Scope:
AT60EDP at f/5;
Location: DAA Observatory, Shelter
Valley, CA;
Dates:
23, 24, September, 17, 23, 24, October 2025;
Camera:
ASI2600MM (Astronomik type 2c LRGB, 6 nm Ha filters);
Exposure:
27.4 hrs
Lum -
184 x 3.5 min (gain-101 1x1)
RGB -
48 x 2 min (gain-101 1x1) each RGB exposures.,
Ha - 138
x 4 min (gain-160 1x1)
Processing:
Data
Collection - N.I.N.A. Sequencer (as FITs). Sub-frame calibration -
Pixinsight (WBPP).
Sub-frame registration and integration (Average combine
- Linear clipping), Lum, Ha (2x drizzle) - PixInsight (WBPP).
Noise reduction - NoiseXTerminator - PixInsight.
Non-linear
stretching, normalization and gradient removal - PixInsight.
Photometric
RGB calibration (SPCC) - PixInsight.
Deconvolution
of Lum, Ha stacks and RGB combine - BlurXTerminator.
Generation
of starless nebulosity Lum, Ha, and RGB images for later processing
- StarXTerminator.
Curves,
Levels, RGB combine - PixInsight. RGB Stars and starless combine -
PixInsight.
Final
finishing - Affinity Photo.
Annotation
- PixInsight, Aladin (Simbad ), and Affinity Photo.
This
image is a Ha screened LRGB starless
construction - with RGB stars added. Image processed at 12496 x 8352 resolution.
Final
Image size is approximately 4318 x 6520.
Description:
North is up in this image. This
image field lies on the southwestern edge of the Perseus OB1 Association
(Per OB1) - which has its own story.
LBN 637, 638, and 640 run from upper to lower parts of this image. Their
distances are not well established, but LBN 638 has been estimated at about
7,000 light years.
The upper part of
this field contains two open clusters - NGC 657, and Stock 4; and two planetary
nebulae - PN G131.4-05.4 and PNG129.6-05.6. The distance of PN G131.4-05.4 is
about 7,000 light years distant.
There are a number
of background galaxies in this field - very distant and appearing small in this
image. Some are identified in the annotated
image along with estimated distances.
The Perseus OB1
Association has an interesting star forming story. O and B stars are not randomly
distributed in the sky but are concentrated in loose co-moving groups called OB
associations and originated in star forming molecular clouds. Per OB1
(roughly centered on the Double Cluster) is not associated with any HII region
or molecular cloud. Per OB1 stars likely blew away its molecular cloud
after star formation. It is suggested that this wave front interacted with other
clouds (creating what is called remnant molecular clouds, RMC's) above the
galactic plane. Wave front energy triggered additional star formation at unusually
high galactic elevations.
In this image
field, LBN 638, and 640 are thought to be RMC's from this expanding wave front
at the edge of Per OB1.
