Posted by: Szabolcs Nagy Comments:0
ISS – two days of test at 4800mm
Since my first few attempts at 4800mm of focal length back in Hungary I simply could not wait for the next ISS flyby season from London. It finally began lately and had two mornings in a row with clear sky. The first was on the 6th September when the maximum elevation of ISS was 79°. I had some trouble with my dobson base, it was pretty stiff when turning so I applied some oil on the teflon pads. Well that was a mistake and I was really struggling with tracking smoothly this the flyby even more so.
Luckily on that evening I did a quick cleaning maintenance work on the dobson base and managed to completely clean off the oil. It was nice and smooth once again and ready for the morning over head pass.
The atmospheric conditions were even better than a day ago, therefore I was really looking forward to the imaging session. The max. elevation of ISS was 63° which I prefer more these days. I think flybys between 60-70° are the most favourable ones, much easier to manually track and the orientation of the station gives away more details of the berthed vehicles and certain modules.
The improvement is vivid compared to all the previous shots taken with this setup at 4800mm. But I am still not really confident with it. I have a sneaking suspicion that for the 10″ dobson a 4x powermate might just be too much. It is simply beyond the capabilities of this tube. But will give a few try if weather permits, because my other feeling about it is that my focus might not be good too. However if the magnification is too much for this telescope that might be the reason for lack of sharpness too.
But if this is not the way forward for improvement, I will not waste too much time with experimenting since I have a good and tested way of using the 2.5x powermate. At the moment it looks like HTV-7 will be launched on very late night of Monday (10th September) and for that I will definitely use the lower magnification setup for sure. Do not want to take any risks with HTV, instead using the confident way. With the 4x powermate inserted I end up with very small amount of frames (around 40 frames this time) versus with 2.5x powermate hundreds of frames.
Anyway here is another photo from the 7th and also I marked Soyuz MS-09 too.
Finally this is a time lapse video. Even from London so many constellations are visible. Nice to see Orion and Taurus constellations once again and Pleiades too. Moon rising on the left and I also caught a satellite, possibly an Iridum flare.
Skywatcher 250/1200 Flextube dobson
Zwo ASI224MC camera
TeleVue 4x powermate