Journal of the Northern Sydney Astronomical Society Inc.March 2019

In this issuePage 1: Editorial Results of the Article

CompetitionPage 3: Results of the Photo

Competition

Hi all, and welcome to the March 2019 edition of Reflections.

Or should it be titled “The Object of the Month” as it is exclusively dedicated to the results of this month competition?

So here are the results:The winner, and sole entrant, in the article category is Greg McCall with, once again, a very well researched and technical article on his quest to the perfect picture.So, it seems that if nobody takes up the challenge, this is going to be a one-horse race!

And, in the picture category, the winner is Chris Vaughan.

A stunning picture that, in my opinion, is of professional quality

This month, we have again 2 runner-ups: our very own president David Stevenson and Phil Angilley who both achieved very commendable results.

Due to your Editor having some other pressing commitments this edition is coming a bit late.

At the last Committee meeting it was decided that Reflections would now go back to a quarterly publication with, maybe if we receive enough material, a special yearly one at the end of the year.

So, again, don’t hesitate to send me your contributions: I’ll need them! You can e-mail them to jean-luc@ozemail.com.au or tonsas.editor@ozemail.com.au

Looking forward to receiving them and, in the mean time, enjoy what the sky has to offer.Cheerio,

Jean-Luc Gaubicher

NGC 1365, the Great Barred Spiral Galaxy is about 56 million light-years

away from us.With its white bar and two spiral arms it is a barred spiral galaxy as well as a ringed Seyfert galaxy.

Seyfert galaxies are characterized by their active nucleus and account for about 10% of known galaxies.At the centre of this type of galaxy is a supermassive black hole.In the case of NGC 1365, its SMBH is spinning at about 84% the speed of light.Being between 5 to 10 million times as heavy as our Sun, its radius, or more precisely its Schwarzschild radius, should be 5 to 10 million times the Sun’s own Schwarzschild radius (6km only!) that is between 30 and 60 millions kilometres.

NGC 1365 is about 200,000 light years wide, which is about twice as wide as our Milky Way galaxy, but still has a mass similar to our galaxy.The bar we see in its centre takes about 350 million years to complete a full rotation.

Photographing the galaxy in February turned out to be a bit of a challenge for a couple of reasons.One, was the size of the object in my field of view.It was to be a smaller object in my photo, so it was not going to look very impressive unless I cropped the final photo but that would end up highlighting noise etc... resulting from the small number of sub exposures and poor atmospheric conditions.

The second challenge was that it was an object low on the horizon and towards the south from Terrey Hills where all the light pollution from Sydney glows.

My opportunity to photograph the object in February was only on the two NSAS observation nights.

The first observation night for February was cancelled due to the poor weather.The second was on but, as it turned out, I could only get a limited amount of data due to the poor conditions on that night.

The Winning Article for February

This was partly due to the occasional thin cloud passing in front of the galaxy and, later, with cloud completely covering it around 2am in the morning.

The chart below shows how low the galaxy was during the night (blue line).After seeing how low the galaxy was, I later thought that I should have altered the order of filters used to take the images. I planned to take 20 images with each filter.The order being Luminance, Red, Green and then Blue.This was basically because I thought of a colour image as RGB, so set the sequence in SGP up in that order.

Continued on page 2

Important Reminder:The Object of the Month for March is M1 Crab Nebula, for April NGC 5139 Omega Centauri and for May NGC 5128 Centaurus A.

Please send your articles or images with a short description of how they were taken to bpetschel@gmail.com by the end of each month.

If this object had been high, and the skies clear, the order would not have mattered.

After the luminance exposure, I perhaps should have taken the blue one, then the green and finally the red.As the galaxy got lower in the sky and its light had to pass through more atmosphere, this would have helped as the higher frequency colours are scattered more by the atmosphere than the lower frequencies.

As the night progressed taking the LRGB images, it looked as if the weather may turn, so I cut short the planned 20 red images at 15 and managed to capture 5 of blue 5 of green before the clouds blocked the sky.

The uncropped and cropped versions of the object:

So the result for the night was 20 x luminance, 15 x red, 5 x green and 5 x blue, each a 180 seconds exposure.In hindsight, if I had studied the expected low altitude of the galaxy during the night, noticed the short amount of shooting time and allowed for the weather, I would have tried for only 15 of each luminance, blue,

green and red, in that order.

Looking at these others charts, it seems that October and November will be the next best opportunities to collect more data for this galaxy (see following charts).

Greg McCall

The Winning Photo for February

Captured over 2 nights 4-5 Jan 2019 from my backyard. Total capture time = 8.2 hours (246 x 2min subs).Taken with an ASI071 ZWO cooled colour camera with a UV-IR filter and an 8” F5 GSO newtonian. Guiding with an ASI290MM camera on a 50mm F5 guidescope. All on a CGEM.Capture software was AstroPhotographyTool (APT) Processed and calibrated with flats, darks and dark flats in Pixinsight.

Chris Vaughan

Editor’s note: this winning picture has been cropped to fit our magazine format.

The Runner-Up Photos for FebruaryFinal image came from Blue 28 frames for 18 minutes,Green 27 frames for 15 minutes,Red 22 frames for 11 minutes,Lum 26 frames for 14.5 minutes.OTAs: • Celestron 8” Edge HD • Skywatcher 120 ED Esprit • Skywatcher AZEQ6 Mount

David Stevenson

I captured this image using my LX200, 8”SCT and an ATIK Infinity Camera.

The image is composed from28 x 20-second images, total time 9 minutes 20 seconds.

Phil Angilley

Reflections is published whenever possible by the Northern Sydney Astronomical Society IncPO Box 56 Lane Cove 1595 Tel: 0423 971 374 E-mail: nsas@nsas.org.au Web site: www.nsas.org.au