Stephenville Symbols - Full David Caron Video Leaked!!, page 17

Star Scintillation - My Sirius Experiment

For those who haven't seen star scintillation and for those who'd like to know how the Stevenville Lights were probably created, maybe this will help.

The following videos were made with a Philips SPC900NC webcam attached to a 10" Meade LX200 telescope. Here's a picture of my setup.

Lx200 Telescope

The scope has f10 optics and was fitted with an f6.3 focal reducer to reduce power and help me to keep the star on the CCD chip.

The videos were shot from indoors through a double-glazed window (I wasn't prepared to set up and align the scope outdoors for something like this). The scope was very roughly AltAz aligned and self driven but it wasn't accurate enough to prevent drift. Drift was corrected manually using the handset seen in the photo. The camera is actually a Philips ToUCamPro 840 which has been converted to the latest SPC900NC spec using an EEPROM upgrade. These cameras are identical internally but by digicam standards are pretty basic. They don't have the fancy exposure routines available to the Stevenville videographer.

The video files were generated using the Philips bundled software. These were then converted to Mpeg to reduce upload size. The idea was to capture a movie of the star Sirius to show the scintillation phenomenon and demonstrate how the Stevenville Lights video could have been created.

The first file shows Sirius as seen by the CCD chip at the scope's prime focus. You'll notice the large image size. This is due to the effective magnification (about 250x), the star's great brightness, atmospheric turbulence, CCD saturation and not least because it was shot through two layers of window glass. The framerate was set to 15 frames/second, but a large number were dropped by the capture software. I guess it was closer to 10fps in reality. Anyway, I believe the results demonstrate scintillation quite well even though the spectral colors are seen only around the edge of the saturated star image. Taken at low power and aperture (eg. a camcorder) the image would be less saturated and would display the spectral colors throughout the disc.

Video 1

In the second video, I introduced some wobble by deflecting the scope. It's a very heavy instrument on a robust stand, so I had to bump it with my hand to induce some vibration. I tried to vary this by thumping the rig at different places and directions, but the natural tendency of the scope is to produce a consistant vibrational pattern. Anyway, I think the results support the idea that the Stevenville lights were created by a similar arrangement. I suspect the shapes observed are the result of cameraman's heartbeat. This was probably unintentional (?) but one wonders why the special exposure nightFX was used. The JVC camcorder has a much more sophisticated exposure control, so individual exposures show colored spectral points rather than the blurs I managed. Point lights were recorded because of the much lower magnification and aperture.

Video 2

The third video was made to show the effect of defocussing a bright point source. These images are frequently referred to as Airy Discs, but they are not. The defocussed images are clearly analogus to the 'UFOs' promoted by David Serada in the so-called 'NASA Tether Incident'. Those are actually the defocussed discs of brightly illuminated particles close to the camera. The notched appearance of Serada's UFOs is most likely the result of a mirror mounting within the telephoto lens. I believe the banding seen in my images is a diffraction pattern associated with the large parabolic mirror in the scope.

Video 3

If anybody has a question on these I'll do my best to answer.

WG3