Hi - I hope this doesn't seem like a stupid question, but when doing CCD imaging, how do you know that you have the object in the field of view? Specifically, I was looking at the Coolpix 995 camera with the Scopetronix screw-on 14mm eyepiece (seems like a very simple approach to beginning astrophotography).
Newbie question
Started by NGC88888, 08/09/2002 03:33PM
Posted 08/09/2002 03:33PM
Opening Post
Posted 08/09/2002 04:00PM
#1
Hi Ryan.
Not a stupid question! There are several ways of making sure the object is in the field of view, depending on your equipment.
The easiest is to use a flip mirror system. This is a movable mirror in a housing that allows you to direct the light either straight through to the camera or to the side where you can view with an eyepiece. The requirements are that you can see the object (or at least identify the field) and that your telescope system will still focus. The system puts the camera 2" - 4" further back.
Another way is just to locate the object by looking through the scope, and then removing the eyepiece and putting on the camera. The problem here is that you must be careful not to move the scope, and that you need to make sure that the camera is in focus. Almost always the camera and your eye foucs at different places! (The sixth corrollary to Murphy's 14th law!) I have found that it is best to fis the focus for the camera and then make do with trying to identify the out of focus object visually.
The third method I have used when using a CCD is just to take a short exposure (eg 10 sec) and then compare the field with a chart. I use this most commonly when I am imaging something too faint to see visually.
Hope this helps.
Maurice
Not a stupid question! There are several ways of making sure the object is in the field of view, depending on your equipment.
The easiest is to use a flip mirror system. This is a movable mirror in a housing that allows you to direct the light either straight through to the camera or to the side where you can view with an eyepiece. The requirements are that you can see the object (or at least identify the field) and that your telescope system will still focus. The system puts the camera 2" - 4" further back.
Another way is just to locate the object by looking through the scope, and then removing the eyepiece and putting on the camera. The problem here is that you must be careful not to move the scope, and that you need to make sure that the camera is in focus. Almost always the camera and your eye foucs at different places! (The sixth corrollary to Murphy's 14th law!) I have found that it is best to fis the focus for the camera and then make do with trying to identify the out of focus object visually.
The third method I have used when using a CCD is just to take a short exposure (eg 10 sec) and then compare the field with a chart. I use this most commonly when I am imaging something too faint to see visually.
Hope this helps.
Maurice
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