Question: In 2012, when the first incarnation of Astronomy SE closed, the community at Physics SE felt compelled to give a home to astronomy questions and overwhelmingly [voted](https://physics.meta.stackexchange.com/q/1197/75633) to expand the scope of the site.

Not long after, however, Astronomy SE [was "reopened"](https://physics.meta.stackexchange.com/a/5327/75633), and is still [alive](https://astronomy.stackexchange.com/) and well, even if still in beta.

A degree of overlap in scope between the two sites is completely unproblematic, of course, but I believe there are questions on the more technical side of astronomy that, when there is an SE especially [geared towards them](https://astronomy.meta.stackexchange.com/a/101), should be redirected there, to the benefit of both communities (and of the OP).

**Question**: Is it time to rethink that decision a bit, and make off topic here questions about technical astronomical topics such as observation and equipment?

Example: [What light pollution levels are required to see the Milky Way?](https://physics.stackexchange.com/q/594633/75633), which a couple of users felt didn't quite belong to Physics SE and voted to close - only to be reminded by [ACuriousMind](https://physics.stackexchange.com/users/50583) that, as it stands, the question is actually fully on topic.

I **propose** the answer is *Yes*, see my answer bellow for details.

Answer: 
Thank you for your thoughtful replies.

In view of the current (3) answers and comments let me spell out my suggestion and perhaps clarify a few points first:

1. Emilio Pisanty [already provided](https://physics.meta.stackexchange.com/a/13232/75633) an important clarification, namely that adding Astronomy SE as a migration option isn't possible as long as the site is in beta; this is unfortunate, as it'd be my preferred option, but let's consider it out of the table, since I don't see us swaying SE on this;
2. Making the whole of astronomy off topic is of course nonsense;
3. *Ban* is also too strong a word - if we decide to make observational astronomy off topic here, it will still be up to the voters to decide themselves, for each post individually, where it best belongs;
4. Some examples of questions I'd personally consider migrating to Astronomy:

	* [Primary focal length of a cassegrain telescope](https://physics.stackexchange.com/q/580554/75633)
	* [What light pollution levels are required to see the Milky Way?](https://physics.stackexchange.com/q/594633/75633)
	* [Definition of a planet](https://physics.stackexchange.com/q/589394/75633)
	* [Group of stars moving](https://physics.stackexchange.com/q/273765/75633)
	* [Need help buying binoculars online for astronomy (10x50)](https://physics.stackexchange.com/q/26145/75633)
	* [Is there a simple yet accurate formula for where on Earth the Sun and Moon are directly overhead?](https://physics.stackexchange.com/q/25396/75633)
	* [What is the distance to the closest star similar to our Sun?](https://physics.stackexchange.com/q/165486/75633)that is, posts asking for observation instructions, equipment advice, etc.

**My two-part suggestion**:

1. Make *amateur observational astronomy* off topic now$^\*$.
2. Add Astronomy SE as a migration option when it becomes possible to do so.

$^\*$ And flag moderators so that they can take care of migrating them. This shouldn't be a lot of extra work, since these questions don't really pop up all the time.
> 
> Is it time to rethink that decision a bit, and make off topic here questions about technical astronomical topics such as observation and equipment?
> 
> 
> 

I would like to see Astronomy SE added to the list of options to migrate a question to, but not to make questions like this completely off-topic here.

This allows the option to either "close" the question by moving it to Astronomy SE or to keep the question alive on Physics SE. This makes it easy to migrate the questions without needing to make a hard and fast rule about what is Astronomy SE and what is Physics SE territories.

I don't think having astronomy off-topic helps users. It will most likely arise with new users and having your question closed and being told to do it all over again on a different SE just puts off new users. Let's help them by helping ourselves easily vote to move questions to the best site.

I know in the past the argument is that this does not arise very often. OK, but it's not a huge change to implement and maybe it will be used more often if we do have the option.

I think we also need to consider that maybe sometimes answers from the Astronomy SE will be more specific and cover more than we do here. Also the rules on Astronomy SE are a little different - there is less of an issue with history related questions and homework closing is no an official reason to close on Astronomy SE. So maybe a question we won't deal with well here could fair better on Astronomy SE.

EDIT :

In view of Emilio Pisanty's very helpful post I would amend my preference to leaving the status quo. No off-topic bans for subsets of astronomy questions and we just suggest the user consider the Astronomy SE site as a better fit if we think that way.

I would still prefer we could migrate directly to Astronomy SE but as Emilio points out it is not possible as it's a beta site, we can only hope SE move it to full status and make the other option viable.