Fun with a Fox Cub

1998 Apr 4

The San Jose Astronomical Association annual swap meet was April 4, 1998. I picked up an exquisite small optical tube assembly -- a 55 mm f/8 Vixen fluorite. On April 7, I set it up on a Vixen altazimuth mount, and tried it out in my yard here in Palo Alto. Intermittent high cirrus and a ten-day-old Moon made conditions less than perfect for faint fuzzies, but the seeing was pretty good.

I started a Messier survey the way I usually do, by chasing after objects disappearing into southwestern twilight. I used a 12 mm Brandon eyepiece, for 37x. Though even 1.5 mm Exit pupil was insufficient to darken the background sky completely, nevertheless I picked out M79 in Lepus with averted vision, as an indistinct spot. I moved north to M42 and M43, which were easy but not very extended against the twilight haze. Even at that low magnification, the Trapezium showed four stars. M78 was another faint target, also detectable with averted vision, and then I moved on to the galactic clusters east and southeast of Orion. (I did not stop to try for the Horsehead Nebula...) Only M41 and M48 could be called resolved, though M46, M47, M50 and M93 all showed the granular texture of incipient resolution. Darker sky and less haze would have improved things.

By that time, the telescope had settled in, so I turned to the Moon and increased magnification. I put in an old 5 mm Celestron Orthoscopic, observed briefly, then added a 2x Celestron Ultima Barlow. This combination of eyepiece and Barlow had a bit of lateral color, visible at the edges of the field, but on inspecting the Moon's bright, western limb where it ran square through the center of the field, I could find no trace of chromatic aberration. The view of the Moon was impressive for only 55 mm, though at 176x, seeing disturbance was noticeable. I could see interior detail in Gassendi -- terracing or an interior ring on the (selenographic) east side. Rupes Liebig was easy. To the north, Sinus Iridium was well illuminated, as were the wrinkle ridges to its south.

I star-tested with the same magnification, on Sirius. Again, seeing was not quite steady, but I saw no trace of chromatic or spherical aberration: Even the out-of-focus star image was color-free. Clouds terminated my session before I could do any more viewing.

This tiny telecope promises quite a lot of fun. I think I am going to have to name the little 55 mm Vixen fluorite the Fox Cub, just because it is so cute, clever, and playful.

Jay Reynolds Freeman; 1998 Apr 8