Tweedledee (IC 4756) and Tweedledum (NGC 6633) Open Clusters

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celeron787
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Joined: Sun Jan 12, 2020 2:30 pm

Tweedledee (IC 4756) and Tweedledum (NGC 6633) Open Clusters

Post by celeron787 »

Taken on the exceptionally clear night on 16/07/2020.
NGC 6633 (top) open cluster lies in a very rich star field in the constellation of Ophiuchus. Just 3° East of NGC 6633 in the tail part of the constellation Serpens, lies the almost equally bright, but larger open cluster IC 4756 (bottom).

Both NGC 6633 and IC 4756 are also referred to as the Tweedle-Dum and Tweedle-Dee clusters due to their proximity in the sky. In Lewis Carroll's classic children's book "Through the Looking Glass and What Alice Found There", it describes Alice's encounter with the "fat little," pugilistic twins called Tweedledum and Tweedledee. The twins' names have become synonymous with any two people, places, or things worthy of comparison.

View plate-solved version here: http://nova.astrometry.net/annotated_full/4387019
Single frame vs stacked vs post-processed image here: https://i.imgur.com/0J5nXZH.jpg

Equipment
Sony A6000
Samyang 135mm F2.0
Sky-Watcher Star Adventurer
Tripod

Acquisition
ISO400
Light frames - 147 x 15secs
Dark Frames - 30 x 15secs
Flat Frames - 30
Bias Frames - 50

Software and Processing
Deep Sky Stacker
Photoshop - Levels stretch, gradient removal using Dust and Scratches filter, crop, levels stretch, luminance mask, curves adjustment, star glow
Lightroom - Adjusted highlights, saturation and colors

Image

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Airconvent
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Re: Tweedledee (IC 4756) and Tweedledum (NGC 6633) Open Clusters

Post by Airconvent »

Nice story behind the names. :)
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