StarTools

Decided to image M20 Trifid Nebula again this year as the weather cleared during the new moon period which is ideal to expose the 3 types of nebulosity.

Southern Hemisphere Skies
Bortle 8 Suburban
6” f6 GSO Newtonian Reflector
Skywatcher EQ6-R Pro mount
ZWO EAF
ZWOASI2600MC cooled to -10C , Gain 100 LRN
No filters
TS GPU coma corrector
104 x 2 minute dithered guided subs
40 x Flats
60 x Bias
EQMOD, Stellarium and APT
Stacked in DSS ( no background calibration)
Processed in Startools V1.7 OSC linear data set

Comments most welcome
Thanks

Extremely good, Martin! Seeing this is coming from Bortle 8 skies..did you face serious gradients? The result looks so nice and even. Are you using a special technique in Wipe or is it just straight forward pumping up the gradient aggressiveness?

Regards
Stefan

Very nice, and to do this in broadband yet still has plenty of red and blue.

You decided to use the 6" for this one?

Thanks Stefan
The 2600MC is an extremely low noise camera when using Gain 100 to start with , zero amp glow and almost zero dark current. 90 sec to 2 minute subs under my City suburban skies seem to be the balance between dynamic range and noise.I dither each sub so that eliminates fixed pattern noise. As for the LP gradient, the more data stacked the less gradient appears.Once you go past 3 hours of data the gradient is not too bad ( 1 to 2 hours of data a totally different scenario) I was hoping for 4 or 5 hours but not be. I just used a basic Wipe with aggressiveness set to 50%
Also using a basic Newt eliminates aberrations and optical issues confronted by some refractors etc…
Of course calibration is paramount with my set I have Vignetting and there’s always dust donuts
I wouldn’t even bother imaging this object with the moon around as it’s primarily a broadband target with emission, reflection and dark nebulosity
Thanks again
Clear Skies
Martin

Thanks Mike
I have 2 imaging locations -

Main residence ,City Suburban Bortle 8 where I use my 6” f6 Newt

Retirement Coastal Rural property Bortle 3 where my NexDome is situated and use my 10” f5 Klaus Helmerich Carbon fibre Newt

I spend time between both locations , majority of time at main residence

M20 is primarily a broadband target during new moon period
I’ve imaged it in Narrowband and colours are terrible

Thanks
Martin

Hi Martin,

Startrek wrote: ↑Wed Aug 03, 2022 11:35 pm As for the LP gradient, the more data stacked the less gradient appears.Once you go past 3 hours of data the gradient is not too bad ( 1 to 2 hours of data a totally different scenario)

Great that this works for you! I'd have thought that the gradient would pretty much stay the same since it's signal, albeit an unwanted one. But maybe the gradient in the image changes as the FOV wanders through different areas of the LP dome and thus it get's averaged out a bit!? Anyway, great to see such sharp and deep images of broadband targets are still possible from Bortle 8 skies!

Thanks!

Stefan