M31 and Aperture

How big of a Newt scope do you need to begin to see dustlanes in Andromeda?

Brian wrote:

How big of a Newt scope do you need to begin to see dustlanes in
Andromeda?

Hi Brian,

I'd say that doesn't so much depend on the aperture but rather
on how dark your skies are. In remote areas, 10x50 binoculars
show the main dust lane easily (and so will 4" Newts with wide-
field eyepieces). In a city, you're out of luck even with large
aperture. You'll see the M31 core, the satellite galaxies and
that's it, everything else blurs into the light-polluted background.

Generally, I can best appreciate M31 and details in it with large
fields of view, in a scope with above-average contrast. It's mostly
low-contrast large-area detail, if your scope is even slightly
miscollimated better adjust collimation before you begin.
If somebody told me I'd have to specialize on M31 and may pick
any scope + eyepiece set for it, I would opt for the perfect
12" f/5 (yes, premium newtonian optics sets aren't cheap), the
31 Nagler grenade for overview (field will be close to 2deg),
and a 13mm Nagler for the details, like the fine lanes extending
from the core outwards.

I've once had the chance to see M33 (pinwheel) in a 40" Dob, under
good seeing conditions. That blows you away. NGC 605 as bright and
detailed as the Orion Nebula in a 4" scope, and actually seeing
stars in a foreign galaxy with my own eyes. I'll never forget that
view. We also looked at M31, and it surely is impressive to see
resolved stars in it and bright knots and filaments of HII regions,
but the large-scale structure got lost since we only had around
..25 deg field of view, at ~160x. The details were overwhelming and
it wasn't possible to take it all in in 5 minutes, since the overall
structure at that magnification is uniform (like the unresolved milky
way, and very much unlike M33 which is "all spotty") and the details
came out only after a while of observation (which is true for small
scopes as well).
I might have appreciated it more hadn't those people waiting on the
ground for me to step down from the 6m-high ladder pushed all the time
to get their share of "view" as well

Ok, to sum my opinion up:

- even small scopes (whether newtonian, SC/Mak or refractor) will
show Andromeda's main dust lanes provided the sky is dark enough.
- brings up point 2: Dark skies win. No nebula/light pollution filter
is very efficient on Andromeda for visual purposes, IMHO. The dust
lanes blur into light-polluted background, at least the finer ones.
The main one on the earth-facing side of the M31 spiral is always
visible if your scope is "large enough", though, but it will be a
boring object under light polluted skies.
- high contrast wins. Andromeda is bright enough that a well-collimated
8" Dob with superb optics will beat the average-collimated average-
quality 14" Dob. This is a Deep-Sky object where having a "planetary
scope" will help.
Means: Good collimation in a Newt or SC is the key to see the low-
contrast details in M31.
- wide field wins. I see M31's dust lanes in my 10" Meade SC. But
the field of view in that scope is too small for my taste, I tend
to move it around a lot within Andromeda to follow the large lanes
all their way around the core. I prefer the 8" Dob of a friend for
the object. Use significantly less magnification than 10x aperture
in inch.
- very large aperture will show "clustery" details in the outer spiral
arms of Andromeda that are not visible with a smaller-aperture scope.
But for the inner dust lanes, large aperture doesn't help (me).
- Think of it like observing our own milky way's dust lanes with your
bare eye. While the bright band of the milky way is readily obvious,
the darker lanes and the fine structure of the bands will be noticed
only if you train your eye for it. Take it in for a while, let your
eye wander around, and eventually you'll notice detail that you've
overseen when your view first swept over it. Take your time.
The finer Andromeda dust lanes aren't a "parade object" for star
parties, IMHO.

Bye,
FrankH.

--
Email: You can use hofmann(at)physik.uni-wuerzburg.de; since this address
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Frank Hofmann wrote:

Brian wrote:

How big of a Newt scope do you need to begin to see dustlanes in
Andromeda?

Hi Brian,

I'd say that doesn't so much depend on the aperture but rather
on how dark your skies are.

Precisely. I used to see them regularly from my back yard in Iowa City with
scopes 6-14" and lost them by 1980, to sky lighting and pollution. My night
photos from that yard through the years show the steady advancement of light
and particulate pollution, like a steadily advancing horizon fromthe downtown

area east, then a large development east to west, the the two meeting and
joining.
It didnt help when a local politician moved in down the block and had to have
a
sodium light on a 30 foot pole over his yard ... to keep the "criminals" out!

That was "criminal". But he got away with it and 10 years later was joined by

others ...

Jerry

"Brian" wrote in message ...
How big of a Newt scope do you need to begin to see dustlanes in Andromeda?

Well, under a very dark sky, I can get hints of them in my 4 inch f/6
refractor at low power, and can begin to see them fairly well in an 8
or 10 inch Newtonian. They aren't tremendously obvious (ie: the view
won't look as brilliant and as obvious as the pictures in books), but
the lanes can be seen with some careful observing. I particularly
like the view at about 90x in my 10 inch f/5.6 Newtonian, as I can see
the arm segment framed by the two main dark lanes west of the galaxy's
brighter core region. Clear skies to you.

David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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"Brian" wrote in message ...
How big of a Newt scope do you need to begin to see dustlanes in Andromeda?

I've seen the main lane with a 4" refractor. With a 6" f/8 and mag. 6
skies you should be able to see one or two lanes. My 12" SCT brings
them out pretty well, as does my 6" refractor. Having a Pentax XL 40
in the focuser helped. Good eyepieces with full coatings increase the
contrast, which, along with image brightness, shows the dust lanes.

[/opinion]

"Brian" wrote in message ...

How big of a Newt scope do you need to begin to see dustlanes in Andromeda?

I would say that they are quite obvious in an 8-inch scope under dark skies
once you know what to look for. Actually, you can see the inner (broader and
bolder) dust lane even in the suburbs -- sort of. Under typical goodish
suburban skies, M31 looks like an oval about 1 degree long. Take a close
look and see how fuzzy that oval is on the M32 side and how crisp the
edge is on the M110 side. That crisp edge is due to the dust lane.

Unlike others, I find that this feature shows poorly or not at all at
low power, but high magnification brings it out very strongly. Of
course, at high magnification you can't see the whole thing in one
field of view -- not even close!

- Tony Flanders

Ï "Brian" Ýãñáøå óôï ìÞíõìá
...

How big of a Newt scope do you need to begin to see dustlanes in
Andromeda?

I've seen the main dust lane with my 11x80 Chinons, under dark skies.
If the main lane shows on a 3.x" , I'd imagine it would show on any larger
instrument under dark skies.
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

As Frank Hofmann indicates, the inner dust lane can be seen with regular 10x50
binoculars under dark skies. The second dust lane further out becomes visible
with 20x80 under the same conditions. They become obvious features with 100mm
aperture from a rural site.

John Bortle

Tony Flanders wrote:

"Brian" wrote in message ...

How big of a Newt scope do you need to begin to see dustlanes in Andromeda?

I would say that they are quite obvious in an 8-inch scope under dark skies
once you know what to look for. Actually, you can see the inner (broader and
bolder) dust lane even in the suburbs -- sort of. Under typical goodish
suburban skies, M31 looks like an oval about 1 degree long. Take a close
look and see how fuzzy that oval is on the M32 side and how crisp the
edge is on the M110 side. That crisp edge is due to the dust lane.

Unlike others, I find that this feature shows poorly or not at all at
low power, but high magnification brings it out very strongly. Of
course, at high magnification you can't see the whole thing in one
field of view -- not even close!

- Tony Flanders

It's unfortunate we can't see the full extent of M31 with the naked eye.
It would really be impressive. I've heard you can see about two degrees
of it when it's overhead in a very dark sky. How much have you seen?


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starman wrote:

It's unfortunate we can't see the full extent of M31 with the naked eye.
It would really be impressive. I've heard you can see about two degrees
of it when it's overhead in a very dark sky. How much have you seen?

Well, its difficult to get exact size measurements for an object which you
have to use averted vision to see its edges, but I would say that from a dark
sky site, I have seen around 3 to 3.5 degrees of length or so. I did some
more exact measurements in an old pair of 10x50 binoculars from my local dark
sky site (ZLM about 6.6) and it came out to around three degrees with not a
lot of uncertainty. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************