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Contains:  NGC 7790, NGC 7788, The star 9Cas
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Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262, 





    
        

            Dave B
Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262

Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262

Technical card

Resolution: 3326x2504

Dates:July 21, 2018Aug. 19, 2018Sept. 29, 2018Oct. 12, 2018Oct. 13, 2018

Frames:
Astrodon Blue: 9x600" -20C bin 1x1
Astrodon Green: 8x600" -10C bin 1x1
Astrodon Ha 1.25" 5nm: 28x900" -10C bin 1x1
Astrodon Luminance E-Series: 107x120" -10C bin 1x1
Astrodon Red: 9x600" -10C bin 1x1

Integration: 14.9 hours

Avg. Moon age: 8.89 days

Avg. Moon phase: 48.40%

Bortle Dark-Sky Scale: 4.00

Mean SQM: 20.00

Astrometry.net job: 2478858

RA center: 359.448 degrees

DEC center: 61.784 degrees

Pixel scale: 2.220 arcsec/pixel

Orientation: 88.584 degrees

Field radius: 1.284 degrees

Locations: somewhere, near Worcester, Massachusetts, United States

Data source: Backyard

Description

This area first caught my eye because of the line of five open clusters and the variety of catalogs that that these clusters are recorded in. It was a good opportunity for me to learn about these catalogs. Also, there are a couple bright nebulae (Sharpless 168 and 169) in the area. So, my first few subs were oriented to capture the clusters along with the Sharpless nebulae. However, my first Ha subs revealed half of a bright circular object that wasn't shown on my planetarium program. It turned out to be Abell 85. So I changed the picture orientation slightly, choosing to capture all of Abell 85 at the expense of losing the Sharpless objects.

With that background, here is a brief description of the DSOs in the image.

* Abell 85, aka CTB 1 - the large, bright red circle in the lower left quadrant. It was originally cataloged as a planetary nebula but was later found to be a supernova remnant. Since the focus of this image was the open clusters, I didn't overly dim the abundant stars in the image, so they drown out the details of this DSO. The "B" version shows the highlighted Ha areas (as well as the center brightening of my Ha filter, unfortunately, which I will be working on eliminating in a future revision).

* We 2-262 - a barely visible small red oval near the top left of the image, much more noticeable on the Ha enhanced version. This was catalogued by Ronald Weinberger in 1977 as a possible planetary nebula. As of 1978 (the latest information that I could find online), it was still classified as a "possible" planetary nebula by Lubos Kahoutek. (Brief sidenote - Comet Kahoutek was one of the first objects that I searched for in my childhood Sears telescope. I never found it, but accidentally did fine Saturn while looking for the comet.)

For the Open Clusters, they (mostly) form a line from the top middle of the picture down to the lower right. They are spaced farly uniformly apart. Starting at the top:

* King 12 - classification I 2 p, indicating a strong concentration, medium range of brightess, and less than 50 stars. I have seen one reference that says there are 15 stars in the cluster, while another lists 27 stars between mag 10-16. It is listed with a visual magnitute of 10.0. This cluster was in the first group of 21 open clusters cataloged by Ivan King in 1949. He added one more cluster in 1961 and five more in 1966.

* Harvard 21 - classification IV 2 p, meaning that it is not well detached from the surrounding star field, medium range of brightness, and less than 50 stars. It is located closer to King 12 than to NGC7788, which is the next cluster down the line. One source list it as containing six stars. Given that is listed with a visual magnitude of 9.0, my guess is that includes the five relatively bright stars that make a small sideways V, but I could be wrong. This catalog was compiled by Harlow Shapely in 1930, and includes 21 open clusters.

* NGC 7788, aka Cr 459 and OCL 275 - classification I 2 p (same as King 12). In the photograph, it does look similar to King 12, which makes me wonder why King 12 wasn't included in the NGC catalog. One reference has it as a visual magnitude of 9.4, with 20 stars in the cluster. The Cr designation is from a catalog of 471 open clusters compiled by Per Collinder in 1931 as part of his graduate thesis.

* NGC 7790, aka OCL 276 - classification III 2 p, meaning that it is detached from the surrounding star field but with no noticeable concentration, medium range of brightness, and less than 50 stars. It strikes me as having a similar concentration to 7788 and King 12 which have a concentration rating of I rather than III. it contains 40 stars, with the brightest at mag 10.9. This cluster contains three Cepheid variable stars.

* Berkeley 58 - classification IV 2 p (same as Harvard 21). This is the last one in the line of clusters in the image, near the bottom right. It is listed as having a visual magnitude of 9.7, with 30 stars, the brightest at mag 15.0. A descriptionm from Deep sky Catalogs on github: "This Catalogue consists of 104 open star clusters, 88 of which were originally published in 1958 by Gosta Lynga of the university of California in Berkeley. Only 21 of these clusters are also included in other catalogues, including 5 NGC and 1 IC object. Berk 42 (= NGC 6749) is now classified as a globular cluster, one of the most difficult NGC globulars in the sky."

There is one more open cluster in the picture, although it is basically impossible to find without a detailed star chart. It is Frolov 1. The book "Star Clusters and How to Observe Them" by Mark Allison describes Frolov 1 as "a tiny, curious little group of 4 or 5 stars visible in a 4" telescope, although a larger instrument will display several more members and reveal some of the fainter background stars. Located just under 3 deg North West of beta Cassiopeiae, the cluster itself is sparse and the brightest member only magnitude 10.6, so the overall appearance is subtle." It has a visual magnitude of 9.2. With the aid of a star chart, I believe that I see the four+ stars that make up the cluster, but I'm not certain.

The clusters King 12, NGC 7788 and NGC 7790 have been studied in a paper titled "The Young Open Clusters King 12, NGC 7788, and NGC 7790: Pre-Main Sequence Stars and Extended Stellar Halos" (https://arxiv.org/abs/1211.6398). The contents are above my comprehension level :-)

One last item of interest is a few stars from the Cool Galactic Carbon Stars catalog, compiled by C. B. Stephenson. These stars tend to be very deep red and not particularly bright.

If I had a slightly wider field of view, I could have included the clusters Stock 17 and Czernik 1.

All told, around a dozen DSO catalogs represented in the small slice of space. There are hundreds of other catalogs, but I found this an interesting learning exercise nevertheless.

Comments

Author

DaveB
Dave B
License: None (All rights reserved)
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Revisions

  • Final
    Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262, 





    
        

            Dave B
    Original
  • Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262, 





    
        

            Dave B
    B

B

Ha minus red to highlight Ha regions

Sky plot

Sky plot

Histogram

Abell 85 / CTB 1, NGC 7788, NGC 7790, Berk 58, Harvard 21, King 12, Frolov 1, We 2-262, 





    
        

            Dave B

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