Saturday, May 07, 2011

occultation happened (Blue Mountains)

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.


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.


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.


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.

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