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Old 20-03-2020, 05:10 PM
Startrek (Martin)
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NGC 5128 Centaurus A Galaxy

Decided to give NGC 5128 a go on Wednesday night as conditions looked ok , but ended up with a very poor image
Probably asking to much to image a 7 mag Galaxy with my old DSLR under Bortle 8 Sydney skies

6” f6 Bintel GSO newt on an EQ6-R mount
Canon 600D with Baader coma corrector and no filters
Home made DSLR cooling fan ( sensor electronics temperature 23 deg C )
Bortle 8 skies
ISO 800
90 x 90 sec dithered guided subs
25 x darks
Dithering set to medium and dithered every sub
PHD2 guiding ( 0.90 to 1.10 arc sec error )
Frame, focus and capture with BYEOS
Navigation, Goto and tracking EQMOD, StellariumScope and Stellarium
Stacked in DSS
Processed in Startools

Realised after 60 subs that focus was drifting off so spent 20 minutes to refocus
Seeing looked ok but jetstream was running +60knots
Even with dithering and darks stacked image was very noisy with bloated stars
Processed and reprocessed image and this is the best result I could get
In hindsight,I shouldn’t take on imaging galaxies in Sydney with my DSLR and only chase them down at my weekender ( Bortle 3 skies ) and I’ve had great results in the past

Thanks for looking , any comments welcome

Cheers
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  #2  
Old 20-03-2020, 06:32 PM
RyanJones
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Still a pretty good effort Martin. I hear your pain in trying to chase galaxies in Bortle 8 skies. I haven’t tried again since upgrading to the 2 larger slopes but I did tackle the hamburger with my C5 a while ago. I’ve got a pair of Galaxies I’m looking at chasing soon that will fit in the FOV of my 8” and I want to try Markarians Chain again. I’d love to be able to both at home but I might be pushing the proverbial up hill.

Just for giggles Martin, why don’t you try and throw another few hours at it and see what happens. Maybe aim for 5 or 6 hours in total. Worst case scenario, it won’t help but everything else up there isn’t going anywhere soon so you won’t miss out.
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Old 20-03-2020, 07:35 PM
Startrek (Martin)
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Thanks Ryan for the encouragement and suggestions
It’s really strange seeing focus drift so much on an ascending object , starting at 35 degrees and arcing up over 70 degrees. I usually spend at least 15 to 20 minutes on nailing my focus as tight as I can. I choose a mag 2 star up at around 50 degrees Alt and take successive 15 sec exposures and use the diffraction spikes and the stars core to nail tight focus. I have a JMI Moto focus fitted to my dual speed focuser with a 2m cable to a 3 speed handcontroller, so I’m sitting right in front of the laptop screen observing each exposure as I tweak the focus. I can then toggle through back and forth and check each exposure until I’m happy, BYEOS has a focus target reticle with zoom control and FWHM read out but I found I can get tighter focus using my visual auto manual method
I “may” capture a whole new set of data on this object when a clear night presents itself in Sydney again ( hopefully a lower Jetstream) and be more rigorous with checking focus
Thanks for commenting
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Old 21-03-2020, 06:46 AM
RyanJones
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You know what Martin ? I’d never considered elevation changing focus before. Tube contraction and temprature yes but never elevation. It makes perfect sense though
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Old 21-03-2020, 07:10 AM
etill (Elliot)
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Relly nice effort. I've tried a few galaxies lately, imaging galaxies was one of the main reasons I started having a go at this. With a DSLR in a suburban setting it seems like mostly noise in each sub most of the time though regardless of conditions.

The southern pinwheel is also farily well placed at the moment, maybe it was luck on the night, but I think I did best so far with that out of all the galaxies I've tried.
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Old 21-03-2020, 05:43 PM
Startrek (Martin)
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Elliot
Thanks for your kind comment
Imaging from big cities is definitely challenging with a stock DSLR
I’ve been using a stock DSLR without filters for nearly 4 years now so I’ve decided to upgrade to a cooled OSC Camera ( with some NB filters ) later this year
My journey in AP has been slow small steps .....
Mono with a coloured filter wheel maybe in another 4 or 5 years time ??
Martin
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Old 22-03-2020, 06:50 AM
etill (Elliot)
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I've just popped the filter out of mine, now waiting for a chance to see what difference it makes. Of course the day I removed it the clouds rolled in and have hung around since. I have a few difference sequences saved so I can go back and redo all the last few images with the mods done and compare.
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Old 23-03-2020, 07:52 PM
LostInSp_ce's Avatar
LostInSp_ce
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Pretty good effort Martin considering the limitations. You have similar skies to me so I know how you feel. I'm too lazy to travel to my dark site these days because I prefer to image from home where the skies aren't as good, but the coffee is better.
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