|Designation: NGC 2070, Caldwell 103, in constellation of Dorado.|
|Visual magnitude: +5.0|
|Apparent size: 40 x 25 arc-minutes.|
|Diameter: 1833 light years.|
|Distance: 160,000 light years.|
One thing you learn in astronomy is to always keep watching the latest weather forecasts. A few nights ago I was expecting an astronomy session but got a surprise electrical storm instead. The next night I was expecting more poor conditions but ended up with a surprise astronomy session.
I decided on the Tarantula Nebula, a fabulous object 31° from the South Celestial Pole and in a part of the sky which is accessible from my observing spot at home. I had not yet imaged this object with my current setup.
The glorious thing about the Tarantula is not just that it is so prominent in our southern sky but also that it is so far away ——> in another galaxy!
It is part of the Large Magellanic Cloud (LMC), 160,000 light years away – yet incredibly it is one of the finest sights in our sky.
Wikipedia states that “this is an extremely luminous non-stellar object. Its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast visible shadows. In fact it is the most active starburst region known in the Local Group of galaxies.”
The Night Sky Observers Guide describes it as “A very bright, large nebulous mass with wisps, loops and hazy tufts…….the central region is very bright and contains the bright star 30 Doradus and another ten stars gathered around it…..one of the sky’s top highlights.”
The ill-fated Robert Burnham Jr. described it as an “object which stands forth without an equal”.
Here is a cropped version of the same image, showing more detail of the Nebula:
There are a number of other interesting objects in the LMC itself but – because it extends well beyond the field of view of most telescopes – imaging the entire galaxy requires either using a stitched mosaic approach or reverting to a DSLR camera without a telescope, something I intend having another go at soon.
I was aiming for two and a half hours exposure but only got 106 minutes because later in the session SharpCap began rejecting frames, most likely because the object was moving towards the blinding new street light installed last year by my local council. @#!&!B@*#!! 🤐
The Tarantula is not an easy image to process, because it is such a congested region. Add to that my impression that WordPress may not be presenting the colours of the image exactly as it was submitted; and the obvious (to me) fact that I have not yet got the hang of producing flat frames which completely eliminate the effect of dust particles located in the optical train.
Other objects in the above image – See my image with:
Astrometry.net annotated overlay.
They include: NGC 2009, NGC 2015, NGC 2018, NGC 2042, NGC 2044, NGC 2048, NGC 2052, NGC 2055, NGC 2069, NGC 2074, NGC 2077, NGC 2078, NGC 2079, NGC 2080, NGC 2081, NGC 2083, NGC 2084, NGC 2085, NGC 2086, NGC 2091, NGC 2092, NGC 2093, NGC 2100, NGC 2102, NGC 2108, NGC 2113 and more.
|Date: 2020-02-19.||Sky brightness (e/px/sec): 0.66.|
|Frame exposure: 45 x 142 sec.||Total exposure: 106 min.|
|Gain setting: 10.||Location: outer suburban.|
|Moon: no.||Conditions: < 5% cloud, calm.|
|Camera: ZWO ASI 071 MC Pro.||Type: CMOS 28.4mm 16 Mpx.|
|Imaging software: SharpCap Pro.||Post process software: GIMP.|
|Guiding software: PHD2.||Polar alignment: 00′ 03″|
|Cropping: (main image) no.|
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor.|
|840 mm focal length @ f/7 with field flattener.|
|Baader L-Booster UHC-S light pollution filter 2458276.|
|SkyWatcher EQ6-R Pro mount.|
|ZWO ASI120 guide camera.|
|QHYCCD PoleMaster polar aligning camera.|
Images © Roger Powell
|[ZWO ASI071MC Pro]|
Output Format=FITS files (*.fits)
Frame Rate Limit=Maximum
White Bal (B)=99
White Bal (R)=60
Auto Exp Max Gain=300
|Auto Exp Max Exp M S=30000|
Auto Exp Target Brightness=100
Anti Dew Heater=On
Apply Flat=C:\Users\powel\Desktop\SharpCap Captures\2020-02-19\Capture\flats\20_20_37.png
Subtract Dark=C:\Users\powel\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\142.1s\gain_10\dark_6_frames_-9.4C_2020-02-19T10_23_28.png
Display Black Point=0
Display MidTone Point=0.5
Display White Point=1
WordPress does a poor job of representing the photos (and it used to be even worse). It’s one reason I often link the photo to a larger version. I think part of the problem is that WP compresses the photo to speed up loading of the page (a good thing) but in doing so the photo seems to lose some of its “snap” (a bad thing).
It’s also why I link to an outside gallery like SmugMug for many of my photos.
There are a few things you can do beforehand to help show the photos better. Don’t upload a huge photo. Process it to be just a bit larger than whatever it will show at on the blog (mine is 640 wide and I usually upload one twice as wide). Also, make sure you process and output using sRGB (what the typical screen will show). Using a wider gamut will force people’s graphic card to squeeze down to sRGB and change colors it can’t represent by mapping them into colors in the display’s gamut range.
That said, they have been getting better.
One more thing: while I used to complain the colors and photos didn’t look right, that was only because I could see the original. To readers, it looks fine because they only see one version.
Case in point, I think that’s a great (and amazing) photo.
Thanks, I researched this a few months ago and the feedback was much like yours. I thought I was compliant but whilst the input complies, I’m not so sure about the output and will need to delve a bit deeper into things I don’t fully comprehend. Your comment about readers not noticing is spot on of course. You’ve given me the impetus to look more carefully about how I process the images.
LikeLiked by 1 person
Hi Roger, Why is it called Tarantula ?
Fran, many individual astronomical objects and constellations were given names in the early days of astronomy because someone said it looks like a (whatever). In this case, someone described the object as looking like a tarantula spider – and of course the name stuck.
To be honest, most astronomers would struggle to see anything more than a passing resemblance.
Thanks for asking. 🙂
That’s a super image. Can’t wrap my mind around the nebula being in another galaxy. A lot of long exposures. Well done.
Thanks, Paul. Distances are a difficult concept to master in astronomy. It’s further away than any of our globular clusters but it is a humongous nebula.
LikeLiked by 1 person
By the way, don’t know if you’ve seen this . . .
Click to access 2002.01291.pdf
LikeLiked by 1 person
Thanks for the link. I had read some news reports of this structure but not researched the originating paper, which is best practice, especially if sharing on social media.