Observation by Robin Leadbeater: JWST Reflectance Spectrum

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Robin Leadbeater


Robin Leadbeater


2022 Mar 26 - 22:10


2022 Mar 27 - 12:56



  • ALPY 200 spectrograph
  • ATIK 428 ex camera
  • Celestron C11 SCT 280mm aperture f5.5

5411 sec


Wigton Cumbria UK

Target name

James Webb Space Telescope


JWST Reflectance Spectrum

About this image

The JWST at around mag 14 at the time proved a nice target for practising guiding the spectrograph on faint moving targets using a variable offset from a field star and the PHD2 software comet guiding option. (See here for examples of comet spectra guided using the same technique).

The spectrum of the reflected sunlight (presumably dominated by the giant sunshield), once corrected for the solar spectrum, suggests a reddish colour with a blue tinge and a deficiency at green wavelengths.   

The NASA page on the JWST sun shield mentions a “pink” colour due to the coatings
This is consistent with the reflectance spectrum and is similar for example to the pink colour seen reflected from the new Baader Bessell V filter which use dielectric coatings to reflect all wavelengths except the green V passband, in place of the traditional coloured glass. 

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