【题目】我一直想掌握天文学方面的知识。

【答案】I've been trying to get the hang of the knowledge of astronomy.
【解析】try to do固定短语，“努力做，尽力做”；get the hang of固定短语，“掌握”；the knowledge of astronomy“天文学方面的知识”，根据句意，句子是现在完成进行时，因此答案为I've been trying to get the hang of the knowledge of astronomy.