When using a digital camera to shoot an image through an eyepiece what is the best focusing technique. Should you use macro or infinity. Auto-focus don't seem to work reliably.

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Bill
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Celestron C130
Orion 100MM F6
ETX90
Celestron Astro Binos

The best approach appears to be to look through the viewfinder, as hard as that can be for faint objects (can point scope at Sirius or the Moon to focus, then move it to the real object). Alternatively, there is software for the purpose, if you connect the camera to a computer so that it can check brightness and disk size of stars. I think the proper setting will be fairly close to infinity, but most cameras do not have "infinity" marked precisely enough for astronomy.

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Todd (Bowie, MD, US, North America, Earth, Sol System, Vega region, Local Bubble, Orion arm, Milky Way Galaxy, Local Group, Virgo A Cluster, Virgo supercluster, the universe in which spock is clean shaven)

Quidquid latine dictum sit, altum sonatur.

personal page: http://blog.astrosketches.info

Turn off auto focus and set the lens for infinity. Its setting is pretty immaterial. If using a zoom lens set it to maximum zoom. Then point the scope and camera at a bright star with a Hartmann mask on the scope. Set the view finder for its highest magnification and adjust the scope until you find focus. Then remove the mask, move to your target and take plenty of shots. Atmosphere will blur many of them but one or two might hit the mark. While DSLRs can often attach to a PC the basic digital camera often can't. If you can lug a TV around that gives a nice big screen at the expense of portability.

I like three triangular holes as they create diffraction spikes on real bright stars that help you tell when the three holes are truly one. At that point you can tell all spikes cross at the same place quite easily. If you don't know how to make one there's plenty of sources on the net. Precision isn't needed here so they are quick and easy to make.

Rick