| Observer | Robert Leyland |
|---|---|
| Location | Novato CA |
| Start Date | 2000/11/2 Time: 2300 PST |
| End Date | 2000/11/3 Time: 0030 PST |
| Temp/Humid | 16°C 51% |
| Limiting Mag | 5+ (semi-rural skies) |
| Seeing | 8/10 |
| Transparency | 9/10 |
| Telescope | 8" F/6 Dobsonian |
| Eyepieces | 17mm Erfle, 21mm Pentax XL, 5.2mm Pentax XL |
My primary reason for going out was to check the collimation of my Dob. I recently flocked the interior of the tube with Edmunds flocking paper to improve contrast, and this would be only it's second night out. I had set it up for Halloween without doing much for collimation since the intended targets were all pretty bright objects.
My preliminary tests looked spot on, but I am concerned that the full aperture of the telescope is not being used. The optical path is closed (the optics are centered in the cheshire, and the auto-collimator blacks out properly), however the image doesn't appear centered in the secondary. I didn't tweak anything much as the basic checks seemed to be excellent. I think I may need to shim the focusser as eyepieces fit very loosely, and the focusser (a rack & pinion) is fairly stiff. Perhaps I could get a fine focusser to insert between the R&P and the eyepiece, and just tighten it all down.
As this was a short observing period I wanted to concentrate on just a few targets, leaving the planets for another night. Specifically I was looking at splitting the trapezium stars in M42, and then scan a few other targets.
M42 is one awesome piece of sky. The breadth, and depth of the nebula is fascinating, and its close proximity to a range of other objects is wonderful. Tonight the nebula appeared grey/green with tinges of reddish/purple near the extremities and tendrils of mist extending beyond my widest field of view. The trapezium is easy to see as four stars in a pattern similar to the southern cross. Using the 5.2mm EP I could make out a fifth star between the closest pair of stars in the diamond. This is the first time I have seen this, so I was quite pleased with the telescopes performance. With averted vision there seemed to be two further stars a little away from the trapezium proper.
This is just plain fun to find, it was easily naked eye visible, and quite straight forward to place in the 7x50 finder. Then the view explodes in the telescope. The 21mm Pentax gives a lovely widefield view of both clusters.
Head for Zeta Tauri, and just of the port bow is a faint fuzz patch known as the Crab Nebula. Tonight it was quite easy to find, and seemed larger than last year. Perhaps this is a reflection on improved observing skills, or the flocking improvements to the telescope. Tendrils from the edges of the nebula were noted, and the usual oval shape seemed more irregular.
Also a favourite view, tonight they were very nice. The telescope brings out dozens of additional stars beyond the 6 I can see directly, (maybe 7 or 8 with averted vision). The 4 brightest stars simply glowed and a faint touch nebulosity surrounded them. To check I looked at some of the brighter stars in Orion, and the Hyades, and then back to M45. The brightest stars have a glow around them, that is the result of light scattering in the optical path, but the stars in M45 are not bright enough to generate the size of "glow" that surrounds them. So I am fairly confident I was seeing nebulosity.
All in all a fun night, and great after the long rainy/cloudy period we've had recently.