Tonight 7/22 between 9:50 pm and 10:30PM (04:50 and 05:30 UT 7/23) Mojo and I observed comet Linear S4 at a darker sky location near our home. The site was located on the saddle of Mount Tamalpais, our resident mountain at 2500 feet in elevation. The Azalea Hill parking area is at an elevation of 1017 feet, and it had a pretty nice 360 degree horizon, with the hill itself rising only 200 feet to the northwest. We drove 10 miles from home to escape a fierce brush fire on hill directly the east of us (with 15 MPH and higher westerly winds blowing black smoke our way).
We set up two telescopes, 10 inch F/7.3 Stardust and 6 inch F/5 Red Dwarf, and aimed at Antares. I thought something must be wrong with the collimatiuon of my bigger scope as the object in the eyepiece resembled Mercury near the horizon. A combination of chilly wind, warm mirrors and very bad seeing were the culprits. We did watch the Milky Way emerge, but it was not a classic dark sky Milky Way night. We could at least see all the little dipper stars, though.
We quickly found the comet, and began our project for the night, to watch the comet move. I sketched the comet at 20 minute intervals. Like the view two nights ago, the comet was situated next to a pretty asterism again. This time it was a "Y" shaped asterism of 4 stars which ranged from 9.5 to 10.46 in magnitude.
The views through both telescopes were similar. .86 degree or 52' using the 32mm Televue Plossl on the 10 incher for 58X and .79 degree or 47' using the12mm Vixen Lanthanum on the 6 incher for 63X. The first sketch was drawn at 9:50 and showed the comet about 10" north of the mag 9.5 star TYC 3441-437-1. Twenty minutes later the comet had moved south about 10' and was now directly above the star. Fifteen minutes later the comet had moved into the center of three stars - the middle of the little asterism. The last sketch showed the comet tail superimposed over two stars with the magnitudes 11.2 and 10.8. These sketches were made throught the 10 incher, though I looked through both scopes during all the intervals.
We had a few visitors. Three teenage boys drove up and were on their way to hike to the top of the hill. They took a look at the comet both before and after their moonless hike. Other than that, we were alone.
We were interested in sketching the movement and the size of the tail, and then measuring both once we returned home. We brought up the comet field on SkyMap Pro. We then placed the comet at 9:50 PM, and clicked off the minutes, watching the movement. The size of the comet was easy to measure using the distances between the stars and the correct field of view. I sketched the length of the comet tail all the way to a pair of double stars (mag 9.6 and 11) about a degree NE of the comet head. I also barely (but clearly) saw and sketched the ion tail on the eastern side of the comet tail. I'm sure if the seeing was better, and it was less windy, we would have seen more and longer tail.
We packed up and drove home. Only four cars had driven by during our hour and a half on Azalea Hill. We'll give this site another try on another night.