I heard several times that according to Jyotish, the moon is related to manas.
Which scripture talks about it? Did any scripture tell about the relation in detail?
Rig Veda 10.19.13. (Purusha Shuktam).:
"candramā manaso jātaś."
"The Moon was born from his (Veda Purusha's) mind."
As moon was born from the mind of the Veda Purusha, it represents the mind (Manas).
तमभ्यतपत्तस्याभितप्तस्य मुखं निरभिद्यत यथाऽण्डं मुखाद्वाग्वाचोऽग्निर्नासिके निरभिद्येतं नासिकाभ्यां प्राणः प्राणाद्वायुरक्षिणी निरभिद्येतमक्षीभ्यां चक्षुश्चक्षुष आदित्यः कर्णौ निरभिद्येतां कर्णाभ्यां श्रोत्रं श्रोत्रद्दिशस्त्वङ्निरभिद्यत त्वचो लोमानि लोमभ्य ओषधिवनस्पतयो हृदयं निरभिद्यत हृदयान्मनो मनसश्चन्द्रमा नाभिर्निरभिद्यत नाभ्या अपानोऽपानान्मृत्युः शिश्नं निरभिद्यत शिश्नाद्रेतो रेतस आपः ॥४॥
I:i:4.:-> He (Self/Atman) did penance with the resolution (of creation). From that austerity, an egg like mouth (face) was born. From the mouth (after parting/cracking) emerged speech (vāk); from speech came Fire. The nostrils parted; from the nostrils came out the sense of smell; from the sense of smell came Vayu (Air). The two eyes parted; from the eyes emerged the sense of sight; from the sense of sight came the Sun. The two ears parted; from the ears came the sense of hearing; from the sense of hearing came the Directions. The skin emerged; from the skin came out hair (i.e. the sense of touch associated with hair); from the sense of touch came the Herbs and Trees. The heart took shape; from the heart issued the internal organ (mind/manas); from the internal organ (manas) came the Moon. The navel parted; from the navel came out the organ of ejection; from the organ of ejection issued Death. The seat of the procreative organ parted; from that came the procreative organ; from the procreative organ came out Water.
ताभ्यः पुरुषमानयत्ता अब्रुवन् सुकृतं बतेति पुरुषो वाव सुकृतम् । ता अब्रवीद्यथायतनं प्रविशतेति ॥३॥
I-ii-3: For them He brought a man. They said "This one is well formed; man indeed is a creation of God Himself". To them He said, "Enter into your respective abodes".
अग्निर्वाग्भूत्वा मुखं प्राविशद्वायुः प्राणो भूत्वा नासिकेप्राविशदादित्यश्चक्षुर्भूत्वाऽक्षिणी प्राविशाद्दिशः श्रोत्रं भूत्वा कर्णौ प्राविशन्नोषधिवनस्पतयो लोमानि भूत्वा त्वचंप्राविशंश्चन्द्रमा मनो भूत्वा हृदयं प्राविशन्मृत्युरपानो भूत्वा नाभिं प्राविशदापोरेतो भूत्वा शिश्नं प्राविशन् ॥४॥
I-ii-4: Fire entered into the mouth taking the form of the organ of speech; Air entered into the nostrils assuming the form of the sense of smell; the Sun entered into the eyes as the sense of sight; the Directions entered into the ears by becoming the sense of hearing; the Herbs and Trees entered into the skin in the form of hair (i.e. the sense of touch); the Moon entered into the heart in the shape of the mind; Death entered into the navel in the form of Apana (i.e. the vital energy that presses down); Water entered into the limb of generation in the form of semen (i.e. the organ of procreation).
Brihad Arankyaka Upanishad.:
अथ मनोऽत्यवहत् तद्यदा मृत्युमत्यमुच्यत स चन्द्रमा अभवत् सोऽसौ चन्द्रः परेण मृत्युमतिक्रान्तो भात्य् एव ह वा एनमेषा देवता मृत्युमतिवहति य एवं वेद ॥ १६ ॥
I-iii-16: Then it (Prana) carried the mind. When the mind got rid of death, it became the moon. That moon, having transcended death, shines beyond its reach. So does this deity carry one who knows thus beyond death.
I hope this clarifies all your queries. Prd..