Melotte 15, the centre of the Heart Nebula, IC 1805, in Cassiopeia. The clouds in this nebula are shaped by the stellar winds and radiation from the massive hot stars in the nebula’s new-born star cluster, Melotte 15. These stars, estimated to be only 1.5m years old, are surrounded by clouds of dust and ionised gas including hydrogen, oxygen and sulphur, mapped here to green, blue and red hues in the Hubble Palette. This view spans approximately 90 to 100 light years across and lies 7,500 light years away from us.
I imaged this target from my back garden observatory in Oxted on the nights of 27th December 2020, 23 January 2021 and 18 February 2021. The image consists of the following sub-exposures: Ha 18x600s; OIII and SII 11x900s each all binned x 2 giving a total exposure time of 8 hours 30 minutes. I used a Televue NP101is (4 inch) refractor at f/5.4 mounted on a Paramount MX using a QSI 690 CCD camera and Lodestar 2 guide camera. Image capture was done with Maxim DL and I used CCD Stack2, Photoshop CS5 and Topaz Labs Suite for further processing. Thanks for looking.
Tim C
Tim,I think you have surpassed yourself, what a fantastic image. I would love to know how you get such vivid colours and detail from the processing.
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Hi James and Trev
Many thanks for your kind comments. I am particularly pleased with this one, especially as it was meant to be a ‘test’ target with my Televue NP101 refractor which had just come back from the manufacturer in the USA having been serviced and re-collimated (not a cheap exercise, especially during 2020 and the transport difficulties caused by Covid 19!) As to the colour saturation, I think this image really benefitted from having 900s (15 minute) sub-exposures binned x 2 for the OIII and SII channels (just to recap, in Hubble Palette SII=red, Ha=green and OIII= blue). The Ha channel is usually stronger and only really needs 10 minute unbinned subs or 5 minute binned x 2 subs. In this instance, as Ha was providing the luminance channel (ie a lot of the fine detail) I used unbinned 10 minute subs to get better resolution and as much detail as possible.
With regard to processing workflow, I use a standard process in CCDStack2 to calibrate, align, stack, data reject and mean combine the sub-exposures to get a master image for each channel which I then save as TIFF files and process further in Photoshop. I use different workflows for broadband and narrowband images in PS and I’ve developed these workflows from research: reading books and web articles, tutorials, seeing what other astro-photographers use and do, plus a large amount of trial and error. I also use a couple of PS plugins for things like fixing gradients and de-noising images. I used to get annoyed reading articles which said that every image is different and one can’t use exactly the same process for every image, but I’ve found this to be true. Different targets and data quality require different processing techniques to draw out the essential features of the target and to create something that is aesthetically pleasing. I would say that patience and the willingness to experiment are essential. I often take 2 or sometimes 3 attempts at processing a target before I am happy enough to publish it. I always try to leave gaps during the processing to come back and re-evaluate the image and think about the next processing step before carrying on with the processing. Don’t rush it. This particular image probably took 6+ hours in total processing time over the course of a week to get to the finished article.
Anyway, I think to say any more about particular techniques would require an offline conversation or session, but I hope that you find at least some of the above to be useful.
Best wishes
Tim C
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On 30 Sep 2021, at 00:02, tcos...@gmail.com wrote:
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