Contains:  Solar system body or event
Spectral analysis of Uranus, 


            Bogdan Borz

Spectral analysis of Uranus

Imaging telescopes or lenses: Altair Astro Wave 115mm APO Triplet (f7)

Imaging cameras: ZWO ASI 290MM

Mounts: Skywatcher AZEQ6

Guiding telescopes or lenses: Altair Astro Altair 60mm 225mm Guide Scope

Guiding cameras: Altair Astro GPCAM3 178C

Focal reducers: Altair Astro Planostar 1.0x flattener

Software: RSpec Spectrum Analyser

Filters: Paton Hawksley Education Ltd Star Analyser 100

Accessory: Pegasus Astro FocusCube v2

Date: Nov. 10, 2020

Time: 21:38

Frames: 30

Focal length: 805

Resolution: 658x394

Locations: Backyard, Toulouse, Occitanie, France

Data source: Backyard


I managed yesterday to obtain the spectrum of Uranus. This time I used the monocamera ASI 290MM and I tried to align the Star analyser grid horizontally in order to match the columns of the camera. This reduces artifacts when the spectrum is oblique and realigned using the software. However I don't know if there is another possibility of aligning the grid horizontally other then unscrewing which loosens the whole system. (the filter seems to be fixed in its ring). The spectrum fits nicely on the chip at this distance.

I used 2s subs and stacked 30 frames in Registax and then analysed the spectrum with RSpec. We can observe nicely the Methane (CH4) absorbtion lines (2.3% of the atmosphere of Uranus in volume). I was pretty glad to see that the lines coincide pretty precisely with the reference (a sign of good acquisition and calibration). I shot Vega again with the ASI290MM for calibration, and the Balmer absorption lines were much deeper than with the 224MC.

I should have acquired the spectrum of a solar G type star around Uranus, at the same level in order to compare the 2 spectra. This is necessary if we want to understand what is absorbed in the planetary atmosphere since Uranus reflects the light from the Sun. Of course, the same light has to pass through the terrestrial atmosphere and the Oxygen and Water absorbtion bands can be seen at 7200 A and 7600 A.

* The presented spectrum was corrected for the instrument response.