Re: finding and centering planets under high magniPosted By Weiman Kissinger |
Russ is right. The focus is way different when you insert a 2x or 3x barlow.
One way to help is to test it out during daylight on a remote object or use that wonderful beacon, the moon. It's bright enough and big enough to allow you to rack the focuser in and out with the barlow inserted until you get a proper focus.
Once a close focus is achieved what I've done then is use a caliper (or ruler) and measure the distances between two fixed points in the setup (top of focuser to bottom of eyepiece holder for instance) for no barlow (camera only). Then I add the 2X barlow, get a reasonable focus and once again measure using the same two fixed points, followed by doing the same for the 3X barlow.
I then cut a small block of wood or dowel rod (1/2" or larger diameter) to each of the measurements and mark one NONE, one 2X and the other 3X.
When I'm ready to capture I insert the camera and rack the focuser until it's snug against the "none" wood block and I know I'm close on the focus and just need to center the planet. If I want to go 2x or 3x barlow I just add the barlow before the camera and use the 2x or 3x wood block in the same manner.
I found it helps out a lot when I know I'm near focus in each setup.
Now, centering the planet at 2x or 3x is much more difficult and is another topic altogether.
Good luck
Weiman
One way to help is to test it out during daylight on a remote object or use that wonderful beacon, the moon. It's bright enough and big enough to allow you to rack the focuser in and out with the barlow inserted until you get a proper focus.
Once a close focus is achieved what I've done then is use a caliper (or ruler) and measure the distances between two fixed points in the setup (top of focuser to bottom of eyepiece holder for instance) for no barlow (camera only). Then I add the 2X barlow, get a reasonable focus and once again measure using the same two fixed points, followed by doing the same for the 3X barlow.
I then cut a small block of wood or dowel rod (1/2" or larger diameter) to each of the measurements and mark one NONE, one 2X and the other 3X.
When I'm ready to capture I insert the camera and rack the focuser until it's snug against the "none" wood block and I know I'm close on the focus and just need to center the planet. If I want to go 2x or 3x barlow I just add the barlow before the camera and use the 2x or 3x wood block in the same manner.
I found it helps out a lot when I know I'm near focus in each setup.
Now, centering the planet at 2x or 3x is much more difficult and is another topic altogether.
Good luck
Weiman
