This was not meant to happen. After 3 consecutive cloud free mornings with good seeing we woke to rain and a howling wind as predicted by the forecast. To our surprise the clouds cleared this afternoon but unfortunately the wind kept howling, gusting 50km/hr northerly. After the last three days of great seeing we were interested to check what the seeing was like in the middle of the afternoon (3pm). The tripod with the SSM needed a 10kg container of lead to tie it down. To our utter surprise the seeing was again very good. This is in contrast to a month back where every day for months had started with bad seeing progressing to abysmal by the afternoon. We are struggling to identify a reason for this change. The measured values for the last 4 days do not correlate with the on-line data from Meteo Blue and Skippy. Thus far the only common denominator we have been able to identify has been a northerly wind of some strength each day.
Even more surprising, the gap in the clouds persisted so we thought we could at least use our small scope for a Ha full disk. We had also wanted to experiment with a filter on the camera. We have for some time been using an IR cut filter on the camera as we had found that it improved sharpness of the images. In the past with planetary, we have found that you definitely need an IR cut filter with an ASI224 as it is sensitive to IR and cannot be focused with the other wavelengths. If it is helping with the Ha full disk images it means that IR has got through both etalons and the Quark blocking filter. This made us wonder whether any other errant wavelengths were also getting through. Ideally as 3nm Ha filter would have been good but we don't have one but we do have a ZWO duo band filter which passes Ha and OIII so thought we would try that instead of the IR cut filter. The histogram was lower than usual with this filter so it appears that something is being stopped by it however it is unclear as to whether it has made any improvement to the images.
The gap in the cloud continued so in keeping with scientific methodology best practice we decided to change something else at the same time
Although we have rotated the two etalons relative to each other on a number of previous occasions and thought that we had the best set up we tried it again and to our surprise, it appears that we didn't have the best alignment. Were we wrong on the first occasions? Has something else changed? There are so many interacting variables with these set ups, even with copious note taking it's hard to be sure.
Long story short, here is our full disk for today - two panel mosaic. Some nice proms and filaments to be seen.
