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Tonight was an interesting night.
I set out to determine the quality of my telescope and it's mirrors. I took the scope outside at 4:30pm and let it cool until 7:30pm so that temperature
differences
wouldn't distort the images. I have a book called "Star Testing Astronomical Telescopes" that describes how to do a star test. A star test involves using high power (200x in my case) on a fairly bright star. You look at the image produced when focused and when inside and outside of focus. From this simple test you can determine a surprising amount of information about the optical system of the telescope. After testing, I believe my main mirror suffers slightly from spherical aberration. Other than that, the mirrors seems to be fine. Most reflecting telescopes are undercorrected, resulting in spherical aberration so I'm not suprised that mine does. I also performed a Ronchi test with a grating I purchased. The lines were very straight and also seem to indicate that the mirror does not have any major problems.
After testing, I decided to actually do a little observing. It was a cold night, 18o F. with a South wind of 13mph which made things feel a little colder. The wind chill was -6o F.
I definately should have put boots on instead of just wearing tennis shoes! After a half hour, my toes got a little cold. I first looked at Jupiter. All four moons were visible, two on each side. I could see the North band distinctly and the South band was also visible. I believe there was a dark spot on the South-East edge of the planet that I thought might be the Great Red Spot. Unfortunately I haven't been able to confirm that yet.
I next moved on to Saturn and was pleased to bag my first observation of one of Saturn's moons. Rhea was just South-West of the beautiful planet. The
Sky - Pocket Edition
running on my Compaq Aero PDA helped identify what moon I was looking at. The other moons were not visible. I was using the 4.8mm Nagler giving a magnification of 191x. The rings looked great. I thought I could see a gap in the middle of the ring but it's tough to say for sure.
M42 in Orion was my next target. I decided to see how many stars of the Trapezium were visible. The Trapezium are a group of stars inside the heart of
the Orion Nebula (M42). I was able to see 4 stars easily. There are 6 but I was only able to see 4. I think the problem lies in not being able to focus exactly, making it difficult to see
faint detail.
Before deciding to head in to the warm house, I turned the scope to Venus, now low in the Western sky. The atmosphere made the image boil a little but
it was very easy to
see the phase. Again, The Sky - Pocket Edition helped verify what I saw, which was that half of the planet was lit, looking very much like a half-moon only smaller. The Sky said the phase was 50.7% and gave it's magnitude as -4.4, a very bright object indeed.
It was certainly a good evening. I feel good about the mirror and am ready to take steps to improve the telescope. I will order a new focuser this week
from Jims Mobile Inc. (JMI). I plan on getting a 2"
focuser with a dual speed manual control along with a
focusing motor. This should help me achieve fine focus which will improve the view tremendously. The focuser I have just doesn't cut it. The only scary part is that I'll have to drill new holes for the screws and widen the opening to the secondary. That should be interesting. The other plan I have is to construct an observing chair. It will be nice to be able to have a chair that can be adjusted to any height, allowing easy viewing at the eyepiece. Right now, I sometimes have to get into strange stooping positions to view certain parts of the sky. The chair will really help.
Until next time, clear skies!
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