The trouble with DHDs

I've typed about this topic on several occasions and had been considering making an outright post about it, but the recent post about the observation of the unique point of origin symbol on the DHD in season two's *The Gamekeeper* prompted me to finally get around to it.

This is going to take a little while, but from what we see in the show, the DHD is fundamentally flawed in the way it's depicted.

First, keep in mind that a Stargate has 39 symbols on its wheel.

* Of these, 38 are constellations, which represent the points in space that define the 3D bounding box containing a destination. These are used for the first six symbols in an address. Note that in the original movie, the Stargate on Abydos had different constellations to represent points in space as seen from that vantage point in the universe, but in the TV franchise, the constellations as seen from Earth are a galactic standard. * The 39th symbol is a point of origin, which is implied to be unique to a particular Stargate. In practice, the off-world Stargate prop has the Earth sun-over-pyramid point of origin on it because it is a static duplicate of the SGC prop. [We even see it in season three's *New Ground.*](https://www.gateworld.net/gallery/displayimage.php?pid=170040&fullsize=1)

In contrast, a DHD has 38 keys on its keypad. With the above in mind, it makes sense to think that the 38 keys would all be constellations, meaning that a user presses six keys and then presses the red dome to enter the seventh symbol and activate the Stargate. However, that's *not* what we see; actors press seven keys and *then* press the red dome. Since the show almost never made unique point of origin symbols for the DHD keypad (*The Gamekeeper* has [one of only four unique point of origin symbols seen in the whole show](https://www.gian-cursio.net/2020/12/abydos-glyphs/)), the seventh symbol that characters press is almost always a constellation, and I think this has led to the recurring misconception that there should 'only' be 38 Stargates in the galaxy because some people think that each symbol is a point of origin for a Stargate.

It gets worse. Bafflingly, one of the symbols on the DHD keypad is Earth's point of origin (you can see it [in the outer ring just above the 9 o'clock position](https://www.gateworld.net/wiki/File:Dialhomedevice.jpg)), meaning that a constellation (Aquila, if anyone was wondering) is missing and any addresses with Aquila in them can't be dialled. Since Earth isn't a constellation, there are no addresses that use it, making its presence on the keypad odd. If a point of origin symbol (that is supposed to be unique, remember) is on the keypad as well, that means that only 36 of the 38 constellations are on the keypad.

I have no idea what happened here, and I can't help but wonder if there was some kind of miscommunication between the art department and the producers.