D&D 3E/3.5 Need help designing a prestige class for a 3.5 Spelljammer campaign

[Twichyboy]

Hello everyone! Recently in my campaign our minotaur barbarian has gotten bored with his character and is going to make a wizard, and he has been hassling me to keep my promise of making a "astronomer" prestige class

My problem is i have no idea what abilities it should have, it would probably only go 5 levels and have full spellcasting progression, but i dont know if the abilites should vary by sphere? or maybe apply to spelljamming ships in general,

So i would love to hear some suggestions for prestige class abilities, the setting is spelljammer converted to 3.5, but the spelljamming in general is in 2nd ED rules

 

[Shaghayegh]

Well, first off, there is no line between astronomy and astrology in pre-modern settings. They are one and the same. A Stargazer class would specialise in divination and have abilities related to analysing the future, but also be able analyze people based on their natal charts. If you know when someone is born, you can use astrology to understand their character and abilities. This would let you predict their actions by knowing their psychological makeup.

Knowing the influence of astrological forces would also let you understand the flow of magical energy better, so you can improve your spell casting. You can also plan actions for "auspicious times" to improve your chances of success by taking actions on days that a more suited to them astrologically.

Stars and planets are also important for navigation and the study of astrology is steeped in mathematics. A Stargazer would get bonuses on skill checks related to making any type of mathematical calculation, from cooking the books to determining the amount of arrows an army needs for a battle to determining how much an wall should weigh based on the type of stone it is made of or determining the distance between points on the globe. Sacred geometry is closely related to astrology, allowing architectural structures to be designed with spells built into them based on their inherant mathematical structure.

 

[Samloyal23]

With a successful knowledge (astrology) check against a person whose birthdate and birthplace you know, you gain a bonus equal to class level on Charisma and Wisdom based skills and all spells used against the subject due to your intimate knowledge of the target's personality and fate.