Acts 1:10, part 1; a periphrastic verb and another genitive absolute

καὶ ὡς ἀτενίζοντες ἦσαν εἰς τὸν οὐρανὸν πορευομένου αὐτοῦ, καὶ ἰδοὺ ἄνδρες δύο παρειστήκεισαν αὐτοῖς ἐν ἐσθήσεσι λευκαῖς

There are three actors in this verse:  (1) 'they' (the apostles, from previous context), (2) 'he' (Jesus, from previous context), and (3) 'two men'.  The last are newcomers on the scene.

We'll look at each of these, starting with the apostles.  What are they doing?

καὶ ὡς ἀτενίζοντες ἦσαν 

Ἀτενίζοντες is the masculine plural nominative, present active participle, of ἀτενίζω, 'I look intently, gaze'.  So the apostles were looking somewhere, or at something.

But we immediately run into another verb form : ἦσαν, the 3-P, imperfect indicative of εἰμί.  

This combination of a present participle and an imperfect form of εἰμί is a periphrastic verb form, or periphrasis.  It corresponds nicely with English usage ('they were gazing'), so should not cause too much confusion.

I've written about periphrasis at a bit more length previously: see it here. 

Now what is Jesus doing?

The basic action is expressed by a genitive absolute:  

πορευομένου αὐτοῦ  -  '(while) he was going'  

Πορευομένου is the masculine singular genitive, present middle/passive (deponent) participle of πορεύομαι, 'I go', 'I travel', 'I depart'.  As a singular form, along with αὐτοῦ, it cannot refer to the apostles.

Going where?

There is a slight ambiguity here, at least in grammar.  The prepositional phrase is

εἰς τὸν οὐρανὸν

which means 'to / into the sky', but is it attached to the apostles' action, or to Jesus's?  In other words, are they looking up into the sky while Jesus goes . . . somewhere?  Or does he go up into the sky while the apostles are looking . . . somewhere?  

The clear sense seems to be that the prepositional phrase refers to both actions: they are watching the sky as Jesus goes up into the sky.

Almost all English translations that I have seen attach 'into heaven' more firmly to the gazing of the apostles, although the New Living Translation begins

As they strained to see him rising into heaven . . . 

In the next post, two men show up.