Tarantula NGC2070 - looking for feedback

[Amaranthus]

My first semi-serious attempt at a DSO target - looking for feedback!

Taken at Stockport on 3 May:
Telescope: Celestron 8SE SCT on single-arm fork alt-az mount (unguided)
DSLR: Sony Alpha NEX-3
Subs: 94 x 25s @ ISO1600 (with 25 darks, 50 flats & 50 bias)

Stacked in DSS, processed in Startools, touch-up in Paint.NET

I wanted at least twice as many subs, but the clouds closed in and abruptly ended the session! (I also took some nightscape subs before I went to prime focus, but haven't processed these yet).

What I'm trying to do is gradually learn the ropes of AP basics, before buying some serious kit (long-term goal is 5" APO, solid EQ mount, cooled CCD). I realise my current equipment is hardly ideal for AP, but Wayne Anderson has shown what can be achieved with similar gear and some talent + perseverance!

My key goal over the next few months is to learn the ropes on stacking and image processing (total neophyte currently), before I think about changing my kit.

After nearly 30 years as a visual-only guy, I've been having fun stepping into the somewhat daunting world of AP over the last few months.

P.S. Original FTS, straight out of DSS, is here, in case anyone wants to muck about with it and show me what can really be done! (33 MB zip [original is 109 MB FTS file]):
https://dl.dropboxusercontent.com/u/15859518/NGC2070_32rationalFTS.zip

[lazjen]

You've definitely got better data there than your current processed image shows.

I grabbed your fits file and had a quick play:

161944

I opened it in DSS and saved out a 16 bit TIFF. From there I used PS to muck around. Since it was quick: auto tone, auto colour, auto contrast, manually adjusted levels, brightness and contrast, ran the HLVG plugin (removes a lot of green), little bit of vibrance/saturation, and "small" sharpness filter.

I think it's possible to do way better given time, effort, etc. :)

Good thing is you can always reprocess these things - I should know since I often end up with multiple versions.

[irwjager]

Not a bad effort at all.
Some things to be aware of when processing in StarTools;
- get rid of any stacking artifacts (you have a few at the borders of the image)
- don't do any pre-processing and keep the data as virgin as possible (to me it appears the data has, at the very least, been color calibrated, while there is also a suspicious lack of background bias.
- i can't be 100% certain but it looks to me like the that the data was pre-filtered or otherwise 'prettied-up' (read: destroyed) before it made it to DSS. You're not using anything other than your stacking solution to convert your RAWs, right? *DO NOT* use any of the software that came with your camera!

[Amaranthus]

Thanks a lot Ivo & Chris.

I was pretty sure I'd turned off all pre-filtering in my DSLR. I checked back through the settings, and the only ones that *might* have done something unexpected to the data is the white balance (left on auto) and the "High ISO NR" (the options are 'auto' and 'weak' - I left on auto). I did turn off the "Long Exposure NR", so that can't be it. The camera also has the colour options "sRGB" and "AdobeRGB" - I left it on sRGB for want of knowledge on which was better. Nothing else I could see that the camera was doing - all other corrections are definitely off.

I must admit to flying somewhat blind in DSS. I read the manual, FAQ and tech details, and watch some vid tutorials, so I'm okay now at running the program and not making gross errors. However, it remains difficult to know what might be the best register and stacking parameters to use for my RAW data. (I definitely avoided doing any post-processing of the image in DSS, so what you see in the FTS file is straight after the stacking).

Does anyone have advice on what might be decent 'default' parameters for DSS, or else what tweaks are typically highly sensitive or things to avoid? I dug around about in the IIS forums but couldn't find a thread that really covered this (might have missed it). I may well have ticked the RGB color calibration box, for instance! I figure I should work on getting DSS as optimal as possible before I start getting serious about the Startools processing (which is why I hadn't bugged you directly yet, Ivo :D ). I guess you are saying that I should let DSS do no corrections except those required for stacking - would this include no hot pixel removal etc.?

I did stack via a custom area (I got rid of the margins of the reference image) and junked the worst 14 images that had obvious blurring or got bad scores, but I guess this wasn't sufficient to remove some stacking artifacts.

[cometcatcher]

I tick hot pixel removal, but I haven't done a comparison to see how it compares to unticked. Most parameters are default that I use. I wind the star detection slider a bit to the right to speed things up a bit.

Your image is pretty good for an early attempt. It's just a matter of tweaking things. I've seen a few full spectrum modified Nex3's pop up on ebay and was wondering what they were like.

[Amaranthus]

By the way, I was not pre-converting my RAWs - they go straight into DSS v3.3.4 (beta), which uses "DCRAW" to decode them. Is this right?

[irwjager]

Yep. Good to hear.

Your settings in DSS should look roughly like this...

[Amaranthus]

Thanks Ivo. I'll have another go at the data in DSS tonight, with the guiding goal of trying to get DSS to do as little as possible to the data short of the alignment and stacking! (I'll send a screenshot of my selected settings).

For the stacking, is the 'median' method preferred other other options (e.g. averaging, or the various bias/variance-correction algorithms?). Is 'drizzle' worthwhile for sharpening the fine detail? (I've found it can crash DSS regularly if the area is not pre-clipped, so I guess this is the major constraint!)

[Amaranthus]

Okay, I redid the stacking this evening. I've updated the OP with the new file, but here it is also (33 MB zip ):
https://dl.dropboxusercontent.com/u/15859518/NGC2070_32rationalFTS.zip

Following the advice above, I adopted the following procedure in DSS:

Guiding principle for Startools pre-import file preparation = minimize manipulation of images in DSS – keep them as ‘virgin’ as possible

[I]Register Settings
Star detection = aim for ~50 stars, no noise reduction by median filter
No automatic detection of hot pixels

Stacking Parameters
Result = standard (or custom), no alignment of RGB channels, no drizzle (except small custom areas)
Light = median, no background calibration
Dark = median Kappa-Sigma clipping, no hot pixel detection, no dark optimization
Flat = median, Bias = median, Alignment = Automatic
No intermediate files, No cosmetic post calibration

Other
No post-processing in DSS, export as rational 32-bit FTS

Attached image shows what the pre-stacking settings look like.

Ivo, I imported this into Startools and have started mucking about. It is already looking better, I think, but any advice would be welcomed!

[Amaranthus]

Here is another attempt using the new DSS output.

I played about in Startools (still not sure what the right workflow might be, so I just followed the general flow from Appendix 1 of the unofficial manual), and I cropped to the area around the nebula.

Does it look better/worse than the original attempt, do you think?

[irwjager]

Better, I'd say.

It looks a bit 'stringy' though (did you use the Flux module by any chance?).

I'm wondering why the colour is so blue - did you use a light pollution filter at all?

Here is a quick process of your latest FTS file;

http://www.startools.org/download/TutorialResults/Amaranthus_NGC2070.jpg

--- Auto Develop
Too see what we got.
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Crop
To get rid of stacking artifacts.
--- Wipe
Parameter [Dark Anomaly Filter] set to [6 pixels]
--- Auto Develop
Final stretch. I created a Region Of Interest over the Great Spider.
Parameter [Ignore Fine Detail <] set to [2.1 pixels] to have AutoDev ignore the noise.
--- Deconvolution
Automatically made mask.
Parameter [Radius] set to [1.8 pixels]
--- Wavelet Sharpen
Default values.
--- Color
I'm having trouble with the colours. There is too much blue (not sure why this is).
Parameter [Cap Green] set to [To Yellow]
Parameter [Dark Saturation] set to [2.70]
Parameter [Blue Bias Reduce] set to [1.29]
Parameter [Green Bias Reduce] set to [1.20]
--- Life
Parameter [Strength] set to [79 %]
--- Wavelet De-Noise
Final noise reduction;
Parameter [Scale 5] set to [50 %]
Parameter [Redistribution Kernel] set to [12.2 pixels]
Parameter [Read Noise Compensation] set to [1.38 %]
Parameter [Smoothness] set to [73 %]

[Amaranthus]

Thanks Ivo - looking fantastic! It seems like you did this on my old DSS extraction though? (in the new extraction, I cut down the stacked area using custom - what you see in the JPG in my post from last night is the full extent of the stacked area [and I didn't use the flux model]).

Anyway, I will try those settings you've suggested on my new DSS extraction too. I really appreciate your help - this is giving me great guidance on what to try.

I agree that it does look very blue. No filters were applied at the telescope, so I'm not sure why that might be :shrug:

[lazjen]

I got a lot of blue in my version I did last year too: http://www.astrobin.com/69307/

Maybe I processed it wrong too?

[cometcatcher]

There's a lot of OIII in 2070, but there's also a lot of Ha. Depending on CCD sensitivity to each wavelength, the colour of the big spider can be anything from red to blue.

This shot is with a CLS on a full spectrum DSLR which lets a lot of Ha through so it ends up red. If you had your Nex3 full spectrum modified, it would let through a lot more red Ha.

There's no right or wrong colour, just a personal preference.

[Amaranthus]

Hah, I'm not sure my wife would be happy with my modding the NEX - she still uses it for all of those banal 'daytime' shots :P

[lazjen]

Good explanation, thanks. :thumbsup: Since my DSLR is unmodded, I guess I get more blue dominance over the red Ha as well.

[Amaranthus]

Another version, focused on just the nebula. Very blue! Time for some new subs I think, I've tortured this particular picture for all it can yield!

[Camelopardalis]

Seriously Barry, you did this on the SE mount? That's pretty impressive!

[Amaranthus]

Thanks Dunk! If figured I'd try to squeeze everything I could out of my existing equipment and really learn the ropes of AP and image processing, BEFORE I invested in some serious AP-dedicated kit.

It's been surprising to me how much signal one can extract out of many stacked 'snaps' (subs <30s) on an unguided alt-az mount. I hope there'll be plenty more images on the way -- once the damned clouds clear!

[Amaranthus]

Here is a first go at the Keyhole Nebula, NGC 3372, again using the 8SE on the single arm alt-az mount. I used 25 min of 10 sec and 25 min of 30 sec subs. Details here: http://www.astrobin.com/98885/

I drew out some interesting colours! But really, I'm still at the 'mucking about' stage in StarTools right now (but enjoying it).

[cometcatcher]

Not sure about the colours on that one. Black point clipping too is hiding some nebula.

[Amaranthus]

Agreed. But there was a lot of colour information in the image, so the choice of colours to focus on enhancing was somewhat arbitrary... so I figured I'd try something a little 'different'. The colours are real in the sense that they are in the image - just not necessarily dominant.

[Amaranthus]

Here is a link to the original FTS (after stacking), if you're interested:

DELETED (114 MB zip file of a 32-bit FTS)

It was made by EWA combining in DSS of two stacks - 150 x 10 sec subs and 50 x 30 sec subs, to create the final HDR image. It needs edge cropping as a first step.

[rmuhlack]

Hi Barry i've had a quick play with your eta fits data using pixinsight.

some field rotation in there due to the alt-az mount, so i've cropped it more tightly around the keyhole. in low signal areas it's a little blotchy, which may be due to your sub frame calibration procedure and/or the temperature of the sub frames vs the temp of the darks.

i've tried to colour balance to something more "mainstream". Quite a bit of detail there considering the sub duration and overall integration time.

[Amaranthus]

Thanks Richard, yes, I did a bit of tweaking with just the core of the Keyhole myself last night, in StarTools, and came up with something similar, see attached. It is the larger vista that presents the colour issues.

The darks are matched well, and I calibrated with flats and bias. The problem, I think, is the subs quality due to the mount (and short exposure). Soon I'll be up and running with my AZ-EQ6 and the game will be afoot!

[Amaranthus]

Here is another version, with a bit more work in ST. I think it's looking decent!
Full image here: http://www.astrobin.com/98885/C/

[raymo]

great job Barry.
raymo

[irwjager]

Hi Barry,

Nice to see continuous improvements.
I had a quick look at the data you posted and there is still something strange going on. Calibration might be the culprit - detail has been introduced that isn't real (the blotches that Richard is talking about). There is also a most peculiuar color gradient that seems to radiate outwards. I'm suspecting the flat frames are not suitable or not applied appropriately (just guess :) ).

[cometcatcher]

I noticed the blotchy artifacts too but I can't quite put my finger on what's causing them. Could it be from the Nex?

[Amaranthus]

I think the NEX is fine - chip is clean and the sensor is an excellent one. Wayne Anderson has gotten some great results from this camera, and it takes beautiful terrestrial shots.

As Ivo notes, it may be coming from my less-than-perfect flats (I was experimenting with using the garage light to take them, but looking at them, they seem vignetted due to uneven illumination. I might try it again, sans the flats, as there were few dust bunnies I could see anyway. Will post a new version soon where I leave out the flats and use only the highest quality subs, and see if that improves things (even with a loss of faint detail)

[Amaranthus]

Here is a link to the a new FTS (after stacking):

https://dl.dropboxusercontent.com/u/15859518/Eta_Car_Amar_21May2014_10subs.zip (40 MB zip file of a 32-bit FTS)

10 x 30 sec subs (i.e., 5 min total integration) with darks and bias but no flats. These were the best of the subs, stacked using 'Average', and I also used a custom area to remove the worst of the field rotation.

Does it look improved in terms of its blotchiness or gradient?

[Amaranthus]

Here is an example of a processed image from the above FTS file, and here is the StarTools log:

-----------------------------------------------------------
StarTools 1.3.5.285
Sun Jun 01 16:39:53 2014
-----------------------------------------------------------
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [2.1 pixels]
Parameter [Outside ROI Influence] set to [15 %]
--- Bin
Parameter [Scale] set to [(scale/noise reduction 35.38%)/(798.89%)/(+3.00 bits)]
--- Crop
Parameter [X1] set to [1135 pixels]
Parameter [Y1] set to [783 pixels]
Parameter [X2] set to [29 pixels (-1161)]
Parameter [Y2] set to [24 pixels (-797)]
File saved [C:\ASTROGRAPHS\Eta_Car_Amar_21May20 14_10subs.tiff].
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [No]
Parameter [Precision] set to [512 x 512 pixels]
Parameter [Dark Anomaly Filter] set to [10 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Mask Behavior] set to [De-ring Mask Gaps, Hide Result]
Parameter [Radius] set to [2.0 pixels]
Parameter [Iterations] set to [50]
Parameter [Regularization] set to [1.00 (optimal noise and detail)]
Parameter [Mask Fuzz] set to [8.0 pixels]
--- Contrast
Parameter [Expose Dark Areas] set to [No]
Parameter [Compensate Gamma] set to [Yes]
Parameter [Precision] set to [512 x 512 pixels]
Parameter [Dark Anomaly Filter] set to [10 pixels]
Parameter [Aggressiveness] set to [75 %]
Parameter [Dark Anomaly Headroom] set to [15 %]
--- HDR
Parameter [Small Detail Precision] set to [Max]
Parameter [Channels] set to [Brightness & Color]
Parameter [Algorithm] set to [Optimize Soft]
Parameter [Dark/Bright Response] set to [1.00]
Parameter [Detail Size Range] set to [20 pixels]
Parameter [Noise Suppression] set to [5 %]
--- Wavelet Sharpen
Parameter [Intelligent Enhance] set to [Yes]
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [8.0 pixels]
Parameter [Amount] set to [175 %]
Parameter [Small Detail Bias] set to [75 %]
--- Life
Parameter [Detail Preservation] set to [Min Distance to 1/2 Unity]
Parameter [Compositing Algorithm] set to [Power of Inverse]
Parameter [Inherit Brightness, Color] set to [Color]
Parameter [Output Glow Only] set to [No]
Parameter [Airy Disk Sampling] set to [128 x 128 pixels]
Parameter [Airy Disk Radius] set to [8 pixels]
Parameter [Glow Threshold] set to [12 %]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [100 %]
Parameter [Strength] set to [100 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [RGB Ratio, CIELab Luminance Retention]
Parameter [Dark Saturation] set to [1.50]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [250 %]
Parameter [Blue Bias Reduce] set to [2.66]
Parameter [Green Bias Reduce] set to [2.98]
Parameter [Red Bias Reduce] set to [1.00]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Wavelet De-Noise
Parameter [Scale 1] set to [90 %]
Parameter [Scale 2] set to [90 %]
Parameter [Scale 3] set to [90 %]
Parameter [Scale 4] set to [90 %]
Parameter [Scale 5] set to [50 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [3]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Redistribution Kernel] set to [2.5 pixels]
Parameter [Read Noise Compensation] set to [1.80 %]
Parameter [Smoothness] set to [75 %]

[rmuhlack]

a definite improvement in both blotchiness and gradient (IMO)

[cometcatcher]

Yep, Ivo called it. It was the flats causing the blotchy.