Well it got migrated anyway, so that's fine. However, I felt 2 points were worth raising:
1) Just because it's more on-topic on one site doesn't make it any less on-topic on another site necessarily. We had a question on travelling to see the eclipse, or another on travelling to see auroras. One might have gone to the astronomy.se site to raise it, or the travel one. And it would have been equally valid to ask either question on either SE site. (Well actually that wouldn't be for me to say - they're valid on here, and I suspect they'd be valid on the other SE site). We shouldn't move something just because it's more appropriate elsewhere if it's also appropriate here - think from the new user's point of view - if they asked the aurora question after signing up, then come back to find their question has been sent elsewhere, it gives the impression they've done something wrong, AND they have to make an account on the other SE site. Now if it's genuinely in the wrong place, sure, we'll move it, and please do flag it for us.
2) Migrating traffic to another SE site because they need traffic is NOT a valid reason to migrate it either. They'll grow if successful, and they won't if not. It took us a long time to increase our traffic and it required a lot of hard work making sure we had the right questions on here as well. Some SE sites were apparently 'too niche' - one I'm particularly disappointed about was Astronomy.SE - but it didn't get the input desired during its time in beta - which is why we have betas, and it was closed down. By all means ask questions and answer questions and contribute to all betas, but we shouldn't be farming questions out to them as it dilutes the pool of sites as well as what makes us distinct.