TheSkySearchers

Attached is another sketch of Jupiter. On the 18th the seeing was not really good, but that funny chain and two festoons were , together with the transit of IO once again reason to make a little sketch.

Initially, the seeing left much to be desired. Magnification dropped along to 100X. Because you do have a sharp image at that magnification, but miss the finer details ( that chain and the festoons, for example) a bit, I ended up taking 150X. This not only made the image darker and a bit less contrasty ( it's like self-flagellation) but I also had to wait longer for quiet moments to catch details ( chain link counting).

The first sketch I left for a few days, I didn't think it was that special either. The image of Jupiter-disc sketched here is from more than 15 minutes before the transit. Later I thought it would be a nice idea to include the observed transit of IO. As a result, the picture is actually incorrect, since at the time of the beginning of the transit the orb had already turned a little further.... Fortunately, as a sketcher you can ignore that when it comes to a nice enjoyable picture.

While observing, I switched the location of the barlow a few times: before and after the Atmospheric Dispersion Corrector. With an ADC corrector, the smallest possible f-number is actually necessary (f/21), so first the barlow and then the ADC. But this turned out to be too high a magnification in combination with the Leica ASPH zoom. So I reduced it a bit: first the ADC and then the barlow. As a result the light cone will be f/7.5 for the ADC, but f/15 for the eyepiece. According to the manual, the ADC then works less well; this is barely visually perceptible. With a camera you will probably be punished.

Enjoy!
John

superb sketch , thx .

Great sketch John. I assume Io is the tiny bulge/speck on the left hand side of the planet?

helicon wrote: ↑Fri Oct 21, 2022 2:56 pm Great sketch John. I assume Io is the tiny bulge/speck on the left hand side of the planet?

Thanks, yes it is.

Great sketch John! I have not seen details like these in years due to bad seeing.

Bigzmey wrote: ↑Fri Oct 21, 2022 5:51 pm Great sketch John! I have not seen details like these in years due to bad seeing.

Thank you.
In that case, I think your SV102 with BBHS diagonal,combined with the XWs and Delites are best suited to beat seeing. As a refractor the SV is the least sensitive to seeing, colorfast images and a lens diameter large enough for details.

I must honestly say that the ADC goes a long way. Without ADC those red and blue images fluttering over each other, with ADC they are neatly laid on top of each other, also makes a huge difference in the calmness and contrast of the image.
A sketch is actually a sum of short good seeing moments. When I have finished all the details of a sketch, sometimes I am surprised by the overall picture too.