Open Clusters RA 17h–19h

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NGC 6520

Observation Details

Location: Buckeye, AZ (33.3705° N, -112.5836° W)

Date: 2026-08-16

Time: 22:09 – 22:44 MST

Sky conditions: Seeing – Good, Transparency – Mag 5, Bortle 5

Instrument: C8, UV/IR Cut filter, ASI533MC Pro

Image capture details: 30x60s subs, mosaic mode, 30 minute integration

Software: PixInsight, Photoshop

Trumpler Class: I 2 m n – strong central concentration, moderate range in brightness, a medium-rich population of stars, and associated nebulosity

Description: NGC 6520 is a small, compact open cluster with a noticeable concentration of stars toward the center. The cluster contains a mix of brighter blue-white stars and many fainter stars packed closely together. One of my favorite features is the nearby dark nebula Barnard 86, which creates a dark patch against the dense star field and makes the cluster stand out even more.

NGC 6530

Observation Details

Location: Buckeye, AZ (33.3705° N, -112.5836° W)

Date: 2026-08-16

Time: 21:20:59 – 23:39:11 MST

Sky conditions: Seeing – Good, Transparency – Mag 5, Bortle 5

Instrument: Seestar S50 – EQ mode, Star Adventurer 2i

Image capture details: 198x30s subs, mosaic mode, 99 minute integration

Software: PixInsight, Photoshop

Trumpler Class: II 2 m n – moderate central concentration, moderate range in brightness, a medium-rich population of stars, and associated nebulosity

Description: NGC 6530 is a loose open cluster embedded within the Lagoon Nebula, Messier 8. The cluster contains a mix of bright and faint blue-white stars scattered across the surrounding nebulosity. I especially like how the stars of the cluster stand out against the glowing gas and dark dust of the Lagoon Nebula, making this much more interesting than the cluster alone.

NGC 6705 (M11 – Wild Duck Cluster)

Observation Details

Location: Decatur, GA (33.7748° N, 84.2963° W)

Date: 2025-08-7

Time: 21:19 – 23:06 ET

Sky conditions: Seeing – Good, Transparency – Mag 4, Bortle 8

Instrument: Celestron C8, Optolong L-eNhance Filter, 0.63x SCT Corrector, ASI533MC Pro

Image capture details: 90x60s subs, 1 hour 30 minute integration

Software: ASIDeepStack, PixInsight, Photoshop

Trumpler Class: I 2 r – strong central concentration, moderate range in brightness, and a rich population of stars

Description: Messier 11 is an incredibly rich and compact open cluster surrounded by the dense star field of the Milky Way. The cluster is made up of hundreds of mostly blue and white stars, with a few brighter yellow and orange stars scattered throughout. The brightest stars form a V-shape that resembles a flock of flying ducks, although this shape is much easier to see visually through an eyepiece than in my image. I especially like how the tightly packed blue and white stars of the cluster stand out against the warmer, golden stars surrounding it.

NGC 6709

Observation Details

Location: Buckeye, AZ (33.3705° N, -112.5836° W)

Date: 2026-08-16, 2026-08-17

Time: 23:46:55 – 00:45:43 MST

Sky conditions: Seeing – Good, Transparency – Mag 5, Bortle 5

Instrument: Seestar S50 – EQ mode, Star Adventurer 2i

Image capture details: 80x30s subs, 40 minute integration

Software: PixInsight, Photoshop

Trumpler Class: III 2 m – no noticeable central concentration, moderate range in brightness, and a medium-rich population of stars

Description: NGC 6709 is a loose open cluster with stars scattered irregularly across the field and little concentration toward the center. Several brighter stars stand out among the many fainter members, with a few small groups and patterns visible throughout the cluster. The edges aren’t very well defined, so the cluster gradually blends into the surrounding star field.

NGC 6811

Observation Details

Location: Buckeye, AZ (33.3705° N, -112.5836° W)

Date: 2026-08-17, 2026-08-18

Time: 22:22:58 – 01:07:42 MST

Sky conditions: Seeing – Good, Transparency – Mag 5, Bortle 5

Instrument: Seestar S50 – EQ mode, Star Adventurer 2i

Image capture details: 218x30s subs, mosaic mode, 109 minute integration

Software: PixInsight, Photoshop

Trumpler Class: III 1 r – no noticeable central concentration, little range in brightness, and a rich population of stars

Description: NGC 6811 is a rich open cluster made up of many similarly bright stars with very little concentration toward the center. One of its most noticeable features is the darker, relatively empty area near the center, which gives it the nickname the “Hole in the Cluster.” I especially like its unusual ring-like appearance, with many of the stars appearing to surround the darker center.

Project Objectives

Open Cluster Observing Program page: https://www.astroleague.org/open-cluster-observing-program/

Record the location (Latitude and Longitude), date and time, Seeing and Transparency, telescope aperture, power, and a brief description of the observed object, the Trumpler classification, and an image of any 100 (Silver Level) or 125 (Gold Level) and include the equipment and processing used for clusters from the lists.

Silver Level, Imaging:

  1. Image 100 of the open clusters on the provided lists.
  2. Classify all 100 of the imaged open clusters using the Trumpler classification system.
  3. All observing techniques may be used under the basic program, including go-to, computer-controlled, star-hopping, digital setting circles, imaging, etc.​

Gold Level, Imaging:

  1. Image 125 of the open clusters on the provided lists.
  2. Classify all 125 of the imaged open clusters using the Trumpler classification system.
  3. All observing techniques may be used under the advanced program, including Go-To, computer-controlled, star-hopping, digital setting circles, imaging, remote telescopes, etc.