Quote:
Originally Posted by Meru
Thanks guys! F/4 works wonders with narrowband, just gotta get the tilt/collimation under control. Alistair, how do you know that its tilt rather than collimation?
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Meru
I had a closer look at the four corners and you can see the left of the image has almost perfectly rounded stars but only the right shows them elongated or elliptical
I could be wrong here but from my understanding, bad collimation would yield teardrop or seagull or comet shaped stars.
the ones on the right dont exactly exhibit that.
the fact that only one side shows elongation and the star shape suggests tilt to me.
its bit hard to judge as the chip doesnt cover the illuminated circle, these issues would be more prominent at extremities.
try a star test. defocus and check if the shadow is centered.
test both intra and extrafocal. I've read they are a good test for collimation errors.
there are a few guides out there.
just to rule out tilt, try tightening one side of the focuser more so it tilts the camera a bit, or add washers on one side of the focuser to induce tilt and then check.
I've got the cats eye and the hubble artificial star with me so happy for you to drop by and fine tune it.
if you've got a vernier and can access the ccd, try measuring the depth to the ccd surface at each corner. thats how I fixed my ccd tilt. got it down to 0.3 mm.
The previous night I used my RC8 to get 6 hours worth of data, but my PA wasn't great and ended up with 2 subs ok-ish subs. And they showed a little less detail than this.
