Does Astrology Work?

[AnumeyJain]

Stars, constellations, planets, Sun and Moon are astronomical demigods yet they are only involved in their own lives & circling around the Meru mountain.

Since they do not affect our personal life then why do we see Tithi etc. before doing a good deed or embarking on a positive action?

[Sulabh]

@AnumeyJain

Stars, constellations, planets, Sun and Moon are astronomical demigods

They are themselves not demigods but are the residence of the demigods.

@Abhay

कर्म की अवस्था देखकर जीव के परिणामों का भी ज्ञान हो जाता है (coincidence),

कर्मो (अंतरंग निमित्त कारण) के साथ coincidence का नहीं अपितु नियम रूप संबंध है, a better comparison will be a mirror effect.
But the astrological factors are बहिरंग निमित्त कारण, so yes it will be a coincidence.

[jinesh]

जिसप्रकार हिरनादिक स्वयमेव गमनादिक करते हैं, और पुरूष के दायें-बायें आने पर सुख-दुःख होने के आगामी ज्ञान को कारण होते है, कुछ सुख-दुःख देने को समर्थ नहीं है; उसीप्रकार ग्रहादिक स्वयमेव गमनादिक करते है, और प्राणीके यथासम्भव योग को प्राप्त होने पर सुख-दुःख होने के आगामी ज्ञान को कारण होते हैं, कुछ सुख-दुःख देने को समर्थ नहीं है।

- मोक्षमार्गप्रकाशक, छठवाँ अधिकार, p. 173, (emphasis mine)

This clarifies that even though they are not directly affecting our personal life, they are seen as indicators / signs (ज्ञापक निमित्त) of anything good or bad that is about to happen.

To draw another analogy, a symptom might be a sign of a particular disease, however, that certainly does not mean that it is causing the disease.

@AnumeyJain

why do we see Tithi etc. before doing a good deed or embarking on a positive action?

Any deed or event will take place on some day, so it is better to choose a day which has more probability to make the event (like a panchkalyanak etc.) successful. Even if it turns out to be true (correspondence between the sign and the event), it nowhere leads to the conclusion that the stars etc. had a significant role (उपादान कारण) to play in the outcome of the given event, let alone an instrumental one (निमित्त कारण).

Such strange is the relation between निमित्त and नैमित्तिक that anyone can easily mistake it to be a real cause-effect relationship. Thus, assuming that movement of stars etc. will do something good / bad to me would be a case of मिथ्यात्व (false belief).

For a clarification on what the example in the above quote is about, pl read from this thread - मोक्षमार्गप्रकाशक में आये हुए एक उदाहरण से सम्बन्धित.