 Despite
its bright integrated magnitude the California nebula is one of the
more illusive objects in the sky. Without the aid of a filter
it is one of the most difficult objects to observe in any aperture.
Burnham's describes this nebula as "A difficult object
visually." But in his day they didn't have the deep sky
filters that are available to us. With an OIII, UHC, or H-Beta
filter it is visible to the unaided eye!
That doesn't make
it easy, however. The basic problem with observing this nebula
is that it is very large. Even though its total integrated
magnitude is that of a 5th magnitude star, this light is spread over
an area larger than 2.5o.
The large aperture instruments that collect the most light also give
smaller fields of view. The result is that the apparent
surface brightness of the nebula is more or less constant with
aperture. In fact, it is probably best detected with a small
aperture that affords a field of view large enough to fit the entire
nebula.
Without the aid of a
filter, observations of NGC 1499 are very difficult. It has
been reported in basic 7 x 50 binoculars, although it is extremely
faint. In my 18-inch at 94x I get a 44' field of view, which
is not optimal to see such a large object. Nevertheless, I did
"sense" a brighter background in the region without the
filter. I was only able to be sure that I was seeing it by
comparing the view with a filter in place.
In my 18-inch an OIII
filter didn't seem to help. It was only when I tried the
H-Beta that the nebula appeared distinctly. It is a very, very
smooth, diffuse haze with fuzzy edges. Actually, it appears as
several distinct hazy blobs. Sweeping the scope back and forth
makes them apparent, leaving no doubt that there is something there.
Orion was getting high
in the southeast by then so I swung the scope over to the Horsehead
with the H-Beta still in place. The Horsehead is one of the
more difficult objects in the sky, for much the same reasons as NGC
1499. I was surprised to see the IC 434 nebula pop out clearly
on this night, including the dark patch in the shape of a horse's
head. It only took a little looking with averted vision to
make out the full profile. The interesting thing is that it
appeared to me that IC 434 was actually brighter and more obvious
than the bright portions of NGC 1499 (with the H-Beta in place).
This is probably the result of the large surface area of the latter
and my relatively small field of view. It does, however,
underscore just how difficult NGC 1499 can be to see in a large
scope even with a filter. 
The field in a 90mm ETX at
31x. North is up and east is to the left.
David Knisely
reports that in a 10-inch f/5 Newt with an H-Beta filter he
"...could see some vague diffuse almost filament-like structure
along the north and south edges as I panned around. It was not
bright by any means, but it was not terribly difficult either."
This telescope gives over a 1o
field of view, which I believe to be the key to his success.
In smaller instruments
look for an elongated glow, like a slightly brighter chunk of sky.
I recently had a try at looking through the H-Beta filter with no
optical aid. It's a bit difficult because the stars are
greatly dimmed. I eventually found the correct part of Perseus
and sure enough, with averted vision, a faint rectangular glow
appeared in the right location.
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