Meade Image Processing Uživatelský manuál stáhnout pdf (Strana 9)

5. Basics of image processing

When an astronomical CCD camera is used to record light, it always comes in the form

of a digital image on a computer. The purpose may be making measurements of the

position, size, color, or something else of an object, or simply producing pretty pictures. As

compared to regular digital photography, there is a price we pay for improved sensitivity

and dynamics, and for the reduced noise: raw images usually look uneven, dirty, still

contain a lot of noise, and their huge image depth virtually suppresses contrast on the

computer screen. Against all appearances, these dismal-looking images are actually not

worse at all than regular camera pictures! The reason is that the “mess” on these images is

bad only in comparison to the extremely faint target. A regular digital camera would simply

cut off all the noise and mess, but

it would completely remove our

target as well!

It takes a significant effort to

remove all this noise and mess,

and to get the images in a

“pretty” shape. It is advisable to

become familiar with this process

before taking your own images. The experience is

rewarding, the resulting pictures are really pretty, and in the process you learn the

technicalities that will help you to make the correct decisions during image taking.

In the first laboratory exercise, you will be using software called CCDOPS to manipulate

images. This same software can handle the camera and the telescope in the dome. It can

align, scale, clean up, add, and manipulate images in many ways.

Fig. 4: Compare an original

to a processed image

Figure 5: The buildup of pixel counts during exposure. Larger numbers indicate a whiter pixel on the image.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 28 29

Žádné komentáře

Meade Image Processing Uživatelský manuál Strana 9