Posts Tagged ‘Astronomy’

An Image of our Sun

May 15, 2011
Our Sun

Our Sun, imaged from Teddington UK by Peter Woolliams. Click for full resolution image.

Peter Woolliams sent me the picture above a couple of weeks ago. Wow! Personally, it blows my mind that this is what our Sun looks like – all that rich texture and those tiny prominences – each one larger than our Earth:-( . What is so spectacular is that this image was not captured by a space telescope or  a special observatory, but by my friend in his garden in Teddington.Beautiful. Amazing. Humbling.

Thanks Peter.

Not quite the full moon

February 17, 2011

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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