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High power in short focal length refractor

Started by adamsdp, 03/05/2005 04:54PM
Posted 03/05/2005 04:54PM Opening Post
I have a Brandon 94 (640mm fl) and DenkII/Powerswitch/Newtonian OCS. Wondering if anyone has any good ideas on how to get to high power (150-300x) without having to resort to short focal length eyepieces.
With the OCS in high power mode (2.5x), I have an effective focal length of 1600mm. To get to 300x, I would need a 5.3mm eyepiece which doesn't sound like a great choice having read posts about troubles merging below about 10mm and the posts about it being better to magnify as much as possible before any binoviewer prisms to minimize optical abberations. Thanks.

Dave Adams
Posted 03/06/2005 05:34AM #1

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