Focusing on the Sun

Hey.
I'm doing some practice photoing the sun to get ready for the eclipse. I can't seem to nail the focus though. Any tips or tricks? I have watched a bunch of youtube videos and read internet articles, but I'm clearly missing something.
I tried to manually focus on the rim of the sun. It was kinda difficult to see the screen because it was bright out.
Ultimately I will have 3 cameras setup, but I'm starting with this one.

Gear:
A7R4, SEL200600G, SEL20TC, Tripod, Mylar Filter

Settings:
Manual mode, Steadyshot on
600mm, No TC, ISO100, f6.3, 1/50
600mm, No TC, ISO800, f6.3, 1/200
1188mm, TC, ISO800, f13, 1/80

I've ordered Helios Filters to replace the mylar, they should arrive over the weekend.

Notes:
1. I did shoot the aperture wide open, if it is clear tomorrow I'm going to try reducing two stops to get closer to maximum clarity.
2. I'm going to use a towel over my head to allow me to see the screen better.
3. Images are cropped and converted to JPG.

Images:

Can't help you with your Sony ... The sun is at infinity - focusing ought to be the simplest part of the whole business.

The sun is very bright, it's an ideal object for autofocus system. Why would you need manual focus? Just put the spot autofocus rectangle on the rim of the sun. But I'm not familiar with the A7RIV autofocus system - does it not cope with this?

I would not recommend f/13 - the diffraction (Airy disk diameter) is four times your camera pixel pitch.

There is certainly convolution at play - could it be atmospheric?

In spite of @leitz's previous comment, the infinity setting on modern lenses should not be relied upon, I would suggest manual focus with magnified live view.

I didn't try the autofocus. From what I've read, you need to use manual focus. Apparently, it is common for autofocus systems to hunt when photographing the sun because other than the rim, there is very little contrast and at the rim there are so few pixels that makeup the edge, autofocus can't determine the focal length.

Though, I will give it a try, some of the newer Sony cameras seem to get close on a rim focus.

I was thinking I could take shots at f5.6 f8 and f11 @ 600mm and 1200mm and compare them to see if there is any difference.
I was using the focus zoom with manual focus. I'm wondering if there is a way to desensitize the manual focus ring since it is a digital control and not a mechanical one.

It could be atmospheric, but, since I'm the weakest link in this technology chain, I figure I did something wrong. I suppose repetition will tell.

Unfortunately, 'focus by wire' may not be what you need your for your work. One of my cameras has that and it's a bit clunky.

I suppose ...

Re-read my comment, you will find that I said nothing about relying on the lens' infinity setting. I use my focusing screens for their intended purpose.

The last time I shot the sun through an inexpensive flexible sun filter, my results looked about the same as those. Maybe more expensive filters make a difference.

OK.

[deleted]

@JS PhotoHobby

If camera on tripod, why Steadyshot is ON?

At such long focal lengths and slow shutter speeds (1200mm, 1/50) you can see the vibrations caused by a car passing or gusty wind against the tripod. I am going to try with steady shot off next time I can with a counter weight on the tripod.
But now it won't be until the end of next week cause UPS just decided they didn't want to deliver my filters today, they are just going to wait until tuesday next week.

Unless your camera's or lens' steadyshot is specifically designed to detect and counter tripod vibrations, it is better to be off on the tripod. I have a Sony FDR-AX700 camcorder and it is recommended in the manual that steadyshot to be OFF on the tripod.

Best image, v1 was cropped and converted to jpg. v2 was auto treated by lightroom.

Getting a lens with a distance dial in the ballpark is easy, but it doesn't take much to be out of focus (even at 93 million or 250 thousand miles) with a ~95mm entrance pupil! They may both appear to be in focus at the same time as if they were both painted on a wall, but they are both very easy to blur with even the slightest mis-focus.

AF will be very slow to acquire, and AF will keep going off and hunting again. If you get AF to work once, and then switch to manual, that might be useful, but to expect AF to help constantly would be a mistake, IMO. Nothing loses shots more than unconfident AF. Better to be slightly off with manual, than way off with auto.

It is GOOD to spread the Airy disk out larger, if the reason is a quality TC, as long as you aren't cropping away part of your composition!

If the lens by itself is sharpest at 600/6.3, then use 1200/13. If it is sharpest at 600/7.1, then use 1200/14. You need the sharpest pupil; not the least pixel-level diffraction.