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Elephant Trunk Nebula in IC 1396

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About this observation
Observer
David Arditti
Time of observation
07/10/2018 - 03:00
Object
Elephant Trunk Nebula
Observing location
Edgware, Middlesex, UK
Equipment
81mm Apochromatic refractor
Field flattener
H alpha, OIII and CLS filters
Artemis 285 mono camera
Exposure
Total 5 hours 35 mins
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This was created using a similar method to the image of the Pelican Nebula that I recently posted: that is, with two narrow band filters and one broad band light-pollution filter. The H alpha signal was mapped to the red channel in the image, the OIII to the blue, and the green channel was created from a mixture of OIII and CLS. The CLS image was also used for the luminosity layer. It is thus a false-colour image that simulates true colour in a way that excludes the worst of my local light pollution.  The method, which might be my own invention, would be a lot easier if all manufacturers made their filters the same thickness, but they do not. Because the CLS and narrow-band filters are from different manufacturers, Astronomik and Astrodon, the focus points and image scales are changed slightly, necessitating careful correction at compositing stage.

IC 1396 is an area of emission nebulosity that is far larger than the field here. The 'Elephant Trunk' is an area of compression of the gas, where winds from stars newly-formed in the small dark dust clouds are pushing back the surrounding envelope.

The 81mm William Optics apochromatic triplet refractor I used was donated to the BAA, and is still for sale, with an undriven mount. Offers invited, see p303 of the October Journal.

The British-made Artemis 285 camera is 12 year old and still going strong.

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