I had a student ask me about doing devotional practice at the Solstices and Equinoxes. This is important, as I understand it, in Wiccan and Neo-pagan practice. (Please forgive my lack of knowledge!)
The equinoxes and solstices are significant in traditional astrology because they show how our tropical Zodiac is aligned to the seasons.
The Sun goes into Aries a the Spring Equinox, the Sun goes into Cancer at the Summer Solstice, the Sun goes into Libra at the Autumnal Equinox and the Sun goes into Capricorn at the Winter Solstice. These are the moveable or cardinal signs, and their meaning, showing change and movement, comes from their seasonal attribution.
This orientation to the seasons is one of the key attributes of the Tropical Zodiac
With our heating and cooling, cars and artificial lighting, we are very insulated from the seasons. My wife tells the story of how, when she was young, she had to daily feed and take care of her horse by walking several miles to the pasture. This was tough in the Midwestern Winter and she really noticed when Spring came. We can fool ourselves with our technology only for so long, however, as we are utterly dependent on the natural world and its cycles.
As far as a devotional celestial practice, however, I have a couple of comments. First, we are basically reverse engineering Picatrix Bk III chapter 7 and other sections of Picatrix and sources, which are written to be used for astrological magic, back to their earlier use as celestial devotional ritual. A lot of information is unavailable to us and some practices, like animal sacrifice, we do not wish to emulate. So we have some broad guidance, and lots of individual methods, but a great deal of possible devotional practices we could revamp or even invent (really discover!) Certainly, there is no reason why we could not do devotional practice using the solstices and equinoxes.
Ok, so what would those practices be? Basically, from an astrological standpoint, we are looking at Solar devotions. While Agrippa, for example, identifies spirits of the signs, Three Books of Occult Philosophy, Bk III, ch 24, and there can be no doubt that there are spirits for all celestial factors, planets, fixed stars, Mansions of the Moon, decans, etc., as between the planets and the signs, it really is the planets that are significantly more prominent and more active. Still, my sense after thinking and writing about this is that one would definitely invoke the Sun and likely also the spirit of the sign. I also am getting a sense that there is a spirit for each of the solstices and equinoxes, though who and what these spirits are, and how to invoke them, I do not know.
A key part of astrological magic and celestial devotion is appropriate astrological timing, and clearly the appropriate time for a solstice/equinox ritual is immediately when the Sun enters the appropriate sign. So, when the Sun enters Aries, for example, we would invoke the Sun and the spirit of Aries, Malchidael according to Agrippa.
As and perhaps more cautiously, if this strand of spirituality develops, guided by our illustrious predecessors and the celestial spirits, the practice of celestial devotions will organically grow and develop.