Horrible image quality because of the poor seeing, short movies, warm telescope, low altitude etc, but the idea is there.
For the believers: the Great Red Spot is on the lower right.
Fist time I tried my UV/IR blockign filter and Televue 2.4x Powermate (very heavy quality).
Images taken on July 15th 2007, at 20h59 and 21h19 UT. The 20 minutes between the recordings should be good for 12 degrees of rotation.
As animated GIF:
Simulation of the GRS position at that time:
Since the opportunities to see the GRS in The Netherlands are rare, I wanted to make sure the transit predictions are correct. Also I wanted to have a tool that gives the right transittimes for older dates (for transit example see first image below) . I could not find something that could reliably do both. Even the old Hallo Northern Sky gave confusing results.
This file contains the final result of this quest: an entry for each day indicating the times at which the GRS transits the central meridian of Jupiter from 1-1-1963 to 31-12-2007.
The times have been calculated using the formulae of Jean Meeus (Astronomical Algorithms, ISBN 0943396611).
The basic idea behind the calculations, is that Jupiter rotates about 870 degrees per day. The GRS however drifts slowly on the “surface” of Jupiter. Therefore you also need to know the longitude of GRS on Jupiter over the years. The following figure shows the whereabouts of GRS during the last 45 years (numbers put in Matlab from www.jupos.org):
So, combining teh knowledge of the rotational phase of Jupiter at the start of the day, rotational speed and the longitude of GRS, the transits times for that day can be calculated. For example: a phot of April 16, 2004, 2:30 UT.
This date, Jupiter starts at about zero degrees (pure coincidence) and the GRS longitude is 90 degrees. It takes Jupiter 90/870=0.1 days=2.5 hours to rotate to 90 degrees. Therefore the first transit can be expected at 2h30. It takes Jupiter about 10 hours to make another rotation. So the other transits can roughly be expected at 12h30 and 22h30.
The following shows this idea graphically (exact transits are 02:35 12:30 22:26).
A photo taken that day:
And now we have all the info we need, we can also use Matlab to generate a simulation of the position of GRS:
Using a solar filter that attenuates the suns light about 100,000 times, it is possible to safely watch the sun directly through a telescope.
From a 4000 frame movie with good seeing (best so far this year).
Sharpening was done using Wiener deconvolution in Matlab with a PSF simulated in Aberrator:
Very bright, but quite featureless (unless imaged in UV).
This is the red channel from a stack of Venus images, which is the sharpest since red light suffers less from bad seeing.
14 arc seconds diameter
magnitude -4
phase: 77%
In an ideal world, a 512 pixel wide Saturn image would look like this:
But if an 8 inch telescope (like C8) would be used in perfect seeing, the resolution would be limited to (simulated with Aberrator):
For the 90 mm ETX90 it would look like:
A high pressure zone, little jetstream… seems like the perfect night. After thorough collimation and focussing the result still was not 100%: March 11th, 2300h.
Using my hoem grown registration/stacking in MatLab:
And another attempt at processing in Registax 4:
And another in Registax using all 4 movies made:
After the rain was gone, the sky was very clear. I was really pleased with the sight through the telescope: a soft “salmon red” colored moon with a white rim, embedded in bright white sparkling stars.
Taken at 00h29m25s CET, note the magnitude 10 star visible in the lower right.
ISO800, 10s, roughly f/10 (N6+2x Barlow)
This exposure time makes clear that the eclipsed moon is roughly 16000 times dimmer than the normal full moon. (Based on the “sunny 16″ rule: shutter time is equal to iso number @ f/16 for sun lit object, so at iso800 one would expect about 1/1600 second shutter time for f/10).
And a wider field of view, including the stars (added from HNSky) as they were visible through the telescope:
Just managed to het this photo before the clouds came in which made it a “more than total” eclipse of the moon.
3/3/2007 23:20:08 CET
The exact moment in HNSky:
