Galaxies for Fun Astronomical CCD photos on peculiar galaxies and other astronomical stuff.
www.galaxies.se - by Ivar Hamberg
REFLECTANCE SPECTRA of the PLANETS.
It is quite interesting that one can obtain a lot of information on planetary atmospheres from just taking some spectra from your backyard! Here are some spectra on MARS, JUPITER, URANUS and NEPTUNE. As reference I have used the reflectance spectrum of the MOON.
URANUS and NEPTUNE Reflectance Spectra, with METHANE Bands:
SPECTRUM:
Date: 2022-11-12, Stockholm.
URANUS: 3x300 sec exposure.
NEPTUNE: 3x300 sec exposure.
MOON: 10 sec exposure. (used as reference)
Instrument: 12" RC, 300 L/mm grating Spectrograph.
Processing: Dark field adjusted, hot pixel removal.
Calibrated to known solar absorption lines.
Data on CH4 bands are from R Walker Spectral Atlas, Plate 78, and Rspec.
COMMENTS:
This is a reflectance spectrum of sunlight reflected off the planets. Most features are from the sun's absorption bands. However, heavy absorption of methane (CH4) in the Uranus and Neptune atmospheres can easily be seen. The 6200 Ångström absorption band is maybe the most prominent. A few Telluric bands are also denoted.
- First diagram: raw profiles.
- Second diagram: flattend profiles.
JUPITER Reflectance Spectrum, with METHANE Bands:
SPECTRUM:
Date: 2022-10-27, hazy weather, Stockholm.
Exp: This is a 60 sec exposure. ASI183MM camera.
Instrument: 12" RC, 300 L/mm grating Spectrograph.
Processing: Dark field adjusted, hot pixel removal, flattened to continuum. Calibrated to known solar absorption lines.
Data on CH4 bands are from R Walker Spectral Atlas, Plate 77.
COMMENTS:
This is a reflectance spectrum of sunlight reflected off Jupiter. Most features are from the sun's absorption bands. However, heavy absorption of methane (CH4) in the Jupiter atmosphere can easily be seen. The 6200 Ångström absorption band is maybe the most prominent. The 7000 Å band is also very easily seen.
A few Telluric bands are also denoted.
2nd JUPITER diagram:
The 300L/mm grating spectrogram is compared to a different setup with a SA100 (100 L/mm) transmission grating used as a slitless spectrograph.
Blue Curve:
Exp: 30sec. ASI183MM.
Instrument: 250mm telephoto lens, with a 1 inch grating in front.
Date: 2022-10-19, Nice.
Red Curve:
See 60 sec exposure data above.
COMMENTS:
The SA100 spectrogram shows the METHANE very clear as well. This spectrogram yields lower resolution but the broad CH4 bands stand out very well. It is interesting to note that a simple transmission grating in front of a telephoto lens can record Methane gas in the atmosphere of another planet.
MARS Reflectance Spectrum:
SPECTRUM:
Date: 2022-11-12, Stockholm.
MARS: 3x30 sec exposure.
MOON: 10 sec exposure. (used as reference)
Instrument: 12" RC, 300 L/mm grating Spectrograph.
Processing: Dark field adjusted, hot pixel removal.
Calibrated to known solar absorption lines.
COMMENTS:
The MARS spectrum is basically a clear solar spectrum, but with a strong reddish hue. By dividing the MARS spectrum with the solar spectrum (taken as the MOON reflectance spectrum), we get a very smooth line. No real features are prominent, other than artifacts from the divisions at strong absorption bands.
The MARS/MOON curve is almost straight in a logarithmic diagram. (The O2 and H2O absorption in the earth´s atmosphere is dependent on object altitude and weather condition, so it is somewhat cumbersome to calibrate this part.)