The Pleiades (M45) - The Seven Sisters

Started Nov 28, 2017 | Photos
RudyPohl
RudyPohl Veteran Member • Posts: 5,889
The Pleiades (M45) - The Seven Sisters
11

M45 - 70 x 30 seconds

Camera: Nikon D5500 unmodified
Lens: Nikon 300/f4 ED
Aperture: f5.1 using stepping rings as aperture mask
ISO: 1600
Exposure: 70 x 30 seconds = 35 minutes total integration time
Tracker: Sky Watcher Star Adventurer
Sky conditions: 1/2 Moon, Ottawa light pollution dome
Pre-stacking: Raw files converted to 16-bit TIFF files in Adobe Camera Raw in Photoshop
Stacking: Deep Sky Stacker
Processing: Photoshop CS5

Note:
35 minutes of total integration time is not nearly enough to yield a good quality astro image, especially in order to see the faint wisps of light blue nebulosity, nor the space dust that surrounds this star cluster. The reason for the short time is because this was my first time setting up in very cold temperatures this year (-17 Cesius wind chill) and I had all kinds of trouble getting things going. When I finally did "get the show on the road" clouds moved in and shut us down by 8:30 pm, hours before we were planning to. Oh well, I'll try to add more time over the next while.

Comment & critique:
Please provide me constructive critique and criticism.
Nikon D5500
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morganman Forum Member • Posts: 76
Re: The Pleiades (M45) - The Seven Sisters

This is a lovely image Rudy. It's great how you've handled the blue nebulosity around the stars. Nicely done. Since you live in the Ottawa area I'm wondering how you handled the light pollution/sky glow in post.

Scott

Rutgerbus Senior Member • Posts: 2,255
Re: The Pleiades (M45) - The Seven Sisters
2

Hi There,

That's funny, I almost used the same setup and also converted my Sony .ARW files first with to .Tiff

Also used the Nikkor 300mm f/4 ED on a Sony A7Rii from my yellow zone (backyard)

Here is how a single 59 sec sub looks @ ISO1600

And this is what I got after stacking 95 subs of 59sec and processing with the new Astro Pixel Processor software and some tweaking in Photoshop!

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Photographic Moments
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RudyPohl
OP RudyPohl Veteran Member • Posts: 5,889
Re: The Pleiades (M45) - The Seven Sisters

morganman wrote:

This is a lovely image Rudy. It's great how you've handled the blue nebulosity around the stars. Nicely done. Since you live in the Ottawa area I'm wondering how you handled the light pollution/sky glow in post.

Scott

Hi Scott,

Thanks for your kind remark!

Regarding the light pollution, sometime I use a Hoya Intensifier filter and sometimes I don't, but either way the key method I use to remove LP in processing is that shared here by Roger Clark which uses the Curves Tool in Photoshop to subtract light.

In a nutshell you open a new layer of your image and with the Histogram displayed you take your mouse and click and drag each color channel so that their left-hand portions align. Make sure to not take them completely to the left edge of the histogram or you will eventually end up clipping the blacks in your image... leave a good .25 to .33 inches space.

You will find that doing this will almost magically eliminate the light pollution including the intense blue in blue chanell from the Moon light.

Good luck,
Rudy

RudyPohl
OP RudyPohl Veteran Member • Posts: 5,889
Re: The Pleiades (M45) - The Seven Sisters

Rutgerbus wrote:

Hi There,

That's funny, I almost used the same setup and also converted my Sony .ARW files first with to .Tiff

Also used the Nikkor 300mm f/4 ED on a Sony A7Rii from my yellow zone (backyard)

Here is how a single 59 sec sub looks @ ISO1600

And this is what I got after stacking 95 subs of 59sec and processing with the new Astro Pixel Processor software and some tweaking in Photoshop!

Hi Rutger,

Very nice job on your M45 images, I like the way you've captured and processed the soft delicate blues, nice sharp stars too! Well done!

Cheers,
Rudy

OllieN Regular Member • Posts: 392
Re: The Pleiades (M45) - The Seven Sisters

Great image Rudy given the pesky cloud intervention.

I must say I do like the results of your strictness on sharpness and roundness of stars.  Something I think I could learn from...

Ollie

 OllieN's gear list:OllieN's gear list
Nikon D5500 Sigma 105mm F2.8 EX DG OS HSM Tokina 11-20mm F2.8 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF-P 70-300mm F4.5-6.3G VR +1 more
RudyPohl
OP RudyPohl Veteran Member • Posts: 5,889
Re: The Pleiades (M45) - The Seven Sisters

OllieN wrote:

Great image Rudy given the pesky cloud intervention.

I must say I do like the results of your strictness on sharpness and roundness of stars. Something I think I could learn from...

Ollie

Thanks Ollie!

Regarding stars, I make getting nice round stars that are not blown out from overexposure my number one priority both when capturing data and when processing. When I'm tracking I check the polar alignment and the star shapes on every test run and I don't bother going any further and doing multiple subs until I get nice round stars. Once that is achieved I set my intervalometer to fifteen 60-seconds subs and check my star shape (and therefor polar alignment), every 15 minutes, and then do another 15, and so on. It seems tedious but it work great!

If for some reason I just can get round stars at 60 seconds I drop the exposure time to 30 seconds and just shoot more of them, but round stars is always the determining criterion. I have found that if I take care of the stars and make them good, the rest of the image falls into line as well.

TIP:
One tip regarding better managing those pesky blue/cyan rings around stars that come from chromatic aberration and/or not having the focus bang on.... I find that using a free Photoshop plugin called Hasta La Vista Green (HLVG) early in in my workflow (right after the stretching) and again later on keeps the green (cyan) at bay and since the rings around the stars have a lot of cyan in them this really helps. Just do a Google search on  "download HLVG plugin".

Also, I find that doing my stretching by using the Levels Tool found in the Edit menu rather than using the Levels or Curves Tools as an Adjustment Layer causes less star bloating and really makes a big difference in keeping your stars small over the lengthy workflow. My stars always seem to turn out half-decent and yet I never bother with using star masks.

A final thought on your workflow..., as you are more or less still ascending the learning curve with respect to Photoshop, I would not advise you to lean too heavily on rnc-color-stretch or any other "black-box" solutions to achieve your final result. These tools are OK to use once you've learned how to do the proper processing in an actual image editor like Photoshop, and thereby learning the key skills. By using rnc-color-stretch  at this time in your journey I'm concerned that you may be short-circuiting your skills acquisition process. Sorry if I've over-stepped here, but I felt I should share this thought with you.

Best regards,
Rudy

OllieN Regular Member • Posts: 392
Re: The Pleiades (M45) - The Seven Sisters

Thank you Rudy!

Interesting to hear there's a difference between the menu tools and the adjustment layer tools, I hadn't appreciated that.

I take your point about learning the craft rather than relying on black box solutions from the start. I shall definitely try that!

I'll also take a look at the HLVG plugin.

Cheers,

Ollie

 OllieN's gear list:OllieN's gear list
Nikon D5500 Sigma 105mm F2.8 EX DG OS HSM Tokina 11-20mm F2.8 Nikon AF-S DX Nikkor 35mm F1.8G Nikon AF-P 70-300mm F4.5-6.3G VR +1 more
morganman Forum Member • Posts: 76
Re: The Pleiades (M45) - The Seven Sisters

Thanks, Rudy,

I will give that a try.

Cheers.

Scott

RudyPohl wrote:

morganman wrote:

This is a lovely image Rudy. It's great how you've handled the blue nebulosity around the stars. Nicely done. Since you live in the Ottawa area I'm wondering how you handled the light pollution/sky glow in post.

Scott

Hi Scott,

Thanks for your kind remark!

Regarding the light pollution, sometime I use a Hoya Intensifier filter and sometimes I don't, but either way the key method I use to remove LP in processing is that shared here by Roger Clark which uses the Curves Tool in Photoshop to subtract light.

In a nutshell you open a new layer of your image and with the Histogram displayed you take your mouse and click and drag each color channel so that their left-hand portions align. Make sure to not take them completely to the left edge of the histogram or you will eventually end up clipping the blacks in your image... leave a good .25 to .33 inches space.

You will find that doing this will almost magically eliminate the light pollution including the intense blue in blue chanell from the Moon light.

Good luck,
Rudy

rnclark Veteran Member • Posts: 3,957
Re: The Pleiades (M45) - The Seven Sisters
1

RudyPohl wrote:

A final thought on your workflow..., as you are more or less still ascending the learning curve with respect to Photoshop, I would not advise you to lean too heavily on rnc-color-stretch or any other "black-box" solutions to achieve your final result. These tools are OK to use once you've learned how to do the proper processing in an actual image editor like Photoshop, and thereby learning the key skills. By using rnc-color-stretch at this time in your journey I'm concerned that you may be short-circuiting your skills acquisition process. Sorry if I've over-stepped here, but I felt I should share this thought with you.

Rudy,

I have seen you mention this black box idea before.  But let me assure you that is not the case, rather it is the other way around: the tools you are using in photoshop are the black boxes.  Just because you have some sliders you can move around does not make what they do clear.

Specifically, when you adjust points in the levels tool or curves tool, the magnitude of the slider changes with scene intensity and at the brighter levels, color is lost.  Are you really sure what these black boxes are doing, and why is color lost?  Do you know the math behind the box with sliders?  How about other tools?  Because I write and publish image processing algorithms, I can guess, but I too cannot be sure, especially because Adobe's tools tend to produce bizarre results when pushed very far, implying what they are doing is a mathematical approximation that falls apart.  Further, it is clear (to me) that the integer math done in Adobe's tools create additional errors, adding noise to an image with each application of one of their tools.  Adobe will not tell you that actual math used in each of their tools.  Thus they are the real definition of black boxes.

To the contrary, rnc-color-stretch has the full code viewable so you can determine exactly what math is being applied.  Thus it is not a black box.  I wrote the program because I determined that the regular stretching tools, like those in photoshop lost color as one stretches the image.

So by advising people to use Adobe's black boxes, which we know is destructive to color, add noise and which are not intuitive as to what they actual do, does not necessarily help a new user.

Roger

RudyPohl
OP RudyPohl Veteran Member • Posts: 5,889
Re: The Pleiades (M45) - The Seven Sisters

rnclark wrote:

RudyPohl wrote:

A final thought on your workflow..., as you are more or less still ascending the learning curve with respect to Photoshop, I would not advise you to lean too heavily on rnc-color-stretch or any other "black-box" solutions to achieve your final result. These tools are OK to use once you've learned how to do the proper processing in an actual image editor like Photoshop, and thereby learning the key skills. By using rnc-color-stretch at this time in your journey I'm concerned that you may be short-circuiting your skills acquisition process. Sorry if I've over-stepped here, but I felt I should share this thought with you.

Rudy,

I have seen you mention this black box idea before. But let me assure you that is not the case, rather it is the other way around: the tools you are using in photoshop are the black boxes. Just because you have some sliders you can move around does not make what they do clear.

Specifically, when you adjust points in the levels tool or curves tool, the magnitude of the slider changes with scene intensity and at the brighter levels, color is lost. Are you really sure what these black boxes are doing, and why is color lost? Do you know the math behind the box with sliders? How about other tools? Because I write and publish image processing algorithms, I can guess, but I too cannot be sure, especially because Adobe's tools tend to produce bizarre results when pushed very far, implying what they are doing is a mathematical approximation that falls apart. Further, it is clear (to me) that the integer math done in Adobe's tools create additional errors, adding noise to an image with each application of one of their tools. Adobe will not tell you that actual math used in each of their tools. Thus they are the real definition of black boxes.

To the contrary, rnc-color-stretch has the full code viewable so you can determine exactly what math is being applied. Thus it is not a black box. I wrote the program because I determined that the regular stretching tools, like those in photoshop lost color as one stretches the image.

So by advising people to use Adobe's black boxes, which we know is destructive to color, add noise and which are not intuitive as to what they actual do, does not necessarily help a new user.

Roger

Hi Roger,

Thanks for your comment, I will need to give the points you make some careful consideration before responding... will reply later.

Best regards,
Rudy

OllieN Regular Member • Posts: 392
Re: The Pleiades (M45) - The Seven Sisters

Thank you for your input Roger,

As a software developer I completely get the value of a solution such as yours where I could inspect the algorithm should I wish (I probably lack the domain knowledge to actually understand it - but that's another matter).

I also completely agree with Rudy, in that I should spend some time learning histograms, stretching and general image processing techniques even if I can't see exactly what the underlying PS algorithm does.

Only when I have learnt enough can I then make an informed decision on what approach suits my proficiency.

As a note, all my attempts to stretch a stacked image in PS so far are tending to wash out the colours as observed by you.  I don't know yet if it is PS or myself to blame, but I can see that Rudy manages to get some nicely coloured images so it must be possible..

Finally thank you both for all the encouragement and advice that you provide through this forum to amateurs like me.

Ollie

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Michael S.
Michael S. Veteran Member • Posts: 8,245
Re: The Pleiades (M45) - The Seven Sisters

Hi Rudy!
That's a very  respective result for just 35mins...with far longer exposure time I'm sure you can pull out all those dust clouds too.
best regards,

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Michael S.
EUROPE; dpreview since 2001
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RudyPohl
OP RudyPohl Veteran Member • Posts: 5,889
Re: The Pleiades (M45) - The Seven Sisters

rnclark wrote:

RudyPohl wrote:

A final thought on your workflow..., as you are more or less still ascending the learning curve with respect to Photoshop, I would not advise you to lean too heavily on rnc-color-stretch or any other "black-box" solutions to achieve your final result. These tools are OK to use once you've learned how to do the proper processing in an actual image editor like Photoshop, and thereby learning the key skills. By using rnc-color-stretch at this time in your journey I'm concerned that you may be short-circuiting your skills acquisition process. Sorry if I've over-stepped here, but I felt I should share this thought with you.

Rudy,

I have seen you mention this black box idea before. But let me assure you that is not the case, rather it is the other way around: the tools you are using in photoshop are the black boxes. Just because you have some sliders you can move around does not make what they do clear.

Specifically, when you adjust points in the levels tool or curves tool, the magnitude of the slider changes with scene intensity and at the brighter levels, color is lost. Are you really sure what these black boxes are doing, and why is color lost? Do you know the math behind the box with sliders? How about other tools? Because I write and publish image processing algorithms, I can guess, but I too cannot be sure, especially because Adobe's tools tend to produce bizarre results when pushed very far, implying what they are doing is a mathematical approximation that falls apart. Further, it is clear (to me) that the integer math done in Adobe's tools create additional errors, adding noise to an image with each application of one of their tools. Adobe will not tell you that actual math used in each of their tools. Thus they are the real definition of black boxes.

To the contrary, rnc-color-stretch has the full code viewable so you can determine exactly what math is being applied. Thus it is not a black box. I wrote the program because I determined that the regular stretching tools, like those in photoshop lost color as one stretches the image.

So by advising people to use Adobe's black boxes, which we know is destructive to color, add noise and which are not intuitive as to what they actual do, does not necessarily help a new user.

Roger

Hi Roger,

Today, as I've mulled over how I might best respond to your comment above in the most constructive way, I realize that I simply can't say it any better or more concisely than Ollie himself said it in his comment to you on the issue.

Concerning his need to acquire Photoshop image processing skills as opposed to simply relying on the rnc-color-stretch algorithm to achieve his processing results, he wrote:

".... I should spend some time learning histograms, stretching and general image processing techniques even if I can't see exactly what the underlying PS algorithm does.

Only when I have learnt enough can I then make an informed decision on what approach suits my proficiency."

I concur completely. Also, please note that I am not advising anyone to not use this or any other image processing algorithm, but rather I am advising them not to become solely or overly dependent on such tools in lieu of learning the basics steps and the intermediate skills of image processing.

Best regards,
Rudy

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