Even more than the dates, it is well known that the Greeks (and many other cultures) were P.I.E. civilizations (Proto-Indo-European), even if only compared based on linguistics the relationship is undeniable, so in the area of astronomy and the comparisons made, the Indians already influenced the Greeks before they ever came to be a group in the first place due to their origins being in the land now called India, but that seems to be discounted in the astronomy statement or at least considered insignificant. On that I disagree personally. Linguistics are known to be very influential on all cultures as they're part of the basis upon which most else is laid within a culture group, regardless of time period. Linguistic influences have fingers that reach into nearly every other aspect of a culture. Just my opinion, but an important one.
The 'Great Thread of History' is woven between the Ganges and the Mediterranean, the Silk Road. Along it has passed back and forth most of the great knowledge and development of the world. The linguistics you reference are a testament to this. Once people start writing, everyone begins influencing everyone else. At times it is coming from India, at times Mesopotamia, at times the Mediterranean, and from further out; many things spreading and mixing. There is no discounting anyone, nor is anything insignificant. It is not a zero sum game. Some people wrote stuff down, others didn't. It is more about trying to follow the weave and understanding the pattern.
I see no issue with the idea that the Greeks were influence by the Indians -- just as I see no issue with the idea that the there was a 'golden age' of Greek/Hellenistic astronomy, were they wrote many things down, making references to Egypt and Babylon; and then a little later a golden age of Indian astronomy where they wrote many things down and made some references to the Greeks; and then a little later a golden age of Arabic-Islamic astronomy where they wrote even more stuff down, making references to both Indian and Greece; culminating into the Renaissance where still more stuff was written down, referencing all manner of things. As it stands this is the thread of astronomy that has woven the debate of geocentrism/heliocentrism, among numerous other things.
The problem with source texts are that there are no ancient ones . Copies of copies .
Certainly the further back you go the more rare "source texts" become. Almost all of "history" is copies of copies. The lost works of Aristarchus are in many ways no different than rumors of some lost papyrii of Ancient Egypt, hidden scrolls of Babylon, some temple hidden in the Jungle, the monks of Tibet -- whatever supposed wisdom from any lost civilization. History is always some part myth, because myth is part of making culture. And in studying the surviving works of history there is always the assumption of mistranslations, copy errors, agendas, etc. "Trustworthy" or not, we have what we have.
The point is that there are no trustworthy sources for ancient astronomy .
I do not agree with this, mainly because I don't know what "trustworthy" is supposed to mean. What is the criteria? It is not that some lost person/work/etc. contained the "truth" -- it's that things get referenced to a point that it at least seems "true" somebody, somewhere was doing something. It's not about "trusting" in Aristarchus or his myth. It doesn't matter if he even existed.
Should one discount or reject works on the premise that they merely reference things no longer extant? Should Ptolemy and all his writing be tossed out because he spends a paragraph saying "this guy Hipparchus did some neat stuff, but I'm gonna do this other neat stuff"?
In the case of Aristarchus, nothing, heliocentrism or otherwise, is predicated on him and nothing is "proved" by his lost works. He is merely someone who other ancients (Archimedes, Plutarch, Strabo, etc) reference as being an astronomer and having made an argument for heliocentrism. Some agreed, many didn't. The ideas have long been debated.
My opinion is that the heliocentric model was written into history retrospectively - by the Jesuits probably.
Of this I am not convinced. Certainly the Jesuits were/are very devious and have long been up to no good. But I'm not sure where they are "writing in" heliocentrism or what "good" that would do. They surely don't seem to be hiding the fact that most of the old writings are geocentric...
I would genuinely like to know which sources you use which formed your views on ancient astronomy
As far as sources go, there are a great many. Astronomy has been one of the most recorded and written about things in history, the world over. It goes back to agriculture; calendars, math, physics, navigation, etc all come out of astronomy. It hard to talk about the history of Astronomy without talking about the history of Math. Many things have been lost, and many more remain untranslated. An understanding of Latin and Greek greatly helps, as would Arabic and Sanskrit. It would help if you could be a little more specific. But I shall offer a few suggestions here and link a few things.
There are the ancient star charts and astronomical tables of the
Babylonians and
Egyptians, their comments on their calendars and the seasons. Ideas on architecture. One can find many things. The Greeks mention getting many things from them, but don't give specifics.
In terms of the Ancient Greeks, astronomy was integrated into their mathematical and geometric studies, as well as the cosmology of the Philosophers. As such many of the famed works of Euclid, Archimedes, Plato, Aristotle, Hesiod, etc. all contain thoughts and ideas on the subject. Of great interest is Apollonius' work on
Conic Sections. Otherwise, yes, many works of Hipparchus, Aristarchus, Posidonus, Meneleaus, etc are "lost". But still they are referenced by others, not because they were "correct" or "true", just as people who did or said certain things interesting to certain areas of study.
There is of course the very famous Ptolemy, the great geocentrist. His works
Almagest and
Planisphaerium (among others) are both of great interest, and have long been studied across the world.
In term of India, their astronomy flourished around 5th century. There is the famous
Aryabhatiya or the
Pañcasiddhāntikā. You also have the very old
Vedanga Jyotisha. Many more.
In terms of the Arabs/Muslims, who for a some time (primarily 9th-12th centuries) did a great deal of work in the astronomy tradition (
anwa). Their works are numerous, bringing together the traditions of Mesopotamia, Greece, and India. They also did much work with the
astrolabe.
One can find a general overview here.
Then of course there are the later works of
Copernicus and
Kepler; Brahe, Galileo, Bruno, Dee, Leibniz, Newton, etc. There are the works of
Portuguese,
Spanish,
English, etc navigators. One can go in so many directions.
So on and so forth. The subject goes very deep. As I have said, it has been long studied, so there are a great many things to look through.