Yesterday, I repeated my Live High Dynamic Range (LHDR) testing with the DS10c, this time using a Celestron 6” Telescope with the Optec NextGen Maxfield 0.33X reducer, which produced about a f/3.3 setup.
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I didn’t get as much detail at this point as I previously had using my 8” with Hyperstar at f/2.  So I decided to try using bin 2, leaving all the settings the same and repeating the process, but changing the gain from 4 to 40 after 5 output images, and from 40 to 80 after 5 more output images, and let it run for 10 more output images (20 total output).  The final captured image is shown below.

Bin 2, 3 second exposure, histogram 7-255, 15 averaged output frames at gain of 4 plus 15 averaged output frames at gain of 40, plus 30 averaged output frames at gain of 80 using live stacking.​

I was pleased with the results of using bin 2 with 3 second exposure on a 6” telescope at f/3.3 using the LHDR process with 4, 40 and 80 gain settings.

Even though this is somewhat “like” an astrophotography process averaging frames with different settings, it still has the “live” feel that makes Video Astronomy so much fun.  I get to see results in near real time in amazing detail and color that I never could see with these eyes of mine looking through a telescope! And you can experiment with different settings and quickly see the results.
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To compare this result to using the LHDR process on a 8” telescope with Hyperstar operating at f/2 see my prior blog post at

remotevideoastronomy.com/blog/ds10c-live-hdr-averaging


12/12/2018 UPDATE: 

Matt Harmston has done some outstanding work expanding the use of this LHDR technique!  He found you could in fact make use of LHDR techniques while using trigger mode.  This opens up LHDR to anyone since video mode is Not a requirement, and thus it is no longer limited to under 5 second exposures.

He found that while using trigger mode you can stop looping without stopping averaging, change the gain, and then restart looping right where you left off still averaging with the prior image!  The key is to not disable averaging during this process.  I have found it actually makes it somewhat easier since you can stop looping at a certain point and take your time to change the gain (and/or other settings).  Then you just turn looping back on and the average stacking continues.  You can do this as many times as you like to continue developing a LHDR image!    Instead of changing the gain, you can also do this varying other settings like the exposure time, histogram, gamma, contrast, etc.

​Some Deep Sky Objects have a wide range of detail, but present a challenge.  For example, you can see the Trapezium stars in the core of the Orion Nebula if you use a short exposure.  To see the fine edge detail you need to use longer exposures, but that “blows out” the core and you can no longer distinguish the Trapezium.  This can be overcome using a High Dynamic Range technique by capturing several images of varying exposure and post process them later to combine them and produce a final image with a good range of detail.  It would be nice to see this in real time though.

I tried something interesting last night that is somewhat like a Live High Dynamic Range (LHDR) averaging technique.  I was using my Celestron 8” with Hyperstar with the DS10c aimed at the Orion Nebula. The 3/4 moon was rising so I was also using a Baader Planetarium Moon and Skyglow filter.  The key settings I used that remained constant were: 1 second exposure (video mode), histogram 65-255 and sharpen at 100. I did not use binning. I started with gain at 4 and turned on planet averaging with align. After it output 12 frames I moved the gain slider up to 40 and let it continue averaging.  After it averaged 12 more frames I moved the gain slider up to 80 and let it continue.  Looking at the screen after it averaged 12 more frames I decided to let it just continue averaging at gain 80.  After it had averaged 19 more frames I captured the final averaged image.  I took snap images each time I changed the gain so I could show how the image “developed”. No post processing was done on any of these images of M42.

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Gain of 4, 1 second, histogram 65-255, 12 averaged frames using live stacking.

On the right is a cropped version of an image capture using gain of 4, 1 second, histogram 65-255, and frame averaging without using this LHDR technique.  You can see the outer fine detail, but the core is overexposed and you cannot distinguish the Trapezium like you can in the LHDR image on the left.
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The Miloslick software for the Xtreme/Xterminator cameras has a HDR mode for objects like the Orion Nebula that can automatically vary the exposure time over several frames combining them in real time to produce a nice detail in the image viewed on the screen.  I could have varied the exposure time instead of the gain during average stacking in video mode in the MallinCamSky application, but chose to vary the gain because I could get a much wider dynamic range in a short period of time by just varying the gain of the DS10c and leaving the exposure time at 1 second. I had to make the changes by hand during averaging with MallnCamSky, but it worked!
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The MallinCamSky application that works with all SkyRaider cameras now has a new Live Align & Stack feature. SkyRaider cameras and other video astronomy cameras enable you “see” objects better than you can looking though an eyepiece and make your telescope seem like a much larger one.  Now with the Align & Stack feature added to MallinCamSky, your mount seems to be a much better one tracking over longer exposure times.  This is especially true if you have an Alt-azimuth mount.
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The stacking feature takes each successive image and adds it to the last one and continuously displays the results for a specified number of images.  Each image update makes stars brighter and shows more and more detail of nebula and other objects.  But there is a catch.  This only works well if each image exactly lines up with the last one. If your mount’s tracking is not exact, you will get a smeared image instead. If you have an Alt-azimuth mount it gets worse due to what is called field rotation.  This is especially true if the telescope is pointed near vertical.

 Unlike an equatorial mount which essentially only has to track in one direction to follow the movement of the stars, an Alt-azimuth mount has to track in two directions.  Picture in your mind how the telescope on an Alt-azimuth mount would rotate around as the mount tracks objects in the sky. If you just stack images, you would see star trails that are longer the closer the stars are to the edge of your field of view.
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Tracking errors (even on equatorial mounts) and field rotation (on Alt-azimuth  mounts) can be virtually eliminated if each image to be stacked is a short exposure so there are little, if any, tracking problems in each image.  Each image is then moved and/or rotated slightly so all the stars line up when you stack each image. See the examples below.

Aligning and stacking images is not new.  Astrophotography has been using this technique for years taking many images obtained during the night and using post processing to align and stack the images.  But Video Astronomy is about real time viewing.  MallinCamSky performs align and stack processing in real time so you see the results immediately after each frame is updated.
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Here is the new Live Stack section in MallinCamSky used to align and stack images in real time.

For my tests, I selected Deep Sky, Stack, Align and 10 images (blue arrows).  I click on Enable and check the Input/Output/Status section until it shows OK (green arrows).  Then I watch the image as stars get brighter and details become clearer. 

If you are viewing a planet, select Planet instead of Deep Sky.  If you want to average several frames to smooth out noise, select Mean rather than Stack.  Instead of adding each image so it gets brighter and brighter, it averages each image and helps reduce background noise.  If you have an equatorial mount that tracks very well (particularly when using autoguiding), you can leave align unchecked and it will just stack images without trying to align them.
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I tested the new Align & Stack feature of MallinCamSky using the SkyRaider entry level AGm and AGc cameras. All SkyRaider cameras use a single USB cable for power, control and image transfer.  Here is my SkyRaider AGc camera with a MFR5 focal reducer attached and a Lumicon Deep Sky filter. 

Viewing conditions are not ideal here in the South in the summer when humidity is above 70% and the temperature is 75 degrees and higher.  But the following video clips clearly illustrate the use and effectiveness of the MallinCamSky Live Align and Stack feature in spite of these conditions (and I live near a city).
The key to getting the Align & Stack to work well is to make sure you have several background stars visible around your target before enabling Live Stack.  If you image does not contain enough stars the software cannot line up the images before stacking them.  When you click on Enable you will notice a pause after the first frame as it analyzes the stars in the image.  If you see OK appear next to Status, it will begin the align and stack process.  If not, you probably should uncheck Enable and see if you can adjust your image to bring out more stars by increasing the gain and/or exposure.  It is also important to adjust the histogram around the visible spectrum of your target.  I reduced the upper histogram range to 100 or less in my tests.  Depending upon conditions, your target area and the size of your telescope, you may not be able see enough stars to use the Live Stack feature on some deep sky objects.  Due to my recent conditions and the position of M51 in the sky, I could not use Align and Stack on the whirlpool galaxy with my 5” scope and Alt-azimuth mount.  Maybe another time when it is cooler and less humid I will have more luck. I was able to Align and Stack using M51 using my 8” scope on an equatorial mount.
Here are a series of video clips of my testing that show how to use the Align and Stack feature.  In some of the clips you will also see the use of the MallinCamSky live dark field correction feature that virtually eliminates hot pixels and amp glow from your image.  (See my blog “MallinCamSky Real Time Histogram and Dark Field Correction Functions” on 03/17/2016 to learn more about dark field correction.)
 
Equatorial Tests

For these tests I used using my SkyRaider AGc camera with MFR5 reducer on my Celestron C8 and CG-5 equatorial mount. Temperature was 76 degrees with 75% humidity and dew point of 66 degrees.
At the start of the next three videos you will also see how before I begin, I first capture dark frames to eliminate hot pixels using the same settings as I plan to use to view the target.


First Video

M13 as target object with 15s exposure, gain of 3, histogram 0-100 and stacking set to 5 frames:

https://youtu.be/KoTyxXmCyFk
 

Second Video

I tried these same setting to align and stack m51, but there were not enough stars visible with a gain of 3 for aligning the images.  I then bumped the gain up to 10 and was able to see enough stars to both align and stack the images.

M51 as target object with 15s exposure, gain of 10, histogram 0-50 and stacking set to 10 frames:

https://youtu.be/q7jF4DjzFzQ
 

Third Video

I reduced the exposure to 5 seconds and used m92 for my next target.

M92 as target object with 5s exposure, gain of 10, histogram 0-50 and stacking set to 10 frames:

https://youtu.be/paA3yKc-mfQ
 

Alt-azimuth Tests

The next night I used my SkyProdigy Alt-azimuth mount.  As I previously noted, the image align feature is key to handling the problem of field rotation encountered with Alt-azimuth mounts when stacking images.

I used my Celestron 5" telescope along with the SkyRaider AGc camera with the MFR5 focal reducer attached. It was 78 degrees with 80% humidity and 71 degree dew point. Seeing conditions were not as good as the previous night.
I successfully tested this setup using two of the same targets I used the night before - m13 and m92. I did try to test with m51 as well like the previous night, but it was too low on the horizon to "see" enough nearby stars for the align feature to be used. 
 
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First Video

M13 at 5 second exposure, gain 10, histogram 2-20, align and stack 10 frames.  I also compared it to stacking without align to show the benefits of MallinCamSky real time align and stack when using an Alt-azimuth mount.

https://youtu.be/rr3czdwG-vQ
 
 
Second Video

M92 at 5 second exposure, gain 10, histogram 2-20, align and stack 10 frames:

https://youtu.be/xkL4T1G5XzA
 

Third Video

M92 stack (no align) using 5 sec exposure to illustrate importance of real time align function when using an Alt-azimuth mount:

https://youtu.be/qBEv7jgtbjQ
 
 
Fourth Video

The next night there was also humidity and it was not the best seeing conditions. Even so, I was able to "see" the Ring Nebula using the align and stack feature as shown in this video.

https://youtu.be/N3DuK0ES4z4
 

Summary

As long as there are enough nearby stars "visible" near your target before stacking, the new align and stack feature of MallinCamSky extends the ability of your telescope and mount to see more detail using a longer effective exposure time while virtually eliminating tracking errors and field rotation issues.

Then what is a live image worth? A lot more! It's not just the image though. It is seeing the live image, the experience of slewing your telescope to a point in the sky you just chose, seeing star trails on the screen until the telescope starts tracking that precise area of the sky, and seeing your target object appear on the screen. Then you fine tune your settings, maybe increase the exposure time a few more seconds, and you see your selected object better than you ever saw it through your eyepiece.

I admit you sometimes can't help but click the capture image button for a permanent memory of what you are seeing live.  Maybe you want something to show so you can tell somebody about it later. But a recorded picture is not the essence of video astronomy. It is the experience itself that is important. And others can experience it right there with you in real time. If you do capture some images, they will probably not be "as good" as astrophotography pictures, but they are still pretty amazing. All camera "pictures" on this site are real time captures of the image being viewed at the time.

Astrophotography is certainly its own worthy pursuit that produces a high resolution picture with even better detail and color. But it's a different process and experience. You will typically spend more time capturing images of just a few targets in one evening. Then you invest more of your time after you put up your telescope to work with your captured images using post processing techniques, and produce the best picture you can get.  For DSO astrophotography, you will typically need very good tracking and maybe even use autoguiding. The efforts you put into astrophotography can be very rewarding, but it’s different from Video Astronomy.  With Video Astronomy you capture the moment.

Extending Video Astronomy inside through RVA techniques provides yet another unique type of experience. Being an engineer and programmer I have always been intrigued with robotics and computer remote control.  Having planetarium software enabling you to slew to your target and then compare the expected image to what you see live on your screen is really great.


It's nice to be inside, pick out an object on your laptop's screen, and then click to initiate your telescope moving to that specific point in the sky from your current spot on Earth, watch the display showing the camera's image as stars stream by, and it slows and settles in on your target. Then after a few adjustments you tell someone nearby ... take a look at this!  And you both look at it together at the same time.

Later on you tell someone, I gotta show you an image of what we saw that night.