Thursday, December 25, 2003

Clear Skies! Finally!

I dragged my Photon Instruments 127mm refractor out this evening--stars, finally! The first look at Saturn was a bit disappointing--then I remembered that this is a big piece of glass, and it has to cool.

After about 30 minutes of excruciating cold weather (I am from California, remember), I was no longer seeing dramatic changes in image. With a 9mm eyepiece (127x), Cassini's Division was visible, although not spectacularly dark. For fractions of second, I could see a dark gray line all the way around the rings, at the ansae, and in front and behind the planet. At least at times, I could see a dark brown stripe in the planet's clouds. Turbulence seemed to be the limiting factor, not the optics. Going to a 6mm eyepiece (190x) did not improve the image in any obvious way. Trying to go above 190x was a waste of time because I am still struggling a little with balance issues on the mount.

Relative to the Ranger, I'm not sure that I am seeing any more detail (in spite of dramatically more aperture), although the image is quite impressively brighter (as well it should be--the Photon has more than three times the light gathering area).

Chromatic aberration? Yes. There is a definite purple fringe to Saturn's rings--something that I don't see in my reflector (of course--the virtue of reflectors), and somewhat more noticeable than in the Televue Ranger--but I haven't done a side-by-side comparison yet, so I can't give you anything more precise than "more." I will say that while I can see the purple fringing, I am not sure yet that I would call it objectionable. It is certainly time to try a Minus-Violet filter, and perhaps a Chromacor, to try either masking or correcting the aberration.

I looked at the Orion Nebula (M42) as well. I can't say that I saw a lot more through the Photon Instruments refractor than I can see with my Ranger, but then again, I was looking through the Ranger in the backyard, which is considerably darker than the front yard, where I had the Photon set up for observation.

One note about the mount: because I have it mounted on a Cave Optical equatorial mount intended for a reflector, the eyepiece on the Photon is down very low--and my neck feels it. The Photon needs an equatorial mount with enough tripod height adjustment to get the Photon up a couple of feet higher into the air.

I would say that the Cave Optical mount is certainly adequately steady for the Photon (unlike the 8" reflector that I usually have on it). No surprise; the 8" reflector weighs 31 pounds, and the Photon weighs 14 pounds.

I knew that I would need to replace the Cave Optical mount at some point, but perhaps sooner rather than later. I need to polish up the Cave Optical mount, and find someone who is restoring a Cave telescope who is willing to pay for a collector's item like this. Its value to a collector far exceeds its value to someone who needs a working equatorial mount.

One aspect of the Photon that was a little disappointing is the 2" diagonal that came with it. I'm not sure if perhaps I need to do some adjusting, but it did seem as though the diagonal was a bit loose in the focuser. This meant that even a little pressure on the diagonal caused significant image shift. I would really like to try using the Photon without the diagonal, but that would require me to lie supine to look through the eyepiece! Don't take this as a slam on the Photon Instruments scope; it isn't built like a Televue or an Astro-Physics, nor is it priced like them, either.

I will try to do a side-by-side comparison of the Photon and the Ranger tomorrow night (weather permitting). At least my initial impression is that the Photon, in spite of its clear advantage in aperture, doesn't do an obviously better job of revealing detail on Saturn than the Ranger. (Of course, I haven't had the chance to find out what really good seeing conditions might do for the Photon.)

The Ranger is cute and compact, and if it were not for the problem of an equatorial mount, the Ranger would be far more portable. Instead, the Ranger is only somewhat more portable. Still, the Photon will fit into my Malibu, and once I get a more modern mount, I should be able to move the whole collection of stuff to a dark sky site without any real struggle.

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