Re post of last night's entry, with more information.
This
is an image from November 18, 2016 of M110.
M110 from last post, image taken a year later.
Compare
this one to the one from the last posting. What's the difference?
The one from November of last year, is a much, much longer exposure
plus combining exposures from 4 color bands, LRGB. LRGB, which is
luminance, red, green, blue, were exposure times of 60L, 9R, 9G, 9B,
so a total time of 60+9+9+9 = 87 minutes vs. 3L for the one from this
year ( 3 minutes in L band). (What's the L band, really? It's
basically a clear filter, except it doesn't allow infra red (IR)
light through. That's important because the camera sensor will
respond quite well to IR. This can throw off the focus, sense we
mostly look for the greatest response of the chip, ie, most output,
to help determine then focus is achieved.)
You can read about M110 in the post from November 20, 2016.
|
NGC 404 |
This
image shows a very bright star called Mirach, which is the brightest
star in the image, and a galaxy to the star's lower left, which is
the “fuzz ball”. The fuzz ball is actually the intended target
for this image and is NGC 404, which is also know as the Ghost of
Mirach. NGC 404 is about 10 million light years away and is described
as a lenticular or elliptical galaxy. The fuzz (nebulosity) around
Mirach is a bit of a puzzle. Mirach is a bright star, about 2nd
magnitude. Because it is so bright, the light from it fills the
sensor receptors and then spills over to adjacent receptors (pixels,
actually). So, instead of the star appearing round, it has a tail
going off to the right, which is where the extra light has spilled.
That much I understand. It's possible that a similar phenomena is the
cause of the dark curved streaks, but I don't know.
|
NGC 891 |
NGC
891 is an edge-on galaxy that is about 30 million ly away. From side
to side, it's about 100,000 ly across.
And
now the 10 second images.
|
NGC 752 |
NGC
752 is an open cluster that's about 1300 ly away and contains about
100 stars.
|
NGC 7662 |
|
Nebula, Shells visible, but not central star |
NGC
7662 aka the Blue Snowball Nebula is a dying star, much like M57, the
Ring Nebula in Lyra. There is a central star that has shed some outer
layers of gas. Images with greater resolution can show the central
star. It's presence is hinted at here, showing a somewhat darker
center than outer edges of the nebula. Distance is not know with any
accuracy. Estimates range from 1800 ly to 5600 ly.
|
NGC 7686 |
NGC
7686 is an open cluster containing about 80 stars. I've found little
information on this cluster, including no estimate of it's distance.