Tom Reichner wrote in post #18817754.
Only 840mm focal length - wow! .
That surprises me.
So now I am thinking that if you got this detail at 840mm, I should be able to get something very close with my 800mm lens at the same relative exposure values. .
Would this be correct?
Before someone butts in and says, "try it yourself"
, please realize that it will be cloudy where I am for the rest of the day today and almost all day tomorrow. .
So I can't try it myself for at least 26 hours, and I don't want to wait 26 hours to know whether this will work or not. .
I wanna know right now..
So, it's not the focal length that matters, it's the aperture that matters. Focal length merely influences imaging scale. Apertures defines resolution with the limit being the seeing. That said, a small aperture (40~60mm) will easily resolve detail on our local star because it occupies 1 degree in the FOV. It's so big. So magnifying it just a little bit, with a little aperture, you can see the small patches of spicules and other features.
A small camera lens can produce this. It has, again, nothing to do with focal length. It has everything to do with (1) the filter being used (ultra narrowband), (2) aperture (defining resolution of what detail you can accomplish), (3) seeing (quality of air turbulence).
You can easily do this with a small camera lens. But you have to filter it down to 656.28nm wavelength to see what I'm producing here. And to that extent, you have to go sub-angstrom (1 angstrom = 0.1nm). This is ultra narrowband. A larger aperture of a lens/scope/etc/ will then resolve more detail (Dawe's limit). From there, focal length merely influences imaging scale and sampling (relate this to focal-ratio and pixel size in micro-meters, this is how you sample resolution appropriately).
So yes, you can totally do it with your instruments. You just need appropriate filtration to eliminate all the light except a single wavelength down to the sub-angstrom level.
The above image was done at 840mm focal length, 60mm aperture (producing F14 focal-ratio). My IMX174 sensor has pixels that are 5.86um in size. Ideally I should sample around F29, but I severely under-sampled at F14 so I lost detail. But, it was the only way I could get a full disc image in the FOV with my setup.
My larger system has a native focal length of 8400mm at F42. That's what produced the larger imaging scale image of the details on the surface. But the detail did not come from resolution, it came from the 200mm aperture (8 inche opening into the OTA).
Unfortunately terrestrial photography gear has the misnomer that aperture is the f-stop number, but it's not. Aperture is the diameter of the opening into the imaging train. Focal-ratio is the f-stop number as a relationship of aperture size to focal length. It gets confusing for terrestrial photography. All that matters in the optical train for resolution is aperture. Focal-ratio just defines imaging scale.