Melotte 15: the heart of the Heart Nebula
timc
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
trevsie7
JR
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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tcos...@gmail.com
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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John Mills
Well, you certainly have mastered the imaging processing for NB images!
That one is a cracker and your best so far ;-)
I see you mentioned you sent your TeleVue NP101 back to the US to get it
serviced and recalibrated? I bet that cost a fortune! My TV F/5 Genesis
could do with a service and having the lenses cleaned.
I cleaned the top doublet by removing the cell a few years ago and using
isopropyl which improved it considerably, but the really dirty lens is
the fluorite element at the bottom end of the tube. No way can I take
(or would) that one out as I couldn't find any screws that would release
the cell and no idea how it is attached.
TBH, I haven't used my TV 4" F/5 Genesis for years. Certainly not for
astrophotography. I always found large blue stars in images were heavily
bloated. It may be a fluorite refractor, but I wouldn't class it as an
APO. My Ikharus 105mm is better in that respect, but even that tends to
bloat stars (but less than the TV) imaged through the blue filter.
Some of the best images I've taken was using Ian King's 10" RCT at
Nerpio a few years ago, but due to collimation issues he no longer has
that scope. He now uses a Skywatcher 150mm APO these days and from a
better dark sky site further south in Spain. That's also a good scope
and well colour corrected.
BTW, no imaging done from here recently... Not forgetting to mention
there's a volcano kicking off a few miles away from my place! A good job
I live on the east side of La Palma and not on the west!
ATB John
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JR
On 30 Sep 2021, at 00:02, tcos...@gmail.com wrote:
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William Bottaci
The Hubble palette choice of colours, we've come across this before; it may seem odd that hydrogen α isn’t red but they have their reasons (like SII is even 'more' red). Other observatories do have hydrogen α as red:
Hubble Space Telescope palette (SHO=RGB),
Canada France Hawaii Telescope palette (HOS=RGB)
but with us seeing Sulphur on earth as being yellow we think it odd. Eventually people tend to like what they are used to. The more scientific you get, the less colour interpretation has meaning.
Amazing what can be done now with small telescopes. With the Hubble ST approaching the end of its life and the James Webb telescope yet to launch, perhaps Tim NASA can use you in between :).
Thank you for sharing; keep up the good work.
William
On Thu, 30 Sept 2021 at 09:28, 'JR' via croydonastro <croydo...@googlegroups.com> wrote:
Well, you certainly got your money's worth having the telescope serviced
James
Hi Tim,
Well, you certainly have mastered the imaging processing for NB images!
That one is a cracker and your best so far ;-)
I see you mentioned you sent your TeleVue NP101 back to the US to get it serviced and recalibrated? I bet that cost a fortune! My TV F/5 Genesis could do with a service and having the lenses cleaned.
I cleaned the top doublet by removing the cell a few years ago and using isopropyl which improved it considerably, but the really dirty lens is the fluorite element at the bottom end of the tube. No way can I take (or would) that one out as I couldn't find any screws that would release the cell and no idea how it is attached.
TBH, I haven't used my TV 4" F/5 Genesis for years. Certainly not for astrophotography. I always found large blue stars in images were heavily bloated. It may be a fluorite refractor, but I wouldn't class it as an APO. My Ikharus 105mm is better in that respect, but even that tends to bloat stars (but less than the TV) imaged through the blue filter.
Some of the best images I've taken was using Ian King's 10" RCT at Nerpio a few years ago, but due to collimation issues he no longer has that scope. He now uses a Skywatcher 150mm APO these days and from a better dark sky site further south in Spain. That's also a good scope and well colour corrected.
BTW, no imaging done from here recently... Not forgetting to mention there's a volcano kicking off a few miles away from my place! A good job I live on the east side of La Palma and not on the west!
ATB John
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 x2 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
That has got to your best image so far Tim. A triumph.
I've said it before, but it could be from Hubble. The colours, detail and clarity are amazing.
How do the colours map to the narrowbands eg Blue = Ha?
James
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.