|
Focusing After many months of trial and error I'm finally getting the hang of this. My images are getting better. Focusing is one of the hardest things you can do when using a CCD camera. I found a real nice trick on the Internet a while back that helps focus. Point at a bright star and over expose it, you should get a set of diffraction spikes, if out of focus you will get a pair of lines. As you get closer to focus the lines will merge in to one line. If your using a SCT you will not get these lines. But that's easy to fix. I took a piece of cardboard and cut out a circle to fit over the telescope. Then I taped some wooden dowels to cross over the opening of the telescope. You can also lay a ruler across the telescope opening. |
| Start with some object near by during the day. This has several advantages. First, it does not cut in to viewing time. Second, no need for tracking. Third, things are easier to do when you have light. I took this shot from about a block away, exposure time, .01 seconds with a lunar filter. Doing this will help you set up a parafocal lens, or to set up your flip mirror. A sign like this is a good choice because of the sharp contrast between the back ground and the lettering. If your wondering, it's a no parking sign taken at f3.3 |
 |
|
Below Image on left is out of focus, notice double lines Image on right is in focus, notice single lines Ignore daggers (bright vertical lines) Image in center is what I made to help produce this effect. Simply place it over the opening of the telescope. |
 |
|
 |
|
Below This is simply a piece of plastic with 3 holes cut in it. I place this over the corrector plate and then take an exposure. If out of focus I will get 3 separate stars. (see left) If I'm going more out of focus the stars will move farther apart, if getting closer, they will move closer until finally becoming one star. (see right) This is the method that I prefer to use, it's easy and accurate. This will only work with a star, it will not work on the moon, planets, nebula, or galaxies. You need a sharp pinpoint light.
|
 |
|
 |
