Omicron Velorum

IC 2391, Caldwell 85, an open cluster in Vela

Magnitude: +2.6Diameter: 10 light years.
Apparent size: 60 arc minDistance: 570 light years.

Live Fast, Die Young

About 36 million years ago – 570 light years from the Solar System – a cloud of gas in the Milky Way, gravitationally collapsed inwards and became a stellar nursery. About thirty stars were born and today we see them as a loose group of hot young stars in the Vela constellation called the Omicron Velorum Cluster.

The cluster is named after the brightest star it contains, Omicron Velorum, which is a Class B star (meaning it is very big, very young and very hot). It is also a pulsating variable star with a period of 2.8 days.

Most of the other bright stars in the cluster are also B Class stars, between 10,000ºK and 30,000ºK. These stars live their lives in the fast lane and will all die young.

Feature image date:2021-03-25
Exposure:25 minutes (7 subs @215.8 sec)
Field of View:76.7 x 51.1 arcmin.

Making Improvements

I’ve been refining my telescope equipment and processes over the last nine months. Hardware additions have been an Ha/OIII duo-pass filter, an electronic focuser and a street lighting glare mitigation screen. I’ve improved my software by installing the ASCOM astronomy platform, EQMOD and Cartes du Ciel navigation & mount control systems, plate-solving and electronic focusing control.

An image from 2020 showing the timber post mounted glare screen (left) which protects the telescope from the unnecessary glare of an over-bright council street light

The bottom line with the software upgrade is that my laptop now has full control of almost everything the telescope does, from polar aligning, focusing, target selection, navigation, sky quality measurement and exposure settings, guiding, imaging and stacking. This leaves six pieces of equipment now surplus to requirement:

All now redundant: telescope hand controller; red dot finder; dual finder bracket; game-pad hand controller; finder-scope; and manual focusing hand controller.

To me the most revolutionary recent improvement in amateur astronomy has been the introduction of plate-solving software – a process which replaces the (time consuming and error prone) need to carry out a three star alignment of the telescope. Once the computerised polar alignment is done, all I need to do is select a target and command the telescope to slew to it. Once it does that, the software analyses the stars in the next image downloaded. It then (i) calculates the exact location which the image (and ‘scope) is actually centred on; (ii) compares it to the location where I intended it to be centred; (iii) calculates the targeting error; and (iv) automatically slews to correct that error and the next image will pop up accurately centred on the target..


Under the Moonlight

After my previous rant about continuous clouds every night, I managed a couple of nights under the moonlight, so I may have a few images to process and post during my upcoming telescope-free weeks.

Thanks for reading this far down the page!

Telescope Details

SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.
Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.
SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.
Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
Software: Telescope control: Cartes du Ciel, EQMOD, PHD2, Imaging: SharpCap, Gimp.
Observatory location: 34° South.

Location of IC2391 in Vela

Location of Vela Constellation

Images courtesy of

If the images do not appear it is because the Astrometry website is sometimes off line.

I’m a founder member of Macarthur Astronomical Society

Images © Roger Powell


  1. Impressive inventory of cutting edge accessories and tools, including the indispensable SLGMS device. The image is awesome (as always) , and I find the age of the cluster to be young, at 36 million years, …an almost comprehensible span as compared to life on Earth (3.7 Billion years.) M 🙂

    Liked by 1 person

  2. It’s a bit like photo processing software . . . it analyzes the image, makes adjustments in alignment, contrast, brightness, highlights, shadows, correct color cast, and more . . .

    Soon, you and I will be able to just relax and read a book while our software enjoys our hobbies.

    Nice photo . . . being so young, did you have to use a rattle and squeeze toys to keep them from wandering off or looking away while you snapped the photos?

    Liked by 1 person

    1. 😂

      Some of my fellow amateur astronomers seem to head off and watch tv or whatever. They have everything completely automated and controlled from indoors. I don’t think I could ever sink that low. 😲

      Besides, I set up out the front, not in the back garden.

      I like being able to control everything from my lap top but I still have one USB cable to the telescope and I also like to be under the stars – but I don’t live in a cold high latitude where it snows.

      Liked by 2 people

  3. Nice image! Next step will be using an executive program (CCD commander, Maxim DL, Voyager etc etc) to run all of that software so all you have to do is turn the equipment and laptop on and open one application 🙂
    By the way I hope you’re keeping the chair, at least I think it’s a chair, the one with the crescent moon and stars on it!

    Liked by 1 person

    1. Hi Dave, good guess but it’s not a chair, it’s a telescope dust protection cover, which my Bride made for me.

      When I get to the level of expertise that you are suggesting I will be sure to consult you first!


  4. Plate solving and the closed-loop correcting slew are indeed magic. When I first read that my system could do it I thought I must have been reading wrong. Can you also do a meridian flip automatically now?

    Beautiful image. Thanks, as always, for the southern tours. Keep up the good work. -Mark


    1. Hi Mark, thanks. Meridian flips were optional on the Synscan hand controller but I always wimped out of trying it. I understand that EQMOD also has that option and I will probably test it one day soon. Do you find that meridian flips function reasonably accurately?


    1. The more massive the star, the shorter the life span.
      Tiny red dwarf M-class stars could live for trillions of years.
      Heavier G-class stars like the Sun might last 10 billion years.
      Truly massive and O and B type stars will burn through their life cycle in just a few tens of million years.

      Liked by 1 person

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