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Siebert 1.3x OCA - First light

Started by cdculbertson, 02/11/2003 06:56PM
Posted 02/11/2003 06:56PM Opening Post
Well, I receieved my 1.3x OCA from Harry last week, and just got a chance to try it out tonight. Transparency was excellent, with seeing rating around a 6/10; pretty "fast" seeing, but still able to get some decent detail from the Moon, Jupiter and Saturn as it did settle out from time to time. Decent night, and at no time did I ever wish that I was using a smaller aperture! ;-)

I was using the HS OCA on a TeleVue BinoVue, and tonight I was using my Starmaster 11" f/5.4 ELT. Eyepieces used were 24mm Panoptics, 16mm T5 Naglers, 15mm Ultimas (Antares), and 12.5mm Celestron Ultimas. The first thing that I noticed was that the OCA does actually give around 1.3x on any given eyepiece.

The OCA itself is pretty well machined, and is threaded for 1.25" filters. This particular unit was made specifically to fit the TeleVue BinoVue by removing the nosepiece and attaching the upper end of the OCA directly to the large ring on the BinoVue. It fits well, but took me a couple of tries to get it just right. I am going to purchase another nosepiece assembly from TeleVue so I can have one dedicated to the Siebert OCA and one for the TeleVue 2x corrector.

There were no reflections either on or off axis with this corrector, and the reason is probably due to a combination of very good coatings, and the fact that the tube of the OCA is very well baffled and pitch black inside. Even when viewing Saturn, which was about 5 degrees from the waning gibbous moon, there were absolutely no reflections seen in any eyepiece pair that I used. There was no loss of contrast on the Moon, Jupiter or Saturn, and I particularly enjoyed watching the GRS transiting Jupiter tonight.

There was also no vignetting with this unit, in spite of the fact that it is a 1.25" unit. The reason is that it uses a fairly large upper lens assembly (30mm?). All of this is explained in great detail on Harry's website.

All in all I must say that I am *extremely* pleased with this OCA. The only downside to binoviewing with decent aperture scopes was the fact that you couldn't get low power views for deep sky objects. While there are other units on the market now that will also accomplish this, I feel that the $159 (now $179?) that I paid for the unit makes it a fantastic bargain.

More as I get a chance to give it a decent workout.

Doug
Midway, FL