I'm using a C11 Edge, at F10 (2800mm FL) to a Canon Ra
Which I calculate to be about 100-120 px for the width of either J or S
I don't know that much about this, (yet) but it seems to me that higher magnification isn't going to increase resolution. The scope is only capable of so much (Dawes limit) But with more subs though should be a way to increase the rez. But what do I know?
Much to learn, and a wk or so before the moon comes up a little later so I can get back to my deep sky projects.
For tonight, I'm going to just see what kind of ISO and shutter speed work the best. If the seeing cooperates. The fastest I can image the traditional way (image, download, image dnld....), the only way I know how to do it at this point, will give me about 20-30 images per minute. And with the Ra, there's no shutter or mirror slap. So, hopefully ....
BackyardEOS supports LiveView capture on the Canon EOS Ra. LiveView capture is vastly superior to single frame capture. At 30 images per minute, you'll get just 90 frames before Jupiter's rotation smudges the image—but you need 1000-2000 images for a stack at a reasonable presentation size. Since the Airy disk defines the resolution limit of an aperture, I like to use pixels per Airy disk (ppAd) as a common image scale for different aperture sizes. I find my optimal presentation size to be 4-5 ppAd, depending on seeing. Like this:
Jupiter w/GRS 2020-07-30 11:14 UTC
Skywatcher 180 Mak, Fujiyama 12.5mm orthoscopic, shimmed
Canon 600D/T3i 5× Live View capture @ 9 fps
2×1024 stacks, scale = 4.1 ppAd
Feature resolution vice detection are two different things. While the resolution limit of an aperture may very well be the Dawes limit, the detection limit of an aperture is the Sparrow limit. And Nyquist is the minimum sampling rate to not lose information—these are 2.0, 2.4, and 2.6 ppAd for Rayleigh, Dawes, and Sparrow, respectively. But for DSLR images of Jupiter, Mars and Venus, I submit there is minimal benefit to skimping on spatial sampling. I regularly sample Jupiter at 8 ppAd—my limit is just keeping the scene (Jupiter plus moons) on the 5× sensor crop. And I do all my processing at 8 ppAd before downsampling. Here's a view of the various scales for reference, along with a comparison of scaling of each to a final output of 4 ppAd (zoom in and compare the Airy disks).
(Click for full size.)
For Saturn, I sample at 4 ppAd, which gives me the same lux on the sensor as Jupiter (so I use practically the same capture settings). But I find I need at least 2000 frames for a good result at 4 ppAd. Like this:
Saturn, Enceladus, Mimas, Tethys, Dione & Rhea, 2020-06-06 16:24 UTC
Skywatcher Mak 180, Fujiyama 18mm orthoscopic, shimmed
Canon 600D/T3i 5× Live View capture @ 8.2 fps
1×2048 frames, scale = 4.5 ppAd
I attach my 600D/T3i to my scope like this:
Rigid T-thread rings means zero clamp slip in a wind storm—capture conditions I encounter frequently in the outback. And orthoscopic (Abbe) eyepieces mean razor sharp images. But most planetary imagers use high quality barlows.
That is all.
P.S. My capture settings are 1/160sec at ISO12800, AWB. But LiveView is fixed at 30 fps, so in actuality the camera is shooting at 1/30sec at ISO2400.
Edited by BQ Octantis, 06 August 2020 - 03:44 AM.