Meade Image Processing Instrukcja Użytkownika Pobierz pdf (Strona 5)

3. A tour of the sky

The only way to really appreciate the achievement that the use of CCD’s represents is to

look at the sky first the way everyone did until ten years ago. In the past, we first became

familiar with the constellations, learned how the Moon and the four bright planets looked.

We learned that we needed to train our eyes to see in the dark, go to the darkest locations

away from streetlights, use the largest telescopes we could, but we still had to use a lot of

imagination to see tiny specks or faint glows of galaxies or star clusters. In a laboratory

setting, stuck on a well-lit university campus, we cannot hope to be impressed by the usual

“wonders of the sky”. Light pollution makes all but impossible to see any of the interesting

astronomical objects, and it hurts our image taking as much as our visual observations.

Nevertheless, it is still a good idea though to draw a baseline, look up at the sky, use

visually the same type of telescope we have available for image taking, and look around to

get an idea. In the process, we will learn how to start up the telescope and how to aim it at a

celestial object. Predictably, we will not be very impressed with the view, unless we have a

chance to do this in a really dark place, far away from all streetlights.

All celestial objects, with the exception of the Moon and perhaps Saturn, hide their

details from the eyes of the observer: they are either faint, or their details are tiny and hard

to make out, or both. It always takes training, effort, and knowledge to actually see all that

there is in the telescope. A cursory look for a few seconds will show ten percent of all

detail, if that, and results in disappointment.

Other than properly setting up the telescope, there are three issues that are the

observer’s “responsibility”: 1. proper dark adaptation, 2. proper focusing, 3. proper visual

effort. Each of these is non-trivial.

1. Dark adaptation

The human pupil slowly opens up in darkness. A fully dark adapted eye lets in about 10

times more light; but it takes 10-20 minutes of walking around in the dark to achieve that.

Do not expect to see any faint objects in the telescope until you have spent those quarter of

hours outside! And just one look at a flashlight or a car’s headlights sets the clock back and

you are “blind” for another quarter of an hour. Or, you lose another ten minutes if someone

just turns on the light inside the lab and you look at the open door from outside … . (You

must be also careful not to shine a flashlight into anyone else’s eyes either.)

We switch off as many streetlights as we can. We can’t get rid of them all; whenever

you look into the telescope, some lights will still shine into your eyes. Shield your eyes with

your palm, and ask another person to stand in the way of any disturbing light bulb. It does

make a lot of difference!

2. Focusing

It actually takes training to look properly into a telescope, believe it or not!

Experience shows that people often tend to place their eyes at a distance from the

eyepiece. If one does so, much of the light will not reach the eye, and the field of vision will

be narrowed down. Always make sure that your eyebrows actually touch the eyepiece! This

is especially hard on people with glasses; one simply cannot place an eye close enough with

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