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Old 20-04-2016, 09:05 PM
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Shiraz (Ray)
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Shiraz is offline
Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,791
Originally Posted by gregbradley View Post
Thanks Ray.

The assistant is easy to use. You simply click start and wait say 2 minutes for the results to settle down and then click on finish and it gives recommendations for min/max move and exposure lengths. You can click on accept and it implements them.

thanks Greg. the only problem I have with the advisor is that I have no idea what is under the bonnet and how to get the best from it - for example, if my best imaging exposure is 0.5 arc sec, but 2 sec is used for the calibration run, how can it possibly sample fast enough to end up suggesting 0.5 seconds. I don't see any way that it can, but the documentation does not explain it well enough that I can be sure. Rather than accept something so "black box", I decided to test the effects of guide exposure in another way. That is not a criticism of the software - it's just that I would prefer to understand how it actually works.

Originally Posted by jenchris View Post
I'm not sure how to compare the results above with my phd2 graphs.
My min mov is set to .14 and .09. My exposure to 2 seconds on a qhy5 on a 102swachro.
Graph attached with target and fwhm graph.
the graph given earlier is a plot of the star sizes (in arcseconds at full width half maxiumum) taken from a series of 2 minute images (taken with an astro camera) and for different guide exposures. It shows how the star size gets smaller as the guide exposure is reduced.
Your screen shot shows the error plot for phd, which is a measure of how much error phd was correcting at any time over a past period. This is not the same as the resolution plot, since the data in your graph comes from the guide camera, not an imaging camera. There is a tenuous tie up between the two types of data (reduced guide errors may possibly result in smaller stars), but there is no direct comparison.

having said that though, your plot looks good to me, with quite low and consistent guiding error. You might try using shorter exposures and see if you get smaller stars in DSLR images, but it already looks like it is guiding OK. FWIW, my EQ6 guides well at 1.5sec guide exposure in most conditions - that is close to your chosen value, so either that is a good choice or we are both wrong.

Last edited by Shiraz; 20-04-2016 at 09:25 PM.
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