Tuesday 17 April 2018

Jazzing up Open Clusters

Hi everyone,

This year has been very lean pickings.  So my apology for the poor frequency of posts.

Of all the deep sky objects, open clusters have proven to be the most difficult to lay down in a way that conveys the sparkle that we see through the eyepiece.  This has been the main reason why I’ve avoided sketching them.

This last Sunday, the sky for once was remarkably clear hear at home, despite the warm day and smoke from major bushfires happening in southern Sydney.  With the Southern Cross being high up early in the evening, I thought it would be a good opportunity to experiment a little with some open clusters and trying to work out some ways to add that sparkle.

There are two magnificent open clusters that are bright and spectacular.  IC 2602 is also known as the Southern Pleiades, is very bright and large cluster just south of Eta Carina.  IC 2606 is just over 1.5° in diameter.  NGC 4755, the Jewel Box, is a gorgeous bright and compact cluster in the Southern Cross.  Its name comes from the lovely colours of white and red that can be seen in the component stars.

I sketched each in turn and photographed each before attempting some jazzing up techniques.  Through the eyepiece, these are quite spectacular clusters.  Being located in the band of the Milky Way, there is a certain background glow that goes to brightening the background, and adds to the pizzazz of the image.  The longer you spend looking at these clusters, the more and more stars you begin to make out as your eye adapts to the view.  It really is quite amazing.

So here are the two clusters.  And as always they appear as just dots on a black page…  <sigh>

Now, how to give some lift to these?

I’ve tried two techniques here.  The first is a very soft application of soft pastel dust to the cluster (Jewel Box), or around the individual component brilliant component stars (Southern Pleiades).  Ok, a little better, but still not enough.  Next, I added something I rarely ever use – the dreaded Ring Of Death… a field of view circle.  Yet this alone isn’t enough to convey the glow that is seen through the eyepiece.  So here I added another soft dusting all around the inside of the field of view circle, being careful to make it fade out coming into the field of view and not be too wide.  The idea here is to lift the overall image as it appears through the eyepiece, but not make too much impact on the cluster itself.  The trick being in the control in application of the dust around the circle.  The application of the dust on the cluster itself also needs to be very careful or it could come across as nebulosity instead of a wee lift in overall brilliance.

So, what do you think?  Any suggestions?

Difficult to convey through digital media, but hopefully the differences can be noticed.

Object:  IC 2606, The Southern Pleiades                         Object:  NGC 4755, The Jewel Box
Telescope:  8” f/4 push-pull dob                                       Telescope:  8” f/4 push-pull dob
Gear:  24mm 82° eyepiece, 33X                                       Gear:  10mm 70° eyepiece, 80X
Location:  Sydney, Australia                                             Location:  Sydney, Australia
Date:  15th April, 2018                                                      Date:  15th April, 2018

Thanks for looking,


1 comment:

  1. Brilliant! Thanks for sharing these images. I love the thoughtful presentation of "before and after" that gives insight into the visualization process.