Dithering means shifting the telescope slightly of target randomly between imager exposures. This allows bad pixels, image artifacts, fixed pattern noise, and even satellite or airplane trails to be removed during the imager stacking process.
SkyGuide uses the imaging camera status to detect the end of a given imager exposure (shutter closed).
When dithering is enabled SkyGuide will automatically dither between imager frames, however the imager must be connected to SkyGuide using either its ASCOM driver our Maxim-DL for this feature to work.
When using a third party software, such as SGP, controlling SkyGuide through its REST API dithering can be automatically imitate remotely.
The detection of the end of the dithering move can also be automatically detected using the current auto-guiding error.
If implemented this way by a third party software there should not be any need to add any delay for dithering settling time anymore, as discussed below. See third party software documentation for further information about how this has been implemented.
To start dithering you must click on the button.
The following dithering settings dialog box appear.
Above the separation line, you will find all settings that must be configured prior start dithering
Dithering range defines the range, in guider binned pixel, that will be used to calculate the random offsets for both axes X and Y.
Maximum allows value for the range is one third of the tracking window.
Dithering uses the guiding aggressiveness to shift the telescope like normal auto-guiding. If the guiding aggressiveness is low, which is often recommended for normal auto-guiding, the time required to shift the telescope can be long. To reduce the shift settling time the fast dithering option uses an aggressiveness of 80%, or the user setting, what ever is the largest, on both axes during the dithering process.
We strongly recommend to use fast dithering option.
Below the separation line, you will find all settings that are calculated by the dithering
Settling time is the number of guider frame that are required to settle telescope to the new location.
Dithering time is the time in milliseconds that is required to shift the telescope to the new location (settling time).
Calculating the estimated dithering settling time requires some guider frames, if the field is empty when you open the dithering settings dialog box one must wait until the estimated value appear in the field.
When using auto dithering option, it become very important to set a delay that is equal or greater than the dithering settling time calculated by SKG after each exposure from the image sequencer software. If there is no delay or if the delay between exposure is too short, the resulting image will have elongated stars.
In MaxIm DL, the delay can be defined by clicking the options button and select Exposure Delay menu item.
In exposure delay dialog box enter the dithering time in seconds
Dithering offset fields shows the offsets on both axes X and Y, that are currently used to shift the telescope location.
When using auto dithering option, new offsets are randomly calculated and applied after each exposure of the imager camera.
To start dithering, click the button.
When dithering is enabled you can open the dithering settings at any time by clicking button
When dithering is enabled, you can calculate new offsets randomly by clicking the button.
Avoid to click the button while exposing with the imaging camera because the resulting image may have elongated stars.
To stop dithering, click the button.