|Home Calendar About OCA E Zine Resources Image Gallery Members|
|www.ocastronomers.org/ gallery/ htm-othr /|
Explanation for Brian Miller's image of Comet Hale-Bopp
Actually, this very unusual looking image is the result of a classic error, which just about every astrophotographer has committed at some time or other. While this image isn't quite what the photographer was looking for, it's an excellent example of what not to do.
The ghostly "companions" to Hale-Bopp in this image were caused by the camera moving (accidentally) during the exposure, instead of staying pointed straight at the comet as was intended. The primary reason for the unwanted movement was the wind, a common nemesis of astrophotographers.
Because the wind was causing the camera to move around while the exposure was in progress, this caused the image of the comet to also move around on the film, creating the ghostly trails seen in the image. These faint loops are actually one continuously blurred image of the comet's head. Where the loops are brighter, the movement was slower; where they are fainter, the movement was faster.
It also appears that another type of movement occurred -- accidentally bumping the camera/mount. Being a sudden movement, this causes the image to shift cleanly without blurring, resulting in what appears to be multiple images on one exposure.
This effect of this is clearly demonstrated by the two side-by-side comet images at center. Notice how the left one is fainter. Note also the separation between the two (distance & angle of orientation). You will see this same pattern repeated for almost every star -- each appears as a pair of stars, the left one slightly fainter, with the same spacing and angle between them as you see between the two comet images at center.
With all due respect to the photographer, this could have been a very nice image. There is no such thing as a bad image, as long as you learn from your mistakes! (Brian did; he tells us he managed to get a good number of nice shots after this one. Thanks for sharing!)