II infinitive inessive and instructive

[garoowood]

Istuin ikkunan ääressä katsellessani kuuta ja ajatellessani Kalevia.
Istuin ikkunan ääressä katsellen kuuta ja ajatellen Kalvevia.

Are they both correct? What is the difference if I express simultaneous actions.

[Upphew]

Istuin ikkunan ääressä katsellessani kuuta ja ajatellessani Kalevia.
Istuin ikkunan ääressä katsellen kuuta ja ajatellen Kalvevia.

Are they both correct? What is the difference if I express simultaneous actions.

Both are correct.

Istuin puhuessani puhelimeen
Istuin puhuen puhelimeen.

[garoowood]

So there is no difference at all and I can use either of them to express simultaneous actions(in case of one subject only)?

[Upphew]

Gnn, I have hard time making the distinction... Jukkaaaaa

What were you doing when you were talking to phone? Istuin puhuessani puhelimeen
How were you sitting? Istuin puhuen puhelimeen.

[Jukka Aho]

Istuin ikkunan ääressä katsellessani kuuta ja ajatellessani Kalevia.
Istuin ikkunan ääressä katsellen kuuta ja ajatellen Kalvevia.

Are they both correct? What is the difference if I express simultaneous actions.

Both are correct, except the latter one has the name “Kalevi” misspelled.

1. Istuin ikkunan ääressä katsellessani kuuta ja ajatellessani Kalevia.
   
   “I was sitting at the window as I were watching the Moon and [as I were] thinking about Kalevi.”, “I was [located] at the place X at the moment when I was doing these two things.” It seems you want to emphasize the first part of the sentence – in this case, the information about your exact location – in relation to what you were doing at the moment. It appears important to note you were at the window right at that moment when you were doing those two things, and not in someplace else.
2. Istuin ikkunan ääressä katsellen kuuta ja ajatellen Kalevia.
   
   “I was sitting at the window watching the Moon and thinking about Kalevi.”, “I was at the place X doing these two things.” Regular straightforward narrative. You’re just casually mentioning where you were but there’s no special emphasis to it.

[garoowood]

Can I also say:
Istuin ikkunan ääressä kastelemassa kuuta ja ajatelemassa Kalevia.?

[EP]

Can I also say:
Istuin ikkunan ääressä kastelemassa kuuta ja ajatelemassa Kalevia.?

Yes.

[Jukka Aho]

Istuin ikkunan ääressä kastelemassa kuuta ja ajatelemassa Kalevia.?

I wonder how that works...

[Rob A.]

Can I also say:
Istuin ikkunan ääressä kastelemassa kuuta ja ajatelemassa Kalevia.?

Hmmm...

" ....watering the moon..."...that brings up a certain mental image....

[garoowood]

My mistake...katselemassa