ASTRO: NGC 4244 The Silver Needle

NGC 4244, sometimes called the Silver Needle Galaxy, is a nearby edge on
spiral in Canes Venatici. It is classed as SA(s)cd: with HII emission.
The blue stars in such HII regions drown out the pink color of the HII
emission. I will need to add H alpha filtered data to pick that up by
holding back the glare of the stars formed in these regions. The
distance to this galaxy is usually put at about 15 million light-years
putting it too far to be in the local group or M81 group. It is
sometimes considered part of the M94 group. It is about 81,500
light-years across if the distance is assumed to be 15 million
light-years. Redshift puts it further away at 23 million light-years.
The redshift velocity is pretty inaccurate at close range so I'll go
with the other determinations that say 15 million. That also fits with
the resolution seen in the HST image. See below for more on that.

Looking through the literature I see a lot of disagreement about the
bright object at its core. Some say it is the core, others it is a
field star. Looking at most images, including mine it looks like a
star. In fact I was going to come down on the side of it being a star
but then looked at the PSF (Point Spread Function) of it in my data.
That shows it certainly is not a star. This is where the numerical data
trumps what the eye sees. Compared to stars of similar brightness on
the image the PSF is very wrong for a star. But looking for more, just
before posting this I checked the Hubble Legacy Archive. They had a
great image of the core region of the galaxy. I did a quick process of
part of the frame. At over 70 meg I had to severely crop it for band
width limits. Those with the right software can go into the site and
see the full frame. It clearly shows the core to look very much like a
miniature M104. Apparently it is round in all images I've seen of the
galaxy only due to our lack of resolution compared to the HST above the
atmosphere. So that "star" is definitely the core of the galaxy. Now
why the core is so obvious but the dust lanes so obscure I don't know.

Then looking further I found this paper using some of the same data I
used for the mono image above but processed further. It calls the disk
a "flattened nuclear central cluster". You can read all about it at
http://www.gemini.edu/node/10989. No need for hip waders as it is a
press release rather than a scientific paper.

My blue data was severely hit by clouds (I sound like a broken record
over this of late). I suspect this has reddened the core region some
with it showing slightly more orange than it really is. Though web
images show quite a wide range of core color from very orange to all
blue. I suspect I'm close but just a bit too orange. I just couldn't
push the weak blue any further without stars going wonky on me. I
refuse to process one part of an image differently than another in this
respect so left it what I feel is likely a bit too orange though most of
the stars do appear about right to me when calibrated against Sloan
photometric data.

Also seeing wasn't what I'd hoped for reducing my resolution. I think
the star clusters should stand out more if I had better seeing. I might
eventually get around to trying again under better conditions.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

Beautiful image Rick. You managed to get good colour in spite of only 2
images for each channel.
And thanks for including the Hubble picture, the core really looks like
M104.

I have also imaged this galaxie this spring. Much longer exposure time (more
than eight hours), but much less signal.
As I am not sure if I have posted it I'll attach it to this post just for
fun.

Stefan



"Rick Johnson" schrieb im Newsbeitrag
. com...

NGC 4244, sometimes called the Silver Needle Galaxy, is a nearby edge on
spiral in Canes Venatici. It is classed as SA(s)cd: with HII emission.
The blue stars in such HII regions drown out the pink color of the HII
emission. I will need to add H alpha filtered data to pick that up by
holding back the glare of the stars formed in these regions. The
distance to this galaxy is usually put at about 15 million light-years
putting it too far to be in the local group or M81 group. It is
sometimes considered part of the M94 group. It is about 81,500
light-years across if the distance is assumed to be 15 million
light-years. Redshift puts it further away at 23 million light-years.
The redshift velocity is pretty inaccurate at close range so I'll go
with the other determinations that say 15 million. That also fits with
the resolution seen in the HST image. See below for more on that.

Looking through the literature I see a lot of disagreement about the
bright object at its core. Some say it is the core, others it is a
field star. Looking at most images, including mine it looks like a
star. In fact I was going to come down on the side of it being a star
but then looked at the PSF (Point Spread Function) of it in my data.
That shows it certainly is not a star. This is where the numerical data
trumps what the eye sees. Compared to stars of similar brightness on
the image the PSF is very wrong for a star. But looking for more, just
before posting this I checked the Hubble Legacy Archive. They had a
great image of the core region of the galaxy. I did a quick process of
part of the frame. At over 70 meg I had to severely crop it for band
width limits. Those with the right software can go into the site and
see the full frame. It clearly shows the core to look very much like a
miniature M104. Apparently it is round in all images I've seen of the
galaxy only due to our lack of resolution compared to the HST above the
atmosphere. So that "star" is definitely the core of the galaxy. Now
why the core is so obvious but the dust lanes so obscure I don't know.

Then looking further I found this paper using some of the same data I
used for the mono image above but processed further. It calls the disk
a "flattened nuclear central cluster". You can read all about it at
http://www.gemini.edu/node/10989. No need for hip waders as it is a
press release rather than a scientific paper.

My blue data was severely hit by clouds (I sound like a broken record
over this of late). I suspect this has reddened the core region some
with it showing slightly more orange than it really is. Though web
images show quite a wide range of core color from very orange to all
blue. I suspect I'm close but just a bit too orange. I just couldn't
push the weak blue any further without stars going wonky on me. I
refuse to process one part of an image differently than another in this
respect so left it what I feel is likely a bit too orange though most of
the stars do appear about right to me when calibrated against Sloan
photometric data.

Also seeing wasn't what I'd hoped for reducing my resolution. I think
the star clusters should stand out more if I had better seeing. I might
eventually get around to trying again under better conditions.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

Your image shows the core about the same color as I got. This one has a
wide range of core color when you look across the net. I often think
some think since the core of some spirals is quite red due to old
population II stars when one doesn't come out that way they artificially
push the core to be what they expect. Same with the blue of spiral
arms. In fact, due to my poor blue data I might be guilt of that with
this image though the stars appear about right.

I usually use 20 minutes of color when using 40 to 60 minutes of L data.
I see a lot of folks saying color per channel needs to be one third
the L in time. I've found that works if you blur the color some.
Though for absolutely best results I find using color equal to the lum
is better for resolving fine color detail as you don't need to blur the
color. To get the same signal to noise ratio you need even more time
for each color since they get only one third the photons. I don't know
anyone doing this! Probably might as well forget the L channel when
doing that!

For some things like star clusters I've even used only one 10 minute
color frame as the stars are so bright that gives them a good signal to
noise ratio. Background however will be nasty with color noise so I
desaturate that. Even with my usual 2 frames that is a necessary step
in my processing. I likely did that with this image. I've had to do it
a lot lately with my sky conditions being so poor.

Rick

On 10/13/2013 4:20 PM, Stefan Lilge wrote:
Beautiful image Rick. You managed to get good colour in spite of only 2
images for each channel.
And thanks for including the Hubble picture, the core really looks like
M104.

I have also imaged this galaxie this spring. Much longer exposure time
(more than eight hours), but much less signal.
As I am not sure if I have posted it I'll attach it to this post just
for fun.

Stefan



"Rick Johnson" schrieb im Newsbeitrag
. com...

NGC 4244, sometimes called the Silver Needle Galaxy, is a nearby edge on
spiral in Canes Venatici. It is classed as SA(s)cd: with HII emission.
The blue stars in such HII regions drown out the pink color of the HII
emission. I will need to add H alpha filtered data to pick that up by
holding back the glare of the stars formed in these regions. The
distance to this galaxy is usually put at about 15 million light-years
putting it too far to be in the local group or M81 group. It is
sometimes considered part of the M94 group. It is about 81,500
light-years across if the distance is assumed to be 15 million
light-years. Redshift puts it further away at 23 million light-years.
The redshift velocity is pretty inaccurate at close range so I'll go
with the other determinations that say 15 million. That also fits with
the resolution seen in the HST image. See below for more on that.

Looking through the literature I see a lot of disagreement about the
bright object at its core. Some say it is the core, others it is a
field star. Looking at most images, including mine it looks like a
star. In fact I was going to come down on the side of it being a star
but then looked at the PSF (Point Spread Function) of it in my data.
That shows it certainly is not a star. This is where the numerical data
trumps what the eye sees. Compared to stars of similar brightness on
the image the PSF is very wrong for a star. But looking for more, just
before posting this I checked the Hubble Legacy Archive. They had a
great image of the core region of the galaxy. I did a quick process of
part of the frame. At over 70 meg I had to severely crop it for band
width limits. Those with the right software can go into the site and
see the full frame. It clearly shows the core to look very much like a
miniature M104. Apparently it is round in all images I've seen of the
galaxy only due to our lack of resolution compared to the HST above the
atmosphere. So that "star" is definitely the core of the galaxy. Now
why the core is so obvious but the dust lanes so obscure I don't know.

Then looking further I found this paper using some of the same data I
used for the mono image above but processed further. It calls the disk
a "flattened nuclear central cluster". You can read all about it at
http://www.gemini.edu/node/10989. No need for hip waders as it is a
press release rather than a scientific paper.

My blue data was severely hit by clouds (I sound like a broken record
over this of late). I suspect this has reddened the core region some
with it showing slightly more orange than it really is. Though web
images show quite a wide range of core color from very orange to all
blue. I suspect I'm close but just a bit too orange. I just couldn't
push the weak blue any further without stars going wonky on me. I
refuse to process one part of an image differently than another in this
respect so left it what I feel is likely a bit too orange though most of
the stars do appear about right to me when calibrated against Sloan
photometric data.

Also seeing wasn't what I'd hoped for reducing my resolution. I think
the star clusters should stand out more if I had better seeing. I might
eventually get around to trying again under better conditions.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick


--
Prefix is correct. Domain is arvig dot net