Problem Images for Comparison Purposes

Frame 1.

In this image there is a uniform amount of noise over the image. This noise is caused by high light cloud cover. In addition the image shows that the back plain (back of the image) is not in focus. See the small star donuts in the back of the image. This shows you that you are not in focus.

Click image to enlarge.

Frame 2.

In this picture a focal reducer was used. The star field is covered with white noise. Notice that the pattern of noise is circular. The problem was that the focal reducer seal had leaked and there was frost and condensation inside the focal reducer. I some cases this could be vignetting.

Solution: Have the focal reducer resealed by the manufacturer. Alternatively buy a new one.

Click the image to enlarge.

Frame 3.

Dark frame errors. The dark frames were not taken at the same temperature as the image frames. Note the small black spots throughout the image.

Solution: Insure that the dark frames are taken at the same temperature as the image frames. During the night the temperatures fall. This effects the temperature at the camera chip. It is advantageous to take some dark frames throughout the night.

Click image to enlarge.

Frame 4.

The camera hit the telescope forks as it tracked towards zenith.

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Frame 5.

During the night shoot session the image became dull and noise began to creep thorough out the image. Dew had fallen and as time passed the dew fogged the telescope glass.

Use a dew shield to protect the front of the telescope from due fall. From time to time use a hair dryer on the cold cycle to remove any fogging. There are also dew heaters for sale at your astronomy store.

Click image to enlarge.

Frame 6.

What happened here is that the camera train was so long. In the camera train was a de-rotator, focal reducer, extent ion tube, filter wheel and then the camera. Because the camera train was so long it caused a focal plain inversion.

Solution: Shorten the camera train.

Click image to enlarge.

Frame 7.

Note that the out of focus star patterns are NOT all pointing in exactly the same direction. In this case the problem was that the focal reducer had been taken apart and reassemble where the glass alignments was not 100%.

Solution: Have the focal reducer repaired/resealed by the manufacturer. Alternatively buy a new one.

Click the image to enlarge.

Frame 8.

Second example of focal reducer alignment problem. See notes above.

Click the image to enlarge.

Frame 9.

Notice that the stars are donut shaped. This means that they are not in focus.

Frame 10. (Blank fully saturated white image)

During the night this image was captured. It is simply a readout error of the video camera. The next image was correct.

There are no solutions. If this continues the camera needs servicing.

Frame 11.

The white line near the bottom right corner is a read out error of a video camera. Shooting bias and dark frames will remove these types of defects from the final image.

Click on image to enlarge.

Frame 12.

The white line running through the image is caused by a camera register error. (The camera has a defective column)

Actually this not really a problem. The line can will be removed when the bias and dark frames are applied. The CCD chip is aging.

Frame 13.

There are 3 problems shown in this picture. They are

• out of round stars caused by tracking errors
• vertical white line is a register error as described above and
• a curved white line running in the bottom 1/3 of the image. This could be a CCD cooling line of a failing CCD chip. As the chip cools (center outward) sometime you will see a circle or curved line. Looks like this CCD chip is just about done.

Frame 14.

The line across the image is from a satellite. Satellite tracks are characteristically thin and uniform in brightness and in thickness.

Frame 15.

Possibly a shooting star. Most shooting star tracks have one or both sharpened track ends and the brightness of the line is not consistent. As the object hits the atmosphere it heats and continues to glow brighter, burns to a peak intensity and then fades out again.

Frame 16.

Notice that the stars are doubled. What has happened is a small gust of winds have vibrated the telescope to create the double stars.

Frame 17.

Second example of a medium wind gusts.

Frame 18.

Third example hard wind gusts. A lot of shaking going on here to cause the curves. It is probably time to secure the telescope.

Frame 19.

Shooting star. Their trail start thin, then thicken and then thin again. Shooting star trails are characteristically spear shape. This is a function of entering the atmosphere and then burning up hence the spear shaped trail.

If you have examples of errors please send them to us with an explanation if you know what the problem was.