Nebula IC2948

Caldwell 100

Image exposure:
16 Minutes
Image Size:
1.96º x 1.31 º
Image date:

With the development of new techniques for astronomical image processing, I’ve noticed an increasing tendency for fellow astro-photographers to regularly eliminate stars from their latest images, in order to accentuate their real targets: the nebulosity.

It’s a wonder they don’t take photos of the Moon and then suppress all the craters in order to accentuate the ‘real’ Moon. It’s their legitimate choice of course. However, I don’t get it and if you ever see me doing this, you can take me out the back and shoot me. (Not literally but metaphorically please).

I like stars. Every star was born in a nebula and they are an integral part of the show. I don’t think the above feature image would be improved by masking all the stars out, using what some might call black magic software techniques.

What really would have improved my image? More exposure to improve the nebula detail! I was fortunate to get a lousy 16 minutes exposure before being forced into giving up for the night. Not to mention an astro-disastrous summer of rain and cloud, I’ve had numerous imaging issues to deal with recently, including fuses rupturing, USB unreliability and software dropouts. . . . . but after making technical improvements, I see lots of stars ahead.


Lambda Centauri (HD 100841) is the very bright (third magnitude) star in the centre.

IC 2948 is the nebulosity around the bright star Lambda Centauri.

IC 2944 is the associated star cluster in IC 2948.

The two detached tenth magnitude nebulae (far right) are Gum 39 and IC 2872

Centaurus In The Sky Down Under

🔹 Images © Roger Powell
🔹 Esprit 120 refractor.
🔹 Focal length: 1680 mm.
🔹 EQ6-R Pro mount.
🔹 Astronomik CLS filter.

Bushfire smoke!
Cosmic Focus Observatory 2023-03-16.

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Images copyright R. Powell



  1. I love the beautiful reds and the spray of stars. I agree with you about leaving the stars in their place. I accept and use software adjustments to increase details that are present. But, the image should remain a testament to what was actually there. Otherwise, is it an image, or a work of art?

    Liked by 1 person

    1. I’ve pondered this for quite a while now and I think they are entitled to remove the stars but to remain true they should always state that they have done so. A bit like assigning colours to an ultraviolet image, they would inform the person viewing it that false colours are used.

      Liked by 1 person

  2. Another impressive image.

    As for the stars . . . I’m trying to imagine what that would look like, but it seems we’d lose structure and texture. A gaseous blob wouldn’t be all that interesting (for example, Trump).

    I imagine just playing with highlights and contrast would eliminate a fair number of the visible stars or at least diminish their visual impact. As you say, it’s a matter of tastes.

    As for letting the audience know what they’re looking at, I agree. If I alter a photo (removing or adding something), I usually inform the viewers of the fact.

    Liked by 1 person

    1. Don’t get me started on that gaseous blob.

      Masking stars to create a slight reduction in their size is ok with me. I’ve never done it but I wouldn’t rule it out. The reason? To the naked eye, stars are very bright pinpoint light sources. To a camera, star brightness is measured by spillage into surrounding pixels. So star reduction is acceptable to me but elimination definitely not!


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