Two of the people have expressed skepticism about the sun dagger, its 'ritual' use, and the 'priests'. Such skepticism is much-too-often warranted with much of the archaeoastronomy reported in the press and on the internet. But not in this case. For the intentionality of sun daggers, we have the large number (~100) of sunbeam/spiral connections that all operate the same way and that all operate only at the solstices and equinoxes. Such a pointing at specific predefined declinations in the sky is essentially impossible by chance, and the only reasonable way to do this is by the knowing intention of the petroglyph makers. And we have many, detailed, and early ethnographic reports (some by eye witnesses even in the 1880s) of Sun Priests going out on both solstices to Sun Shrines performing what can only be called rituals of planting rows of feathers, making offerings (often of corn meal), and chanting prayers (usually for a good harvest). These are known for many Pueblo tribes, direct descendants of the people who made the Fajada Butte Sun Dagger, all with very conservative religious practices, while such Sun Priests are also known for most groups within California and surrounding areas, all with many sun daggers. So, yes, we do have strong evidence that the sun daggers are a part of Sun Shrines and used for what we should call 'rituals' by 'priests'. The perceived-necessity for the point of the wedge to touch the spiral center is just a modern ideal. But the reality for the many operational sun daggers is only that the wedge-shaped sunbeam touches close to the center spiral, sometimes with the base doing the touching, sometimes the wedge center, and so on. This is showing us what the old Southwestern cultures actually valued, as opposed to our modern guesses. For the Picture Rocks Sun Dagger, near the end of the video, you can see that the center of the spiral does pass inside the middle of the wedge. So all is fine.
Skepticism is a good tool, especially for archaeoastronomy, where the majority of the claims in the press and internet are for known wrong anachronisms. Quickly popping to mind for the US Southwest are the Chaco Canyon (Penasco Blanco) "Crab Supernova" pictogram (a proven sun-watching station, not a depiction of any supernova), the lunar standstill alignments at many places (including the Fajada Butte Sun Dagger), claimed 'Cross Quarter Day' alignments for a number of sun daggers, and various alignments at Casa Rinconada. Unfortunately, the field is popularly known mainly for certainly-wrong spectacular claims, while the real and fun results are mostly known only to researchers. For the case of sun daggers in general, with their initial discovery in 1979, the evidence was too weak to convince anyone other than popular writers. This all changed dramatically in 1996, at the V Oxford Conference (the big international quadrennial meeting for archaeoastronomy). All in one session, three groups of researchers got up one after another and showed their results from their three massive surveys of sun daggers, with little overlap, all throughout the Southwest. They reported large numbers of sun daggers, and all operating in the same way. They proved sun daggers to be *intentional* constructs, and they proved how the sun daggers operated, and they proved that sun daggers were universally used by cultures from the Baja to Colorado, and from northern California to central Texas, all for times c.500-1300 AD. I was skeptical of sun daggers going in to the Oxford Conference, but I was completely converted by the strong evidences to knowing that sun daggers are real, and I even said so in the published conference summary. Around about that time, many workers (notably Zeilik and McCluskey) collected the ethnographic evidence supporting the details of the usages as a Sun Shrine, and worked out the details of Hohokam and Ancestral Pueblo astronomies. All of this is given in great detail with citations in the paper linked by today's APOD. So, yes, skepticism is good, but for the case of sun daggers, we can be very confident that they are real, intentional, and operate as a wedge of sunbeam (with apex angle of 3°-40°) that somehow covers the center of spirals on either the solstices or equinoxes, and that these were used by people we would call 'priests' for 'rituals'.