//*** Optimize Exposure determines the best exposure time for the target star
public static double OptimizeExposure()
{
//Get the best exposure time based on the target ADU
//
//Subrountine loops up to 4 times, taking an image, and calulating a new exposure that comes closest to meeting ADU goal
//
//Take an image with current exposure set from last guider exposure
//If the max ADu is 100 or less, then there was no star at all. Double the exposure upto MaxGuiderExposure
//If the returned exposure is 64000 or more, then the star was probably saturated. Halve the exposure down to no less than the minguider exposure.
//If not within 20% of targetADU, then recalculate and rerun
//If within 20% then recalculate and done, then update the exposure settings and return the exposure
//
LogEvent lg = new LogEvent();
SessionControl openSession = new SessionControl();
TargetPlan tPlan = new TargetPlan(openSession.CurrentTargetName);
double exposure = tPlan.GuideExposure;
double tgtADU = tPlan.GuideStarADU;
double maxExposure = tPlan.MaximumGuiderExposure;
double minExposure = tPlan.MinimumGuiderExposure;
//set the maximum number of iterations based on the maximum number of halves or doubles that could be performed.
lg.LogIt("Attempting to find optimal guide star exposure");
//Only take at max 4 shots at getting a good exposure, otherwise return the max or min
for (int i = 0; i < 4; i++)
{
//Start at the initial exposure. This is a minimum.
//Take a subframe image
//Get maximum pixels ADU
//
double maxPixel = GetGuideStarADU(exposure); //Uses SexTractor engine
lg.LogIt("Guide star ADU at " + maxPixel.ToString())
;
//Check through too low, too high and just right
if (maxPixel < 500) //way too low
{
exposure = LimitMaxMin((exposure * 2), maxExposure, minExposure);
lg.LogIt("Guide Star exposure too low. Reset to " + exposure.ToString("0.00") + " secs");
}
else if (maxPixel > 60000.0) //too close to saturation
{
exposure = LimitMaxMin((exposure / 2), maxExposure, minExposure);
lg.LogIt("Guide Star exposure set too high. Reset to " + exposure.ToString("0.00") + " secs");
}
else if (!(NHUtil.CloseEnough(maxPixel, tgtADU, 20.0))) //if not quite close enought recalculate exposure try again
{
if (maxPixel > tgtADU)
{
exposure = LimitMaxMin(((tgtADU / maxPixel) * exposure), maxExposure, minExposure);
lg.LogIt("Guide Star ADU is " + maxPixel.ToString("0") + ": Exposure too high at " + exposure.ToString("0.00") + " secs");
}
else
{
exposure = LimitMaxMin(((tgtADU / maxPixel) * exposure), maxExposure, minExposure);
lg.LogIt("Guide Star ADU is " + maxPixel.ToString("0") + ": Exposure too low at " + exposure.ToString("0.00") + " secs");
}
}
else
{
exposure = LimitMaxMin(((tgtADU / maxPixel) * exposure), maxExposure, minExposure);
break;
}
}
lg.LogIt("Guide Star target exposure set to " + exposure.ToString("0.00") + " secs");
return(LimitMaxMin(exposure, maxExposure, minExposure));
}