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Originally Posted by Bassnut
Jase
Have you actually used these plugins, if so, how do you find them to use?.
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Yes Fred.
I use to operating the guider settling script when using the FSQ/STL11k with the internal guide chip. As the shutter closes to read out the main imaging sensor, guiding could not continue. Once the read out and download was complete, the guider was reinitialised...sometime the original guide star had moved several pixels from where it was at the before the shutter closed. To ensure MaximDL didn't start the exposure before the guider recentered the star, I used this script. In maximDL you can alter the time between exposures to address this too. Now using ACP, the guider error tolerance level is integrated, so I no longer use the script.
Multi star guiding is something else. Initially I though it sounded too good to be true, but its actually very effective. Some report that guiding on multiple stars reduces the impact of seeing, but in reality I don't see how this could be. If you're guiding on axis with a narrow field of view, you've probably only got on or two stars on the guide chip to start with. Secondly, if you're guiding with a wide field instrument, the seeing conditions are hardly going to be detected. My philosphy was probably too simple given Jim McMillan's analysis who wrote an extensive paper on guiding breaks it down further stating;
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Regarding seeing, at least in my location, the effects are not just rapid, random oscillations around a point, but can also consist of rather large movements where one oscillation may last for many seconds at a time. For the sake of this discussion, I will call the rapid oscillations “fast seeing” and the multi-second oscillations “slow seeing.” My suspicions are that slow seeing is caused by multiple heat/cold sources typical of suburbia that create a number of columns of air at varying temperatures (think chimneys, ponds, grassy areas, rooftops, parking lots, trees, etc.). The effects of fast seeing are quite different over a very small FOV while the effects of slow seeing are similar over a relatively large FOV. Therefore, using multiple guide stars with a FOV of about 30 arcmin virtually eliminates the effects of fast seeing but is much less effective in eliminating the effects of slow seeing.
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What Jim also confirms is that multi star guiding increases the signal to noise empowering the calculations of the guiding algorithm. In short, it allows you to guide on fainter stars as the centroids across them all are inputs to the algorithm. I can testify this actually works well. Again with the FSQ/STL11k using the internal guide chip, I had no issues in guiding on faint stars though a Ha filter (admittedly it wasn't a 3nm filter), but it has its uses.
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Perhaps most interesting to me is the effect Guide Star S/N ratio has on the accuracy of the centroiding algorithm. While it is understood that Guide Star S/N ratio is an important component of this calculation, I did not appreciate how critical a component it actually is. When using multiple guide stars, you have the opportunity to compare the Guide Star S/N ratio of each guide star to the range of values computed for their centroids. This comparison is valid because these values (Guide Star S/N ratio and centroid) are computed for each star at the exact same time (e.g. same seeing conditions) over a number of guide cycles. As expected, the higher the Guide Star S/N ratio, the lower the range of computed values for their centroids. What is surprising is how high the Guide Star S/N ratio needs to be for the calculation to be reliable.
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If you haven't tried them, they're worth a shot. Even simply from the educational perspective getting to know your set up further.
Can you guide with precision not using these plug-ins,
most certainly! Guiding algorithms from product to product these days compute centroids extremely accurately, however some products make it easier to tweak and understand whats going on (again feature rich).
Of course there are many factors at play here when it comes to guiding;
A) Software configuration not correct
B) Calibration is not accurate to calculate the correct X/Y movement
C) Equipment that is not accurately polar aligned, exhibit flexure, or is not well balanced
D) Troubled by the seeing conditions
At the end of the night, it doesn't matter what software you use if you've got the above issues, you're going to have guiding problems!!!
That all said and done - MaximDL
