Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Help needed with Nebula EAA imaging & Sharpcap

Celestron CMOS collimation EAA reflector
  • Please log in to reply
66 replies to this topic

#26 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 24 August 2019 - 10:08 PM

I completely missed the Binning at 2...the pixel size is now very large (~9) and the arc sec/ pix is almost 4, while the resolution of the scope is 0.82...use Bin 1, Gain 300 and what ever exposure time is needed (15 to 30 seconds) and the results will be better....Pat Utah smile.gif

 

I completely missed the Binning at 2...the pixel size is now very large (~9) and the arc sec/ pix is almost 4, while the resolution of the scope is 0.82...use Bin 1, Gain 300 and what ever exposure time is needed (15 to 30 seconds) and the results will be better....Pat Utah smile.gif

 

I completely missed the Binning at 2...the pixel size is now very large (~9) and the arc sec/ pix is almost 4, while the resolution of the scope is 0.82...use Bin 1, Gain 300 and what ever exposure time is needed (15 to 30 seconds) and the results will be better....Pat Utah smile.gif

Pat:

Atmosphere will normally limit my resolution to 1.5-2.0 so my scope's theoretical resolution of 0.82 will never be realized. I take your point about Bin 1 since this would result in 1.9 a-s/pixel which parallels the atmosphere limits on resolution. Although I doubt my AZ mount will handle 30 sec exposures, I can push up towards 15 seconds and keep the gain down around 300. Thank you for helping me oout.

Gary


  • Alien Observatory likes this

#27 goldtr8

goldtr8

    Vostok 1

  • *****
  • Posts: 138
  • Joined: 29 Apr 2018

Posted 25 August 2019 - 06:48 AM

Thanks for your insights Goldtr8.

I'm surprised by the suggestion to 'reset' the color balance since so much Sharpcap chatter relates to adjusting color settings. Also, when we adjust color in Sharpcap, I would not expect that we are resetting the color settings in the camera itself. I would expect that any color setting changes made in Sharpcap would be maintained only for that imaging session and that the camera would start up fresh next time with the factory settings. I would have no idea how to reset the colors in the camera.

 

If my observations above are incorrect, could you possibly provide a link to the SC forum where all this is discussed?

Many thanks!

Gary

https://forums.sharp...82&p=8805#p8805

 

Below is the statement from Robin in the post 

"My approach is to never touch the colour balance controls that come with the camera (leave them at their default settings or set them back to those if you have changed already). The problem is that for most cameras the colour balance is performed as a digital manipulation of the post ADC image data, meaning that it is somewhat destructive to image quality. I believe there are a few cameras where the colour balance controls actually are implemented through separate analogue gains for the R/G/B channels, which would be fine to use, but it is unclear which manufacturers or models work this way."

 

Once I reset my camera and left this setting alone and only changed the color sliders in the histogram then stuff started to work much better.

 

 

Also you can adjust your mid-level to the left and the picture will not show as being underexposed.   I was making similar errors until I started to look at what folks had shared with u-tube and watched how they manipulated the sliders and then it made sense to me.  I just searched sharpcal 3.2 as a starting point and just kept looking at what guys were doing.   It is very insightful to see someone else use the software and then the light came on.

 

For clarity on what I am doing I used the virtual camera in sharpcap pro and restacked the Bubble Nebula.   My camera color balance settings are at the factory defaults which means my saved frame FITS are not modified.    I then use the histogram to get everything close and I watch the display histogram for alignment of all color balances and then do a final trim of settings using the display histogram.   Anyway I did the screen shot so you can see what my histogram looks like and how I use them.   Its no longer the saved as viewed last night but you can see settings and how I got to where I was at.

 

Bubble nebula showing how I manipulate the stacking histogram and also the display histogram.    The camera was set to 10 sec exposures and 300 gain and there was 113 frames in the stack I saved last night.   However I am not showing the saved picture only the restacked within Sharpcap so I can share my workflow.

 

bubbe sharp cap.JPG


Edited by goldtr8, 25 August 2019 - 07:26 AM.


#28 barbarosa

barbarosa

    Vanguard

  • -----
  • Posts: 2170
  • Joined: 11 Apr 2010
  • Loc: 139 miles W of the Awahnee Hotel

Posted 25 August 2019 - 01:39 PM

You could watch Don from PA using his 294 cam on NSN...He is on Now...Pat Utah smile.gif

 

https://www.nightskiesnetwork.com

This is a great suggestion.

 

 

 

There are at the moment several NSN broadcasters who use cameras with the 294 sensor. Don in PA and Black Wickett (Chris) are two you should look for. Chris favors the color controls at the midpoint approach, while Don inclines to adjusting the camera controls and then the color controls in the live stack window. Both of these guys are happy to offer suggestions or run what amounts to an online seminar or help session. The other night Doug Bock gave a short demo in quick post processing  while his automated observatory was at work on a long  imaging series. 

 

At the moment NightSkiesNetwork.com has an audio problem with 2 way audio. Viewers who want to hear and speak must download and use an older version of the standalone browser Chromium Portable. I use Version 61.0.3153.0 (Official Build) (64-bit). You can download it here. I only use it for NSN.

 

There is a chat box but those of us with limited screen area or who are engrossed in something may not notice a post immediately. 

 

There is also an NSN  site in Canada (.ca) which is primarily used by Mallincam owners. It uses Flash which may or may not be a concern. It appears to be less active. 

 

Check us out, join and learn or just have fun on those cloudy nights. Guests welcome and questions welcomed, comments welcomed. Requests to see Nemesis or the UFO moon base politely refused.

 

Sometimes in the wee hours the chat is a bit freewheeling, but any astronomy related question has priority.

 

Good luck with the good advice you received so far - expert status will arrive soon.



#29 donstim

donstim

    Explorer 1

  • -----
  • Posts: 95
  • Joined: 13 Aug 2018
  • Loc: Seattle Area, WA USA

Posted 25 August 2019 - 02:13 PM

I am confused over the comments regarding the SharpCap color settings.  The default settings for the camera Gary is using (ASI 294 MC) is 50/50, which is what Gary's screenshot of his first post show he is using.  So, why the comments about setting his camera color controls back to default?  I use Chris' approach of leaving the camera color controls at default (50/50) and adjust color in the live stacking window.  Autocolor correction in that window usually works very well for me although you may have to apply it multiple times as the stacking and stretching process proceeds.  Don's (PA) approach of adjusting the color camera controls appears to me to be a special case to deal with whatever LP filter he is using that affects the red channel so much that the live stacking color controls don't have enough range to provide acceptable color balance.


  • roelb and GaryShaw like this

#30 Alien Observatory

Alien Observatory

    Viking 1

  • *****
  • Posts: 852
  • Joined: 13 Nov 2015

Posted 25 August 2019 - 04:05 PM

Pat:

Atmosphere will normally limit my resolution to 1.5-2.0 so my scope's theoretical resolution of 0.82 will never be realized. I take your point about Bin 1 since this would result in 1.9 a-s/pixel which parallels the atmosphere limits on resolution. Although I doubt my AZ mount will handle 30 sec exposures, I can push up towards 15 seconds and keep the gain down around 300. Thank you for helping me oout.

Gary

The Great advantage of the 294 sensor is its Full Well Capacity (~70 ke), and to take advantage of that, it takes more time or more aperture. As you are aperture limited at 142 mm and FR @3.6 any addition time you can collect photons the more details and nebulosity will be captured.  I only use Alt Az mounts,  so I understand your exposure time limits.  

 

When I am looking to the SE or SW (at home), sometimes I can get +20 sec, but usually 15 is normal for due South or straight overhead....Pat Utah :)



#31 goldtr8

goldtr8

    Vostok 1

  • *****
  • Posts: 138
  • Joined: 29 Apr 2018

Posted 25 August 2019 - 04:13 PM

I am confused over the comments regarding the SharpCap color settings. The default settings for the camera Gary is using (ASI 294 MC) is 50/50, which is what Gary's screenshot of his first post show he is using. So, why the comments about setting his camera color controls back to default? I use Chris' approach of leaving the camera color controls at default (50/50) and adjust color in the live stacking window. Autocolor correction in that window usually works very well for me although you may have to apply it multiple times as the stacking and stretching process proceeds. Don's (PA) approach of adjusting the color camera controls appears to me to be a special case to deal with whatever LP filter he is using that affects the red channel so much that the live stacking color controls don't have enough range to provide acceptable color balance.


When I do a reset in Sharpcap my defaults are not 50 50. So if my defaults are different why would this be?

Edited by goldtr8, 25 August 2019 - 04:15 PM.


#32 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 25 August 2019 - 06:09 PM

I use a ASI294MC uncooled camera with an 8 in SCT with .63 focal reducer on an AVX mount.     I also use sharpcap but I have upgraded to PRO which gives more knobs to turn.    So here are my observations using the same camera and software but with a different OTA.

 

Need to get better focus go to Highpoint Scientific and there is a white paper on their home page written by one of their tech guys and discusses his focus technique.   I use the  mask technique on a bright star and zoom when focusing to see the lines very clearly.     I also focus with a max of 2 sec exposures and crank up the gain so I get fast response time of the picture updating, you can not have long exposure time when focusing.

 

Stop binning with the CMOS camera.   Its software binning and it also increases your pixel size.

 

I use the pro version and it gives you more options on the histogram for adjustment.   Plus you can have darks and flats which really improves the live view and stacking experience.

 

Reset the color balance for your camera to the factory setting and don't mess with them anymore.    There is a section in the sharpcap forum that explains why and it does make a difference.   In my early uses of the camera I moved them around but I learned that is something I no longer touch.

 

I also would try and lower your gain if possible, I do go as high as 350 but that's the limit for me and I see you are at 359, not much of a difference. 

 

So keep working at it and you will get there I did.    

 

For reference here is my M16 taken a few weeks ago.

 

M 16 Eagle Nebula-Stack_77frames_616s also 8 second exposures no filters in the system.   

This is my as viewed save within SharpCap so you can see the camera is fully capable.   

 

attachicon.gif M 16 Eagle Nebula-Stack_77frames_616s.jpg

Hi Don:

I've read the white paper you referenced several times and find it very helpful except for the focusing method he starts to outline but never seems to finish. Once the exposure is dropped to minimum he says nothing about how he then refines the focus. I dont follow how you can easily refine focus on a tiny, barely visible star and he says nothing more about it. I like your method with the mask. Are you using the mask in conjunction with the Sharpcap Bahtinov focusing assistant or just on its own?

thank you,

Gary



#33 donstim

donstim

    Explorer 1

  • -----
  • Posts: 95
  • Joined: 13 Aug 2018
  • Loc: Seattle Area, WA USA

Posted 25 August 2019 - 06:23 PM

What color balance do you get when you do a reset?  I've tried resetting to default per the instructions Robin gave in the link  you provided.  However, although I get parameters like color space and exposure reset to different values than I had set before I did the reset, the reset does not affect whatever color balance values had been selected.  In other words, if I have 50/50 selected, it will come back with 50/50 regardless of whether or not I hold the CTRL key down when I reconnect the camera.  (Edit - Note:  I have the Pro (cooled version) of the camera, but I wouldn't expect for that to make a difference.  Eidt 2:  I see you also have the Pro version of the camera.  Can you confirm whether or not it makes any difference to the color settings when you hold down the CTRL key when connecting the camera?)

 

Regarding the 50/50 color balance that I was quoting as the default color balance for the ASI 294 MC (Pro?) camera, it came from several different sources, including a post in the link you provided about resetting to camera defaults.  The manual for the camera doesn't contain that information, and if it's true that "resetting to default"  in SharpCap doesn't actually affect the color balance settings, then I assume it is not  in the SDK for the camera either.


Edited by donstim, 25 August 2019 - 06:30 PM.


#34 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 25 August 2019 - 06:31 PM

I am confused over the comments regarding the SharpCap color settings.  The default settings for the camera Gary is using (ASI 294 MC) is 50/50, which is what Gary's screenshot of his first post show he is using.  So, why the comments about setting his camera color controls back to default?  I use Chris' approach of leaving the camera color controls at default (50/50) and adjust color in the live stacking window.  Autocolor correction in that window usually works very well for me although you may have to apply it multiple times as the stacking and stretching process proceeds.  Don's (PA) approach of adjusting the color camera controls appears to me to be a special case to deal with whatever LP filter he is using that affects the red channel so much that the live stacking color controls don't have enough range to provide acceptable color balance.

Don

I leave the color settings at 50/50 on the sidebar settings since this is the procedure for taking Darks. I don’t usually fuss with the color sliders on the live stacking histo but on these images I tried it to see if I could bring out the nebula better. 

 

I do do wish it was more clearly stated somewhere which settings, color and otherwise, are based on known performance versus which ones are more governed by ‘art’. Many folks have said the midtone histo line is positioned per ‘taste’ and the dark line should be just left of the ‘peak’ but no other guidelines have stood out to me so far.

Gary



#35 donstim

donstim

    Explorer 1

  • -----
  • Posts: 95
  • Joined: 13 Aug 2018
  • Loc: Seattle Area, WA USA

Posted 25 August 2019 - 07:24 PM

Gary,

You said it.  An awful lot of this is governed by 'art,' which can also be labeled 'experience.'  For me, personally, I started by using settings and techniques used by others whose posts or images I liked.  Then, I "tweaked" my process by experience.  When live stacking, what I do now for my ASI 1294 MC Pro/Celestron Evolution 8 combo is to leave color balance at 50/50, color space to RAW16 for DSOs or RAW8 for planets (though I recently acquired an ASI 224MC for planets), binning set to 1, gain set to 300, brightness set to 4, exposure as needed (anywhere from 2 to 30 seconds), and cooler temp of -15.  I wait until 3 frames have stacked, then I hit the autocolor button in the live stack window and start adjusting the mid and black levels in that same window.  (I rarely adjust the white level, though it depends on the object.)  Sometimes, I will use the auto-stretch button just to see how well that looks and where it is setting the levels, but I usually reset it and manually adjust the levels.  (The amount of stretch the auto-stretch applies can be set in "File" "Settings,")

 

Once I start stretching, I use the small  "Display Histogram Stretch" histogram on the right side to see the affects of my slider changes.  I do not make changes using the Display Histogram Stretch control; I only use the histogram to see the effects of the changes I make in the Live Stacking Window (because the Live Stacking Window histogram is not indicative of what you are seeing on the screen).  It is the setting of the black and mid-level sliders where 'art' or 'experience' really takes over.  You just need to start playing around with them to see how they affect the image.  I start by moving the mid-level to the left a fair amount, then reduce the "over-exposure" by moving the black level to the right.  Watch the Display Histogram Stretch histogram to keep the black level from clipping (i.e., make sure that the base of the histogram peak at the left side is not cut off --have a little bit of it visible to the left of where it starts that sharp rise to its peak).

 

For finding and focusing the object, I usually use a gain of 500 to lower the exposure time, which makes it easier to make framing and focusing adjustments.  As I bring the object into focus, I reduce the gain a bit to lessen the noise.


  • GaryShaw likes this

#36 Gork

Gork

    Explorer 1

  • *****
  • Posts: 95
  • Joined: 21 Feb 2014
  • Loc: Tucson, Arizona

Posted 27 August 2019 - 12:18 AM

One tool I use religiously is astrobin.com   If you are not familiar with it you should go there frequently.  There are images posted from all over the world and forums for everything.  When you open the site you will see the Image of the Day.  At the top of the page you will find a "search" window.  Before I bought my ASI294MC Pro I did a search for the camera.  I got hundreds of images with all types of telescopes.  I also did a search for my Orion EON 130mm Triplet before I bought it.  I will look at the images and wander around until I find somebody with the same combination of hardware/software that I have.  I can then go to their individual pages to search other images by the same person.  When I choose new targets I do a search for those targets to see what to expect.  I can spend hours just going through various configurations.  It is a tremendous tool, and its fun too!



#37 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 27 August 2019 - 12:19 PM

One tool I use religiously is astrobin.com   If you are not familiar with it you should go there frequently.  There are images posted from all over the world and forums for everything.  When you open the site you will see the Image of the Day.  At the top of the page you will find a "search" window.  Before I bought my ASI294MC Pro I did a search for the camera.  I got hundreds of images with all types of telescopes.  I also did a search for my Orion EON 130mm Triplet before I bought it.  I will look at the images and wander around until I find somebody with the same combination of hardware/software that I have.  I can then go to their individual pages to search other images by the same person.  When I choose new targets I do a search for those targets to see what to expect.  I can spend hours just going through various configurations.  It is a tremendous tool, and its fun too!

 

One tool I use religiously is astrobin.com   If you are not familiar with it you should go there frequently.  There are images posted from all over the world and forums for everything.  When you open the site you will see the Image of the Day.  At the top of the page you will find a "search" window.  Before I bought my ASI294MC Pro I did a search for the camera.  I got hundreds of images with all types of telescopes.  I also did a search for my Orion EON 130mm Triplet before I bought it.  I will look at the images and wander around until I find somebody with the same combination of hardware/software that I have.  I can then go to their individual pages to search other images by the same person.  When I choose new targets I do a search for those targets to see what to expect.  I can spend hours just going through various configurations.  It is a tremendous tool, and its fun too!

I will check it out 

Thank you Gork!



#38 Rickster

Rickster

    Viking 1

  • *****
  • Posts: 800
  • Joined: 09 Jun 2008
  • Loc: NC Kansas Bortle 3 SQM 21.8+

Posted 27 August 2019 - 12:42 PM

Gary,

I think I may have an easy answer to your bloated stars.  Last night I was getting the same thing.  And then I realized that the white slider had moved from the far right and was actually inside the histogram hump.  I moved it back to the far right.  The bloated stars shrunk and the dynamic range improved in the core of the galaxy that I was shooting.  (The core was blown out before).  I just now looked at the original screen shot that you posted, and sure enough, your white slider is well to the left and touching the histogram tail.  Try moving it to the right.



#39 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 27 August 2019 - 01:40 PM

Gary,

I think I may have an easy answer to your bloated stars.  Last night I was getting the same thing.  And then I realized that the white slider had moved from the far right and was actually inside the histogram hump.  I moved it back to the far right.  The bloated stars shrunk and the dynamic range improved in the core of the galaxy that I was shooting.  (The core was blown out before).  I just now looked at the original screen shot that you posted, and sure enough, your white slider is well to the left and touching the histogram tail.  Try moving it to the right.

Hi Rick:

The white slider in that original screenshot was hidden behind the camera settings panels but is way to the right side - similar to the location it has in the screenshot on post 22.

 

Last night I tried applying the advice from this thread and did move the while slider to the left somewhat (see attached). While doing that I did not notice any change in the bloating of the stars. They always seem bloated in my images - no matter what. The focus was decent last night so the causes may be:

 

- zooming in too much (how else to get detail out of the imaged object?)

- unknown issues with my old Comet Catcher's optics

- unknown and incorrect settings in Sharpcap - have reduced gain and increased exposure as recommended.

- unknown / unknown...?

 

Thank you for following through and trying to help.

Gary

Attached Thumbnails

  • M63 12min(cropped).png


#40 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 27 August 2019 - 01:48 PM

Gary,

You said it.  An awful lot of this is governed by 'art,' which can also be labeled 'experience.'  For me, personally, I started by using settings and techniques used by others whose posts or images I liked.  Then, I "tweaked" my process by experience.  When live stacking, what I do now for my ASI 1294 MC Pro/Celestron Evolution 8 combo is to leave color balance at 50/50, color space to RAW16 for DSOs or RAW8 for planets (though I recently acquired an ASI 224MC for planets), binning set to 1, gain set to 300, brightness set to 4, exposure as needed (anywhere from 2 to 30 seconds), and cooler temp of -15.  I wait until 3 frames have stacked, then I hit the autocolor button in the live stack window and start adjusting the mid and black levels in that same window.  (I rarely adjust the white level, though it depends on the object.)  Sometimes, I will use the auto-stretch button just to see how well that looks and where it is setting the levels, but I usually reset it and manually adjust the levels.  (The amount of stretch the auto-stretch applies can be set in "File" "Settings,")

 

Once I start stretching, I use the small  "Display Histogram Stretch" histogram on the right side to see the affects of my slider changes.  I do not make changes using the Display Histogram Stretch control; I only use the histogram to see the effects of the changes I make in the Live Stacking Window (because the Live Stacking Window histogram is not indicative of what you are seeing on the screen).  It is the setting of the black and mid-level sliders where 'art' or 'experience' really takes over.  You just need to start playing around with them to see how they affect the image.  I start by moving the mid-level to the left a fair amount, then reduce the "over-exposure" by moving the black level to the right.  Watch the Display Histogram Stretch histogram to keep the black level from clipping (i.e., make sure that the base of the histogram peak at the left side is not cut off --have a little bit of it visible to the left of where it starts that sharp rise to its peak).

 

For finding and focusing the object, I usually use a gain of 500 to lower the exposure time, which makes it easier to make framing and focusing adjustments.  As I bring the object into focus, I reduce the gain a bit to lessen the noise.

I really appreciate this Don but I dont actually understand the manipulation and use of the 'live stack' histo versus the 'display' histo. I have yet to do anything with the latter. I'll do some more research on these in the manual and hope it's ok if I get back to you with a question or two...

thank you!

Gary



#41 Howie1

Howie1

    Mariner 2

  • *****
  • Posts: 281
  • Joined: 22 May 2013

Posted 27 August 2019 - 07:36 PM

;)  How to focus on a very dim star .... Wind the focus knob inwards or outwards until you just see it disappear off the image using 1sec or 2 sec frames at whatever gain you are at. When you see it just disappear note the focuser knob position and put your index finger at the 12 o'clock position. Wind it so the dim star once again appears, and keep winding through that until it once again just disappears. Correct focus is half way from when it first appeared to when it disappeared. With a dim star you will often find the distance you wind the focus knob through that appear to disappear point is only half a turn of the fine focus knob of a two speed focuser. So wind the focus knob back quarter turn and you will be in focus ;)

 

If using an e-focuser some come with software which shows some scale representing amount of mm in/out travel. So use the scale to figure out where it 'appeared' and 'disappeared' then half way between those two scaled numbers is focus.

 

If your e-focuser does not have that software, but maybe just uses a button press in/out travel, then you have to just guess by length of time you press the button. It's the least accurate way of doing this. 

 

Or .... every goto mount I've owned, be it hand control or 'proper' ASCOM control, will show you the current RA and DEC (or ALT AZ) plus also allow you to define USER DEFINED OBJECTS. Note the current position of your target object as displayed by the mount control system (HC or ASCOM software). Put that position into the mounts USER OBJECTS list. Every mount I've had allows you to do this either by manually entering the RA/DEC or ALT/AZ or automatically! By automatic I mean there's no need to note down the mounts current on-target coords! As soon as you get into the User Defined Objects menu and tell it to create a new user defined object the current RA/DEC or ALT/AZ is automatically displayed! Simply press the SAVE button to save the position displayed as your new User Defined object. Anyhow ... once that nicely framed objects current mount coords is saved, slew to any bright star nearby and use the mask or whatever to focus. Then get back into the USER OBJECTS menu and tell it to slew to that user defined position. It will be almost perfectly on-target from where you left it.

 

For what its worth, here's why the above posts on color balance are bang on when they say if you use filters or a modded or astro cam then use the main camera control histogram to correctly balance with that filter on. Classic mistake by down-under Aussie noobs is Tarantula Neb which is actually greenish-blue. They get themselves a modded camera and filters and blast off to the tarantula and see truly weird colors based on what they've seen on the web where nebulas have masses of red hydrogen. So they process it like that using the stacked histogram sliders to get the sky background looking kinda of black/grey and in the process end up with a red Tarantula and even stars look weird colors. Totally wrong colours. 

 

But, sticking the filters onto your camera and then using the main camera controls to find the correct color balance using a daytime view of your neighbourhood means you can note down the RGB settings for what is 'correct color balance'. At night, you set those in the camera controls. So then when you go to an object and start to stack, at least you know that the color of the light reaching the sensor from that position in the sky including the colors from the object are going to be correct color balance and a true representation of the 'glows' coming from that area and object. So when you start to stack, and thus increase the SNR, you'll see the noise decrease, and more details start to who up, and if you use darks and flats you'll see all this change the overall histogram with each and every frame stacked. So the stacking histogram is used to refine that stacked image with respect to getting rid of the LP but still retain as much dim nebulosity etc. As the image darkens the sky and adds detail with each new stacked image, through better SNR, or you getting rid of LP, you may see the colors dim somewhat or change with respect to the darker sky background ... so you'll increase gamma / midpoint curve to make them 'pop' a bit more. But brightening and adjusting the image may alter the colors somewhat .... and that's when you'll fine tune the color sliders to compensate for those slightly altered colors. 

 

When you use this technique then you end up with correct color balance images of the blue-green Tarantula and still with red and blue stars showing and a nice dark grey/black sky background rather than the whole thing being red'ish. Tada ... isn't that what EAA is all about? Observing with a camera using short exposures. 'Seeing' the true colors in your short exposures EAA you will say "WTH !? How come this neb is blue-green?" So you'll look up and research online why they are those colors and discover far more about the wonders of the Universe which you would never have discovered, nor even seen, if you'd only color balanced using the stacking histogram.

 

So color balance with camera control on single images (preferably in the daytime on green grass, blue sky, white cloud, brown tree trunk scenery in the distance and using various filters and note the rgb settings down with each). Use the stacking histogram to just fine tune to get rid of LP/Skyglow, brighten/pop the colours, then adjust them to suit your taste whether you like brilliant colors or just lighter shades of color.

 

Cheers


  • tmaestro likes this

#42 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 28 August 2019 - 12:45 AM

Hi All

I get that there are 3 separate histogram tools in Sharpcap but after reading some of the posts above, I’m now feeling more confused than ever about the role of each and when each should be used. The Sharpcap manual talks about what each does but it doesn’t address the typical observing ‘workflow’ that experienced observers use to put each histogram to work at the appropriate point in the observing process and how to utilize it in the correct way to optimize the image.

 

Does anyone know of a resource that more directly explains how and when each histogram is used during EAA observing? Perhaps there’s another specific CN topic or post, or a YouTube video, or some other outside white paper or tutorial that addresses the timing and use of Sharpcaps histograms.

 

I’ll really appreciate any suggestions on how to better understand and utilize the 3 Sharpcap Histograms.

 

Many thanks!

Gary



#43 39.1N84.5W

39.1N84.5W

    He asked for it

  • *****
  • Posts: 3912
  • Joined: 24 Oct 2006
  • Loc: cincinnati

Posted 28 August 2019 - 05:18 AM

When stacking is on I just use the stacking histogram.
Before stacking is on I will click on the lightning bolt button of the display histogram to "overexpose" the screen and center my composition. Typically I'm doing 1 sec subs during this composition stage. When I'm happy with this step then I click the reset button in display histogram. Then I change my exposure sub time to 8s. Then I click on live stack.
I'm using a 294mc gain 300 brightness 10. My cooling is anywhere between 40-65%.

Does this help?

#44 descott12

descott12

    Viking 1

  • -----
  • Posts: 977
  • Joined: 28 Sep 2018
  • Loc: Charlotte, NC

Posted 28 August 2019 - 05:45 AM

 

When you use this technique then you end up with correct color balance images of the blue-green Tarantula and still with red and blue stars showing and a nice dark grey/black sky background rather than the whole thing being red'ish. Tada ... isn't that what EAA is all about? Observing with a camera using short exposures. 'Seeing' the true colors in your short exposures EAA you will say "WTH !? How come this neb is blue-green?" So you'll look up and research online why they are those colors and discover far more about the wonders of the Universe which you would never have discovered, nor even seen, if you'd only color balanced using the stacking histogram.

 

So color balance with camera control on single images (preferably in the daytime on green grass, blue sky, white cloud, brown tree trunk scenery in the distance and using various filters and note the rgb settings down with each). Use the stacking histogram to just fine tune to get rid of LP/Skyglow, brighten/pop the colours, then adjust them to suit your taste whether you like brilliant colors or just lighter shades of color.

 

Cheers

Excellent post. Very good idea. I will try this (as soon as my 2 months of clouds goes away!)



#45 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 28 August 2019 - 11:08 AM

When stacking is on I just use the stacking histogram.
Before stacking is on I will click on the lightning bolt button of the display histogram to "overexpose" the screen and center my composition. Typically I'm doing 1 sec subs during this composition stage. When I'm happy with this step then I click the reset button in display histogram. Then I change my exposure sub time to 8s. Then I click on live stack.
I'm using a 294mc gain 300 brightness 10. My cooling is anywhere between 40-65%.

Does this help?

Definitely. It’s helpful to hear how others have worked out their observing process. You apparently don’t use the main menu histogram in your process and use the display histogram during only the early image compositional stage. 

Thank you 

Gary



#46 39.1N84.5W

39.1N84.5W

    He asked for it

  • *****
  • Posts: 3912
  • Joined: 24 Oct 2006
  • Loc: cincinnati

Posted 28 August 2019 - 02:25 PM

The third histogram (located at the top row) is used to determine my desired sub length. After I set my gain of 300 and brightness of 5 or 10 for the 294mc and the desired filter in the optical chain... then I try different sub lengths and observe where the peak ends up. This peak should just clear the little orange bar along the top of this histogram window. For some reason I can't attach pics to CN right now. The 294 sensor (as well as 1600 sensor) doesn't need long sub lengths of 30+ seconds. With a light nebula filter like idas P2 I use 8 sec subs. For tri-band narrowband filter like idas NB1 I use 20 sec subs.

By the way... once you determine your sub length then you can 1)cover your camera/scope and 2)capture master darks of 10 subs. If you change any setting like gain, sub length, brightness, binning then you have to capture new master darks for these new settings.

Short story...
1)display histogram for composition
2)upper histogram for sub length
3)live stack histogram for real time adjustments of your DSO

Edited by 39.1N84.5W, 28 August 2019 - 02:26 PM.

  • saguaro and GaryShaw like this

#47 Howie1

Howie1

    Mariner 2

  • *****
  • Posts: 281
  • Joined: 22 May 2013

Posted 28 August 2019 - 08:50 PM

Here you go Gary ... a video on how to use the main histogram. After you watch this it should give you a better idea as well as some hints for using cameras on scopes.

 

The main camera control histogram and its use is shown in the video. You use it to setup the frames so that stacking will work.

 

Without first using that main image control histogram, stacking either wont work or have issues, and your color balance will be much harder to do. 

 

https://youtu.be/c1NarA4_qxY



#48 mikenoname

mikenoname

    Messenger

  • *****
  • Posts: 471
  • Joined: 29 Jan 2015
  • Loc: Death Valley Region (Bortle 2 - SQM 21.9+)

Posted 29 August 2019 - 12:19 AM

Anyhow ... once that nicely framed objects current mount coords is saved, slew to any bright star nearby and use the mask or whatever to focus.

 

Howie hit it on the head. Use a bright star to focus with the mask. It makes the job way easier.

 

In my normal setup procedure I do the 2-star alignment and, while still on the second bright star, pop the B mask on and adjust focus. I never need to do an exposure of more than 1 sec to get nice, big spikes (though I do have my gain high at 500). Trying to use the mask on a dim star is like trying to light a match in the wind.

 

If I want to check/adjust focus mid session, I will slew to the nearest bright star, focus, and slew right back to my imaging object.


Edited by mikenoname, 29 August 2019 - 12:22 AM.

  • GaryShaw likes this

#49 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 29 August 2019 - 02:26 PM

The third histogram (located at the top row) is used to determine my desired sub length. After I set my gain of 300 and brightness of 5 or 10 for the 294mc and the desired filter in the optical chain... then I try different sub lengths and observe where the peak ends up. This peak should just clear the little orange bar along the top of this histogram window. For some reason I can't attach pics to CN right now. The 294 sensor (as well as 1600 sensor) doesn't need long sub lengths of 30+ seconds. With a light nebula filter like idas P2 I use 8 sec subs. For tri-band narrowband filter like idas NB1 I use 20 sec subs.

By the way... once you determine your sub length then you can 1)cover your camera/scope and 2)capture master darks of 10 subs. If you change any setting like gain, sub length, brightness, binning then you have to capture new master darks for these new settings.

Short story...
1)display histogram for composition
2)upper histogram for sub length
3)live stack histogram for real time adjustments of your DSO

Thank you Cincinnati! 

A very helpful summary - I shall try to put it all together tonight.

Gary


  • 39.1N84.5W likes this

#50 GaryShaw

GaryShaw

    Mariner 2

  • *****
  • topic starter
  • Posts: 260
  • Joined: 28 Nov 2017
  • Loc: Boston

Posted 29 August 2019 - 03:18 PM

 

Here you go Gary ... a video on how to use the main histogram. After you watch this it should give you a better idea as well as some hints for using cameras on scopes.

 

The main camera control histogram and its use is shown in the video. You use it to setup the frames so that stacking will work.

 

Without first using that main image control histogram, stacking either wont work or have issues, and your color balance will be much harder to do. 

 

https://youtu.be/c1NarA4_qxY

That was a great video Howie. I wish he’d do the one on live stacking that he mentioned. Anyway, it helped fill in a piece of the procedure that I’d not been doing in that way - especially the exposure, gain color balance process. 

 

One comment above involved somehow setting the color balance during the day, but this video suggests, if I followed it correctly, that you just align all 4 peaks at 15-20% using the sidebar sliders so I’m unclear what the daytime process was all about. I’ll have to re-read.

Thank you for all the help, I do feel things are getting better in my night sessions. 

Gary

 

Actually, the daytime color setting comment was yours...I’ll have to study this one and try it. From the video, it seemed the balance was set by aligning the 4 peaks just before live stacking.


Edited by GaryShaw, 29 August 2019 - 03:25 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Celestron, CMOS, collimation, EAA, reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics