6th February 2007
One of the few good nights available to me for imaging Saturn this apparition.
As usual I used my 222mm F8 Newtonian telescope, in combination with a 2x Barlow extended by 75mm. This gives me an effective focal ratio of about F30, about 6.6 metres focal length.
The image of Saturn projected onto the webcam sensor is tiny, even at this focal length, just a few millimetres across. Fortunately webcams have tiny sensors, which is what makes them perfect for planetary imaging.
Three images were taken...
The first image was taken with a standard colour ToUcam 840. Approx 4500 frames from two videos were processed and about 3000 were stacked using Registax 4. A Baader UV-IR block filter was also used for this image.
The second image was taken using a modified Philips Vesta 675 webcam, with a monocrome CCD. The camera was fitted with a near Infra-red pass filter (685nm+). Again this is 4500 frames processed and approximately 3000 stacked.
The details for the third image are the same as for the second except the image uses a deep IR filter, only passing IR from 742nm and longer wavelength. The webcam is sensitive to about 1000nm.
The left hand column shows the images slightly enlarged (120%) and processed differently to give a more "natural look". The left hand column doesn't show the 742nm+ image as the noise in the image was greater than the other two due to the smaller number of photons hitting the sensor on the filtered image. The Right hand column is processed harder to try to bring out more detail
Notice how the inner C (or Crepe) ring is much brighter in the 685nm+ image when compared to the RGB and the deeper IR 742nm+ images.
|