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Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis

Rosette SHO with RGB stars: Kepler KL4040 First Light

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Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis

Rosette SHO with RGB stars: Kepler KL4040 First Light

Equipment

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Acquisition details

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Description

This image is the “first light” image for our new Kepler KL4040 sCMOS camera. It takes some getting used to, as it delivers two images for each frame, with high and low gain. Luckily I’ve had good advice from Tolga which has helped a lot. As there’s no TheSkyX X2 driver for this camera yet (it’s expected very soon) I’ve been using Windows (instead of my usual macOS) and the ASCOM driver.

Following Tolga’s advice, the way forward is to calibrate and combine the high and low gain data independently (being careful to use the same reference image for alignment in each case), and then blend the master frames. One way to do that is with FLI’s own software, another is with an equivalent expression in PixelMath. In my testing though, I found that PixInsight’s HDR Composition tool gives as lightly better result.

I still have a little bit of work to do to fine-tune the image train tip-tilt, but was impatient to get this first-light image ;-)

The Rosette Nebula in Monoceros is a stellar nursery, where new stars are born from the gas and dust of the nebula. The cluster NGC 2244, at the centre of the image, consists of stars only a few million years old, but their powerful stellar winds have cleared the central region of the nebula, a cavity estimated to be about 50 light-years across. The nebula is about 130 light-years across and is about 5200 light-year from Earth. It is catalogued with several entries in the New General Catalogue (NGC), published in 1888. This demonstrates that the optical observations on which the catalogue was based were unable to reveal the full structure of this nebula, which is almost 3 times the diameter of the full moon in the sky.

The bulk of the image has been taken with narrow-band filters, in the SHO scheme of the Hubble palette. But I also made an LRGB image so that I could import the full-colour stars into the false-colour, narrow-band image.

Acquisition details:

Camera: FLI Kepler KL4040

Guide-camera: LodeStar X2

Telescope: Officina Stellare Ultra-Corrected RC360

Mount: Paramount ME II

Image scale: 0.94 arcsec/pixel

Total exposure: 6h 50m + 2 hours for stars

Filters:

H-alpha: 14x 600 sec

O III: 13x 600 sec

S II: 14x 600 sec

For the stars:

Luminance: 6x 300 sec

Red: 7x 300 sec

Green: 6x 300 sec

Blue: 5x 300 sec

Comments

Revisions

  • Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis
    Original
  • Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis
    B
  • Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis
    C
  • Final
    Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis
    D

B

Description: A few Photoshop tweaks, since the rendering on the AstroBin page is more subdued than it seemed on my PixInsight view. So, here, it looks more garish than it did, but hopefully after the Astrobin induction, it will look more as I intended.

Uploaded: ...

C

Description: I noticed that the image after introducing the RGB stars had changed colour. Clearly the alpha channel of PixelMath is not behaving as I had assumed and the red-dominated nebulosity is coming in too. So now I tried another approach to get the same result.

Uploaded: ...

D

Description: Another go at this -- I'm still learning ;-) For this one I left out the RGB stars as I can't get them looking natural yet, even though I have now found out what I was previously doing wrong. And I improved the contrast a bit. Again, like the others, this one has the colour profile attached, and we'll see if the colours on Astrobin match those I see in Pixinsight and Photoshop. Answer: no.

Uploaded: ...

Histogram

Rosette SHO with RGB stars: Kepler KL4040 First Light, Richard Francis