Planet observation with near
infrared light

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Projectmanager/Author: Silvia Kowollik
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Optical planet observation usually is done during the night. An exception of this rule is the observation in the near infra red between 665 and 1050 nm. This also can be done during daytime. Apart from a longer observation possibility over the year, two further advantages arise as a result of the larger wavelength of the electromagnetic radiation: Turbulences in the terrestrial atmosphere obstruct the resolving power in IR not as much as in the visual range and with ir one can look deeper into the atmosphere layers of the other planets of our solar system.

For a successful observation within the near ir range with the 80 cm mirror telescope of the observatory extensive searches and tests are necessary in front of the observation  relative :

- the selection of a suitable filter
- the selection of a camera, which is sensitive enough in the planned wavelength coverage in order to catch the weak light.

  665 nm Longpass from Astronomik, based on Schott RG 665
  800 nm Longpass from B+W # 93

Image not availiable at the time

  1000 nm Longpass from Edmond Optics
  Spectral sensitivity characteristics of Videomoduls SK 1004-X

After the selection of filter and camera on june 07th 2006 a first test with an 8"Newtonian f=5 was done in eyepiceprojection. The test served for the examination of the theoretical initial considerations.

Left of Jupiter stays the 5.5 mag bright moon Europa, at Jupiters surface (-2.5 mag) cloud belts, the Great Red Spot and "Red Jr." are visible as well as right of Jupiter the 5.3 mag bright moon Io.

Image captured with 6" Newton and eyepiceprojektion,
Effective Focal Length: about. 3700 mm
Camera: Videomodul SK 1004-X
Filter: 800 nm IR Longpassfilter (# 93 von B+W)

Capturing and Imageprocessing with Giotto

30% of 1200 Singleframes, Contrast enhanced, Seeing : 3-4/10



51 single images from 11.06. until 14.06.2006, stepp: 10 minutes (= 6 )

Captured with 6" Newton and eyepiceprojektion, Effektive Focallength: 6000 mm

Camera: Videomodul SK 1004-X
Filter: 800 nm IR Longpassfilter (# 93 von B+W)

Captured with K3CCD-TOOLS (10 f/s)
Imageprocessing with Giotto (70% of 1800 images each step)

Filtertest 21.06.2006 with 6" Newton:

This test was done at worst seeing with an filterwheel.

Used filter:

- 495 nm (yellow, Longpassfilter, Baader)
- 570 nm (orange, Longpassfilter, Baader)
- 665 nm Longpassfilter from Astronomik
- 800 nm Longpassfilter from B+W # 93

As expected, the brightness of the live images was decreasing with longer wavelength, additional the contrast during the work with the 800 nm filter was decreasing by thin cirrus clouds...




on16.07.2006, 19:26 Uhr - 21:41 Uhr UT

Captured with 6" Newton and eyepiceprojection
Camera: Videomodul SK 1004-X
Filter: 665 nm IR Longpassfilter (Astronomik)

Captured with VirtualDub (25 f/s)
Image processing by Giotto (25% of 3000 images)

ZM: 172,07  - 253,64 W  (Jupiter II)



The treatment of the pictures was divided into 3 steps:

- subpixelexact averaging
- contrast rise
- sharpening

  Saturn on 16.2.2007, with 800 nm Longpassfilter, captured with 8" Newton f/5, eyepiceprojektion, effective focal length 7,5 meter, Videomodul SK 1004-X.
  Saturn on 11.3..2007, with 665 nm Longpassfilter, captured with 8" Newton f/5, eyepiceprojektion, effective focal length 8 meter, Videomodul SK 1004-X.



Jupiter on 19.05.2007 00:32 -00:34 UT

Jupiter with 8" Newton, eyepiceprojektion, effective focal length 8 meter and 665 nm Longpassfilter. Captured with Videomodul SK 1004-X in origin size.

45 % of 3.000 singleframes

Captured and image processing with Giotto 2.12


  Map from two images captured on 00:33 and 01:41 UT on 19.05.2007 processed with programm WINJUPOS. This map shows fine details in the cloud belts of Jupiter.

With IR-Images substantially more details than within the visual range can be illustrated and maps of the cloud belts can be made. Images made during a period of several month show changes in the cloud structures, which can be measured very well.

These first tests with different IR - filters at amateur telescopes with 15 and/or 20 cm mirror diameters showed that the filters fulfill our expectations.
The light of the planet atmosphere is effectively weakened.

With suitable weather conditions further tests are accomplished in 2008.

In September 2008 Uranus will be seen at the night sky and we will observe Uranus during the following month to detect clouds on the planetray disk.

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