Focus is hard at night

I took this shot Thursday night up at Mauna Kea. I thought I was doing really well with the photography, but when I got home and imported the images, all of them were blurred. There wasn’t any wind, and I thought the scope was polar-aligned well enough, so for the moment I’m blaming this on manual focus.

The purple stuff is digital sensor noise, which I find kind of shockingly high. I took a “dark frame” (photos of similar exposure, but with the lens cap on) and can use Photoshop to subtract out the noise, but it’s not worth it for a fuzzy photo like this.


To give you a sense of what can be done with modern digital cameras, great lenses, Photoshop, and talent, take a look at this amazing photo

3 thoughts on “Focus is hard at night

  1. Hi Larry,

    That sure is a lot of noise :)

    But the unsharpness, when focusing at this distance shouldn’t you just focus at infinity? That stars should be fare away enough to be sharp. Also how open your lens is, if your using the 3.5 – 6.5 kitlens, the sharpest pictures are between f8 and f10. Although I’m not sure if this could even get enough light on the sensor..

    Depending on your exposure time it could also be that the fuzzyness is cause by the earths rotation and not correcting for it :)

    But also a cool thing to do is create a star time lapse:

    Have fun experimenting :)

  2. I must have accidentally moved the focus ring off infinity early in the evening… :-(

    The shots were all several minute exposures at 3.5. I piggy-back the camera on my telescope’s electric mount, which should compensate for the Earth’s rotation.

    The star time lapse is absolutely something I want to do. My camera does not have a built-in intervalometer, but I’ve put one together using an arduino and an IR LED. I just have to assemble it into an enclosure that I can take up onto the mountain with me!

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