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Build your own Burgess OCA

Started by DonDurbin, 03/21/2005 03:43AM
Posted 03/21/2005 03:43AM Opening Post
To all,

My experiments with my Burgess binoviewer have yielded some interesting results.

I purchased the Orion shorty Barlow that we talked about earlier.
08711 1 Shorty 2x Barlow

The magnification was as expected.. too high. I was going to do a full report with exact magnifications and I still might. In the mean time I think this is what some of the people on this forum are looking for.

To the Shorty Barlow add for SAC a .5 focal reducer.
SAC's .5/.3 combo focal reducer $65 plus $7 shipping.

The SAC .5 focal reducer comes with a 1 1/4" extension tube. This is normally used to increase the effectiveness of the focal reducer to .3.

To build an OCA for a Newtonian telescope, screw the focal reducer into the Burgess unit, screw the extension tube into the focal reducer, screw the Barlow element into the extension tube. This assembly came to focus very easily in my 8" Orion Atlas. It looked to be about a 1.5X OCA

To use this setup in a refractor, screw the barlow into the front of a good 1 1/4" diagonal. Screw the focal reducer into your Burgess unit and place it into your diagonal. For more reduction use the 1 1/4" extension tube supplied with the focal reducer in between the Burgess and the focal reducer.

Keep the empty Barlow tube handy, you may find that it can be used as a spacer between the diagonal and the telescope. I found that an inch or two of focus helped in my refractors. The gain of the OCA when the extension tube was used on the focal reducer was very low. I would say less than 1.5X.

The SAC focal reducer is too high a power to use as a focal reducer in an SCT.

You can use either a Siebert focal reducer or a 1 1/4" Denkmeier Star Sweeper module with your Burgess in an SCT.

I would like to give some credit to Harry Siebert for this. Working with his multimag is where the idea for this came from. I also need to mention that Harry has a Burgess OCA advertised for $69. I do not have one and I do not know the specifications.

Enjoy,
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.
Denk IIs
Denkmeier 2" SCT Star Diagonal (Modified)
Denkmeier 2" Star Sweeper SE
Denkmeier 1 1/4" Star Sweeper SE
Stellarvue AT1010
Meade ETX90
Stellarvue 102APO
Orion 100ED
Celestron C9.25
Orion Atlas 8"
Meade 152ED

Posted 02/28/2007 12:16PM #1
Donald Durbin said:

......To build an OCA for a Newtonian telescope, screw the focal reducer into the Burgess unit, screw the extension tube into the focal reducer, screw the Barlow element into the extension tube. This assembly came to focus very easily in my 8" Orion Atlas.....


Don,

I'll give it a shot! Thanks for the idea.

George N