My first Narrowband Image

[szymon]

Ahh forgot to mention my scope is a lot slower than yours, an 80ED at f/7.5. That will also likely increase necessary sub length.

NGC6960, the Witch's Broom Nebula, also known as the Western Veil

Exposure:

• Total Lights 2 hours 15 minutes

• 3 x 900 seconds each of Ha, Oiii, Sii

• 20 Flats individually for each filter

• 20 corresponding DarkFlats for each filter

• 19 x 900 seconds Darks



Hardware:

• Altair Hypercam 183M

• Celestron 80ED

• SkyWatcher Motor Focuser

• SkyWatcher HEQ5

• Xagyl USB Filter Wheel

• Altair 1.25" 7nm Ha Filter

• Altair 1.25" 6.5nm Oiii Filter

• Altair 1.25" 6.5nm Sii Filter

• SkyWatcher ST80 Guide Scope

• QHY5L-iic Guide Camera

• Altair 0.6x Focal Reducer (for guide cam)



Software:

• SharpCap

• Cartes du Ciel

• PHD2 Guiding

• Deep Sky Stacker

• StarTools

[dariv]

I live in London, England, known fondly to those of us who astroimage as “LPLondon”. The light pollution is basically at the levels of Victorian Smog. My back garden is Bortle 8. I do not have Dark Skies. That said, this is why I have 7/6.5nm narrowband filters, so that I can ignore the light pollution!

The figure for “unity gain” comes from Nick at Altair Astro so I am pretty sure if he says it’s 400 then it’s 400 . That said I previously tried 300 second captures at gain 400 and got basically no visible nebulosity. This is why i went up in gain...

I found some specs on the hypercam.
the gain goes from 100 to 5000. I believe from the graph 400 is indeed around unity. A little internet poking around and I find advice not to exceed unity on this sensor because of the loss of dynamic range.
there is a loooong thread here: https://www.cloudynights.com/topic/5994 ... %20asi183m
Clear Skies!

[admin]

Those are wonderful results -- especially the last one! I don't suppose you have a beta program for people to test the latest latest bleeding edge v5? Happy to send my qualifications if you're interested, I believe I could provide useful input and am happy to keep pulling in updates and won't complain if things don't work

I will send you a PM shortly...

I am surprised that you found you had to align the three channels -- I thought I actually did that properly in DSS! I first marked one of the Ha images as a reference image:
When I put them together in StarTools, it seemed to me that they were correctly aligned. What did I do wrong?

It sounds to me you did everything right! I don't really have an explanation for why the datasets are mis-aligned regardless.

I am interested as to why this is a challenging data set -- in particular, I would like to learn what I can do to make it better next time.

The challenge was mostly dealing with the extremely heavy noise. This may simply have to do with imaging from London; filters unfortunately aren't perfect and may still allow light from other wavelengths through. Depending on you instruments and optical train, there is always the possibility something else is contributing noise (e.g. thermal noise, stray light) over such long exposures. While you can usually model and subtract (using Wipe) any bias this "other" signal introduces, it is impossible to subtract the noise this "other" signal introduces. Otherwise, the data looks to follow best practices perfectly. Star shapes vary a bit however and the H-alpha set is a bit out of focus (donuts instead of neat points).
It's a seriously nice effort for a first go and you should be chuffed!

would the fix for that for me to capture binned 2x2? My camera is a Hypercam 183M which has very small (2.4um) pixels and lots of them (5440x3648). If I binned at 2x2 or more, I'd have bigger pixels and more sensitivity.

This is most definitely worth a try![/quote]

(45 minutes each is really not a lot!).

Honestly, that's probably the crux of the "problem" (if you can call it that), as you seem to have a decent handle on the other aspects.

(My favourite of all of your renderings is the HOO bi-colour at the end; when I can get those kinds of fantastic results myself from StarTools I'll be over the moon!

Let's get you to that point asap!

Also, thanks DaRiv for weighing in - it's so much more helpful to hear from someone with similar gear!

[szymon]

Is this dataset any cleaner?

Ha: https://www.dropbox.com/s/b908pmkkkqg0u ... .fits?dl=1
Oiii: https://www.dropbox.com/s/i69nl2apbw790 ... .fits?dl=1

I need to reprocess it but this is what I did quickly last night:

Code: Select all

-----------------------------------------------------------
StarTools 1.4.352
Tue Jul 16 02:27:41 2019
-----------------------------------------------------------
Loading red channel data
File loaded in LRGB module [C:\Users\szymon\Desktop\SharpCap Captures\final_ha.fits].
Loading red channel data
Loading blue channel data
File loaded in LRGB module [C:\Users\szymon\Desktop\SharpCap Captures\final_oiii.fits].
--- LRGB
Parameter [Cap Green] set to [No]
Parameter [Channel Interpolation] set to [On]
Parameter [RGB Blur] set to [1.0 pixels]
Parameter [Blue Ratio] set to [1.00]
Parameter [Green File] set to [1.00]
Parameter [Red Ratio] set to [1.00]
Image size is 5440 x 3648
Type of Data: Linear, was not Bayered, or was Bayered + white balanced
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [5440 pixels (-0)]
Parameter [RoI Y2] set to [3648 pixels (-0)]
--- Crop
Parameter [X1] set to [350 pixels]
Parameter [Y1] set to [311 pixels]
Parameter [X2] set to [5320 pixels (-120)]
Parameter [Y2] set to [3493 pixels (-155)]
Image size is 4970 x 3182
--- Bin
Parameter [Scale] set to [(scale/noise reduction 25.00%)/(1600.00%)/(+4.00 bits)]
Image size is 1242 x 795
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [0 %]
Parameter [RoI X1] set to [386 pixels]
Parameter [RoI Y1] set to [213 pixels]
Parameter [RoI X2] set to [886 pixels (-356)]
Parameter [RoI Y2] set to [524 pixels (-271)]
Mask used (BASE64 PNG encoded)

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--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Mask Behavior] set to [De-ring Mask Gaps, Hide Result]
Parameter [Radius] set to [1.5 pixels]
Parameter [Iterations] set to [6]
Parameter [Regularization] set to [1.00 (optimal noise and detail)]
Parameter [Mask Fuzz] set to [8.0 pixels]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [Temporary AutoDev] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [7 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [0 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [85.27 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Rotate
Parameter [Angle] set to [180.00]
--- Wavelet De-Noise
Parameter [Filter Type] set to [Distance Weighted Outlier Rejection]
Parameter [Grain Size] 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 [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [6]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Grain Size] set to [1.0 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [80 %]
File saved [C:\Users\szymon\Desktop\SharpCap Captures\m16_eagle.tiff].

[szymon]

This was taken over two nights, again there is not much data, but it's taken with Gain set to 400 (which should be close to "unity gain"). It's not binned from the camera, but I was able to bin 25% in StarTools -- it seems to me that StarTools is basically doing the same as camera binning, but is more flexible, so I'm probably not going to bin while capturing.

Exposure:
Total Lights 1.5 hours
9 x 300 seconds each of Ha and Oiii
20 Flats individually for each filter
20 corresponding DarkFlats for each filter
25 x 300 seconds Darks

[Rkonrad]

Here is my try (bicolour version):

Since the log file has a lot of characters regarding the masks - it takes a *long* time to load the information. I'll send it a bit later.

The luminance is a blending of HA and Oiii. I the processed the ha and Oiii separatly assigning the ha to red and the oiii to green and blue. I tend to reduce the green somewhat which give the red a more realistic colour (what's real?:)

Thanks for the data - that was fun.

3.jpg (411.15 KiB) Viewed 5918 times

[admin]

This was taken over two nights, again there is not much data, but it's taken with Gain set to 400 (which should be close to "unity gain"). It's not binned from the camera, but I was able to bin 25% in StarTools -- it seems to me that StarTools is basically doing the same as camera binning, but is more flexible, so I'm probably not going to bin while capturing.

Exposure:
Total Lights 1.5 hours
9 x 300 seconds each of Ha and Oiii
20 Flats individually for each filter
20 corresponding DarkFlats for each filter
25 x 300 seconds Darks

That looks pretty decent!

It appears something has gone wrong with the flats though (especially in the Ha set)? There are a good few dust specks visible, as well as some concentric ring like structures (top right in the O-III stack and 5 o'clock in the Ha set). Any idea what caused them? It's a shame, as the Ha set by itself has good signal!

(also, I like your rendition of the Broom, Richard! )