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Hi Liz,
Let me repeat a post I made about this target a couple of years ago.
The difficulty with which it can be seen can change dramatically in the space of hours and also from individual to individual. You can take it to the bank that while I have observed it in scopes down to 10", it is a very difficult target in any scope under 16".
The ease with which it can be seen are dependant on many things:-
1) How dark the skies are.
2) How transparent the skies are.
3) How clean the optics in the scope are
4) How well baffled the scope is. This has a major effect on contrast.
5) How good are the optics in the scope. High grade optics yield better contrast than low grade optics, making it marginally easier to see.
6) Did the person use an eyepiece yielding a suitable exit pupil? 3mm to 5mm is ideal as this effects contrast and target luminosity
7) Did the person use a high quality eyepiece with good light throughput and contrast.
8) Did they use a filter. A H-Beta filter helps enormously and a narrowband or UHC filter helps a lot.
and last but not least and by far the most important.
9) How sensitive to RED light are the individual observers eyes? A very significant portion of the light emitting from the background emission nebula IC434 is at the red end of the spectrum and observers with eyes that are less sensitive to red light will simply not see it irrespective of the conditions, because they cannot see the background emission nebula very well.
I have observed it on countless occasions in my 18" Obsession and on some occasions felt that it was easily visible "to me" . I have then moved aside and let someone else have a look and the person cannot see it. Some of those have been exceptionally experienced observers. A beginner has then followed and seen it easily.
In a nutshell, sometimes it's easy, many many times it isn't so easy. It depends on many things.
Cheers,
John B
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