Quote:
Originally Posted by jenchris
Horsehead is visible with an 8" but you have to have really complete darkness and eyes that have been dark for an hour - I managed it fleetingly with my 8"SCT but when I looked a few minutes later, it was gone.
I was out at our dark sky site which is 100k from civilisation
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Hi Jen,
Are you sure you weren't looking at the Flame Nebula (NGC 2024)? This is a very very common mistake people make.
If you have a look at the two images I have attached, in colour and in grayscale, you will see that when you are observing visually where you only see black and white, how easy it is to confuse the "notch" in the Flame Nebula for the Horsehead Nebula. The Flame is to the left of Zeta Orionis (Alnitak) and the Horsehead is a bit further from Alnitak and below it.
It takes an exceptionally experienced observer, an exceptionally good telescope and outstanding observing conditions, to see it in any telescope under 12" aperture. On top of that a UHC filter helps somewhat and a H-Beta filter helps a lot. I have spent dozens of hours searching for it in 8" and 10" telescopes (good ones) with and without filters, without success. I remember I spent over an hour searching for it in my 10" scope at Wiruna ( at 2002 SPSP?) with Glen Dawes (co author of the Astronomy yearbook) under superb conditions without success. On the other hand, the Flame Nebula (NGC 2024) is very achievale in an 8" scope from dark skies.
The Horsehead is doable in my 14" under superb conditions and reasonably easy in my 18", with a filter. Under excellent conditions it is doable without a filter using averted vision. In the 25" scope it is visible with direct vision unfiltered.
Cheers,
John B