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Fainter than faint
http://www.boltonastro.co.uk/forums/viewtopic.php?f=18&t=914
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Author:  DRatledge [ Wed Nov 30, 2016 12:38 pm ]
Post subject:  Fainter than faint

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.

Attachments:
abell5-OIII-rough.jpg
abell5-OIII-rough.jpg [ 139.12 KiB | Viewed 2004 times ]

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