Lens test

[Fay]

Oh well, just come in from outside lens test & I could not get it to focus.

I tried it with the filter wheel, but just had really big out of focus stars. I took filter wheel off, & thought it would focus, then, as I know it does with a SX H9, which has a back focus 17. The Atik back focus is 12.

And ideas gratefully received!!!!!!

[MarkS]

Do your initial tests in daylight - it's so much easier.


When I've had to do something similar (using a webcam with a new lens) this is what I've done:

Go somewhere where you can see a obvious landmark a mile or two away (the further in the distance, the better).  With the lens on a tripod pointing at this landmark, hold the camera directly behind it and view the image on the laptop whilst you move the camera slowly further from the lens.  At some point the landmark will reach focus - then you know roughly what camera spacing you require.

You could do this twice - once with the lens focused at infinity and once with it focused at closest distance.  This will show you the range of possible camera spacings that will work with this lens.

Then put everything together at a spacing that will work, tweak the focus on the lens so the landmark is sharp and remember this focus setting.

Next time you point it at stars it will just need slight tweaking of the focus to get it dead sharp.

Job done!

Mark

[Fay]

Thanks for that Mark, but when I rack it right out I still have big unfocused stars & I am thinking I have to cut back somewhere, but not sure I have any where to do it.


I will take it to Kelling & if there is some daylight time, perhaps you can suss my spacing out for me. I will not use it up there. Have you got one of those accurate measuring devices?

ALSO

Am I sensing disaster here, with the Icelandic volcano????????????

[MarkS]

if there is some daylight time

You're worried that the volcanic ash will completely block out daylight?

[Fay]

No screw the sky up!