Lunar, ZWO ASI120MC, mosaics, 129fps achieved

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Lunar, ZWO ASI120MC, mosaics, 129fps achieved

Post by turfpit » Sun Sep 08, 2019 9:45 pm

Captured when waiting around for darkness. 56% waxing moon, intermittent cloud.
The mosaics were 1,000 frames per panel, stacked with Autostakkert!3 and the AS!3 sharpened _conv stacks were stitched with Microsoft ICE, final processing in Gimp.

General capture details - SER, RAW8, gain 30%, exposure 2ms - 7ms. Vixen 81s refractor + ZWO ASI120MC (USB2), no filters.

Capture speeds summary (over USB2)
1280x960 = 27 fps
1024x768 = 42 fps
800x608 = 69 fps
640x480 = 109 fps
320x240 = 129 fps

21-54-51-3-panel-mosaic-1024x768-43fps-1000frames.jpg (230.63 KiB) Viewed 352 times
(717 Bytes) Downloaded 18 times

21-04-52-2panel-mosaic-1280x960-27fps.jpg (219.45 KiB) Viewed 352 times
(712 Bytes) Downloaded 18 times

21-11-49-640x480-109fps-5000frames.png (588.75 KiB) Viewed 352 times
(717 Bytes) Downloaded 19 times

21-13-45-320x24-129fps-5000frames.png (210.55 KiB) Viewed 352 times
(715 Bytes) Downloaded 16 times

21-16-25-320x240-129fps-5000frames.png (220.07 KiB) Viewed 352 times
(717 Bytes) Downloaded 15 times

Capture videos played back using SER Player from the PIPP website.

320x240-129fps.JPG (44.14 KiB) Viewed 352 times

640x480-109fps.JPG (50.02 KiB) Viewed 352 times


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Re: Lunar, ZWO ASI120MC, mosaics, 129fps achieved

Post by turfpit » Mon Sep 09, 2019 10:27 am

This is a screenshot of one of the above lunar captures in progress. Some points to note:
  • In my Celestron Nexstar+ hand controller, the Tracking Rate was set to Lunar.
  • For focus, I used Zoom at 150% and targeted my efforts on a crater which had a feature inside.
  • For exposure, I selected FX highlight over-exposed from the dropdown list in the toolbar. Over exposed areas are highlighted in red (colour camera) or black (mono camera). Backing off the exposure until the red areas disappear helps with the exposure setting. This may result in the image on the screen looking dark - this is not an issue, as post-processing can deal with brightness. Post-processing, however cannot deal with over-exposed (burn-out) crater rims.
  • I always check for over exposure when zoomed to at least 100%.
  • The camera gain is set at 30%. I use gain 30-40% across a variety of cameras when lunar imaging.
  • Increased gain results in lower exposure settings and hence faster fps.
  • The reticule is turned on to help centre the object, plus monitor drift.
  • The histogram is undocked to make better use of the screen (personal preference).
  • The luminance (white) channel on the histogram is about 60% on a logarithmic histogram.
  • The colours on the histogram are not balanced - this gets sorted in post-processing and I prefer a mono image anyway.
  • The histogram shape is about right - touching left hand side as there is black surrounding the object. Maximum at 60%, therefore not over-exposed.
  • RAW8 for Colour Space, the 5000+ frame captures get the detail.
  • SER for Output Format, essential when dealing with 10,000+ frame captures which can result in files > 10Gb.
  • With the ASI120MC the Turbo USB setting of 80 seems a good choice as I experienced no dropped frames when capturing at > 100 fps. This was writing to a conventional SATA2 hard drive, running on an i3 laptop and connected via a 2m USB2 cable connected to a USB2 port on the laptop.
  • I always take a small capture, say 200 frames, and process at the capture machine, before making large captures. Better than finding out the next day that some setting was less than optimal.

lunar-capture-in-progress.JPG (70.09 KiB) Viewed 337 times

Lucky imaging? No - its all in the histogram. Following the above steps has enabled me to obtain consistent results with my lunar imaging. These are the results of 2 years of experimentation plus evaluation and 2 x 300 mile round trips, 1 year apart, to attend Damian Peach's 6 hour Lunar Imaging Workshops. My cameras for lunar imaging are all USB2. Maybe one-day I will come across a used ZWO ASI174MM at the right price.


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Re: Lunar, ZWO ASI120MC, mosaics, 129fps achieved

Post by BlackWikkett » Mon Sep 09, 2019 2:22 pm

Some great images Dave, lots of detail and great explanation of your process. When capturing Lunar images I usually use auto setting for red and blue in image controls. This gives me a fairly good white balance while using my IDAS D1 LPS filter. I see you didn't use a filter and don't seem to use auto setting for white balance during live capture. Is this not an option for the ASI120MC or is this your chioce?

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Re: Lunar, ZWO ASI120MC, mosaics, 129fps achieved

Post by turfpit » Mon Sep 09, 2019 8:04 pm


Thanks for the encouraging words.

The lack of filter was an experiment to see what I could get with the most basic configuration - a proof of concept for some members of the local astronomy club. I usually use an IR685 filter for lunar but have experimented with a Wratten #25 red as well. Plenty of examples on my Astrobin page I have recently acquired a Baader UV/IR Cut /L filter ... ilter.html to have a look at.

With RAW capture for later processing I am not too bothered about white balance, as only me sees the capture. Normally I use a QHY5LII-M for lunar imaging - the mono camera has a QE of ~70% whereas the QHY5LII-C has a QE of ~50%. My usual lunar capture scope is a SkyWatcher 127 MAK or Celestron C8 - both better because of the longer focal lengths. I think I could get better images with the ASI174MM as it is USB3

I have noticed that is seems harder to get better quality with the 320x240 captures. Also the difference in display across various devices is quite surprising. The iPhone 6 seems to present the above the best.

It was an opportunity to experiment with both the Vixen 81s (focal length 625 is not ideal) and the ASI120MC while I waited for M33 to achieve a good position.

My next lunar objective is to try to obtain some decent images of the left hand side of the moon when it is around 25% waning. At the moment, the moon rising gets entangled with sunrise but in winter, the moon should be up well before the sun. I have heard this called 'the unseen side of the moon'.


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