Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.


A Cluster of Pearls in the Southern Skies ( NGC 3766 "The Pearl Cluster" in Centaurus ) - updated

Recommended Posts

21st April: Re-processed to better show the colour of the fainter stars ...





Shimmering like a pearl to the naked eye, this open cluster of mostly young blue stars ( known as the "Pearl Cluster" ) is approximately 5500  light years from Earth and was discovered by Abbe Lacaille in 1752 from South Africa.  

This HDR image is constructed from 11 sets of exposures ranging from 1/4 sec ( to capture the centre of the brighter stars ) through to 240 seconds ( for the fainter stars of the Milky Way ).  Total exposure time was around 5 hours.


A Cluster of Pearls in the Southern Skies ( NGC 3766 " The Pearl Cluster" ) 
( please click / tap on image to see larger and sharper - a full size image can be found here )

12 April 2018


Image details:

Field of view ..... 58' 49.8" x 39' 36.4"
Image center ...... RA: 11 36 03.890  Dec: -61 35 30.17
Resolution ........ 0.586 arcsec/px  ( full size image )
Orientation: North is up

Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ).
Corrector: ASA 2" Coma Corrector Quattro 1.175x.
Effective Focal Length / Aperture : 1470mm f4.7

Mount: Skywatcher EQ8
Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 

Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.91um pixels)

Blue Mountains, Australia 
Moderate light pollution ( pale green zone on darksitefinder.com map )

Capture ( 12 April 2018 ):
11 sets of sub-images with exposure duration for each set doubling ( 1/4s to 240s ) all at ISO250.
( 70 x 240sec + 10 each forthe other durations )

Calibration: master bias, master flat and master dark
Integration in 11 sets
HDR combination 

Pixinsight April 2018

Edited by MikeODay
  • Like 9

Share this post

Link to post
Share on other sites
17 hours ago, pi_co100 said:

Beautiful! Thanks for sharing.

Cheers, thanks for that.

Share this post

Link to post
Share on other sites
4 minutes ago, Allinthehead said:

Wonderful work Mike. Your hdr method works very well with star clusters.

Thanks Richard.  It certainly helps to bring out the subtle colours :)

Share this post

Link to post
Share on other sites

A subtle tweak to lift the background a little ...


What do you think, better or not ?

Edited by MikeODay

Share this post

Link to post
Share on other sites

And some crops from the full size image ( the top two can be enlarged further by clicking on them, the bottom three are already at 100% ).












I fascinated by the twirls, swirls and straight lines formed by the apparent positions of the stars.

Edited by MikeODay

Share this post

Link to post
Share on other sites
8 hours ago, MikeODay said:

What do you think, better or not ?

Yes the second is better, slightly brighter without making the stars bigger.

Share this post

Link to post
Share on other sites

Thanks Richard.  After working on and looking at an image for a long time I sometimes find it hard to judge the impact of small changes so another pair of eyes are much appreciated :)


Share this post

Link to post
Share on other sites

Re-processed to bring out the colour in the fainter stars ...










Edited by MikeODay

Share this post

Link to post
Share on other sites

Some more 100% crops showing patterns and the colours ranging from bright blue to deep orange











Edited by MikeODay

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By StarMich
      I'm aiming for the best possible field illumination for my Explore Scientific PN208 f/3.9 imaging newtonian. The scope is 5 years old now and while doing maintenance I wanted to do something about the design flaws as well.
      With the current secondary holder design it's impossible to center the mirror beneath the focuser. My question is: is this really an issue when the entire primary is visible? I read about optimal field illumination when the secondary is centered, but this isn't achievable with this telescope.
      I attached an image showing the (very bad aligned and already degrading) secondary at the moment. This is as far down as I can go, I would need to replace the holder screws with longer threads to go further but I don't know if it would make any difference for field illumination?
      Thanks in advance,

    • By EMG
      Recently I bought a ZWO ASI178MM for planetary/lunar/deep-sky imaging and last weekend i had clear skies so I was able to capture videos of the moon in two panels. I have already processed the videos in AutoStakkert, I used 3x drizzle because I intend to print the image so now I have two 120MB TIFF images that i would like to combine in a two panel mosaic. I tried doing it in Hugin, a free panorama stitcher but the program crashes due to the file sizes being too large. I have searched for tutorials on using DynamicAlignment in PixInsight but it seems to me that i'll need a reference image to be able to create mosaics in PixInsight. Is there any way to go about this, I feel like this should be a pretty straightforward job but I am not very experienced in PI so I would really appreciate some advice.
      I tried using DynamicAlignment as you can see in the attached screenshot but the result was just a cut version of the target image, aligned perfectly to the source image. It would be perfect if it didn't cut off the lower part of the target image.

    • By runway77
      Hello, I am having a problem with a relatively expensive flat field eyepiece in a combination with a newtonian reflector. I am unable to achieve proper focus with that eyepiece because when I focus it on axis, the edges are blurry. When I focus it at the edge, the center field is out of focus. I don't want to mention the concrete type of this eyepiece because I received it with a spot on the bottom barrel, therefore I cannot be sure whether it has been dropped. This eyepiece has very good reviews on this forum. Optically it looks good and there is no rattle. My question is whether these flat field eyepieces are usable with newtonians as these telescopes doesn't generally suffer from the field curvature. Many thanks for help.
    • By Spacecake2
      What telescope brand would you choose?
      Reply below for your favourite telescope brand. It would be really helpful to know which brand to buy.
      Celestron, Meade, Orion, Skywatcher  etc.  
      Thank you for viewing
    • By Spacecake2
      Does anyone know if I should upgrade my telescope? I have a Celestron Nextar 127slt and I've been using it for a few years now. I want to see more detail on Jupiter, Saturn and Mars.
      Does anyone have any suggestions from Celestron?
      Kind Regards
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.