Sunday, February 22, 2004

Declaring Victory on the Photon Instruments 5" Refractor

I took it to a star party last night. I had a chance to look at Saturn through several different telescopes, both reflectors and refractors, under the same sky, and the same conditions of darkness. There was only one telescope that showed more detail on Saturn than my Photon--and that was an Astrophysics Starfire 7" apochromatic refractor. (These aren't made anymore, but I am sure that I could buy one used for $7500-$8000.)

I looked through a 6" Chinese achromat sold under the Galileo brandname. Cassini's Division was invisible, and there was no detail on the planet itself. I looked through a Meade 8" Dobsonian. Ditto.

The Starfire was indeed an impressive view--but it did not show dramatically more detail on Saturn and its rings than the Photon Instruments 5" refractor. In both cases, Cassini's Division was black at the ansae (the left and right sides of the planet), and visible in front and back of the planet. It was perhaps a little blacker in the Starfire, and there was more detail visible in the clouds on the planet.

Now, the Starfire's image was definitely brighter and whiter, as you would expect with almost twice the surface area to gather light. The Photon's image would have broken down at the magnification that the Starfire was using, and this is definitely one of the virtues of the apochromatic design--it tolerates high magnification much better. The Starfire was also color-free, while the Photon definitely a slight violet haze around Saturn. Still, the difference was not startling between the two, and I feel like my Photon Instruments was a real bargain.

I had a chance to look at Jupiter as well through both the Starfire and the Photon Instruments. Jupiter was still low in the sky, and seeing conditions necessarily limited what either refractor could do. Still, the Starfire's advantage in image detail (once you ignore a bit of color fringing) was not dramatic.

The next step is to install a Chromacor, and see how much better I can make this.

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