May 16, 2009: Henry Coe, AP Gran Turismo

Jay Reynolds Freeman

I took my Astro-Physics Gran Turismo (130 mm f/6.3 Christen triplet) to the outer parking lot of Henry Coe State Park, near Morgan Hill, California, on the evening of May 16, 2009, with some eyepieces to test but no other particular plans. The transparency was pretty good, and the seeing was near-excellent at times: High magnification showed the Airy disc and a ring or two continuously, with very little motion.

I finished a comparison of six eyepieces of 24 or 25 mm focal length; as I write these words the detailed results are on the "Astronomy" page of my web site, which is http://web.mac.com/Jay_Reynolds_Freeman. The summary is that the 24 Panoptic delivered the widest apparent field and had no visible aberration even at the edge of the field -- but was sufficiently expensive that the used 24 mm University Optics Konig might be a better choice, the Vixen Zoom Lanthanum 8-24 mm is most useful -- because it zooms, and the 24 mm Brandon and the old University Optics 25 mm Abbe orthoscopic appear to scatter the least light -- probably because they have old-style magnesium fluoride coatings.

I also had two new eyepieces of a more modern design to try; they are unmarked as to brand or manufacturer, but I believe are well-done copies of the "planetary" eyepiece design by the late Thomas M. Back. I learned after I had ordered them that there is perhaps some controversy about rights to produce the design, and I would certainly have researched the issue thoroughly if I had known that beforehand. Anyway, what I have is a 3.2 mm and a 9 mm "Wide Angle Planetary" from Teton Telescope. They both worked well in the Gran Turismo. The 3.2 gave 256x, and it is a testimony to the seeing that Saturn was rock solid at that magnification, and the long eye relief and 58 degree apparent field of view were welcome. The 9 gave 91x, a most useful magnification for galaxy gazing with this instrument, but its actual field was less than half that of my Vixen 8-24 mm Zoom Lanthanum when zoomed to its longest focal length, so the Zoom is rather more useful.

I also briefly borrowed a Tele Vue 3-6 mm Zoom Nagler from another observer. As it happened, I had just bought one of these through AstroMart, on the basis of reviews and personal recommendations, but had not yet taken delivery. I was almost reluctant to try the borrowed eyepiece, on the theory that if it had been a mistake to get one I wanted to put off finding out about it for as long as possible, but I relented. As far as I could tell in the few minutes I had it, it worked fine with the Gran Turismo.

Saturn was the showpiece of the night, a very solid and pretty view at 256x showing two dusky belts on the planet, a nice shallow-angle view of the rings, and several moons. I had had a similar view the night before through a friend's AP 155 f/7, in perhaps a tad softer seeing. The aperture advantage of the larger instrument was noticeable, if my memory is correct, but it was nice to know that my 130 was nipping at the heels of its big brother.

Also at 256x, I logged excellent and solid splits of epsilon Boo and epsilon Lyr. The latter was only ten degrees or so above the hill line when I split it, again a testimonial to fine seeing. M13 looked very good at this magnification as well -- I don't usually see much resolution of M13 with this small an aperture, but the high magnification was bringing out a grainy appearance very nicely. M57 did not take so well to high magnification, it was better at 91x.

NGC 4565 -- my favorite external galaxy -- is always a treat. I looked at it for a long time at 91x. The sharp edge of the dark lane, the central lens, and the star-like nucleus were all easy, and I could occasionally hold the dimmer side of the galaxy, across the dark lane, without averted vision. With averted vision I could trace the galaxy across about half the width of the field. M104 was similar but not so dramatic. Planetary nebula NGC 4361, near the top of the quadrilateral of Corvus, was notably brighter near the center, and easily showed its central star.

I closed the evening with a rather casual look at M65 / M66 / NGC 3628, under the hindquarters of Leo, and then a romp through the Markarian's chain area of Virgo. I am very pleased with the Gran Turismo; it is fast becoming my favorite easily portable telescope.

-- Jay Reynolds Freeman, Deep-Sky Weasel