Quote:
Originally Posted by SkyViking
Hi Paul,
Thanks for providing that, always good to see what conditions others face.
In order to compare I calculated that your ST-i give a resolution of 2.63"/pixel at 580mm (assuming you guide unbinned) and RMS of 0.106 is then 0.28". That's actually very similar to mine which is around 0.25"-0.30" on good nights.
However, I don't think my loaction is exceptional and here FWHM is hovering around 2" on the best nights. Are you sure you really have sub arc second seeing? Not saying that you don't but it sounds extreme and in that case I would have expected much smaller RMS at your location.
Cheers,
Rolf
|
Rolf I can only go by the readings I was told and by my own experience here. Planetary imaging here is pretty good to exceptional. At focal lengths of around 11-12 meters the seeing can often be very still here. My only Saturn image last year was taken from Clayton, and I only needed to take one lot of data to satisfy my want to get a great image .My previous Saturn shot was the year before and the seeing that night was very good but a night before the seeing had been truly exceptional. I did not image Saturn that night but kicked myself later for not taking data. My Mars shots from 2012 were taken from Clayton too when it was just 13 arc seconds in diameter. The beauty is that seeing is so good that I only need to take a few nights or in the case of Saturn one night to get the shot I am looking for. You cannot do great planetary images unless the seeing is approaching sub arc seeing. Yes the software is very good but you cannot make great images from average data in planetary. Just a small amount of blurring is enough to reduce the data to an average looking image.
I think I am currently running binning 2x2 on this STi. That makes it 5.15 arc seconds per pixel, but I don't know if that makes the calculations better or worse. I am assuming better; to make it 1x1 I divided the RMS by 2 and get a figure of 0.14, but I could be completely wrong here. Feel free to correct me here if I am wrong. Certainly interested to know how the calculation works.
All I know is my shots with the TSA here are very sharp coming out of the camera and I never use decon at all. I use some subtle selective sharpening on my final image sets, but not a lot. I don't think the scope has exceptional optics (good for sure) and I have to put the quality of the image sharpness down the seeing conditions. The mount I am using is certainly a factor in this too.
I have also noted in the last month that the images seem slightly sharper now since changing over to full robo focus. I was using the MHP to control the focusor but now am using the Robofocus module to totally control focusing. The images have picked up a little in sharpness, but again it could simply be some better seeing conditions and transparency. Nothing else has changed
In any event I think I will have to get the instrument officer back here to do some more tests. The 36" scope the society is building needs to be housed in a spot of good seeing and hence why testing was performed here. It will be certainly interesting. I know the Freeling tests in the Flinders outperformed Siding Springs by a significant factor and the only real reason why the telescope was not built there was due to remoteness of the location at the time. Yes that is 700km away from here but Freeling gets laminar seeing just like here.
I think this is certainly an interesting debate and welcome others experience. Excellent guiding can be dictated by a lot of factors such as mount, stability of pier, flexure and settings as well as seeing. I am certain though I have good seeing here and that it is far better than two arc seconds on many nights. Feel free to comment guys.
