Posts Made By: Donald Durbin

I also have his profile shot. It seems that they know when I want to take a picture and hide from me. >

Bill,

I agree with Mark. If the eyepieces you are using are not vignetting then they will not vignette with a focal reducer designed to work with your equipment. The biggest problem I have seen so far when using focal reducers with binoviewers is reaching focus. As a general rule of thumb, The closer you can get the focal reducer to the nose of the binoviewer the better chance you will have of reaching focus. The further the focal reducer is from the binoviewer the greater the focal reducer effect will be.

Using too powerful a focal reducer could cause the field of view to shrink and appear as vignetting.

Don Durbin

Dave,

I have had really good luck with putting a Barlow in front of the diagonal. Some of the Televue Powermates would probably be the best choice here. You could also try using a Sieberts Ultra Barlow. They are the same basic design as the Powermate, and less expensive.

I have found and continue to find many interesting combinations using Siebert and Denkmeier accessories together.

Don Durbin

Burgess BV125 Model C
Original 22mm BlackNights with Diopters and focal reducer
45mm Elite BlackNights with Diopters
Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag
Denk IIs OCA.
Denkmeier 2" SCT Star Diagonal (Modified)
Denkmeier 2" Starsweeper SE
Denkmeier 1 1/4" Starsweeper SE
Stellarvue AT1010
Meade ETX90
Stellarvue 102APO
Celestron C9.25
Orion Atlas 8"
Meade 152ED

James,

A lot depends on the manufacturer. I have never found a pair of Televue EPs of the same power and type that do not match. I have bought single Televue EPs at different times from different places without problems. My 21mm TV plossls are a good example. One has the lettering at the top of the EP, one has the lettering in the middle of the EP, they are still parfocal.

I have a pair of 2" 19mm and a pair of 2" 16.8mm Gary Russell EPs. The eyepieces were bought at different times from different people on Astromart. I had to put parfocal rings on them to make them easier to use.

All of my binoviewers have diopter adjustments but it is really a pain to have to equalize a set of eyepieces before you can use them.

I imagine if some manufacturer let tolerances slip or changed design, you could end up with eyepiece of slightly different power or FOV. These EPs could cause you to have problems, maybe even headaches when using them. Generally buying two EPs of the same type, from the same place, at the same time, will yield a closely matched set.

Don Durbin

Burgess BV125 Model C
Original 22mm BlackNights with Diopters and focal reducer
45mm Elite BlackNights with Diopters
Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag
Denk IIs OCA.
Denkmeier 2" SCT Star Diagonal (Modified)
Denkmeier 2" Starsweeper SE
Denkmeier 1 1/4" Starsweeper SE
Stellarvue AT1010
Meade ETX90
Stellarvue 102APO
Celestron C9.25
Orion Atlas 8"
Meade 152ED

If thy binoviewers offend thee, then pluck them out.

Or at least switch to a lower power.

Stuart,

The Stellarvue binoviewers and the Burgess binoviewers are basically the same unit.

To me their biggest advantage is their relatively short light path. Of course the fact that they sell for $200 also helps.

The quality of the unit is surprisingly good considering the price.

Like most binoviewers, they will not need any corrector when used with an SCT. Their short light path makes it possible that they will not need any corrector in some of the newer premium refractors. I own a TAK FS-128 and they work fine with no corrector using the 1 1/4" visual back and a 1 1/4" Lumicon Lumibrite diagonal.

If you have not owned a pair of binoviewers before this the Stellarvue binoviewers are certainly a good place to start. They will compete head to head for detail with other units at two or three or even four times their cost on most of the bright objects in the sky.

Don Durbin

Burgess BV125 Model C
Original 22mm BlackNights with Diopters and focal reducer
45mm Elite BlackNights with Diopters
Sieberts 1.3X OCA, Sieberts UltraBarlow, Sieberts Multimag OCA.
(Semi)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

David,

I tried to duplicate your image with my unit. I have placed the two images side by side with mine on the left. I have repeatedly measured the opening of the bottom of the eyepiece holder on my Burgess and it is 20mm.

If you have a compass or something similar, try carefully inserting the compass into the eyepiece holder and setting it to the width of the opening, Then remove the compass and measure the distance you have it set to.

The true clear aperture of these units is measured at the bottom of the unit and they are roughly 22mm. There is a little bit of edge clipping by the prism that makes me say roughly.

Don Durbin

Hi Jim,

You may have mentioned this before, but what size prisms did you use in your binoviewer?

Don Durbin

Larry,

An XT10 does not have the range of focus to use the Burgess binoviewers by themselves. You will need an Optical Corrector or at the very least a Barlow. A Barlow by itself will result in a very high magnification factor. This is because the eyepieces are located so far from the Barlow lens. A Burgess binoviewer has a light path of 100mm. A combination of a Barlow and a focal reducer will work. The quality will be hit or miss.

A while back I posted a message on how to make your own OCA.

https://www.astromart.com/forums/viewpost.asp?forum_post_id=313188&poll_id=&news_id=&page=2

Siebert Optics makes an OCA specifically made to work with the Burgess and most reflectors. They also make a Multimag adapter that will work with reflectors and refractors alike.

If you have an SCT you do not need an OCA to reach focus. Also since a Burgess binoviewer has such a short light path, some refractors will focus without an OCA.

I have a TAK FS-128 and I can use my Burgess binoviewer without any corrector. I also have an 8" Orion Atlas and half of an XT10. These need an OCA to reach focus.


Don Durbin

David,

I am concerned about your thread problem. If you are saying you cannot screw the OCA into the Burgess, then you need to contact Burgess for a replacement barrel. If you cannot screw the front optic into your 1 1/4" diagonal then you need to replace the diagonal with one that will take optics. Try a 1 1/4 filter and see if it screws into the diagonal and the Burgess.

The two inch diagonal is not really buying you anything here except extra out-travel you do not need. There are plenty of good 1 1/4" diagonals around that will easily support the weight of a Burgess unit. The Burgess binoviewer is one of the lightest on the market.

Relocate the forward element of the OCA to the front of a 1 1/4" diagonal. Since you have a plastic diagonal try relocating the forward element and then supporting the binoviewer while focusing. Once you have made sure you can focus, you can go out and get another metal 1 1/4" diagonal.

You may actually get enough in-travel with a 1 1/4" diagonal that you will not need to relocate the forward element.

Don