NGC6334 Cat's Paw Nebula in Ha

[strongmanmike (Michael)]

Originally Posted by naskies

Thanks Mike! No offended at all, if anything I'm actually rather curious... I think I know the types of false-signal artefacts you're referring to; they're particularly infamous amongst the planetary imagers.

To the best of my knowledge, all the structures that I can see in the final result are visible in the raw screen-stretched-only stack (so they're "real" as far as I'm aware).

I've attached two crops with no processing. The first image is of a very high SnR region that has been linearly stretched (0, 0.5, 0.33) in PI, followed by 200% resampling using nearest neighbour for clarity. The second is of a very low SnR region in the background - linearly stretched (0, 0.5, 0.0125) and 200% resampled again. In both cases, there was *no* other processing - no wavelets, no multiscale processing, no sharpening, no deconvolution, etc applied.

When I compare the raw stretches to the final result - I can see the same fine structures in both. The "spotty background" is just noise from the depths of my CCD due to the extreme stretching (20 subs isn't really enough to smooth out the background given the amount of thermal noise I have with 60 min subs @ -10 deg C). At 86 hours, I'm definitely at the "diminishing returns" point of further data collection

I think the "black magic" you refer to comes from PI's amazing ability to compress dynamic range. There's a huge amount of subtle detail in the Cat's Paw, but I think it tends to get swamped by the dynamic range. I'm very much a PI newbie though so it's sledge hammer strokes rather than fine tooth comb at this stage

Anyway, thanks for your honest opinion. I'm curious what you think (or anyone else) after seeing the unprocessed crops?

Yeah ok.

I think, like what we saw with the various processing approaches taken on Berts free Eta Carina data a few months back, this is just a new style of processing ...my eyes are slightly alarmed by it that's all, kind of looks processed not that that is a bad thing of course, at times pushing things is done to emphasise the extreme and that's ok, and I do this at times myself

Again very impressive looking and dramatic result

Mike

[Ross G]

What an amazing photo Dave.

Fantastic detail!

Ross.

[naskies (Dave)]

Originally Posted by strongmanmike

Yeah ok.

I think, like what we saw with the various processing approaches taken on Berts free Eta Carina data a few months back, this is just a new style of processing ...my eyes are slightly alarmed by it that's all, kind of looks processed not that that is a bad thing of course, at times pushing things is done to emphasise the extreme and that's ok, and I do this at times myself

Again very impressive looking and dramatic result

Mike

Mike, I think you're absolutely right. Being very new to the astro world (and skipping film, early CCDs, etc), I've never become acquainted with what an astro image traditionally looks like... and I've never looked at the Cat's Paw through an eyepiece either. The fine detail in the nebulosity is just as interesting to me as the big paw print

Originally Posted by Ross G

What an amazing photo Dave.

Fantastic detail!

Ross.

Thanks Ross!

[multiweb (Marc)]

Yeah top shot. Very deep with a wealth of details. Great contrast as well. Well done.

[naskies (Dave)]

Thanks Marc!

[Stevec35 (Steve)]

Now that is impressive! Certainly the deepest cat's paw I've ever seen.

Cheers

Steve

[dvj (John)]

Originally Posted by naskies

Thanks Jason. Much appreciated, especially considering your imaging experience

We definitely had a lucky run of good weather in Brisbane in August (a pleasant surprise considering the first half of the year). I certainly wasn't originally expecting to be finished before October!



Thanks Mike! No offended at all, if anything I'm actually rather curious... I think I know the types of false-signal artefacts you're referring to; they're particularly infamous amongst the planetary imagers.

To the best of my knowledge, all the structures that I can see in the final result are visible in the raw screen-stretched-only stack (so they're "real" as far as I'm aware).

I've attached two crops with no processing. The first image is of a very high SnR region that has been linearly stretched (0, 0.5, 0.33) in PI, followed by 200% resampling using nearest neighbour for clarity. The second is of a very low SnR region in the background - linearly stretched (0, 0.5, 0.0125) and 200% resampled again. In both cases, there was *no* other processing - no wavelets, no multiscale processing, no sharpening, no deconvolution, etc applied.

When I compare the raw stretches to the final result - I can see the same fine structures in both. The "spotty background" is just noise from the depths of my CCD due to the extreme stretching (20 subs isn't really enough to smooth out the background given the amount of thermal noise I have with 60 min subs @ -10 deg C). At 86 hours, I'm definitely at the "diminishing returns" point of further data collection

I think the "black magic" you refer to comes from PI's amazing ability to compress dynamic range. There's a huge amount of subtle detail in the Cat's Paw, but I think it tends to get swamped by the dynamic range. I'm very much a PI newbie though so it's sledge hammer strokes rather than fine tooth comb at this stage

Anyway, thanks for your honest opinion. I'm curious what you think (or anyone else) after seeing the unprocessed crops?



Thanks Bob! This is pretty much the only astro thing I've been working on since we last caught up in Leyburn... definitely a labour of love

I think the artifacts that Mike is referencing look like a speckled noise pattern across the entire image. This not evident in the 2 close up images you posted here. you have really good data to work with. Worth a re-process.

[Greg Bock (Greg Bock)]

I think it's worth mentioning here (in case no-one else has, and I haven't read thru all posts yet) that this is a fantastic effort by Dave, not only for the result but also for the way he achieved it.

In particular, Dave doesn't have a permanent observatory to allow such a long period of data gathering. Instead, his setup is 'protected' from the elements in his backyard under a tarp and tent combination which is located only 20 minutes from Brisbane under very light-polluted skies.
It goes to show the remarkable results that are obtainable from conditions that are far from ideal. Well done.

[multiweb (Marc)]

Originally Posted by Greg Bock

I think it's worth mentioning here (in case no-one else has, and I haven't read thru all posts yet) that this is a fantastic effort by Dave, not only for the result but also for the way he achieved it.

In particular, Dave doesn't have a permanent observatory to allow such a long period of data gathering. Instead, his setup is 'protected' from the elements in his backyard under a tarp and tent combination which is located only 20 minutes from Brisbane under very light-polluted skies.
It goes to show the remarkable results that are obtainable from conditions that are far from ideal. Well done.

Too true. I can totally relate to the astro-gypsy thing. I'm also forever hauling my a$$ everywhere. I probably spent more time packing and unpacking than imaging over the past few years. Those observatory yuppies forget that sometime. Repeatability can be a b||ch at best of times for us commoners Good reminder.

[strongmanmike (Michael)]

Originally Posted by Greg Bock

I think it's worth mentioning here (in case no-one else has, and I haven't read thru all posts yet) that this is a fantastic effort by Dave, not only for the result but also for the way he achieved it.

In particular, Dave doesn't have a permanent observatory to allow such a long period of data gathering. Instead, his setup is 'protected' from the elements in his backyard under a tarp and tent combination which is located only 20 minutes from Brisbane under very light-polluted skies.
It goes to show the remarkable results that are obtainable from conditions that are far from ideal. Well done.

Too true, it's great that narrowband imaging, like Daves effort here, is not really affected by the lights of a big city, thank god I did almost exclusive narrowband imaging from mucky Newcastle skies for 18 months up until a year ago, even resorting to producing hybrid RGB images using narrowband data ....the new dark and steadier skies of semi rural Canberra are a dream, especially for galaxies

Mike

[naskies (Dave)]

Thanks gents! Narrowband imaging - especially through 3 nm filters - is such a godsend In fact, it was the main reason why I decided to switch from DSLR to CCD imaging.

Oddly enough, now that I have my backyard set up running smoothly, acquiring the 86 hours of data for this image actually took less time than packing / driving / setting up for a single dark sky weekend

However, a lot of time obviously went into getting my menagerie of poorly behaved equipment to work... the 86 hours of data is nothing compared to what I've thrown away from failed experiments so far this year

Like most of us, I have dreams of one day having a remote dark sky obs...

Originally Posted by dvj

I think the artifacts that Mike is referencing look like a speckled noise pattern across the entire image. This not evident in the 2 close up images you posted here. you have really good data to work with. Worth a re-process.

Thanks for the feedback, John. It sounds like it would be definitely worth a re-process for a smoother background and to fix up some of the other artefacts.

I'll keep it in mind for a rainy day... but in the mean time, we're getting another rare run of crystal clear nights from dusk-to-dawn