In the "What have you been up to lately?" thread, I previously mentioned that I had removed the lithium grease from the bearing surfaces that made them too slippery and replaced it with a stickier dry lube that gives me better stiction on the six inch diameter friction push bearings leading to smoother push tracking of targets.
The 1/2" machine screws arrived and $%&#!!! they are American UNC threads not BSW's. I built my mount in the 1970's all tapped with BSW. Half inch BSW and UNC threads have the same pitch, 13 TPI but the thread angle on a UNC is 60 degrees, while a BSW is 55° thread angle. A 55 degree BSW male can screw into a 60 degree UNC female but not the other way around. I should be able to run a 1/2" BSW die over the UNC male thread to convert them. Meantime, I cleaned up the exisiting rust using steel brushes on my drill and reassembled the mount.
The weather report indicated perfectly clear skies until 11pm, it's mid-summer and 11pm is only 1
The scope
During nautical twilight, I observed Jupiter. I used my recently acquired Pentax XF 6.5-19mm zoom. Interesting. When used during the day with a small refractor, the eyepiece is very sensitive to the eye being on the optical axis. On the 6" f7 reflector, it was much more forgiving. I don't have an explanation for this and will need to recheck my impressions. The seeing was very good and I had no trouble verifying that the eyepiece is sharp throughout the range from 19mm(55x) to 6.5 (161x) with nice N&S equatorial belt details and the Great Red Spot..ok the Pale Salmon Spot visible.
I removed the zoom and inserted my Denkmeier D21 [ 50x, 1.3 deg, 3mm exit pupil] and went inside for another 30mins to wait for astronomical twilight. I turned off the house white lighting and turned on the red lighting (silent running) to dark adapt my eyes. I went out at 11:00UT.
It didn't take long to star hop to the comet. It was conveniently located immediately adjacent to the Hyades.
WOW. I was suddenly very glad I had dark adapted inside. The sky transparency was exceptional and the background sky was very inky black. What a pity it was going to be short lived. The
The
High cloud was expected within 30 mins. By the time I started doing out of focus comparisons, the high cloud would be changing relative magnitudes compromising brightness estimates so, no brightness estimates were made.
Here is a sketch made with Photoshop of my visual impressions of 144P.
Right on cue, the clouds started appearing in the west. Jupiter, by now much lower in the sky suddenly went diffuse an before long, I noticed the field of the comet in Taurus (low in the north) fall away and lose intensity. Orion, higher in the sky, was still clear. With the high transparency, I swung up to the Great Nebula in Orion. Ok, wow. It is a good transparency night. In the brightest side wings of the nebula I could just detect the faintest hint of pink and the loop faintly extended out and all but closed.
Cloud approaching, head south. I swung over to Eta Carina and again marvelled at the inky black in the dust lanes contrasting with the gorgeous detail in the nebula and variety of star colours in the field stars.
Time for one more. I swung up to the Large Magellanic Cloud. Rather than heading straight for the Tarantula, I took a star walk along the length of the galaxy. Telescopically, the
A very enjoyable if too short a night.
Joe
