Fainter than faint

Blog the previous nights viewing. Link to images on the gallery or simply describe what you observed the night before. Leave the technical and howto in another forum.
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DRatledge
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Fainter than faint

Post by DRatledge » Wed Nov 30, 2016 12:38 pm

Was asked by Owen Brazell if I had an image of planetary Nebula Abell 5. The big dob boys had been unable to see it - they generally use an Oxygen OIII filter on PN. I now know why it is difficult (impossible) to see as it has the faintest OIII signal I have ever recorded. Below is 4 hours worth of OIII (12 x 20 mins) and after 4 x log stretches -no other processing yet though. There is just the faintest of rings.

The H-alpha signal on the other hand shows the nebula well but this wavelength is not visible to those who look through telescopes - our eyes don't see the deep red at night.
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