Friday, 2 December 2016

UK Astrophotography Utopia!

26-30 November, 2016

It’s been the longest clearest spell of weather I’ve ever had for imaging since starting in this hobby in 2002.

I had 4 nights of clear skies on the 25th, 28th, 29th and 30th of November, 2016 – unheard of. This clear spell has come not only during the longest nights of the year (with it getting dark at 5pm) but also without the Moon above the horizon. It doesn’t get any better than that.
I started on the 25th of November imaging the Elephant Trunk Nebula (IC 1396) in the constellation Cepheus.

What I know about the constellation Cepheus

Image courtesy of Starry Night Pro-7

Easy to spot as it looks like a house in the sky

It represents King Cepheus, king of AEthiopa

Cepheus’ wife was Cassiopeia and his daughter, Andromeda (who also has a constellation named
after her) can be found near the constellation Pegasus.

This constellation contains 27 delta Cephie, a star who’s variability was found to be useful when
measuring the distance from us to distant deep sky objects – with impressive accuracy. Wiki
Cepheid Variables for more.

What I know about the Elephant Trunk Nebula
Image courtesy of Starry Night Pro-7

The hole in the head of the nebula may have been cleared by the two very young stars in centre of it.

The star in the centre of the nebula is ionizing the interstellar gas that is surrounding it
and colliding with the dense gas of the Elephant Trunk nebula it has triggered star 

The reason I wanted to image this object is that I have found it to be my second favourite object in the night sky (only surpassed by the Horsehead Nebula). The combination of the wide, red nebula with its bright central star and the Elephant Trunk framed perfectly at the bottom of it provides a picture-perfect composition – that I simply can’t get wrong.

I’ve imaged it before with my one-shot colour camera – a QHY8. The best of my efforts with that camera appear below.

The first is taken with a 115mm refractor in October of 2013.

And this second one was take with the same scope as this article relates to, a 65mm astrograph  taken in 2012

The second one has been one of my favourite Astro-images that I’ve taken ….until now.

I recently bought a ZWO ASI1600MM-Cool (meaning cooled…not that it is…cool, although I think it is) and as it’s mono I have to use 7 different filters to capture the images I want. This sounds appalling when you consider the QHY8 required 0 filters, but I think you’ll agree looking at the results below that it is more than worth the extra effort.

And there’s a twist – the ASI1600 has a CMOS (complementary metal-oxide-sensor) chip instead of a CCD (charged coupled device). The technical differences between the two can be discovered on wiki – the key for astrophotography is that with the CMOS you take many very short, high gain subframe exposures (anywhere from 30 – 300 seconds at 139 gain) whereas with the ccd you take much longer ones at lower gain (with my OSC camera mentioned above I took 20 minute exposures at 0 gain).

What this means is that there are some talented individuals out there getting spectacular images on quite inexpensive set ups because they can take very short exposures without the need to guide (another scope locked on a star firing corrections via a webcam, to the mount to keep it centered on target) during the capture.

As my observatory is setup to run guided – I continue to – especially as I am taking 5 minute exposures for the narrow band filters – still a short time but my mount would not stay centred on target without guiding for 5 minutes.

And so to the 4 evenings details of data captured and the results.

Ha           : 12 x 5 min subs @ 139 gain = 1 hour
Oiii          : 12 x 5 min subs @ 139 gain = 1 hour
Sii            : 12 x 5 min subs @ 139 gain = 1 hour

I was extremely happy with the results from this night and processed my first narrow band image from this data. Of course when I did I didn’t realise I’d be getting another 3 nights of clear skies to get more data.
November 28th, 2016
Narrowband on IC 1396

Ha           : 12 x 5 min subs @ 139 gain = 1 hour
Oiii          : 12 x 5 min subs @ 139 gain = 1 hour
Sii            : 12 x 5 min subs @ 139 gain = 1 hour

Another great night, some minor equipment issues with Nebulosity 4 freezing once forcing a reboot of the PC and all 3 cameras and the mount controller – but that went quickly.

LRGB on IC1396

Luminance          : 90 x 60 sec subs @ 139 gain = 1.5 hours
Red                        : 15 x 2 min subs @ 139 gain = 30 min
Green                   : 15 x 2 min subs @ 139 gain = 30 min
Blue                       : 15 x 2 min subs @ 139 gain = 30 hours

No interruptions due to technical issues. Here’s a shot from WOBSCAM that I use to keep an eye on sky conditions

November 30th, 2016
Luminance on IC1396 and Ha on NGC 7380
Luminance          : 60 x 60 sec subs @ 139 gain = 1 hours
Ha                           : 24 x 5 min subs @ 139 gain =  2 hours

Looking like the last clear night for a while so I tried to get as much done as I could.

December 1, 2016
Oiii on NGC 7380
Oiii          : 9 x 5min subs @ 139 gain = 45min

It was very clear to begin with but soon clouded over. Luckily enough time to get some Oiii on the Wizard nebula to go with the Ha

And now to the results

I have had 4 good clear nights to image in with the ASI1600MM-Cool.

My equipment (TS65mm) has performed as never before, with ease and reliably.

I have captured about 12 hours of data on the Elephant Trunk Nebula - an unheard of amount of data for Welford Observatory on ANY object in the past 10 years.

I'm using PixInsight to process and although not an expert I feel confident in the few scripts and processes I use.

What can possibly go wrong....:-)

You be the judge, jury and when and if you slaughter my results with accurate and technically focussed feedback saviour...:-)

I've posted really bad low res screenshots below to keep SGLs servers from bloating to popping point but you can see the higher res images on my site under "Images"

I still have a full set of LRGB data to process so and off course bi-colour and now its finally cloudy I can do some processing haha!

These images below have had flats/darks/bias applied, the SHO image is 2hrs on each channel - the Ha is 2hrs.

.....and as this is my first real foray into nb imaging - I'm quite pleased with the results...and looking forward to processing the LRGB and bi-colour now :-)

These are quite low resolution examples of the originals

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