I had travelled solo to the Carr Astronomical Observatory to video record an asteroid occultation. I was looking forward to a successful event using Denis's kit and the CAO computer controlled mount. The weather looked promising. And I gave myself lots of time to prep.
The occultation of the 11.6 magnitude star (TYC 0758-00544-1u) by asteroid (510) Mabella happened. But I'm not sure if I got it... I reviewed the video but still wasn't sure. I'll have to transfer it from the camcorder and look at it on a big screen.
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During set-up, I saw that I was getting a lot of electrical interference using my home-grown 120-12 volt adapter. I hijacked the battery from the lawn mower and MacGyvered the wires in place.
9:56 PM. I had everything ready to go. I was just waiting.
Checked conditions with the SQM. 19.93. 8 degrees.
I didn't want to use such a high integration setting but I need to use 4 to draw out the star. Similarly, I needed max gain and hi gamma. Ugh. The video image was grainy and noisy.
10:14. The star was supposed to go out (or rather, drop 4 magnitudes) for approx. 2 seconds. I watched the event live. I don't think I saw anything. But then the seeing was borderline with the target star... It flickered in and out.
10:23. I watched video screen on camera. I couldn't see it go out. I'll definitely need a big monitor. And to go through it frame by frame.
Or, is it simply a miss? The rank was low: 33.
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Cranked up the integration and gain and recorded for a while longer. If the asteroid was in fact magnitude 15.8, maybe I could coax it out!
But I realised later, my math was off. If I had been recording through the C14, with a mag 14 or 15 limit, and then going 2 deeper with video intergration, sure, I might have been able to see it.
The limited magnitude of the TV 101, I calculate to be 12.7.
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I don't know why, exactly, I decided to do this but I removed the focal reducer from the camera for this occultation. I just thought I'd have tons of light given the dark location, 11 km from the centreline. But should I have kept it in? Particularly given the small aperture of the TV101? I didn't think I would need it with an f/5 'scope. Did the Moon lighting interfere? Kinda kicking myself now...
I tried to use the Vixen flip mirror as well but it added too much length to the light path, combined with extension tube. That just slowed down focusing.
Saturday, May 07, 2011
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