2009/07/01

A day of sun & stars

Yesterday was a fruitful day for me. I had solar observation with my students and stargazing at night. After the lunch, I found that it was possible to do some solar observations, although there were some clouds in the sky. I called up a few students to help me to bring the equipment to the school roof. I used the Thousand Oaks Optical Solar Filter Type 2+ and C5.

There was no sunspot at all. The image was flat visually as the filter was basically light reduction. After some visual observations, I tried to take some photos with my D80. I found that the image was so big that it was hard to be captured by the sensors.

However, I was in rush to leave the school. I have no time to try out the reducer. Anyway the photo was something like this. Before the arrival of my Lunt’s LS35TDX, I will use C5 and Thousand Oaks for most of the solar observations. By all means it is good for eclipse & planetary transitions.
After having the dinner and disciplined my daughter, I went out at about 9:30pm. When I arrived Pak Tam Chung, the half moon was pasted the zenith. Saturn was almost set. I didn’t setup my stuff at once, but browsed around. A friend of mind got a new toy, 110ED. He was busy testing his toy with other stargazers. Their focus was the moon. I shared with him my Sky-Watcher’s 2mm and 5mm eyepieces. These two eyepieces pushed the 110ED to 770/2= 385X and 770/5 = 154X respectively. The 2mm eyepiece definitely drove the scope beyond its maximum practical magnification. (i.e. roughly 110x0.04x50 = 220X). In term of visual, the performance is acceptable.
I just got a Porta mount and Equinox 80ED last night. It was because I need to spare my boot to carry stroller next day. Well I star tested by Equinox again. Both the diffraction spot inside focus and outside focus were round, concentric and symmetrical. The bright star was pin-sharp at the focus. Actually I just repeated what Mirror God told me last time. However this time I examined the diffraction spots carefully. One funny thing I found was that when I used a 2mm eyepiece on my 80ED, the image of the bright star cannot be focused to a spot but a diffraction spot with several Newton’s rings. Which means the image of a bright star become a quite large diffraction spot. The diffraction spot was still round and concentric. This reflected the Equinox is a good telescope. Lucky me! I will try to do the same test on other scopes and see if this phenomenon is general. It would be interesting that for those known famous telescope, if one pushes the magnification beyond its maximum practical magnification, what would be seen for the bright star image visually.

2 comments:

  1. Glad to see that the C5 is receiving sunshine!

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  2. Yes! I use C5 for lunar & solar observations!

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