Wednesday, June 6, 2012

Venus transit 2012

Had a fantastic transit experience at Charlottenlund Fort, Copenhagen! Will be posting some pictures here as they are processed - stay tuned. Become a follower of this blog to get updates automatically.

Sun had just cleared clouds at horizon.
I'm at work right now and better get back to it!!
Home from work, get Astrid in kindergarten, go to playground, make dinner, wash floor. I am pretty tired now - I only got two hours of sleep in the past 36 hours. I just got to try and process some data from my new solar telescope. I only got time to try it ONCE before the Venus transit. Just did some basic processing; see result below (click here for full resolution). I am HAPPY! Will play more tomorrow, but now I'll go to sleep with a smile.
Venus with a small protuberance - just before the show ended.
Had a terrible headache yesterday, which I often do after going all-out for some crazy event. Today I feel fine and I tried to see if the refraction of light in Venus' atmosphere was captured in some of my images. The setup I am using with a H-alpha filter is not optimal for this purpose - it transmits a very small fraction of the Sun's light, forcing me to use long exposure times which in turn will be more susceptible to blurring from our own atmosphere. I think that a white light filter would have been better. Anyway, between third and fourth contact I tried shooting at several (longer) exposure times:
Changing the exposure time to catch a glimpse of sunlight refracted in the atmosphere of Venus
Looking closely at the image with the longest exposure time I can just barely make out a faint arc of light that follows Venus' limb! It is visible for roughly 30 degrees across the north pole of the planet. I tried manually selecting the best images in the sequence, then stacking and tweaking curves. I also applied a DDP filter and unsharp mask to enhance the arc further - see the result below.
Processed image revealing sunlight refracted in the atmosphere of Venus.
This sighting is nowhere near the quality obtained by others in 2004 - I think this is due to the low altitude of Venus as seen from this part of the world. For the ultimate view of this effect check out this image from the Hinode spacecraft!
Working through all the images I took on June 6th I have now completed basic processing of all the image sequences - 27GB in total, consisting of 24410 individual images. 'Basic processing' means using Registax v.5 to sort, align and stack with a focus on the disc of Venus. The Venusian disc will then be sharply defined, but orbital motion of Venus will cause a slight blurring of the Sun. I therefore do a second processing run using AviStack v.2 and focussing on the solar surface while ignoring Venus. I typically stack 60 images since this (in my experience) is a good compromise between using only the sharpest images and keeping the noise level down in the final result. Each stacked image is sharpened using wavelets, then the two are combined in Photoshop to get both Venus and the solar surface sharply defined. Final touches include colorizing the image and tweaking of levels and curves. My latest result is shown below - taken at precisely the moment of third contact (full resolution is HERE). The resolution, contrast and colors are better than on the previous close-up view shown above - maybe because the first one was made in a zombified state of fatigue..!?
Venus transit - moment of third contact.

1 comment:

  1. Fantastiske billeder! Imponerende databehandling - jeg haaber du bruger scripts ;-) Glæder mig til du samler de færdige billeder i en film.
    Michael Cramer