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.
As I noted in my prior post, this LHDR technique only works in video mode since you adjust the gain while average stacking (you cannot change the gain when looping in trigger mode). Because video mode only supports exposure up to 5 seconds, you need a fairly fast setup. I was able to use a 3 second exposure setting at this f/3.3 setup. I tried it both without binning and with binning.
As before I used three gain settings of 4, 40 and 80 without binning. I set the gain to 80 (my max gain settings) and adjusted the histogram lower setting to 7 to slightly darken the background. I left the upper setting at 255. I changed the gain to the low setting of 4, set the number of frames to average to 10 and turned on Planet averaging with align. After 15 output frames I moved the gain from 4 to 40. Note that the key is monitoring the number of output frames, not the number of input frames. After 15 more output frames (30 total) I moved the gain from 40 to 80. I let it run for 30 more output frames at gain 80 (60 total output frames) resulting in the following image.
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.
As before I used three gain settings of 4, 40 and 80 without binning. I set the gain to 80 (my max gain settings) and adjusted the histogram lower setting to 7 to slightly darken the background. I left the upper setting at 255. I changed the gain to the low setting of 4, set the number of frames to average to 10 and turned on Planet averaging with align. After 15 output frames I moved the gain from 4 to 40. Note that the key is monitoring the number of output frames, not the number of input frames. After 15 more output frames (30 total) I moved the gain from 40 to 80. I let it run for 30 more output frames at gain 80 (60 total output frames) resulting in the following image.
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 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.
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.
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.
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.
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.
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