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Telescope

Index

• 1 Imaging
  • 1.1 Why do I get a bright glow to the left in my images?
  • 1.2 What are the doughnut shapes on my images?
  • 1.3 I'm getting a shutter error and can't take pictures. What do I do?
  • 1.4 There is an object in my images that fades away. Is it a UFO?
• 2 Telescope Operation
  • 2.1 How do I align the dome and telescope?
  • 2.2 Why might the telescope and dome both be non-operational?
• 3 Miscellaneous
  • 3.1 Are there any other telescopes in the area?

1.1 Why do I get a bright glow to the left in my images?

There are two ways to fix this: use a non-blue filter, or flat-field later on.

The sensitivity w.r.t. colour of the CCD varies on the surface of the CCD. The CCD is much `flatter' in the red than the blue. Observing with the Clear, U, B, or V filters lets in blue photons. Indeed the problem is most acute with the Clear and B filters, the CCD being almost dead when used with the U filiter.

See Selecting Filters to change the filter.

1.2 What are the doughnut shapes on my images?

These are "Dust Doughnuts". They are caused by dust on the window covering the detector, and on various other optical elements in the light path. These can be calibrated out with flat fielding.

The distance from the detector can by easily found by measuring the size of the tori and multiplying by the f-ratio.

For example, a typical torus is 210 pixels across. A pixel is 9 microns in width. This gives a diameter of 1.89 mm. The telescope has a focal ratio of f-8. So the dust grain is about 15 mm away from the detector surface.

1.3 I'm getting a shutter error and can't take pictures. What do I do?

Reset the camera.

• Go up into the dome.
• Unplug the camera power cord from the power strip on the telescope.
• Plug it back in.
• Go back downstairs.

1.4 There is an object in my images that fades away. Is it a UFO?

This occurs after a bright object has been imaged which has 'burned' an image onto the CCD frame, as may happen after the alignment of the telescope has been checked by acquiring a bright star.

To fix, simply take a few short-exposure frames. That will clean it up.

2.1 How do I align the dome and telescope?

See Aligning the Dome in the Users Guides.

2.2 Why might both the telescope and dome be non-operational?

3.1 Are there any other telescopes in the area?