Cheapest priced copy (Innistrad: Double Feature): $0.35 at Card Kingdom, near mint, their price list as of .
Obsessive Astronomer 
Creature — Human Wizard · 2/2 · Uncommon · Innistrad: Double Feature · #152
If it's neither day nor night, it becomes day as this creature enters.
Whenever day becomes night or night becomes day, discard up to two cards, then draw that many cards.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 152 | Uncommon | $0.35 | $0.49 |
| Innistrad: Midnight Hunt | 152 | Uncommon | $0.35 | $0.49 |
6 rulings from Wizards of the Coast
- 24 September 2021Before a player untaps their permanents during the untap step, the game checks to see if the day/night designation should change.
- 24 September 2021Day and night are designations that the game itself can have. The game starts as neither. Once the game becomes day (or less commonly, night), the game will be exactly one of them—day or night—going back and forth for the rest of the game.
- 24 September 2021If it is day, and the active player of the previous turn cast no spells during their turn, it becomes night.
- 24 September 2021You may choose to discard no cards when the Obsessive Astronomer's triggered ability resolves.
- 24 September 2021If a triggered ability triggers whenever day becomes night or night becomes day, it only triggers if it was already either day/night and becomes the other. It does not trigger when the game becomes day or night for the first time.
- 24 September 2021If it is night, and the active player of the previous turn cast two or more spells during their turn, it becomes day.