I've just fitted it to my 569 unit for indoors.
My frame lens is my normal prescription as the +0.5 doesn't work for me (I did have a lens made up to try it). The good thing with the 530 is that you can dial in the +0.5 if you need it. I can get the best image I've ever had. I would add that most of my focusing problems seem to be due to the light levels at our 25yd indoor range and the fact I'm shooting at the end of the day. I don't seem to need the 530 unit for my 50m sights as the light levels are better outside.
I don't believe astigmatism changes with hydration etc. The one thing I would say is that with the 570-579 you'll need to check the unit is set up to match any cant angle you have in the rifle and your head. If the unit doesn't align with your eye correctly it could make matters worse (if you've dialled it into your persciption rather than working it out in position). Glasses always keep the lens aligned to you eye. Indoors I also use the green filter for the best contrast.
Sorry to complicate your situation.
No, you're not complicating my situation! I'm here to learn!
You say your frame lens is your "normal prescription"... I'm guessing that is is NOT a progressive prescription (which is sort of like bifocals, with a gradual change from near to far as I understand it). My prescription is progressive, and that is really bad for shooting, from everything I've read. And my own lousy scores seem to bear that out.
I am a little confused though about what you are using... Earlier you talked about a 50300, and now you mention 530. Those are two different beasts, aren't they? I'd actually ordered a 530 iris but returned it without even trying it because my optician told me that with my astigmatism it would absolutely positively NOT work for me. Which is why I ordered the 579 (which does correct for that) plus the 570 with +/- 4.5 diopter correction. I don't have it yet but I have already looked at the manual that comes with it, and setting it up is quite a task. There's even a special target (not shooting target but visual target) that you need to use to fine-tune all the adjustments once you have it in the ballpark according to your prescription. Thank you for pointing out how important it is to get it right (including cant angle, etc.).
The 569 iris looks like it's a great one! Especially with the colors and nd filters. I don't see the size specifications but at least from photos in the Gehmann catalog it looks not much different in size than the 570-579 combo. That is, if you are using the 50300 you mentioned earlier plus the 569.
You sound like you really know this stuff. One of my disadvantages (of many!) is that I have to order this stuff sight-unseen mail order, and also the few 10-meter rifle shooters at my club all seem to have perfect vision and don't wear glasses. At least I have a 10-day return possibility if it really doesn't work for me.