M20 Trifid Nebula from NexDome Obs

[Startrek]

I had to do an overnighter at my retirement retreat down the south coast for some maintenance Quotes / jobs , so as the weather was looking good , took my Astro bag with me just in case.
Opened up the Obs and decided to capture M20 Trifid Nebula again and compare it to my recent Sydney capture.
Clear night but poor conditions

No moon
Bortle 3/4 skies
10” f5 Klaus Helmerich Carbon fibre Newt
Skywatcher EQ8-R pro mount
ZWO2600MC cooled to -10C , Gain 101
Orion 60mm guide scope with helical focuser
ZWO290MM guide camera
EQMOD and Ascom Stellarium
APT
PHD2 Multistar guiding ( 0.75 to 1.0 arc sec ) chasing the seeing Ra see sawing
138 x 60 sec subs ( dithered every second sub )
40 x Flats
60 x Bias

Stacked in DSS
Processed in Startools V1.8 OSC Linear Data Set

One notable difference between Sydney’s M20 image and this image was the noise level, this image was so clean I really didn’t need to apply any noise reduction , where in Sydney it’s a must , generally 4 to 6 pixels

Also just over 2 hours of data ( Sydney was 3.5 hrs ) using the bigger 10” Newt resulted in more fine detail
I also attached the difference in laptop screen views during capture Bortle 7/8 Sydney and Bortle 3/4 South Coast ( green vs black )

Astrobin link below …..

https://www.astrobin.com/8fs7m9/

Attached original frame version ( 200KB compressed )
Attached Crop version ( 200KB compressed )
Attached M20 Sydney sub capture laptop screen
Attached M20 South Coast sub capture laptop screen

Comments welcome
Thanks
Martin

[strongmanmike]

Excellent Martin, love hearing about your imaging ventures :thumbsup:

That laptop comparison is pretty telling huh? :eyepop: when the great unwashed, who only know photography as point-click-done, see our final products, little do they realise what it might have started out as, huh? ;)...let alone the bloody work that went into processing...

Mike

[strongmanmike]

Excellent Martone, love hearing about your imaging ventures :thumbsup:

That laptop comparison is pretty telling huh? :eyepop: when the great unwashed, who only know photography as point-click-done, see our final products, little do they realise what it might have started out as, huh? ;)...let alone the work and time that went into processing it...

Mike

[Startrek]

Thanks Mike,
The effects of heavy light pollution not only on Astrophotography but on our lives in general cannot be understated
My pet hate is wasted or unnecessary artificial light
I thought I’d throw the comparison in for all , especially the visual folk

Cheers
Martin

[marc4darkskies]

Nice rendition of this favourite Martin! :thumbsup:

FWIW though, if it were mine I'd tone down the saturation just a tad..

[Dave882]

Nice work Martin. A lovely Trifid!
Yeah the affect that the city Lp has on each sub is terrible. Sometimes we kinda just get used to the sub-optimal results until you go somewhere dark and you realise how bad it really is. :sadeyes:

[Startrek]

Thanks Marcus
Agreed !

[Startrek]

Thanks Dave,
Yeh pretty happy with this image on the fly ……
Drove 220km south, met some subbies , cleared the cobwebs out of the Dome , installed the camera and lappy , powered up , imaged for a few hours that night until late , breakfast , locked up the Dome , did the lawns , tidied up the place and headed back to Sydney the following day.

Whoosh what a couple of days

I’ve never done a comparison with the same object under a new moon period on the lappy screen before. I can’t believe we both image under Sydney’s muck !!!!

Cheers
Martin

[Stephane]

Martin, well done for producing a beautiful Triffid. I particularly like the rainbow diffraction spikes on the brightest star. Good old Newts! Thanks for sharing.

[Ryderscope]

Nice comparison Martin. Whilst great results can be achieved from the 'burbs', there is nothing like getting away from the city lights :stargaze:

[Startrek]

Thanks Stephane,
Appreciate it
Only a couple hours needed under those dark skies to resolve some nice detail , different story in Sydney
Being down at my Dome on a clear moonless night imaging is an absolute joy, then when I have to return to Sydney and image under all that heavy LP muck not to mention the moon when it’s up , makes you appreciate what you have.
I love my big 10” Carbon Newt , to me it’s big but compared to a CDK17 or CDK20 it’s tiny , but in my Dome it’s a monster , she just fits inside.

After weeks of testing and tweaking my new 8” f5 Carbon fibre in Sydney is now dialed in properly.
I had to rebuild my secondary holder with longer screws and central bolt and spring as the supplier KH , the drilling pattern for focuser and Spider were 12mm out compared to my old metal GSO Newt
I also had to shift the focuser around by 5mm as it was not centrally aligned to the secondary. Plus the north / south spider vane was out by 4mm
If I ever buy a third carbon fibre newt , I’m going to have it supplied with no holes and drill my own , that way there’s no mis matching or foul ups
It’s been a frustrating and timely exercise I must say ( no fault at all to Sidereal or KH as it’s a standard product with standard drilling pattern )
Anyway the move to Carbon fibre option for Newts has proved successful

Cheers
Martin

[Startrek]

Thanks Rodney
At least I can talk about what it’s like to image from both ends of the spectrum
Bortle 8 and Bortle 3
The funny thing is I enjoy both as they require different approaches which keeps you on top of things

Cheers
Martin

[Stephane]

Great to hear you’ve been able to fine tune it so nicely. I’m still fine tuning and finding it more challenging that I expected. I still have a circular artefact which I suspect could be due to the coma corrector rather than the tube itself - something you suggested a while back. Cosmetic correction during processing seems to deal with it ok, but it definitely needs eliminating. Carbon fiber has greatly reduced weight and stabilized focus due to less thermal contraction, however my guiding is actually worse than it used to be. Not sure why: could be the mount playing up, or it could be that my new guide camera on the OAG is more sensitive and is giving a more accurate reading? Who knows.

For the level of detail you get at 2 hours under dark skies, how long do you think it would take to get that sane level from Sydney? I’m asking as I’ve been toying with the idea of traveling to dark skies for a while now, but will need to fix my equipment issues first.

[Startrek]

It was suggested to me a while back to go f4 , but I weighed up the benefits and risks and decided to stay at f5 , glad I did
My new 8” Carbon fibre is guiding better than my old 6” metal tube Newt so I’m stoked
In regard to reflections and artifacts just make sure your TS GPU CC isn’t protruding into your tube and for that matter the focuser tube as well, that can cause issues
Yes an OAG can be the culprit so more testing, why don’t you pop your guide scope back on and try guiding with it ??

As far as comparing capture hours under dark skies and LP skies it’s hard to put a figure on it as it’s a moving target in both Broadband and Narrowband but I’d say as a guess my Sydney LP sky needs at least 50% to 75% more data than my dark sky location. We’re talking Cooled OSC cameras here, Mono is a totally different scenario

Cheers
Martin

[Stephane]

Thanks for those suggestions. I’ll have a further look.

Yeah I would have guessed about 75% ish, maybe more. It’s amazing what dark skies can do. Thanks.

[matlud]

Lovely trifid Martin! I saw an equation once to work out what the equivalent integration time would be between different Bortle skies: n hours / 2.51^(sqm2 - sqm1). So if Bortle 7/8 Sydney SQM is ~18.5 and your Bortle 3 dark site SQM is ~21.5, then 2 hours at your dark site would be equivalent to 31.6 hours of Sydney data :eyepop:
CS
Mat