clear sky chart

Job 9:9

Job 9:9-10
9 He is the Maker of the Bear and Orion,
the Pleiades and the constellations of the south.
10 He performs wonders that cannot be fathomed,
miracles that cannot be counted.

Thursday, June 9, 2011

Focusing tip

I was imaging the moon last night, and I came across a neat little trick, maybe you guys know this, maybe not.  As you know, I'm using an f5.5, 127mm refractor.  The focusing is quite critical with such a fast lens.

When I image the moon, I use an el-cheapo Meade 2X barlow.

What I did last night to get an almost perfect focus was to focus as best I could normally.  then I de-focused just a wee bit on the inward side.  I then loosened the camera to barlow screw and slid the camera out of the barlow very carefully, and I was able to get a much finer focus.  The barlow acts something of a "vernier", making the focus a little less touchy.

a useful tip for us guys using fast scopes......which kinda makes sense, as a barlow actually increases the focal length by a factor of X, which would increase the acceptable focus adjustment by a factor of X.

I've done that trick on the 70mm which is a bit slower too.  Also, as you slide the camera out of the barlow, you get a little bit more magnification.  


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