter and do the math.

There is also a third way using a star and a graduated eyepiece. Kill the tracking drive and allow the star to cross a fixed distance in the eyepiece and compare with the eyepiece in the binoviewer with the corrector. (Hint.. Don't use Polaris )

Don

Dan,

I own the Burgess, Siebert 22mm BlackNights, Siebert 45mm BlackNights Elites, and Denkmeier Optical Premium Deepsky Binoviewers. I also have access to a Televue binoviewer. There is very little difference in the view through any of these units when using 21mm or higher powered 1 1/4" eyepieces. As you go to lower powered eyepieces you begin to see some vignetting in the different models. All the 1 1/4" binoviewers will vignette with some power of eyepieces. Even the 2" 45mm Elite binoviewers will vignette at some point but the largest pair of 2" eyepieces I have is only 42mm.

With the Burgess, Stellarvue, and Celestron binoviewers you do not have self centering eyepieces holders. This can result in the eyepiece not seating correctly and can cause problems with merging. I have to say I have not had this problem with my Burgess unit but others have reported it.

I have found the image in my Burgess to be very bright. I think this may be due to the BK4 glass. Many people have fought many battles over this. I can only report what I see.

I have had a pair of 30mm Echelons on order from Siebert Optics forever! ( I understand that Harry Siebert has a lot of 2" units he wants to build first but...) I once asked Harry if he could put BK4 prisms in them for me. Harry said that he buys the prisms in lots and a lot of people would have to make the same request.

It seems the binoviewer manufactures made the decision for us that BK7 glass was best. I wish they would offer both so we could decide ourselves.

My Denkmeier binoviewers have a big advantage over the other units. I have a single arm PowerSwitch that I use with them. I also have a Denkmeier PowerSwitch Diagonal. The optics have been replaced in it so it works with binoviewers. When I use the PowerSwitch with the PowerSwitch Diagonal on my Celestron 9.25 I have 6 powers available through a single pair of Eyepieces. This is really a nice feature. I think the latest version of Denkmeier PowerSwitches have the same capabilities. I just wish the powers were not in such large steps.

The ideal device would be an optical zoom allowing the user to reach the max magnification for any given set of conditions.

The Siebert 45mm Elites offer the best low power views out of any of my binoviewers. I really like using the 2" eyepieces with them. My club has a 16" SCT with a focal length of 7000mm and a 8" Refractor with a 3000mm focal length. With instruments like these you need as low a power as you can get with your binoviewers and nothing else I have comes close to the Siebert 45mm Elites with the Sieberts Multimag OCA.

Don Durbin
Burgess BV125 Model C
Burgess binoviewer corrector
Original 22mm BlackNights with Diopters and focal reducer
45mm Elite BlackNights with Diopters
Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag OCA.
(Semi, almost)Denk IIs
Denkmeier 2" SCT Star Diagonal (Modified)
Denkmeier 2" Star Sweeper SE
Denkmeier 1 1/4" Star Sweeper SE
SAC focal reducer
Meade ETX90
Stellarvue 102APO
Orion 100ED
Celestron C9.25
Orion Atlas 8"
50% Orion XT10
Meade 152ED
TAK FS-128
Coronado SM-40/BF10

To All,

I brought out the 8" Orion Atlas tonight and focused on Jupiter. I used a pair of Siebert 24mm Ultra wides. I had to go all the way out on the focuser on this scope using a single Siebert 24mm Ultra wide. There have been some EPs that I needed a short extension in order to reach focus when using this scope.

This scope has always had good in-travel. With the Siebert 24mm Ultra wides in the Burgess and the Burgess corrector installed. I had to rack the focuser almost all the way in to reach focus. I measured the in-travel I needed to focus at 1.4" or 35mm.

Don Durbin

Hi Jean,

All the binoviewers on the market today will work with your SCT. However your SCT has a 2800mm focal length. So when using lower powers you will experience some vignetting depending on make and model of your binoviewer.

I myself believe that vignetting is way overrated. You place the object in the center of the field and the dark edges of space are a shade darker when vignetted. You could probably make a case for improved contrast out of that. Other people seemed to be really bothered by it so I believe it should be a consideration.

The Burgess/Stellarvue/Celestron binoviewer can use 21mm EPs without noticeable vignetting. That still gives you a magnification of 138X. (I added the 100mm length of the binoviewer to your 2800mm focal length and divided by 21mm.) You can attach a Denkmeier 1 1/4" Starsweeper or a Siebert Optics focal reducer to the Burgess/Stellarvue/Celestron binoviewer and reduce the magnification to under 100X. The Burgess optical corrector may or may not allow you to focus in your DOB. An easy way to determine that is to focus with a single eyepiece that you plan on using in the Burgess binoviewer and measure the remaining in-travel available on your DOB. You will need 1.4" or 35mm of in-travel to reach focus with the Burgess/Stellarvue/Celestron binoviewer and the Burgess corrector. The Stellarvue/Sieberts corrector is adjustable and will allow you to reach focus on your DOB but it also costs a bit more than the Burgess corrector. The Burgess/Stellarvue/Celestron binoviewer is also the lightest weight system putting less strain on focuser and making balancing the scope easier. A big knock against this unit is the lack of Self Centering EP holders found in the more expensive models. I have not had any real problem with cocked EPs but other people have reported the problem.

Another package available is the Denkmeier 'Big Easy' package. This may be the best bang for the buck in an 1 1/4" format. I do not have one of these packages and I have not seen any reviews specifically on this package. My understanding is that this is a Denkmeier standard binoviewer with self centering eyepiece holders and a Modular 1 1/4" Optical Corrector system. This unit should focus in a DOB with out any problem. With the modular unit you have the focal reducer element that when used alone in your SCT will give you wide views. Aside from the Self Centering EP holders, this unit also has an advertised 26mm clear aperture. This should allow use of lower powered eyepieces probably in the range of 27mm without noticeable vignetting. Depending on the optics in the Modular 1 1/4" Optical Corrector system there may be a problem with intrusion into the DOB light path as reported by Sky and Tel. Also when the Denkmeier II came out, a lot of people remarked on how much brighter is was over a Denkmeier standard.

There is also the Siebert 22mm BlackNight unit. This unit has a 22mm Clear Aperture in which 24mm EPs can be used without noticeable vignetting. It has Self Centering EP holders. Sieberts makes a wide array of Optical Correctors for Astronomy and often offers a discount on them to BlackNight owners. Again this unit is a 22mm Clear Aperture and will experience vignetting with 27mm EPs.

Another choice would be the Televue binoviewer with 27mm Clear Aperture and a X2 optical corrector. This unit will focus in an Orion XT10 and will work with or without the X2 corrector in your SCT. This unit has Self Centering EP holders.

The ultimate for Deep Space viewing through your C11 would have to be the Siebert 40mm or 45mm Elites. These are true 2" binoviewers that give outstanding wide field views without need of any Optical Corrector when used with an SCT. The Sieberts Multimag OCA will allow you to come to focus with any telescope that has a 2" focuser. The only negatives about these units are the price and the weight. So far I have not had any real problem with the weight, but where balance is critical this could be a problem.

Weight should be a consideration with any binoviewer setup.

Don Durbin
Burgess BV125 Model C
Burgess binoviewer corrector
Original 22mm BlackNights with Diopters and focal reducer
45mm Elite BlackNights with Diopters
Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag OCA.
Denkmeier Premium Dielectric Coated(Semi, almost Denk IIs
Denkmeier 2" SCT Star Diagonal (Modified)
Denkmeier 2" Star Sweeper SE
Denkmeier 1 1/4" Star Sweeper SE
SAC focal reducer
Meade ETX90
Stellarvue 102APO
Orion 100ED
Celestron C9.25
Orion Atlas 8"
50% Orion XT10
Meade 152ED
TAK FS-128
Coronado SM-40/BF10

Michael,

Are you talking about a refractor and are you talking about a dual switch? If so I think it will require more in-travel for the focal reducer side. The Barlow side should work though.

The single switch that I have is a focal reducer. It works great on my C9.25. I do not think it worked on any of my refractors without a Barlow in front of the diagonal.

Don

Jim,

Assuming your scope has a two inch focuser, have you tried your lowest profile 2" 1 1/4" adapter?

Do you have any kind of 1 1/4" barrel extension? You could try using it between your binoviewer and the OCS. It will increase the magnification but it will also give you more in-travel

Have you tried different EPs? Look for EPs with Barlow lenses built into the bottom of them. (Orion Expanse, Televue Naglers, Burgess Planetary) These eyepieces require less in-travel.

Finally I believe Siebert Optics sells an adjustable OCS for that binoviewer.

I do not recommend modifying you scope to make a binoviewers work.

Good luck,
Don

Jim,

How did you determine that the BO has a larger aperture? Is this something you measured? Or are you just going by the written specifications?

The reason that I ask is because there has been a lot of confusion on what the true clear aperture of these units are and the correct method to measure it.

Thanks
Don Durbin

Hi Buck,

I have a pair of 12mm Nagler T2 that I use with my binoviewers, but I still find my favorite pair of EPs are my 18mm Radians.

When I use my TAK FS-128 I do not need any OCA/OCS for my Burgess, Denks, or my Siebert 22mm binoviewers. For really high power views on good nights I find I can use my 4.8mm Naglers on all of those units.

I like the 4.8mm Naglers and the Burgess unit because of the low weight of those units.

For low powered views I like my Siebert 45mm Elites with Siebert 36mm EPs in my Celestron 9.25.

Don

Hi Charles,

I have a Celestron 9.25 which is known for its limited focus range. Your C14 should have more focus travel than I do so you should have no problems focusing without the OCA.

I have Burgess, Denk, and Siebert binoviewers. I can tell you that a Denk 1 1/4" StarSweeper, or a Siebert 1 1/4" focal reducer cell should work fine with your new binoviewer.

I also have a Celestron SCT focal reducer but I am not sure I have ever tried using it with my binoviewers.

As far as stacking goes, I suggest you try using the Siebert focal reducer or the Denk StarSweeper with the OCA in front of it.

Don Durbin