It's been a long while since I did any imaging of the planet Venus. But now I have a Baader U-Filter to try out, to see if any detail is possible in the clouds of Venus.
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Venus 6th February 2007
An early attempt in the season at imaging Venus in UV light.
The seeing was terrible and many frames were completely unusable. This is not surprising as Venus was quite low in the South Western sky. However... success! there is an obvious cloud band visible.
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This is te original image after stacking. As you can see there is a secondary image to the lower right of the UV image. I am pretty convinced that this is an IR leak from the Baader Venus filter. This is a little disappointing as it will affect the final image. I had to use the clone tool in Serif PhotoPlus to remove the "ghost" image. I understand that Baader have withdrawn this filter now because of the IR leak.
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20th March.
Seeing terrible.
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26th March
seeing terrible
again!
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4th April
Slightly better seeing
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5th April
Seeing improved enough to see some faint cloud detail
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| Just in case you were wondering: "Seeing" is what astronomers call the wobble in the air. If you look over a hot surface on a sunny day you will see the air wobble and things in the distance will appear fuzzy and distorted. When looking through a telescope that effect is magnified. The twinkling of stars is caused by the movement of air acting as a weak and ever moving lens, distorting the image in the telescope. So bad seeing is when stars twinkle a lot and telescopic images lack detail. Good seeing results in steady stars and good telescopic images. Sadly, in the UK very good seeing is quite rare, maybe seen once or twice a year. If a planet is low in the sky seeing is generally worse, just because you are looking through more unsteady air. At shorter (bluer) wavelegths of light - such as UV (Ultra-violet) bad seeing is at it's worst. That makes Venus' cloud tops hard to image. Because it is usually close to the sun in the sky, low in a evening or morning and best imaged in UV. |
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April 6th
Seeing Very Bad!
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April 16th
Still Bad seeing but imaged at F20 in UV and some hint of Cloud detail is seen.
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April 16th (again)
This time imaging in IR light (807nm+). With much more light available and the longer wavelength the seeing is better and I could image at F30 again.
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Venus 2nd May 2007
These images were taken in the best seeing I have had so far this year.
The imager was a ToUcam 740 with the CCD replaced by a monochrome CCD and RAW modified. The telescope is a 222mm F8 Newtonian - Barlowed to F30.
For once the UV image shows clear detail in the clouds, but I was also surprised to see cloud detail in the IR image. The colours are artificial, added to bring out the detail in the combined image - and because it looks nice
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Baader U-filter
"Venus Filter"
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IR 870nm+ Pass filter
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UV - IR images combined
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