Planet observation with
methane band filter

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Projectmanager/Author: Silvia Kowollik
Page 3
Update 23.06.2008

On 22.06.2008 the next test with the methanebandfilter at the 80 cm mirror telescope of the observatory and the camera DMK 21AF04.AS was done. The sky was brightend by the light of the full Moon and the seeing unfortunally was high frequency disturbed. 

  Between 01:50 and 01:54 Uhr MESZ (23:50 and 23:54 UT) a colour image of Jupiter was captured with an IR-GB Filterset (Astronomik) at a focal length of 8 meter. The seeing forced an exposure time of 1/1000 seconds each single frame.

With this short exposure time the camera reaches its limit with colour filters. So the colour image is very noisy.

     
  With the programm Winjupos a map projektion of the colour Jupiter was created. The position of all 4 hurricanes was measured in System II:

- GRS:         124 West
- "Red Jr.":  132 West
- No. 3:         140 West
- No. 4:         193 West

     
After the capturing of the IR-GB images the filterwheel was opend and the filters were exchanged with UV-Filter (Schuler, 340 - 400 nm) and the methanebandfilter (Asahi Spectra, 890 nm, FWHM = 12 nm). A test with these filters should show whether all 4 hurricanes on Jupiter can be proven.

Only regions, which appear bright in the methane range and in the UV dark, exceed over the normal cloud top of Jupiter.
     
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The methanebandfilter is a strong filter - it swallows much light. Therefore  2.000 singleframes with 1/8 second exposure time where captured between 02:14 and 02:23  MESZ (00:14  and 00:23 UT).

The processed image of Jupiter with methanebandfilter shows at the left edge the GRS as huge, bright spot. Right above "Red Jr." is seen as further spot.

On the same jovian latitude as the GRS one recognizes also the new, third red hurricane as a weak spot. This hurricane was build in the past month and approaches to the GRS at present. It will probably collide in few weeks with the GRS. Whether it dissolves thereby, or is diverted by the GRS to another latitude, is one part of the present jovian observation.

Even a fourth hurricane seems to form at present. On the right side of the planet disc a fourth weak spot in the SEB one can see. At this position something likewise exceeds  the normal cloud top.

     
  With the programm Winjupos a map projektion of the methanebandfiltered Jupiter also was created. The position of all 4 hurricanes was measured in System II:

- GRS:         125 West
- "Red Jr.":  133 West
- No. 3:         139 West
- No. 4:         194 West

These positions agree very good within the margins of error with the positions within the visual range.

     
  The UV filter has a larger half width - it lets 4 times as much light through as the methane band filter. Therefore the singleframes with the UV filter could be captured with an exposure time of 1/30 second.

The images where captured between 02:25 and 02:28 MESZ (00:25 and 00:28 UT).

During this short time Jupiter rotates only a few arc seconds - details in its cloud bands are shown better on this image.

The GRS is shown as a huge, dark area at the left edge of the planetary disc, right above "Red Jr." is seen as faint dark shadow. On the same jovian latitude as the GRS one recognizes also the new, third hurricane as a weak dark spot. On the right side of the planet disc a fourth weak dark spot in the SEB one can see. At this position in the methaneband filtered jovian image a weak bright spot is shown.

     
  With the programm Winjupos a map projektion of the UV filtered Jupiter also was created. The position of all 4 hurricanes was measured in System II:

- GRS:         124 West
- "Red Jr.":  130 West
- No. 3:         143 West
- No. 4:         194 West

These positions agree very good within the margins of error with the positions within the visual range.

     
With these two images in the methaneband- and UV-light not only the 3 admitted hurricanes where found, to our surprise a fourth hurricane likewise was detected! The attempt was a complete success.

The camera was placed with the filter wheel directly in secondari focus of the 80 cm mirrortelescope of the observatory. With exposure times under 1 second no Darks must be taken up. The treatment of the images was divided therefore only into 3 steps:

- subpixelexact averaging
- contrast rise
- sharpening

With suitable weather conditions further observations are accomplished in the summer 2008.

In September 2008 Uranus will be seen at the night sky and we will observe Uranus during the following months also with the methane band filter in order to capture images of the ringsystem of Uranus.

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