The Pleiades

The Pleiades is a cluster of stars in the constellation of Taurus, relatively close to Earth – and is a bright object which can be easily seen without optical equipment.

The stars are mainly hot middle aged Class B stars.

Some of the blue reflection nebulosity surrounding the group has been picked up in this twelve minute image, which was cut short by cloud intrusion.

This was not even one of my original targets for the evening. I have always believed that when things go wrong in the field, then find a way to avoid going home with no image in the camera. With only minutes left before the entire sky was wiped out, it was necessary to choose an object quickly and start shooting.

The Pleiades is worthy of a future imaging session with clearer sky and longer total exposure time.

Object Details:

Messier 45, M45, Mel 22, Seven Sisters, Suburu
Constellation: Taurus.
Visual magnitude: +1.5
Apparent diameter: 120′ (about 4 Lunar Diameters).
Actual diameter: 15.1 light years.
Distance: 430 light years.
Altitude: 15° above northern horizon.


Exposure: 11.8 min: 19 @29.6 sec
Stacked:  19 of 24
Gain: 342
Date: 2019-02-03
Location: The Oaks, NSW.
Sky: semi-dark rural.
Cloud: 30% –> 95%.
Moon: no.
Image acquisition: SharpCap.
Stacking software: DSS.
Image post-processing: GIMP.
Cropping: no.
Trailing: no.
Image size: approx 1.5° x 1.0°

Imaging telescope: Skywatcher Esprit 120ED Super APO triplet refractor.
Focal length: 840 mm, focal ratio: f/7.
Imaging camera: ZWO ASI 071 MC Pro
Telescope mount: SkyWatcher EQ6-R.
Polar aligning method: QHYCCD PoleMaster.
Polar alignment error: ShatpCap averaged 1′ 32″
Guiding: not essential.
Field flattener: yes; filter: no.

Observing Notes:

A difficult night with increasing difficulty chasing diminishing gaps in the clouds.

Hopefully my alignment problems with the EQ6 mount were finally resolved, as I obtained 100% accuracy on six test objects. However,  time will tell.

Acknowledgments to my friend John who advised me that the Pleiades were still visible in a sky which seemed clouded right over.

For some reason live stacking in SharpCap produced star trailing but subsequent restacking in DSS resolved this.

Also Relevant:

Pleiades & Comet Lovejoy

Geek log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=PNG files (*.png)
Capture Area=4944×3284
Colour Space=RAW8
Hardware Binning=Off
Turbo USB=100
Frame Rate Limit=Maximum
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=50
Cooler Power=0
Target Temperature=-15
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Anti Dew Heater=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1

Images © R.Powell



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