Galaxies
In
November 2018, a few moonless nights with low humidity and calm winds allowed
some relative deep-sky imaging. The
C11-Edge telescope was mounted on my MyT Paramount in my suburban backyard,
with estimated naked-eye limiting magnitude about 4. A Celestron 0.7x focal
reducer produced a focal length about 1960mm. A ZWO 1600 monochrome CMOS camera was
used, resulting in 0.41 arcsec per pixel resolution. A luminance filter was
used in the 15second exposures.
Dark frames and a twilight flat were used to calibrate the image. The ZWO gain was set at 150, giving
about 1 electron/ADU. This camera uses a 12-bit digitizer.
M31
The
first image is a view of M31, the Andromeda Galaxy, with DEC increasing in the
vertical and RA increasing to the left.
The second image is a close-up of the central core, with less image
stretching. The measured stellar resolution
in both images is 5.9 pixels, or 2.4 arcseconds. The best 35 images (out of 60 images)
were aligned and stacked, providing 8.75 minutes total exposure. This was just
a test, since the galaxy is so much larger than the camera field of view. Dark lanes are seen near the central
core. A mosaic would be required to
get the entire galaxy.
M33
The
next images are a view of M33, the Triangulum Galaxy, with DEC increasing in
the vertical and RA increasing to the left. The second image is a close-up of the
central core, with less image stretching.
The measured stellar resolution in both images is 5.4 pixels, or 2.2 arcseconds. The best 185 images (out of 225 images)
were aligned and stacked, providing 46 minutes total exposure. The sky was hazy
from nearby brush fires, reducing transparency to about 70% compared to the
test images taken the previous night, and increasing the sky brightness. Additional images were taken with green
and red filters, but those were not used.
M74
The
next image is M74, the Phantom Galaxy, with DEC increasing in the vertical and
RA increasing to the left. The
measured stellar resolution is 6 pixels, or 2.4 arcseconds. A total of 302 images were aligned and
stacked, providing 75 minutes total exposure.
NGC 7479
The
next images are a view of NGC7479, a barred spiral galaxy about 100 million
light years away, with DEC increasing in the vertical and RA increasing to the
left. The second image is a stretched
view to show the stars further from the center and the third image is enlarged
and less stretched, to show detail near the central core, including a dark bar. A nearby 15th magnitude star
just happens to be positioned just next to the core. The measured stellar resolution in the
images is 4.8 pixels, or 1.9 arcseconds.
The best 148 images (out of 200 images) were aligned and stacked,
providing 37 minutes total exposure.
Two dim galaxies are easily seen in the upper right of the middle image;
they are 1.6 billion light years away. (See this paper for more details. https://www.aanda.org/articles/aa/pdf/2003/39/aa3868.pdf)
All text and images are owned by Stellar Products, 1992-2018. Any use by others without permission of Stellar Products is prohibited.
Links to other Stellar Products pages: