Meade Image Processing Bedienungsanleitung PDF herunterladen (Seite 13)

Review questions

It is now time to make sure that the reader understands and remembers the important

points of astronomical imaging. The following questions will serve as a guide for studying.

It is best if you know the answers to these questions; if not, you must return to the

appropriate pages and read off the answer from the text there.

1. Why are most objects a less than impressive view in the telescope?

2. What is needed to make those images great-looking? Note: the answer is not simply

“to have a CCD camera”.

3. How does a CCD camera work?

4. In what form is an image stored in a computer?

5. How do we take color images with a CCD camera?

6. How do you expect a raw, unprocessed image of a galaxy would look like?

7. What does it mean that a pixel is clipped on an image? Give an example in terms of

three numbers: pixel reading, white point, black point.

8. Point out a clipped pixel on an image.

9. What three sources cause noise on an image?

10. How is a “dark frame” taken, and what does “dark subtraction” mean? What sort of

improvement does dark subtraction provide?

11. What is the mechanism of reducing noise through cooling?

12. How is a “flat frame” taken, and what does “flat fielding” mean? What sort of

improvement does flat fielding provide?

13. What do you do when you need a 1-hour exposure to make your object visible in the

picture but the telescope can only follow the stars precisely for 20 minutes?

14. When you have three images, one in each color of blue, red and green, you do not

add the pixels readings on each with software. Why not?

15. Write down the five most important steps of image processing in the proper order.

(aligning, adding images of the same color, flat fielding, dark subtraction, color

composition). What happens if you do these steps in the wrong order?

At this point we suggest that the reader does the image processing laboratory.

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Meade Image Processing Bedienungsanleitung Seite 13