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Old 26-11-2020, 11:40 PM
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strongmanmike (Michael)
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Fornax A - shells, massive halo and recently identified faint loops and tidal tails

I recently did a deep image of Fornax A (NGC 1316) and a mate, Scotty Alder (Tornado33), made an interesting comment regarding this image on Facebook, that got'a me to a thanking....hmmm?

Scott commented that he would like to see me push my big fast scope to see how deep it can go, hey a bloody great idea ...but then I thought, hmm? I took 10hrs of Luminance data with a 300mm dia scope at a fast F3.8 under reasonably dark skies, so I wonder just how deep I had already managed to go..?

So I searched for deep images or even better, quantitative empirical papers on the brightness of some of the faint outer tidal tail regions of NGC 1316. Well low and behold it didn't take long and I found one

A paper by E. Iodice et al from 2017 shed some very interesting light on my enquiry. This paper used deep imaging data from the ESO VLT Survey Telescope (VST) a 2.6m F5.5 modified Ritchey-Chretien optical layout with a two lens wide-field corrector and located at Cerro Paranal in Chile.

In fact this paper revealed that some of the very faintest structures captured in my data were only identified as recently as 2017 and reported in this paper, the faintest of which (labelled L9 in the annotated image at the link below) shine at an almost impossibly feeble 30.1 mag/squ arc sec!! (which is about 2000X fainter than the core region of the galaxy!)...but never the less, still detectable with amateur equipment

So the initial answer to Scotty's question is..well? in 10hrs worth of 10min exposures through my 12" F3.8 Newt, using a modern commercial cooled CCD camera (SXVR-H694) we can record faint structures with surface brightness's fainter than 30mag/square arc sec!...that's BLOOD FAINT...in this case, so faint in fact, that even for a significant and regularly studied galaxy like NGC 1316, they weren't identified until just 3 years ago!

Here is the image analysis showing the depth reached (remember to have your screen adjusted properly with brightness turned up as these features are very faint)

The full colour image is HERE

A reminder to look deep and carefully into your data, you never know what you might dig up or discover

Mike
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Last edited by strongmanmike; 27-11-2020 at 12:01 AM.
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Old 27-11-2020, 08:32 AM
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gregbradley
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It is amazing how deep we go.

Here is my effort 2 hours 40 total exposure CDK17. Not sure about the colours but no real reason to disbelieve them.

https://pbase.com/gregbradley/image/168843238/large

I'd like to add to this seeing as its a very interesting target. Your image is very sharp.

Greg.
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Old 27-11-2020, 09:20 AM
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strongmanmike (Michael)
Woohoo it's clear

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Quote:
Originally Posted by gregbradley View Post
It is amazing how deep we go.

Here is my effort 2 hours 40 total exposure CDK17. Not sure about the colours but no real reason to disbelieve them.

https://pbase.com/gregbradley/image/168843238/large

I'd like to add to this seeing as its a very interesting target. Your image is very sharp.

Greg.
Hi Greg

I can see a clear hint of the small hook that is L6 there in your shot and perhaps even the very start of an indication of L7 & L8 but it's not clear, obviously need more exposure to confirm, the large SW Loop is not clear and mostly out of your frame anyway but looks like you have something there and the super faint L9 is out of your frame.

Yes, quite cool what we can do in modern amateur imaging ...always seems crazy compared to what we expected or were happy with as amateurs back in the good'ol film and print days

Mike
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