Telescope Reviews: ALERT - Comet 17/P Holmes in mega outburst

After a nice walk home from work, I was good and dark adapted, so I got the 100mm f/6 refractor back out again. The comet was still quite an easy naked-eye object, again fairly comparable to the brightness of Algol (perhaps 2.6). It is non-stellar but still fairly small. In the refractor at 25x, it was a beautiful sight, showing the usual brighter inner coma and faint outer halo. I put in the Lumicon Deep-sky filter and the view improved noticeably, with the halo now standing out quite well and the overall view showing a very nice level of contrast. Doing transit timings gave a diameter of about 37 arc minutes for the outer halo and 13.2 arc minutes for the inner shell. In fact, there were hints of radial details in the halo, so I kicked up the power to 43x (still with the Deep-sky filter). The outer halo showed a rather ragged edge with several broad faint diffuse radial filaments noted mainly in the southern and western portions. The brightest one was pointing nearly south from the inner coma and was probably the longest. The others were noticeably fainter, with perhaps two or three visible with difficulty and perhaps a few others suspected. The inner coma showed a little of the "annular effect" illusion at low power, but mainly along the eastern and northern sides. The southern and western sides of the inner coma were noticeably more diffuse and a little irregular. The color was very difficult to discern, but may have been off-white to maybe slightly yellowish. The magnitude 7.6 star HD 23104 was well within the inner coma perhaps two or three arc minutes south-southwest of the nuclear condensation. The middle of the inner coma held the large central brightening which is losing much of its earlier fan shape. Indeed, I had difficulty seeing anything of the actual nuclear condensation other than as small slightly brighter spot near the edge of the central brightening and off-set a little distance from the geometric center of the coma. I kept increasing the power in an attempt to see the nuclear condensation, but below 150x, I could only see a tiny diffuse spot. Finally, at 188x, I could just barely catch a glimpse of a small stellar dot in the middle of the smaller brightening, and I would estimate that this pseudonucleus was definitely fainter than 12th magnitude and probably closer to 13th. Thus, the condensation has faded significantly over the past few days, and may soon require the additional aperture of my NexStar 9.25 in order to be seen. At high power, I could catch some vague variations in brightness in the large central region of the inner coma, possibly the remnants of broad radial bands running away from the nuclear condensation. Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info