Using dithering with LVI II
發表於 : 2011-12-01, 15:34I bought the LVI II for some time, but there is not much time to explore its functions. Usually, the weather and my works are the killers. They just ruin my sky time. Anyway, I tried to experiment the dithering last night. I went to my school's roof and did the test for 45 mins and rushed back home. I just mounted the guide scope to the HEQ5Pro and collect the 40D to LVI II via the LVI shutter cable. I didn't do real imaging, but just see if it works. At 6:15pm, the sky was not very dark. The only two stars I could see were Vega & Altair. What a lovely pair! I pointed the guide scope to Vega & LVI stared to guide with dithering.
If dithering is turned off, the guide star will stay at the same point on the sensor. Under ideal condition, the guide star will stay at the same point on the sensor through out the guiding, but so as the hot pixels, bright pixels, dead pixels etc. This is very hard to remove these defects in post-processing. When the dithering is enabled, LVI II will search the guide star after each exposure again. This will result in a shift of the guide star on the sensor. Those defects, hot pixels, bright pixels & dead pixels etc will move around and the corresponding defect image can be easily removed in post-processing.
Before the guiding with dithering, I need to set the exposure time for each frame, delay time, interval between subsequent exposures etc. When everything set, off we go!
There is one drawback of dithering is that it takes about 2 more mins for LVI II to find (to displace) the guide star and load the calibration again. So the profit is higher if one images longer exposure for each shot. Since this is the first time, I tried the dithering. I don't know how fast other guiding systems are. Maybe 2 mins is already a reasonable or fast dithering.
If dithering is turned off, the guide star will stay at the same point on the sensor. Under ideal condition, the guide star will stay at the same point on the sensor through out the guiding, but so as the hot pixels, bright pixels, dead pixels etc. This is very hard to remove these defects in post-processing. When the dithering is enabled, LVI II will search the guide star after each exposure again. This will result in a shift of the guide star on the sensor. Those defects, hot pixels, bright pixels & dead pixels etc will move around and the corresponding defect image can be easily removed in post-processing.
Before the guiding with dithering, I need to set the exposure time for each frame, delay time, interval between subsequent exposures etc. When everything set, off we go!
There is one drawback of dithering is that it takes about 2 more mins for LVI II to find (to displace) the guide star and load the calibration again. So the profit is higher if one images longer exposure for each shot. Since this is the first time, I tried the dithering. I don't know how fast other guiding systems are. Maybe 2 mins is already a reasonable or fast dithering.
