Tadpoles SHO reworked

[emyliano2000]

Hi guys.

This weekend I tried to improve my narrowband processing and I'm not yet convinved if it better.

The first photo is my first go at full SHO and the second one is what I managed to do over the weekend.

Somehow I feel the second one is more natural in colour but I still feel that a lot of the things that I've done are still wrong. Feel free to zoom in and tell me what you think.

Everything has been done in photoshop and lightroom.

Thanks

Emil

[Adreneline]

Hi Emil,

I like them both and would be more than happy if I had taken them. In answer to your question I feel the second one reveals better defined detail in the structure of the nebula. As for natural colour - what's that?! - I much prefer the colour of the second one as well.

If I were you I would be convinced it is better

Adrian

[vlaiv]

To me - second one as far as color rendition.

First one in terms of denoise control - second one is full of denoising artifacts. First one has some of them too, but second one is too much.

Also, are spikes artificial? They are way too tight to be natural diffraction spikes. If they are then they have been sharpened quite a bit and stand out from the rest of the image - it is not so sharp.

My guess about them is that they are artificial because some stars have them in first image while not in second image. I personally don't like synthetic diffraction spikes.

Although this seems to be rather popular method of rendering SHO, I have a question for you - can you point out regions of SII from your image?

[newbie alert]

Hi Emil, as above like them both but prefer the colour of the bottom one..scorcher..!

[emyliano2000]

6 hours ago, Adreneline said:

As for natural colour - what's that?

I was meaning to say, colour that's not too much in your eyes 😁

6 hours ago, vlaiv said:

To me - second one as far as color rendition.

First one in terms of denoise control - second one is full of denoising artifacts. First one has some of them too, but second one is too much.

Also, are spikes artificial? They are way too tight to be natural diffraction spikes. If they are then they have been sharpened quite a bit and stand out from the rest of the image - it is not so sharp.

My guess about them is that they are artificial because some stars have them in first image while not in second image. I personally don't like synthetic diffraction spikes.

Although this seems to be rather popular method of rendering SHO, I have a question for you - can you point out regions of SII from your image?

Indeed I have a lot of denoising artefacts in the second one and I don't know yet how to fix them. The more I stretched the uglier the noise and I ended up with the artefacts when I tried to remove it. 

I added the artificial spikes because the original ones bacame too ugly when I stretched the image. I would love to have nice spikes without feeling the need to add the artificial ones. I am a fan of spikes and because they weren't very pretty I thought of adding them. I won't have them from now on as I don't own a newtonian anymore.

In terms of pointing the Sii in the image, to be honest I could only do it if I look at the Sii stack.

3 hours ago, newbie alert said:

Hi Emil, as above like them both but prefer the colour of the bottom one..scorcher..!

Thank you. Not really happy with any of them to be honest. I would like them to look good even when you zoom in. I don't think it's the data, I think it's my processing skills that are very far from being up to the standard skilled processor.

I would really, really love to see what other people can do with the data. I have the Ha, Sii, Oiii and R, G and B stack all aligned and I will post a download link for them.

Please, please feel free to try your best. I'm sooo curious what can be achieved with data shot from my back garden.

Emil.

[emyliano2000]

Here's the link to the files.

https://we.tl/t-fIe7EhfUsq

It's 72x300sec for Ha, 71x300sec for Sii, 73x300sec for Oiii and 23x120sec for each of the R,G and B

20 hours total exposure time

Please feel free to tell me what you think of the data and feel free to have a play with it.

Emil

[carastro]

Excellent for a first "go" at Hubble Palette.  that said the 2nd one is a much better rendition.

Well done. 

Carole 

[dave_galera]

I definitely like the second image more in keeping with SHO, well done

[vlaiv]

4 hours ago, emyliano2000 said:

In terms of pointing the Sii in the image, to be honest I could only do it if I look at the Sii stack.

That was a trick question , sort of.

I've noticed that many people like this sort of "SHO palette" but in my view it's missing the point. We use three colors to represent three different wavelengths of light. Once you start changing hue of this color combination to be more pleasing to the eye, you loose ability to differentiate wavelengths and respective elements in the image. Although you get more pleasing result, you loose "scientific" or rather in our case informative value.

Green looks unnatural in astro images and most people decided to avoid it even in false color narrow band. Predominant combination now seems to be blue for OIII, yellowish for Ha (rather than green) and red for SII. To make things more pleasing to the eye hues of these colors are also shifted a bit. Most people aim for "sky blue" rather than "sea blue" for OIII - much like in your second image, golden yellow for Ha and red/brown for SII.

I think that you've got OIII and Ha colors/shades real good in second image, but I think that you are missing SII or brown/red component - and hence trick question.

[andrew s]

There are no natural colours just convention and personal preference. 

There tends to be a convergence to the norm. 

For me it depends on what you want as @vlaiv  said science, personal satisfaction or whatever.

Regards Andrew 

[emyliano2000]

 

1 hour ago, vlaiv said:

I think that you've got OIII and Ha colors/shades real good in second image, but I think that you are missing SII or brown/red component - and hence trick question

You are right. Looking at the stacked Sii photo I can see where the Sii is but as you said, you can't really distinguish it in the SHO photo

I have another question. Looking at the Ha, Sii and Oiii stacks, the Sii and Oiii ones are quite noisy compared to the Ha one. I have the same number of exposures for each of them, how come there is so much noise in th Sii and Oiii?

Am I doing something wrong? Should I use different camera settings to get cleaner Sii and Oiii stack?

[vlaiv]

4 minutes ago, emyliano2000 said:

I have the same number of exposures for each of them, how come there is so much noise in th Sii and Oiii?

There is no guarantee that light emitted in SII and OIII wavelengths will be of the same intensity as Ha. Each target has it's own "signature" - both in terms of shape of gas distribution but also how bright it is in particular wavelength.

You don't need any sort of particular settings to handle this - what you need is to get more data on fainter wavelengths until you get acceptable SNR. If you have "limited" budget, then in general Ha tends to be the strongest signal, so take more subs in OIII and SII to get smoother image.

Another trick that you can use is to use Ha as luminance layer and compose in similar fashion as you would LRGB, but in this case it will be HSHO (LRGB). This depends on target and you need to examine your stacks in each wavelength to see if indeed Ha covers everything.

[david_taurus83]

9 minutes ago, emyliano2000 said:

 

You are right. Looking at the stacked Sii photo I can see where the Sii is but as you said, you can't really distinguish it in the SHO photo

I have another question. Looking at the Ha, Sii and Oiii stacks, the Sii and Oiii ones are quite noisy compared to the Ha one. I have the same number of exposures for each of them, how come there is so much noise in th Sii and Oiii?

Am I doing something wrong? Should I use different camera settings to get cleaner Sii and Oiii stack?

Theres just so much more signal in Ha so your really swamping the noise. Not so much with Oiii and Sii so it looks more grainy. I've taken 15 minute subs with the ASI1600 at -20 and the stacked Ha literally needs no noise reduction. But 15 minute Oiii is still noisy.

[emyliano2000]

1 minute ago, vlaiv said:

Another trick that you can use is to use Ha as luminance layer and compose in similar fashion as you would LRGB, but in this case it will be HSHO (LRGB). This depends on target and you need to examine your stacks in each wavelength to see if indeed Ha covers everything.

That's a very good tip. Thank you very much 😊

Emil

[emyliano2000]

6 hours ago, vlaiv said:

what you need is to get more data on fainter wavelengths until you get acceptable SNR

Maybe I should increase the exposures for the faint ones. I had a search online and found that I can go up to 600sec with the qhy183m and the AT106 in narrowband under my sky conditions. I remember a while ago I even did 900sec with a dslr on a 1000mm f5 newtonian and I got really good results on targets close to Zenith.

Maybe I should even try some 900sec to see what I get, I'm pretty sure the mount can handle it, since I put it on a pier my guiding is great.

Edited July 30, 2019 by emyliano2000

[vlaiv]

9 hours ago, emyliano2000 said:

Maybe I should increase the exposures for the faint ones. I had a search online and found that I can go up to 600sec with the qhy183m and the AT106 in narrowband under my sky conditions. I remember a while ago I even did 900sec with a dslr on a 1000mm f5 newtonian and I got really good results on targets close to Zenith.

Maybe I should even try some 900sec to see what I get, I'm pretty sure the mount can handle it, since I put it on a pier my guiding is great.

Difference between shorter and longer subs (for same total imaging time) depends on read noise. qhy133m is already quite low read noise, so I doubt that you will see much difference - there will be some but not as much as one would hope.

What you can do with this data set to improve things is to maybe look at binning x2. Qhy183m has rather small pixels, and if I'm correct AT106 has 690mm FL, which gives 0.72"/px sampling rate - and that is almost certainly oversampling. Bin x2 will give you x2 boost in SNR which is equivalent of getting another x3 number of subs for each channel.

This would be very easy to try out - take your stacks in all three wavelengths and do integer resample in PI (select average method and reduce by x2), and then see what noise looks like and try processing that.

 

[alan potts]

Really like the second image, could you tell my the NGC number of this or what ever it is.

 

[vlaiv]

51 minutes ago, alan potts said:

Really like the second image, could you tell my the NGC number of this or what ever it is.

 

IC410

[alan potts]

1 minute ago, vlaiv said:

IC410

Many thanks for that, may have a bash at it with the Canon.

Alan

[emyliano2000]

10 minutes ago, alan potts said:

Many thanks for that, may have a bash at it with the Canon.

Alan

This is a winter target in the Auriga constellation so you might have to wait a bit until it's up in the sky again.

I shot it at the beginning of March.

[MarsG76]

I Agree that the second one looks more natural and is better overall, but I also think that the blacks are clipped so a mixture of the first one with the second one will be perfect, say 35% of the first and 65% of the second image.

[emyliano2000]

Please guys, have a go at my data, I'm just curious. 

https://we.tl/t-fIe7EhfUsq?src=dnl

Edited July 30, 2019 by emyliano2000

[daz]

Are the TIFFS because you are stacking in DSS then bringing into PI to process?

If so, could you stack in PI and produce the .xisf or .fits files? And do you have the master darks/flats/bias to go with them?

May as well have the full stack to play with

 

[emyliano2000]

1 hour ago, daz said:

Are the TIFFS because you are stacking in DSS then bringing into PI to process?

If so, could you stack in PI and produce the .xisf or .fits files? And do you have the master darks/flats/bias to go with them?

May as well have the full stack to play with

 

Yes, I stacked in DSS and I do my processing in photoshop. I only use Pi to sort them out with Blink and sometimes for stacking but I do it the long way and it takes me a while so if I only have data shot with one setup I tend to do it in DSS. I don't know much about Pi, I don't even know how to stack using the batch processing.

I already had a go at stacking in Pi and something wasn't quite right so I gave up and did it in DSS.

I think it would be faster to put them on a stick and post them to you. 🤣

[vlaiv]

2 minutes ago, emyliano2000 said:

Yes, I stacked in DSS and I do my processing in photoshop. I only use Pi to sort them out with Blink and sometimes for stacking but I do it the long way and it takes me a while so if I only have data shot with one setup I tend to do it in DSS. I don't know much about Pi, I don't even know how to stack using the batch processing.

I already had a go at stacking in Pi and something wasn't quite right so I gave up and did it in DSS.

I think it would be faster to put them on a stick and post them to you. 🤣

If you could sort out stacking in PI that would be great - it has some advantages over DSS (at least I think so).

- it will calibrate subs using 32 bit precision (I think DSS is limited to doing that in 16bit - at least it was in version 3.3.2 - last I have used, there are later versions now and that might be fixed).

- it can use Lanczos resampling when doing registration / alignment of frames - that is a big plus I believe (DSS uses bilinear / bicubic still?)

PI should provide you with cleaner stack and tighter stars, also try to save your work in 32bit format, preferably FITS - as it is standard for astronomy software.