10-12-2011 Total Lunar Eclipse at Hong Kong

What a wonderful lunar eclipse! This is the first time I imaged the whole total lunar eclipse. I was so luckily that the weather was exceptionally good in Hong Kong. I enjoyed the total lunar eclipse for about six hours! However, due to lack of experience, my photos were not good. I did every in rush. Now after reflection I summarized the reason of these bad photos.
1. I pointed the scope to Jupiter and got it focused with the focusing mask. It is no good to use planets to do focus. They are extended objects, the diffraction spikes are wide. It is hard to make judgment whether it is in focus. It is by all mean pick a bright star to do focusing.
2. My scope was placed inside my car’s boot for an afternoon. I guess the temperature is around 20oC to 23oC that day. However, the average temperature while I took the photos is about 14oC and the lowest temperature was 11oC. I checked the focus at the end of the eclipse by pointing the scope to Sirius. It was out of focus! According to previous testing, the focal shift was about 6x7=42um (6 divisions in electric Feather Touch focuser and each division is about 7um displacement). So I should check the focus regularly, say every 30 mins.
3. During the whole lunar eclipse, the brightness of the moon varies a lot. In my case, I set the ISO to 800, the corresponding shutter speed varies from 1/4000s to 1/10s. In addition, I need to pick different exposures for selections later. Originally I set the interval of the programmable shutter to 1 min. I noticed that I need more exposure for selection in the middle of the imaging. It is luckily that I can still make it by doing bracketing exposures for every time intervals. So it is quite an involving job!
4. The shutter speed would be slow at totality, if the ISO is not high enough. In my case of ISO 800, the shutter speed was down to 1/10s. For tele-photography, one should use high ISO. So get a low noise camera and set high ISO.


My first successful solar mosaic!

I tried several times, but failed. This is the first time, the image looks decent.
LS80T, DMK21, EQ3Pro, mosaic of 6 panes


26-1-2011 A sunspot with a scar & a big prominence

There are two sunspots and one of those with a scar. Isn’t it funny? The seeing today is bad. Originally I intended to use TV 5X & DMK 21 to do a high magnification shot, but it sucks because of the bad seeing today. These images are taken with TV 2.5X & DMK21.

LS80T, TV 2.5X, DMK21


19-1-2011 Solar Observation

The activity is low. Anyway, this is a chance for me to practice solar imaging with this new LS80T. The focal length of the LS80T is 560mm. The CCD size of DMK 41 cannot capture full solar disc in one go. Therefore a drifting approach is needed. In order to align the full disc properly, one needs to select those alignment points which appear in the whole video. Otherwise misalignment or non-uniform brightness will be resulted.

LS80T, DMK41

LS80T, DMK41

LS80T, DMK21, TV 2.5X


17-1-2011 lots of proms today

The sun got lots of prominence and one sunspot today. I tried to image the sunspot at higher magnification. But I cannot make it because I have lessons to go!
Equipment: LS80T, DMK41, DMK21