MartinFransson

1 minute ago, Allinthehead said:

That's a great image Martin, i don't recall ever seeing that blue area on the left. Was that in the rgb?

Thanks! No, it didn´t show up in the RGB (although I didn´t have much of that), it was from the O3-data used to enhance blue and green channels.

1 hour ago, ampleamp said:

Thanks Martin; i will be going back to see if i can make anything better of this but didn't want to keep doing the same thing over and get no improvement. Trouble is that there is literally nothing visible, certainly on individual subs and pushing the data is everything here; or just loads more data from a better quality sky??? 

Dark sky is everything on a target like this I´m afraid. That and loads of data

5 hours ago, Tommohawk said:

Re focusing, yes always refocus between filters, but I still got large blue stars until I switched to Astronomic deep sky blue - you can get them separately. See here - the blue cuts at 420nm.

I just checked and I have some star tests I did with ZWO blue filter compared to Astronomic blue - I'll post later. Unfortunately I only had a short window and tested with Capella which isn't very blue. It make more difference on bluer stars.

This is very interesting as I have problems with blue on my 1600MM-Cool and with Zwo filters! Could you also recommend a Lum-filter that does not give the bloated stars that I get with the Zwo Lum?

I would very much like to see star tests. Could you tag me if you start a new post with that?

Wow, that´s deep. I think you could back off on the noise reduction even more. The background looks too smooth and I´m sure you are losing the smallest and faintest galaxies there. Also, I find that a small amount of noise makes the image look more "real".

That´s deep! Looks great, although I would (no I wouldn´t, but it might be a good idea ) back off on the stretching just a tad. I get the same type of granular noise when overstretching my data. There is just not enough signal to be pushed that hard. With even less data I tend to also get some larger, blotchy noise patterns.

30 minutes ago, Taman said:

It's hard to know when to stop! 🙂

Wait, what?! It´s possible to stop? 😮🤣

That´s a really nice Soul Nebula but man what a pain to have all those issues with the scope... having wrestled with some technical issues myself I can relate.

Ooh, that´s looking nice! And I can seriously feel the urge to get that last RGB data That is the pain of mosaics - waiting for the final data for that last panel.

That´s looking good so far! I like how you didn´t go overboard with noise reduction despite there being some noise. I prefer this more natural looking edit rather than the "plastic fantastic" look that can result from over smoothing the noise

I finally managed to get some LRGB for my second panel of the mosaic I shot of the Monoceros area. I already had the narrowband mosaic finished. I used the Ha and O3 to enhance the R and B channels and also some of the O3 in the green channel. I used the @ollypenrice method of blend mode Lighten i the channels in PS. I also created a combined Lum from the Ha and O3 and blended that in at about 30% in the final image.

Total exposure for both panels about 12,5 hours:

L: 73*60s
R: 35*60s
G: 31*60s
B: 34*60s

That is a very nice narrowband Soul Nebula mosaic! I think you did a very pleasing work with the editing as well.

1 hour ago, carastro said:

I have the same problem with my blue stars, my filters are Baader LRGB.  Blue always produces larger stars and I do them separately as I have to re-focus.  I tend not to bother to stop and re-focus with Red and Green as they are normally the same focus as Luminance.  I check the whole lot before I start imaging and anything not the same focus (I use a Bahtinov mask) I do separately and it always seems to be the blue.  

It makes processing quite difficult as these days I try to shrink the blue stars to match in post-processing, but it doesn't shrink the blue halo sufficiently.  See my latest M42.

Is there a solution? 

Carole 

Here is another one with the large blue stars. Regardless of what scope or lens I use, blue (and O3) always produce bigger stars. Even with the Astrodon 3nm O3-filter there is a huge difference compared to 3nm Ha. Don´t know if the camera (ZWO 1600 MM-Cool) has a problem with blues or if that´s just the way it is.

Anyway, that M45 looks like it could be good if you collect some nice, tight Lum to go with that RGB. Have you tried stopping the 200mm lens down? It is possible by attaching it to your DSLR selecting for example f/4 and pressing the depth of field preview button and detaching your lens before letting the DOF button go.

I would ditch that LP filter. There might be good ones but in my experience they cause more problems than they solve if the LP is not worse than what you´ve got. Great start!

That is not at all bad for considering the equipment used and the short total exposure time! It looks like you need a field flattener for that scope, though.

Now that is a lot of dust! Awesome capture! And I like how you handled the (very) bright stars.

I collected some LRGB for one of the panels to my Rosette to Cone mosaic yesterday. Today I´ve been working at editing the LRGB and then combining with my Ha and O3.

Turned out really well I think!

Samyang 135mm lens at f/4
Zwo ASI1600MM-Cool
Zwo LRGB filters, Astrodon 3nm narrowband filters.
27*5min Ha
29*5 min O3
15-18*1min each for R, G and B
38*1 min Lum

Hope you like it!

18 hours ago, Mr Spock said:

That's a startling image. Seriously good.

Thank you!

36 minutes ago, celestron8g8 said:

It’s definitely what i call a wall hanger ! What would be max print out size without degrading the pixels be ? Just curious . 

The size is 6240*3333 pixels so that would be about 21*11 inches at 300 dpi, but for larger prints I find 200 or even 150 dpi is enough so that would be up to 42*22 inches. The thing is - the larger the print, the further away you watch it from  I have printed a 5 megapixel image at 3*2 meters and it looked OK since you had to stand far away to see it properly.

12 minutes ago, celestron8g8 said:

That is a fantastic capture and edit ! Love that WF mosaic !

Thank you! I´m very pleased with it myself... might even print it  

6 minutes ago, vlaiv said:

No, no, it is fairly simple, you start with stacked linear raw color images. Let's call those R_raw, G_raw, B_raw. Those are images that you would do regular RGB combine and stretch to create usual image.

You wipe them so that you remove any gradient and to remove any color cast due to sky flux. Then you color balance them (you don't have to, but if you do - this is the stage when it should be done if you want to do it properly).

This creates R_regular, G_regular, B_regular. Next you create ratio images as:

R_ratio = R_regular / max(R_regular, G_regular, B_regular)

G_ratio = G_regular / max(R_regular, G_regular, B_regular)

B_ratio = B_regular / max(R_regular, G_regular, B_regular)

simplest way to get above is to create mini stack of only 3 subs - three channel images and stack them with max function. This is only stacking involved and it is not regular stacking - it is just trick to get max values out of three images.

In the end ratio combination goes like this:

R_stretched = L_stretched * R_ratio

G_stretched = L_stretched * G_ratio

B_stretched = L_stretched * B_ratio

and that is it.

If you want to be correct in your color handling than you need to modify above with two changes.

1) when color balancing, you need to make sure you are color balancing to sRGB linear color space

2) Final combination should account for sRGB gamma in following way: R_stretched = gamma(inverse_gamma(L_stretched) * R_ratio) instead of R_stretched = L_stretched * R_ratio

That is it.

OK, that sounds like I might be able to try  Just one thing, how do I colour  balance a single (mono) channel? In my world only an RGB image is possible to colour balance...

Thank you for taking your time to explain!

28 minutes ago, vlaiv said:

It's fairly simple technique. I'll describe it in "pixel math" terms, but you can accomplish it in Photoshop with layers as well.

You take your R, G and B subs, wipe them (this is not needed if you aim only for star color, but if you do regular LRGB composing - it should be done) - meaning remove background and gradients from LP, and do color balance (however you do it - whether it is single star / multiple star color calibration or color ratio or whatever).

Next thing you do is add small offset to each of channels. It needs to be same and needs to be just enough so it moves all pixel values to be positive (this is in case that your wipe puts background at 0 and due to noise there are some negative values, you don't want any negative values in any of your subs, and also adding small offset reduces color saturation of background which is good thing as it reduces color noise in background sky if you do full LRGB image - again, not as important for stars only).

Then you stack those three channels with max function (not average but max). Next you divide each of colors with this max stack. This has prepared your color data for "transfer".

Next you take your stretched luminance layer and just simply multiply it with each of color ratio channels to give you proper R, G and B channel of final image. Btw - stretched luminance needs to be in 0-1 range, and above process of creating ratios will certainly put each ratio sub in 0-1 range.

Not above is not strictly correct way to do it in terms of color accuracy. Proper way to do it would be to first apply inverse gamma to lumiance, then multiply then apply proper gamma to result (multiplication needs to be done on linear data) - but that will create proper colors and most people will think that something is wrong with your image as they are used to much more colorful and saturated images . Most images in proper color look rather dull compared to renditions that we usually see and are used to it.

Do you mean that each individual sub in R, G and B has to be processed (wiping, offsetting etc) and then stacking them? Or is that a process for the stacked R, G and B images? Seems like A LOT of work to process each individual sub! 😮

Honestly, I think this process is above my skill level at the moment  

23 minutes ago, vlaiv said:

I think that following approach is worth a try (you can even try it out with this data set to see how you like it):

Make starless version of both OIII and Ha with starnet++ and combine them to produce color version of nebulosity. From Ha stretched version and it's starless counterpart extract stars (subtract layers).

In this version just layer stars on top of combined nebulosity with lighten blend mode (this will give you pure white stars).

In RGB version collect only RGB data as you won't need luminance. Use stars only as luminance and do RGB ratio to transfer color to those stars. Again, transfer RGB colorful stars on top of above nebulosity.

In both bases (with RGB and without) your stars will be as tight as in Ha image, and in most cases those stars tend to be fairly tight.

Thank you! I´m not sure I follow what you mean by "do RGB ratio to transfer color to those stars" but I´ll give it a try  I use Pixinsight and Photoshop.

Started this in 2017 and finally got some O3 for my mosaic of the Monoceros area.

Two panels of Ha and O3, combined to look more like an RGB image.

Ha: 27+27*5 minutes
O3: 29+31*5 minutes

Ha collected at f/2.8, O3 at f/4 for tighter stars. Samyang 135mm lens.

Thinking about collecting some LRGB but I find it hard to blend that in without the stars overpowering the image. Thoughts?

Thanks, I am pretty happy with this one

So, I got a new (used) scope a few weeks back and have started testing it now. I think I need to fiddle a bit with the spacing but it looks OK (not perfect). I gathered a few hours of O3 and combined it with some older O3 and Ha from my Sigma 500mm tele lens.

This is 45*5 minutes of Ha and 111*5 minutes of O3.

ZWO ASI 1600MM-Cool with Astrodon 3nm filters.
Sigma 500/4,5 EX DG HSM lens
TS Optics Photoline 80mm f/6 triplet