Observation by Martin Butcher: Melotte 20 (1) - The Alpha Persei Cluste...

Uploaded by

Stuart Morris


Martin Butcher


2010 Oct 11 - 04:29


2021 Mar 27 - 12:00


The Alpha Persei Cluster (Melotte 20)
Collinder 39

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Field centre

RA: 03h22m
Dec: +49°22'
Position angle: -1°49'

Field size

6°32' × 4°20'

  • Meade LX-90 8" telescope fitted to its field tripod by an equatorial wedge.
  • LX-90 Periodic Error Correction enabled.
  • Dew Removal straps fitted to telescope and camera lens
  • Telescope and camera powered by Mains Power.
  • Stock Canon 40D with 200mm f/2.8 lens stopped down to f/4
  • Telescope driven but unguided

Six sub-exposures each 5 minutes long taken at ISO800.


Isle of Colonsay

Target name

Melotte 20


Melotte 20 (1) - The Alpha Persei Cluster

About this image
Melotte 20,  The Alpha Persei Cluster, also known as Collinder 39, is an open cluster of stars in the northern constellation of Perseus.


Processing details:- After quality control 5 sub-exposures calibrated with Dark, Flat-field and Bias master frames before being combined in Images Plus. This image was then further processed in Photoshop CS3 and Noise Ninja. North is at the top. Image field of view 6.3 degrees x 4.2 degrees.




Narrative description:- Three days after New Moon, the Moon had set before the images were taken. The weather was cold and clear with a stiff breeze from the north east (the telescope was therefore set up to the west of my house). With the wind there was no dew. In hindsight I am surprised that I was able to take 5 minute sub-exposures without any star-trailing but on checking my manuscript notes it is clear that this was so.


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