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Processing M45 (Pleiades) in PS

astrophotography beginner dslr
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#1 T-Rango

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Posted 12 November 2019 - 04:50 PM

Hi all, 

 

I recently imaged M45 for the first time and would love some input on my processed image. Overall, I’m somewhat happy with the results as this was taken from my backyard close to Denver (bortle class 6-7).  I was surprised I was able to pull as much nebulosity as I did but feel I over processed the image at the same time and created too much noise. It seems like if I don’t over process the image I get very little nebulosity. I also noticed a lot of vignetting as I stretched the curves and adjusted the levels which led me to crop heavily. The image still has a lot of vignetting and appears very soft. I am wondering if something is off about the AutoSave TIF file. Maybe something didn't register properly when stacking in DSS or maybe it's user error while doing the imaging and or in post smile.gif  Still new to this hobby and trying learn and improve. 

 

Here is the link to the raw file:

 

https://drive.google...LmC7BtWKGTLPt43

 

Feel free to give it a stab if you would like. Would love to see what other people can come up with. 

 

 

Additional details below:

Total Exposure: 1hr 44 min
156 lights
15 darks
15 flats
ISO 400
Canon70D
William Optics Z61 w/field flat
Skyguider Pro
No LP filter
Stacked in DSS

 

 

Thanks and I look forward to your input!

 

- Tim 


Edited by T-Rango, 12 November 2019 - 05:34 PM.


#2 T-Rango

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Posted 12 November 2019 - 05:02 PM

Apologies- here is the image I came up with. 

 

M45.JPG


Edited by T-Rango, 12 November 2019 - 05:17 PM.

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#3 scadvice

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Posted 12 November 2019 - 05:03 PM

Welcome to CN!

 

Why don't you post us a image here? Just make it a PDF and reduce it to under 500k when you post. Edited out.

 

 

We can actually tell you more by seeing what you came up with and make suggestions for correcting your processing.

 

OK...Focus is a little soft...That's very common for most all of us starting out. Look into getting a Bahtinov Mask. The WO61 usually has one in the lens cover.  If you think it was in focus did you use a image process that softens the picture? If so you may have over done it.

 

You have Vignetting around the edges... Did you darken it with the photoshop backdrop? If not, there is maybe a problem with your optical train. Also, Canon has some settings that may be causing it but I don't have enough knowledge to address that.There are people here that do so hopefully they will speak up.

 

 

For an hour and 44 minutes your image looks to stretched enough...but you could try playing with curves and saturation. Color is very nice. That's all I got! Again welcome!


Edited by scadvice, 12 November 2019 - 05:40 PM.

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#4 Adam Bomb

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Posted 12 November 2019 - 05:40 PM

OK...Focus is a little soft...That's very common for most all of us starting out. Look into a getting a Bahtinov Mask. The WO61 usually has one in the lens cover.  If you think it was in focus did you use a image process that softens the picture? If so you may have over done it.

 

My opinion as I am a novice myself.

 

+1 on slightly missing focus.

 

Make sure you take proper darks and flats and plenty of them.

 

The brightness of the background sky makes it tough to find where the nebulosity starts and the light pollution ends.

 

This is my go at processing your data. Thank you for supplying it as I enjoy processing!

 

Welcome to CN!

 

AutosavePS.jpg


Edited by Adam Bomb, 12 November 2019 - 05:42 PM.

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#5 wrnchhead

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Posted 12 November 2019 - 06:31 PM

I think it’s darn good especially considering the Denver factor!  I didn’t do as well from my smaller city my first try that’s for sure.  My vignetting problems have always been taken care of with flats although I used Photoshop for a year I have moved on to Astro pixel processor and it seems to have an easy and intuitive light pollution and vignetting fix. Someone more skilled in Photoshop could show you how to use the gradient tool and correct it I would imagine.  That being said it’s a good picture I would be sending that to everyone I knew if I were you!



#6 Skyshooter

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Posted 12 November 2019 - 08:08 PM

Hey Tim, Welcome to Cloudy Nights...

Here's my two cents for what it's worth...

First off, I think focus is quite a bit off. Do you use a bahtinov mask to focus with?

If not, now is the time to make one. It makes it simple to nail focus with. Google it.

There are instructions for making and using one on line.

Second, even with light pollution I believe you could get away with at least 2 minute subs

on that target. I would also bump up my ISO to 800. Your sky will probably look pink in your

autosave.tif file but no worries, you can process that out.

Third, how did you do your flats... a good master flat should take care of most of your vignetting.

I use a whit t-shirt stretched over my objective pointed at an evenly illuminated sky. Use the AV setting 

on your camera for exposure. More is better. I usually take 20 or more flats. Remember, these are same

ISO as the rest of your calibration frames and the camera cannot be moved from the orientation and focus

point of your light frames.

Fourth, when you process your autosave.tif file in photoshop use very small steps in levels and curves.

A LOT of small steps... There are tutorials on youtube you can find that will help you with this.

A BIG part of this hobby is in the processing... Don't give up! you'll get it.

 

Hope this helps.. will be looking forward to seeing your progress !!!

 

Clear Skies, Ed


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#7 BQ Octantis

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Posted 12 November 2019 - 11:33 PM

I love processing challenges!

 

A couple of observations:

 

The vignetting is pretty severe and very different between colors. I suspect either an unsuccessful flat capture or an erroneous application of the flat in software. And I'm too old and lazy to build a per-channel correction.

 

vignette.jpg

 

Your image is plenty sharp and in focus; the softness in your posted image is due to processing almost exclusively. Here's a crack at bringing out some detail:

 

work.jpg

 

Cheers,

 

BQ



#8 17.5Dob

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Posted 12 November 2019 - 11:50 PM

How did you shoot your flats ?  The vignetting is extreme and looks like they are not working at all.

But let me get this straight. You shot 156- 40" subs (1 hr 44 min/ 156), at ISO 400, with a Canon camera, and the Z61 @ f5.9 ??

40" is way too short an exposure with a Canon at ISO 400. It's too short an exposure for any camera besides an extreme EAA high QE camera "Snapshot" at f5.9...

This is my last attempt at M45, only 25 subs, (but 360") just a few miles away from you with a 65mm, f6.5 and ISO 200....

 


Edited by 17.5Dob, 13 November 2019 - 12:10 AM.


#9 BQ Octantis

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Posted 13 November 2019 - 09:57 AM

Can you post one of your flats? Or your flat stack if you've got one. The vignette rolloff is really close to the left side of the asterism, so it's hard to find the extent of the nebulosity. Here's a stretch with no other processing at 50% scaling; note the black background in the upper left corner:

 

Autosave2.jpg

 

BQ


Edited by BQ Octantis, 13 November 2019 - 10:29 AM.


#10 DubbelDerp

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Posted 13 November 2019 - 01:24 PM

Here's my meager attempt in Astro Pixel Processor... there are some hot pixels on the left hand side that I had to crop off, and some color mottling in the background, but there's a lot of nice detail in there! Wish I could do more with it, but that's the limits of my post processing abilities.

 

Autosave-mod-lpc-cbg-csc-SC-St.jpg



#11 T-Rango

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Posted 13 November 2019 - 01:33 PM

First off, thanks everyone for the replies. Very informative.

 

For my flats, I put a white t-shirt over the objective and place a tablet or phone with a white illuminated screen over it. I keep the exact same settings and focus as my lights. I do rotate the telescope (pointing up) so that the phone/tablet can balance over the objective. For my darks, I just put the telescope cap back on and keep the same settings. Maybe I need more darks & flats? What is the general rule of thumb? I assume the more exposure, the more flats & darks are needed? I did a fairly aggressive initial stretch just to see if something looked funky with the raw file that could be causing some of the issues and noticed some halos or gradient problems (see below). Is this normal or supposed to have been fixed with the flats? 

 

Stretched M45.JPG

 

As far as focus, I do have bahtinov mask but forgot to use it (rookie mistake). I will defiantly be using it going forward!

 

I also wonder if my imaging train, more specifically the field flatterer is causing issues. I use the adjustable WOZ61 Field Flatterer but still get star trails and vignetting around the edges. May be a stupid question but, how does this field flat adjust? Is it supposed to turn/rotate so that I can adjust it? I've tried turning the threads (shown below) to adjust but it won’t budge at all.. Seems stuck or not supposed to rotate.

 

 

Field Flat.JPG

 

 

Thanks again for the replies!

 

- Tim 

 



#12 Noobulosity

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Posted 13 November 2019 - 01:38 PM

Lots of great advice here. I also suspect am issue with the flats not calibrating out the vignetting like they should. I'd also suggest longer subs or higher ISO to capture more of that nebulosity. Just be careful not to over-expose the stars, which can happen quickly considering their brightness.

I also process in Photoshop, and I found the tutorials from Astrobackyard's YouTube channel very helpful in improving my skills. But he also utilizes am action set and a gradient reduction plug-in. I bought those both, and they've made a world of difference. It also really helped me to actually see someone walk through the steps, rather than read a written tutorial.

#13 T-Rango

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Posted 13 November 2019 - 01:53 PM

Lots of great advice here. I also suspect am issue with the flats not calibrating out the vignetting like they should. I'd also suggest longer subs or higher ISO to capture more of that nebulosity. Just be careful not to over-expose the stars, which can happen quickly considering their brightness.

I also process in Photoshop, and I found the tutorials from Astrobackyard's YouTube channel very helpful in improving my skills. But he also utilizes am action set and a gradient reduction plug-in. I bought those both, and they've made a world of difference. It also really helped me to actually see someone walk through the steps, rather than read a written tutorial.

 

Hi Noobulosity,

 

I've also watched Astrobackyards tutorials. He has some great stuff on his channel! I purchased the action set as well but not the gradient reduction plug-in. I will have to look into that.  I will also try longer subs or higher ISO on my next attempt. I'm always worried about light pollution and over exposing tho. Just need to trust it I suppose.

 

Thanks for the comment.

 

- Tim 



#14 DubbelDerp

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Posted 13 November 2019 - 02:01 PM

The ring in your image with the bottom arrow is a locking ring. The smooth tapered piece below it onto which your t-ring threads is the adjustable portion and can be threaded off the flattener. You tighten the thin ring above it once you have it adjusted to the correct length to "lock" it into place. Give the bottom piece a good counter-clockwise twist, and you should be able to unthread it completely off the flattener, showing the scale underneath. Side note, there's a 2" filter thread hidden under there as well.



#15 BQ Octantis

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Posted 13 November 2019 - 05:19 PM

For my flats, I put a white t-shirt over the objective and place a tablet or phone with a white illuminated screen over it. I keep the exact same settings and focus as my lights. I do rotate the telescope (pointing up) so that the phone/tablet can balance over the objective. For my darks, I just put the telescope cap back on and keep the same settings. Maybe I need more darks & flats? What is the general rule of thumb? I assume the more exposure, the more flats & darks are needed? I did a fairly aggressive initial stretch just to see if something looked funky with the raw file that could be causing some of the issues and noticed some halos or gradient problems (see below). Is this normal or supposed to have been fixed with the flats? 

The rule of thumb for flats and darks is to have the same number of each as you have lights. I've found the noise statistics to stabilize after 100 frames at 30 seconds, so it's diminishing returns after that.

 

The halos in your stretch are the vignette rolloff of at different locations per color channel. Those should have been eliminated by the flat. If you post your flat, I can see if it got applied or not by DSS. If not, you can apply a master flat as a divide layer in Photoshop.

 

BQ



#16 JDShoots

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Posted 13 November 2019 - 07:25 PM

Ok, I stretched it a little in StarTools, and wow, I agree, the vignette is crazy.  I can't help with your equipment, but I have made one mistake with DSS a couple times.  

When you go in to select your files, DSS remembers the last place you were and takes you there.   So twice now I processed a stack with bias frames from a different session!   I almost wonder if you selected a incorrect folder and used flats from a different setup, or bumped the aperture or something?  



#17 T-Rango

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Posted 13 November 2019 - 09:22 PM

Hi All

 

Update: I was finally able to get the field flattener to adjust. It was crazy hard to get it loose but I was finally able to it. I think this was part of the issue I have been having, especially related to star trails and bloating around the edges. I'm excited to take some images with it adjusted properly smile.gif Thanks to your comments and some additional research, I believe my flat frames and how I am taking them is causing most of the issues. I was taking them with a crappy white t-shirt (probably wrinkled) and a white screen on my phone over the objective, but I set the screen brightness to max. I thought the brighter the better.. but it seems you need a certain balance. I also thought you need the same exposure time for each frame so I was doing 40" same as my lights.. probably way too bright? I didn't change focus or ISO.. Everything was the same, except for the telescope pointed up to rest my phone on top. 

 

What is your method for taking flat frames? 

 

I really appreciate everyones input. This is my first post and dang, I feel like I have learned a lot!

 

Thanks,

 

Tim 


Edited by T-Rango, 13 November 2019 - 09:29 PM.


#18 DubbelDerp

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Posted 13 November 2019 - 09:44 PM

I’ve struggled with flats, and still being a rookie, I’m sure there are better ways. But what has worked best for me so far is leaving the camera attached to the scope and taking flats the next day with the scope pointing straight up to the daytime sky. Two layers of cloth rubber banded around the objective. 
 

I use APP for calibration and processing, and one of the methods of generating a flat is to calibrate the master flat with a master bias of the same ISO as the flat frames. Not necessarily the same iso as the lights, but might as well keep them the same. With the daytime sky as the light source, the exposure time is really short so the bias works fine. Then for calibrating the lights, I use a master dark that is the integration of dark frames at the same iso, temp, and exposure time only (no bias), and the calibrated master flat. 
 

This so far has worked really well for me. 



#19 scadvice

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Posted 13 November 2019 - 10:46 PM

I use a Canon T3i modified and for flats from the beginning, I've been using this light screen.

 

https://www.amazon.c...dt_b_asin_title

 

I set it on it's lowest brightness setting for the flats. I've tried it with a white T shirt...one layer...two layers ...and even three. Without a T-shirt is the way I'm doing it now as there was not improvement or change with the T-shirts or different brightness. At this point and using the DSLR I've had no flat problems (that I know of).

 

Next week I'm going mono so that may all change.

 

As you are using a Canon I suggest trying the light panel... If it doesn't work for you your only out 20 bucks or so. 



#20 BQ Octantis

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Posted 13 November 2019 - 11:32 PM

What is your method for taking flat frames?

White dress shirt (high thread count) pulled tight over the aperture, aimed at my LCD TV screen at max brightness. ISO, f-stop, and white balance set to what I used for capture; aperture priority mode for flats. Shoot in blocks of 5, moving and rotating setup and shirt after each block to eliminate patterns. Shoot 100 frames and then stack.


Edited by BQ Octantis, 13 November 2019 - 11:48 PM.

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#21 JDShoots

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Posted 13 November 2019 - 11:37 PM

I do the tee shirt rubber band thing.   I bring my camera inside and put it on my tripod.   I leave the dew heater on since coming inside with cold glass will cause condensation.  (trust me on that one:)  Then I position it inches away from my 23" computer monitor, the 5" front objective centered on the screen.  That leaves 3 or more inches of monitor all around.  Then, and here is the high tech part, I open a window of Microsoft notepad:)  That gives me 99% white screen.  I set the camera to aperture priority and rattle off 50-70 frames.  I make sure not to touch the focus or change the aperture or ISO.  

Condensation on the glass a new fingerprint, and dust on the sensor will all affect the flats along with light falloff from any cause.  

Hope that helps.  



#22 Noobulosity

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Posted 14 November 2019 - 09:16 AM

Hi Noobulosity,

I've also watched Astrobackyards tutorials. He has some great stuff on his channel! I purchased the action set as well but not the gradient reduction plug-in. I will have to look into that. I will also try longer subs or higher ISO on my next attempt. I'm always worried about light pollution and over exposing tho. Just need to trust it I suppose.

Thanks for the comment.

- Tim

The rule of thumb on exposure time/ISO is to aim for a histogram that has a peak about 1/3 from the left side, which is the dark side of the graph. If you aren't using the histogram on your camera, I'd highly recommend it. Use test exposures to figure out where this point is, then shoot subs with that time/ISO combo.

As for the flats, you're waaay too bright. They're almost certainly getting totally blown out on the light end of the histogram, which makes them useless. That's probably why they aren't doing anything when stacking.

You'll need a shorter shutter speed to get good flats, and likely a lower ISO. But it's fine that they don't match the light frames. (If you take dark flats, you'll want those to match the settings in these flats, though.) Again, use the histogram here. Shoot for the peak about 1/2 way, right in the middle. That gives you enough light to capture vignetting and dust motes, without blowing out the highlights. I think you'll discover this fixes your vignetting issues.

Lastly, while the gradient reduction plug-in is not completely necessary, I did find it really improved my image backgrounds. It seems expensive for what it does, but I use it on every single image now. To me, that's good value and worth the cost.

Edited by Noobulosity, 14 November 2019 - 09:22 AM.


#23 JDShoots

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Posted 15 November 2019 - 07:50 PM

T-Rango, have you tried to redo the flats and re-stack the image?  

I mean same lens, same Aperture, same ISO and focus on a star first.   I would redo them and see what you get, to rule out (or in), other issues you may have.  

 

I mean 40" probably over saturated the sensor in all but maybe the corners.   So redo them and see.  



#24 17.5Dob

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Posted 15 November 2019 - 10:29 PM

You'll need a shorter shutter speed to get good flats, and likely a lower ISO. But it's fine that they don't match the light frames.

no, No, NOOO !!!!

Shutter speed does not have to match your lights, you just want a "normally exposed" shot with the histo centered,  but ISO HAS TO match the lights.....

 


Edited by 17.5Dob, 15 November 2019 - 10:31 PM.


#25 Noobulosity

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Posted 16 November 2019 - 12:59 AM

no, No, NOOO !!!!

Shutter speed does not have to match your lights, you just want a "normally exposed" shot with the histo centered, but ISO HAS TO match the lights.....

It was my understanding that darks and lights have to match, and flats and dark flats have to match in order to calibrate properly. Bias is used to eliminate inherent read noise at specific ISOs that's consistent in every image at that setting, regardless of exposure time.

Is this not correct?

Either way, my advice wasn't all wrong. Even if ISO does need to match, taking 40-second flats is way too long. Usually flats are a couple seconds or less.

Edit: According to Jerry Lodriguss, who has extensive knowledge and experience in astrophotography, flat ISO does not need to match lights.

https://www.cloudyni...-iso/?p=6322909

And this makes sense. The signal-to-noise ratio in flats is pretty big, swamping out the inherent noise heavily. Low-light frames (lights/darks/bias the same, flats/dark flats the same) is where matching everything is more critical.

Edited by Noobulosity, 16 November 2019 - 01:31 AM.



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