Unlike the photography industry, the astronomy industry doesn't necessarily have a standard for tripod mounts per se and most adapters are custom-made. In other words, the "tripod" and "head" are typically sold as a matched pair (and may have some proprietary way of attaching) but often the telescope mount itself (what a photography might think of as the "head") will have either an industry standard mounting saddle (there are two... the Vixen style and the Losmandy style) or a completely proprietary mounting method (low-priced telescopes sold as a complete kit often use a completely proprietary mounting method but more expensive mounts tend to use one of the industry standards because they realize those astronomers will mix & match equipment to fit their needs).

While your tripod isn't using any industry standard ... it should still be relatively easy and inexpensive to adapt this for photographic use. This is because in the photography industry, there is a standard. Photographic camera heads nearly always use a 3/8" threaded mounting hold with 16 threads per inch (commonly abbreviated as 3/8"-16 ... or 3/8"-16tpi). This means you can attach nearly any photographic camera head to nearly any photographic tripod as long as they use that particular thread size. So to make this work... you just need a way to use a 3/8"-16 threaded rod with your tripod.

1. Measure the hole on the tripod and make sure it can accommodate a 3/8" threaded rod (likely it can).

2. Select the photographic tripod head of your choice and verify that it has a 3/8"-16 mounting hole in the base.

3. You will then need a 3/8"-16 threaded rod to go into the base of your tripod head and then put the other end of the rod through that hole on the tripod. Measure the length you need and it's ok if it's a bit long. Just make sure it isn't a bit short. McMaster-Carr is a popular online website for ordering all sorts of threaded parts and in whatever material or length you need (and I would probably select stainless). See: https://www.mcmaster.com/threaded-rods/stainless-steel-threaded-rods/

4. Lastly, you'll need a knob with a 3/8"-16 threaded hole... like this one: https://www.woodcraft.com/products/knob-five-star-with-through-hole-3-8-16-insert (I did a web-search for 3/8"-16 knob and this was just one of many examples that came up in the search results). You should also use a washer (between the knob and tripod). Since this knob allows the threaded rod to pass completely through the knob to the other side... being "too long" wont be a problem.

And that should do it!