If all will pardon the name drop, I'm listing my all-time most revered astronomy resource. It's not quite what is was 20 years ago, and I no longer look up much, but I've managed to get a smile from it with each visit. It's one of the few websites I still have an affection for.
At first I thought this was only a list of night time objects to view, but then I saw the site has an extensive tools section.
One of those tools is a Bahtinov Mask, which I’ve never heard of, but I’m going to 3d print one from this site and use it to try and focus my scope.