Hal Mueller's photos



This is a JPG of an AVI taken on Oct 14 8:38 pm and the moon was about 60-70 degrees in elevation (2000 frames stacked) via a Vixen ED130SS apochromatic scope and a Celestron NexImage Solar System Imager and stacked using Registax 2.1. Crater is Aristarchus.

Colour possibilities (By Doug Welch)

The brownish tinge is almost certainly an effect of the telescope/camera/colour mapping - i.e. not the Moon itself. I can think of a number of possible explanations and I don't know which one is right, but I bet one of them is!

  1. All colour-corrected objectives are tuned for no noticeable colour in the visible part of the spectrum. However, outside that region all bets are off and some lose their achromaticity very rapidly to longer and shorter wavelength. The spectral sensitivity of a webcam or digital camera is different than the eye and it may be picking up this difference.
  2. The objective itself may introduce some net transmission difference in colour. I doubt this is the correct answer but some of the weirder glasses used in constructing multi-element lenses aren't "white".
  3. The mapping algorithm for colour is being tested by the pure grayness of the target.
  4. The Moon was low in the sky and a colour shift was being introduced by differences in atmospheric transmission.

Personally, I favour choice 1 as the explanation. You may recall that the Orion Nebula looks greenish but most images show it to be a pinky-red. This is because the chips tend to have more sensitivity further in the red than the eye. However, there may be another correct explanation. What I am most certain about was that it wasn't the Moon itself doing anything unusual.

Update from Hal Mueller

I agree that the colour is caused by "optics". It's been a while since the images were captured and I now remeber using a barlow (Parks - memory isn't what it used to be).

I recall that the CCD "eyepiece" didn't slide into the Parks but was perched atop it. A misalignment probably caused the "reddish to bluish" colour "smear" from left to right.

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