British Astronomical Association
Supporting amateur astronomers since 1890

BAA Images Robin Leadbeater

Observation by Robin Leadbeater: "Small… Far away” - A...

Uploaded by

Robin Leadbeater

Observer

Robin Leadbeater

Observed

2020 Apr 15 - 22:55

Uploaded

2021 May 10 - 13:51

Objects

NGC6214
M101
Spectrum

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

11x600s NGC 6214 5x600s M101

Location

Three Hills Observatory Wigton Cumbria UK

Target name

NGC 6214, M101

Title

"Small… Far away” - An estimate of the Hubble Constant

About this image

 

“Small… Far away” -  An estimate of the Hubble Constant

Fans of the TV programme “Father Ted” will likely be familiar with the reference to the illusion of relative size due to perspective  (external link to You Tube).  Inspired by Nick Hewitt’s webinar marking a century since the "Great Debate”  , I decided to use this, combined with spectra of a couple of galaxies with similar morphology and spectra but very different apparent sizes (M101 and NGC 6214), to make a rough “back of envelope” estimate of the constant in Hubble’s law, the rate at which distant objects are receding from each other due to cosmological expansion, depending on their distance.  Remarkably, the result was close to the currently accepted value. (Flatteringly so given the assumptions and approximations) We cannot really say much from a sample size of 1 but additional measurements of similar galaxies might  give an idea of the precision.

Files associated with this observation
Like this image
Copyright of all images and other observations submitted to the BAA remains with the owner of the work. Reproduction of work by third parties is expressly forbidden without the consent of the copyright holder. By submitting images to this online gallery, you grant the BAA permission to reproduce them in any of our publications.