Observation by Robin Leadbeater: QSO PS1 J161737+595020 spectrum at z=4.3

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Robin Leadbeater


Robin Leadbeater


2021 Apr 07 - 00:16


2021 Apr 08 - 19:12



  • ALPY 200 Spectrograph
  • ATIK 428 Camera
  • Celestron C11 telescope

6 x 1200 sec


Wigton Cumbria

Target name

QSO PS1 J161737+595020


QSO PS1 J161737+595020 spectrum at z=4.3

About this image

Prompted by the article on this Quasar by Steve Barrett in the JBAA  I decided to see if it would be possible to record a spectrum and measure the redshift. At a magnitude of  19.8 g/17.8 r (SDSS), it is the faintest object I have recorded a spectrum of to date and at a published redshift of 4.315 also the most distant (and to my knowledge perhaps also the faintest and deepest amateur spectrum) EDIT: At the time but I was able to go a bit deeper still.


The measured spectrum (red) is shown overlaid on the published spectrum (grey)  from The Extremely Luminous Quasar Survey in the Pan-STARRS 1 Footprint (PS-ELQS).  The agreement is good and the Lyman alpha emission peak shifted from 1216 Angstrom and used to confirm the redshift is clear.  Note the spectral content in the sky background of the raw spectrum from a mixture of natural airglow and artificial light pollution which was subtracted from the Quasar spectrum.

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Hugh Allen
Hugh Allen, 2021 Apr 08 - 20:15 UTC

Awesome Robin. The redshift is so high the Lyman alpha is almost at the Balmer alpha position! Really a great achievement.

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