Chizuk Emunah (Pt 2) Under the Microscope: Chapter 64

Acts 7:43, "Yea, ye took the tabernacle of Moloch, and the star of your god Remphan, figures which ye made to worship them, and I will carry you away beyond Babylon." This quotation from the prophecy of Amos is incorrect. In chapter 5:26, 27, it is thus expressed: "But ye have borne the tabernacle of your Moloch, and Chiun your images, the star of your God, which ye made to yourselves. Therefore I will cause you to go into captivity beyond Damascus," etc. Quotations misapplied, or garbled, destroy the authenticity of a work instead of supporting it.

Let's take a look at the sources first:

But God turned away and gave them over to worship the host of heaven, as it is written in the book of the prophets: “‘Did you bring to me slain beasts and sacrifices, during the forty years in the wilderness, O house of Israel? You took up the tent of Moloch and the star of your god Rephan, the images that you made to worship; and I will send you into exile beyond Babylon.’ (Acts 7:42-43 ESV)

You shall take up Sikkuth your king, and Kiyyun your star-god—your images that you made for yourselves, and I will send you into exile beyond Damascus,” says the LORD, whose name is the God of hosts. (Amos 5:26-27 ESV)

Compare Acts in the Greek:
καὶ ἀνελάβετε τὴν σκηνὴν τοῦ Μολὸχ καὶ τὸ ἄστρον τοῦ θεοῦ ὑμῶν Ῥεμφὰν, τοὺς τύπους οὓς ἐποιήσατε προσκυνεῖν αὐτοῖς καὶ μετοικιῶ ὑμᾶς ἐπέκεινα Βαβυλῶνος

to Amos in the Septuagint:
καὶ ἀνελάβετε τὴν σκηνὴν τοῦ Μολοχ καὶ τὸ ἄστρον τοῦ θεοῦ ὑμῶν Ραιφαν τοὺς τύπους αὐτῶν οὓς ἐποιήσατε ἑαυτοῖς καὶ μετοικιῶ ὑμᾶς ἐπέκεινα Δαμασκο 

The first part of Stephen's quote is exact. The Septuagint renders it "and the star of your god Raiphan" rather than Chiun.  Stephen does take a creative liberty by stating that the exile took place beyond Babylon, rather than beyond Damascus, but this is hardly an error. The people of Judah were indeed exiled to Babylon, and even as far as Persia.

Remember that quotation marks are an artifact of the printing press, and that the line between direct quotation and paraphrasing was not as well-defined in antiquity as it is in modern times. Since Troki was a Karaite, he might complain that people paraphrase when they should be using direct quotation. The rabbis, however, paraphrased the text all the time, such as the "al tikri" passages in the Talmud. Quite often the rabbis would say "do not read it as this, but read it as that" and none of the rabbis complained about such a use of the text.