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Comet 17P Holmes, October 29th, 2007

Original drawing made using lead pencil on white paper:

Same drawing reversed:

Comet 17P Holmes, October 29th, 2007, 3:30 - 4:30 UT. Clear skies with the limiting magnitude around 4.0 with the light of the Moon a couple days past full. Seeing 5 - 6 (fair - good).

TMB Optical 175mm f/8 refractor on a homemade Dobsonian-style mount. Magnification 88x-156x, field of view approximately .65 degrees. I estimated the comet to be around magnitude 2.3.

The comet appeared noticeably larger through this telescope than when I observed it on October 26th, 2007. Also, while the color of the pseudo-nucleus and inner coma or condensation still appeared light yellow, the outer coma or bright envelope appeared green at low power and blue-green at higher power.

In addition at low power the outside edge of the bright envelope did appear to have somewhat of an annular look to it but this was not as noticeable at higher power. The outer coma showed some variation in tone. There were two stars visible in the outer coma. By comparison the pseudo-nucleus appeared more diffuse.

I was curious if I could see more clearly the fainter envelope around the outer coma that I noticed last Thursday night. The envelope on the right hand side of the coma had a smooth round appearance to it and reminded me of a parabolic hood. I was able to trace it as it arced around the top and bottom of the comet. However as I studied the as it came around the bottom of the coma and up towards the left-hand side it no longer appeared smooth and round. Rather my eye kept detecting what looked like striations of lighter material coming off of the fainter envelope.

To make sure this wasn't an optical illusion I spent a long period of time trying magnifications from 87x to 156x using the TMB Super Monocentric eyepieces and different filters, as well as techniques I use to enhance subtle detail in deep-sky objects. This included taking long deep, slow breaths to increase the oxygen level to the brain, gently tapping the telescope tube, and moving the comet outside of the field of view and letting in drift back in while determining when there was a change in the sky background. To help reduce stray light when looking for fine detail I pulled the jacket hood up over the top and side of my head and cupped my hand around my observing eye and eyepiece.

After a while I was able to determine that some of these striations of lighter material were coming off of the bottom left hand side of the fainter envelope at a 45 angle, as well as straight back from the fainter envelope. There were some of these striations of lighter material coming off on the upper right hand side but they were not at the same angle or as prominent. It appears this lighter striations were the beginning of a tail. A few days after my observation I learned that two other observers obtained photographs of the tail showing similar detail.