Is there any monospaced font with Greek where the diacritics are distinctly legible around 10 points? I'm now using DejaVu Sans Mono, but to be sure, especially about spiritus, I have to increase the font size.
I tested a few out. The spiritus in DejaVu Sans Moto looks actually fine to me at 12 pt, the older standard font size.
I wonder if it's a platform issue rather than a font issue?
Either way, some other monospace fonts I found that had legible Greek diacritics:
These are all screenshots I took on my computer. For showcasing the letters, I used LibreOffice on Fedora Linux at 12pt font size. At ten point, you're going to have a hard time with any font. Still, I could make them out clearly at about 1 foot away. The only other real options are to make the font bigger or get closer. If you're on a phone, I believe most have a magnifying glass app that can help read it.
On optical size
I’ll add this as an answer, as it might be helpful in guiding your future searches for good fonts. For recommendations, I do not have anything to offer which has not already been mentioned by @C.M.Weimer. However, this is an issue which may be solved more easily with some typographical insight.
What you should look for, is a font with more than one optical size. Many – if not most – fonts found online, are designed from only one optical size, then resized by the computer to whichever font size is necessary. This is unfortunate, and does not reflect what typecasters learned over the centuries of font development since Gutenberg – and, to wit, before him as well in all the illuminated volumes.
It is quite common for a good typeface to be delivered in for example 8 pt and 12 pt optical sizes. Take a look at the below example:
The upper font sample is in what in Germanic countries are known as Cicero size: 12 point size; it is based on a font size cast at 12 points, and is a good choice for text which is meant to be body text. The lower sample is cast at the so-called Petit size: 8 points. This means it is a good font size for example for foot notes. Notice how it is wider, has a slightly modified shape, and appears to be quite bold; in fact it is not. Rather, it is meant to be displayed at a smaller size, and to appear to have the same font weight as the 12‑point size, it has to be wider and fatter to appear to be of the same weight. Here are a couple of letters stacked on top of each other; red is 8‑point and black is 12‑point optical size:
Both text samples are rendered at the same size, but the 8‑point optical size has slightly wider serifs, slightly wider downstrokes, and in this case is in fact a bit shorter. Here is an example of two pages side by side, the left where all text is rendered in 12‑point optical size, the right with footnotes rendered in 8‑point optical size, whilst the body text is rendered in 12‑point optical size.
Notice how the footnotes on the left-hand side appear to be more slender and how their weight appears obviously lighter than the body text; this is because it is the wrong font weight for that text size. On the right hand size, the footnotes appear to be more or less of the same level of ‘blackness’ on the page as the body text; this is because it is rendered in the 8‑point optical size, which is designed for text that small.
What you need to look for to find a font which has good legibility at lower size, is a font which is specified to include more than one optical size. Good fonts will have at least two optical sizes, usually one for footnotes (which would be roughly the size you are looking for) and one for body text. Excellent fonts will include an optical size for headings as well, but heading fonts can often be supplied as a separate font file.
I hope this will make it easier for you to find what you are looking for. Should there be any more information which may be of help, please let me know in the comments.
A possible solution that I'm employing while learning myself as well as teaching others is to stop using the smooth breathing at all.
EDIT: Hey there;) So to respond to your questions in comments:
I don't know of any materials that would use this convention so far, but I plan to change that. Personally I know a few people, that have adopted it, and I wasn't even the first. One of the teachers at AVN (with very good mastery of AG) uses it, likewise I also met some academic from Britain doing the same (can't give the specifics, as I think I should ask for permission first, since they don't publish on their own so far, and so it is not a widely known fact).
Just as you assumed, Joonas, smooth breathing is recognized by the absence of a breathing mark. Since that with utmost probability it wasn't pronounced in any way, there's no point in preserving it, and if it proves otherwise sometime in the future - we can adopt.
I've used the convention in all the materials I'm preparing for my students, and the main reason is that I noticed on quite a large scale (100+ people), that it at most confuses students, if anything, especially at the beginning, when there are more important aspects of the language and its alphabet to draw their attention.
As for the technique - for every text, that I have available in editable format I just apply a few letter swaps before proceeding to read it or use it in class.