The "Extra" page of the Setup dialog has a new entry called "Rotator Angle"
If you don't change the angle of the guide camera you can ignore this and leave it at zero
But if you either have a rotator, or you manually set the OAG angle to a particular degree value, you can use this to keep track of the guider calibration so you don't have to recalibrate when you move the guider.
To use it - before you do a guider calibration make sure the rotator angle is entered correctly. Then do the calibration as you normally would. If you want to re-use the calibration setting in the next session - save the Setup file and it will store the calibration info, including the rotator angle.
If you change the rotator angle later - just enter the new rotator angle and when you press "Guide" MG will adjust the calibration for the new angle setting.
If you find the calibration isn't working, try checking the "Reverse Rotator Calibration" checkbox to reverse the direction of rotation.
MetaGuide will now store hot pixel lists for a guide camera and load them automatically. There is also more control on how the hot pixels are found.
To find the hot pixels, set up your camera for guiding, in terms of the number of pixels in width and height, the exposure, etc. Then cover the telescope and/or camera and go to the Scope Setup page. There is a new button called "Find Hot Pixels." Press that button and follow the instructions to close the dialog. This will find the hot pixels and store them in a single file in the MG directory called MGHotPixels.txt. That file will be loaded automatically the next time you use MG.
To kill those hot pixels you must also check the "Kill Hot Pixels" checkbox at the bottom of the setup page. If you then save the Setup Dialog, those same hot pixels will be killed every time you use MG.
To see how many hot pixels were found, go to the Extra page on the Setup Dialog and read the "N Hot Pixels Found" value at the bottom.
If you found too many hot pixels then you can reduce the sensitivity by increasing the "Hot Pixel Sigma Reject" value. The higher it is, the fewer hot pixels will be found. For many cameras, approximately 100 is a good number of hot pixels to find - but it depends. Values for Hot Pixel Sigma Reject could range from 2 to 10 or so. You can change that value and click "Find Hot Pixels" many times until you get it right. Then save the setup file.
There is only one hot pixel list stored by MG - so make sure the list is correct for your current camera and settings. It's easy to make a new list just by pressing the "Find Hot Pixels" button. You may need to do this after changing camera settings also.
You can tell everything is working if you have Kill Hot Pixels enabled - and the StarThresh is set to a value so that you don't find the crosshairs locking on background noise. You should be able to tune things so that the crosshair cursor only locks on to true stars in the field.
This is a more subtle setting that improves the way guiding works during automated imaging with something like Sequence Generator Pro.
SGP is designed to control MG by turning "Lock" on and off to lock on a guidestar or release it - followed by turning Guide on or off. If you are guiding on the brightest star in the field and it stands out from the others - then "Lock" will automatically lock on that same star every time. In that case it is better to use GuideXY instead of Guide - so that the same star will be guided at the same x,y location when you resume guiding. The checkbox "Remote Guide -> GuideXY" will cause guide commands to place the star back where it was - which will avoid it drifting away after multiple guide sessions.
This should be used with care since if you do lock on the wrong star - it will shift the image away instead of holding it in the same place.
Make sure you have killed hot pixels and set the StarThresh to a good value so it doesn't lock on noise in the scene.
Copyright Frank Freestar8n 2010