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juliangeorgeshaw

The best globular cluster in the sky?

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Kiwi astronomers are divided. Half of them think Omega Centauri is the best globular cluster and the other half think it's 47 Tucanae. M13 just doesn't rate!

This is my image of Omega Centauri taken earlier this year with my trusty Tak Baby Q and an HEQ5 with cut down legs that I took with me by plane in two suitcases to New Zealand. (To save weight I bought new counterweights in NZ, mail order from NZ Telescopes in Timaru; recommended.) My subs were RGB using Astrodon filters, 9x360 sec each filter. (The subs were only 6 mins long on account of my modern, high sensitivity Atik 460ex camera  :evil: and, possibly naively, I was afraid of burning out the core.) 

I started imaging at Stargazers B&B in Kuaotunu, on the Coromandel Peninsula of the North Island of New Zealand. I finished at a motel on the shores of Lake Taupo where they kindly turned off their floodlights illuminating the lake at 11 pm. (This is what Kiwis are like, really helpful people, the antithesis of jobsworths.)

Stargazers is a luxurious B&B run by the charming Alastair and Harriet Brickell:   

http://www.stargazersbb.com/

This was my first attempt at imaging in NZ and I was afraid something wouldn't work. Alastair was very encouraging, he let me set up my gear beside his dome and he even lent me a cable at 3AM!

Alastair is not an imager, he's a fanatical visual observer with a C14 in a big dome and he gives "astronomy tours" (they are included in the B&B or bookable separately). Now we have all been to astronomy outreach events and some of us have even given them. Clouds permitting people get a squiz at a few nice objects through a telescope which is great. But I have to say visitors often leave not having learned much about the universe.

Not so with Alastair's tours. Perhaps it's because he's a geologist but he combines the requisite star gazing with a superb lecture with lots of Socratic questioning and huge collection of fascinating physical props in his study. It's quite long but it holds everyone's attention, a model for astronomy outreach. Hugely recommended if you ever get to NZ.

Anyway, back to my image. As usual my processing is a Pixinsight muddle through, based on my interpretation of and varying ability to follow Harry's workflow. All comments/criticism welcome.

Here are two comments/questions from me:

a) If I play around with curves I can see an artefact that looks like roughly 0.5cm mesh netting across my image, especially in the vicinity of the core. Did it come from Local Histogram Equalization which seems useful though possibly too potent in my hands? Or something else?

B) I would like to increase the saturation slightly to get more star colour but when I do I lose a bit of the core. What should I have done?

http://www.astrobin.com/206346/

         

post-24339-0-96693800-1440696498_thumb.j

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Nice photo!  There is no denying that Omega Centauri is a sight to behold.  Difficult to argue when it subtends an angular diameter on the sky that is equivalent to the the Moon.  However, as you mentioned, 47 Tuc takes the crown for me.  Visually at the eyepiece, I think it is more interesting.

Thanks the B&B recommendation.  I will definitely check that out.

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Glad you had a great time here. Your image is stunning! I don't do AP but I can appreciate the effort required.

I have a foot in both camps when it comes to the best globular cluster - Omega Centauri because it's just so big and 47 Tucanae although smaller looks more like a typical globular cluster.

Peter

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Excellent story. Please don't increase the saturation to boost the star colour.  I really like it as it is.  Too many folk try and show that they have captured all spectral types by banging up the colour.  Let's enjoy that bright core as it is!

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Nicely done...I saw Omega Centauri a couple of years ago...makes M13 look tiny in comparison...

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That's lovely.

You ask what you should have done about colour in the core. And you know what I'm going to say! :evil:  Use Photoshop and layers to blend a softer stretch for the core into a harder stretch for the rest.

Is this LRGB or RGB? I'm never sure about L for bright globulars. It can cook the cores. If it's LRGB you could try blending an 'RGB only' core into the LRGB. When cores are nearing saturation the colour seems to be the first victim.

Regarding LHE, it is highly adjustable but I still prefer to apply it as a layer exported into Ps. That makes it adjustable in real time. It seems such an obvious way to use it.

Olly

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