Quote:
Originally Posted by ausastronomer
Hi Tony,
I have observed the Horsehead on dozens of occasions over a large number of years. There are some "tricks" to observing it which I will pass on.
Firstly the technical stuff. I believe and I am open to be corrected, that the correct target designation for the Horsehead Nebula is Barnard 33 (B33) which is the dark nebula made visible as the Horsehead, against the illuminated background of emission nebula IC434.
Now to observing it. First and foremost let me say there are some people who may never see it visually, irrespective of how dark the skies and how big the telescope. The reason for this is that IC434 emits its light in the far red end of the visible spectrum at near infrared wavelengths. Some peoples eyes are not sensitive enough at the red end of the spectrum to actually see the emission nebula IC434. If they can't see IC434 they can't see the Horsehead.
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5) A H-Beta filter is the filter of choice but if you do not have one don't despair. A wide bandpass UHC filter helps a lot. You need to use a UHC filter that has a high bandpass in the H-Beta line at 486nm and a bandpass in both OIII lines at 496nm and 501nm. My Astronomiks UHC filter works very well in my 18" Obsession. Not quite as good as my dedicated H-Beta filter, but not far behind it.
I think that just about covers it. Good Luck !!!
Cheers,
John B
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Jonn
Interesting description.
My only comment though would be that if you are using a H-beta filter you are filtering out all light except for the green coloured H beta line.
For this line it doesn't matter whether you eye is sensitive to the deep red of a H-a
I don't know how much H-beta IC434 emits but there should be some.
Terry