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Old 14-08-2014, 08:48 AM
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Shiraz (Ray)
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Shiraz is offline
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,892
Originally Posted by alistairsam View Post
hi Ray,

Interesting results, I have the older Orion Steadystar AO where the OAG prism can actually be tilted to point to a different area in the FOV, would this help at all if tilted to point toward the centre?

Secondly, do you think using the lodestar in 2x2 binning had any effect on your results? the lodestar has fairly large pixels at 8.2micron. when you bin, don't you lower the resolution of the guiding component and would this affect centroid calculations especially if it is a bright star?

I had a brief chance to test the AO on my 10inchF4 with the stf8300 and it showed very promising results, this was with an NEQ6pro, and not very windy conditions. I normally use an OAG.
did you do any tests with 1x1 bin of the lodestar?

I got a lodestar X2 and had no issues with getting a guidestar at 100ms from a very LP backyard.
cloudy as hell, but I'll post some results as well when it clears up.

Looks like the benefits are more evident in a system with a higher resolution, typically less than 0.7 arcsec/pixel.

Hi Alistair.

Don't know if angling the prism will move the aimpoint much - have you tried it?

I tried the Lodestar at 1x1 and 2x2. The only perceptible difference was that the update was slower at 1x1, so I used 2x2 (as recommended by SX) for all testing. The centroid finder in phd is apparently able to resolve to much better than a pixel (below 1/10 pixel with good SNR). I used stars with >30 SNR, so expect that the centroids were accurate to a small fraction of an arcsec.

My impression is that AO has most benefit when using a mid quality mount (eg EQ6) with a fairly heavy load under most seeing conditions - and when using a high quality system under very good seeing conditions. Agree that pixel scale is important - there is probably not much point in improving the guiding by 1/2 an arcsec if you are imaging with a pixel scale of say 2 arcsec - you won't be able to see the difference.

What sort of improvement did you see when using AO on your system - better resolution or rounder stars?

Regards Ray

Last edited by Shiraz; 14-08-2014 at 09:09 AM.
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