Not quite the full moon

Full moon tonight and our adventure with my son’s telescope continued. We tried again to take some pictures of the full moon, but this time from the comfort of the loft – looking at the moon as it rose through a Velux window held open with a plastic bag full of old toys. The process is complicated and full of tricks and I just thought I would mention how its done, even as you can see, we haven’t quite got it right yet! Click the thumbnails below to see the kind of quality we have achieved so far.

Composite picture of one half of the moon
Composite picture of the other half of the moon

Composite pictures of the two halves of the moon. Click each one to enlarge.

How does one do this?

  • First you point a telescope at the moon. Then you replace the telescope eyepiece with a webcam. I am the kind of person who has more money than sense time and so I bought a commercial camera sold for this purpose. If I had more time I would have bought a better quality camera and adapted it by gluing it into a 1 1/4 inch diameter tube.
  • Then you plug the camera into a PC – a laptop is obviously an advantage here. To view the image I abandoned the truly appalling software sold with the commercial camera and downloaded the splendidly simple Craterlet.
  • Viewing the image ‘live’ on the laptop, one then needs to focus the telescope which is critical and really hard.
  • With my son’s telescope, the natural view covers only around one eighth of the moon. So one needs to take several pictures that are ‘stitched’ together.
  • The first real trick is to take movies rather than photographs. We took 10 second movie clips with a fixed exposure (not automatic) , each clip capturing pictures at around 30 frames per second. Over 10 seconds the moon shifts in the field of view and it is necessary to gently track the moon to keep the field of view approximately constant. one then covers the moon sequentially till there are movie clips of each part of the moon. As you can see we missed some bits this evening.
  • Now for trick number two. One then uses ‘stacking software’ to sift through the movies frame by frame and realign each frame with the previous one. The software then rates each frame for quality (how blurred it is) and stacks the good frames, averaging out noise and enhancing detail. Very very clever. We used Registax, but my friend recommends Avistack. Both are free and well written and regularly updated – but devilishly hard to understand!
  • And then one applies a third trick. The final image produced from each movie by the stacking software is then enhanced using a ‘wavelet’ filter – a mathematical analysis tool that I just cannot explain in this short space –  but if used correctly can bring out detail almost magically.
  • The final trick is to stitch all the pictures together. This would be very difficult without Microsoft’s free Image Composite Editor (ICE). One simply selects all the images that need to be stitched together and providing there is reasonable overlap between the images, ICE solves the ‘jigsaw problem’ and puts them all in the right place relative to each other! One can then export the ‘stitched together’ image as a ‘jpeg’ or ‘tiff’ image.

So what you see above is all the work of me and my son, and some very smart and kind people around the world. If it is clear tomorrow we will try and do this again and this time properly! But complicated as this process was, I was constantly distracted by one simple fact: the more one looks at the moon, the more amazing and beautiful it seems.

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5 Responses to “Not quite the full moon”

  1. Peter Says:

    Well done! Just shows how much you can achieve with modest kit and the wonders of free software and the amateur community. Try imaging through the month to reveal many subtle features that are only visible when close to the edge of the day/night divide. You may want to try the Lunar 100 list of different geological features. A copy of the Sky and Telescope Field Map of the moon would help a lot!

    All the best, you beat me to a higher resolution composite image!

    PEterW

  2. Michael Says:

    Peter: We will definitely try again: all we need is a clear night. Once we got used to it, we could get the data fairly quickly. Using Craterlet really helped with this because it increments the capture file number automatically. M

  3. Peter Says:

    I find that “zooming” the image on screen makes it easier to see the changes in focus. I agree that once set-up getting the data can be done really quickly, processing less so!! Saturn will become a target in the next month or so… probably still a bit after bedtime at the moment…. it is supposed to be quite a hard planet to image…. give your little colour camera a workout.

    PEter

    • protonsforbreakfast Says:

      Peter. Thanks for that tip – as one gets close to the focus it becomes very difficult to spot when one is right there – a quarter of a turn and its gone.
      Next time the clouds part we will give it a go. And thanks for the heads up on Saturn – I have never seen Saturn through a telescope and would love to get a picture of that. M

  4. Telescope for Christmas? | Protons for Breakfast Blog Says:

    […] an expert colleague, Maxwell and I managed to attach a web-cam and after many hours we got some nice pictures of the moon. We were really […]

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