You are correct that "objectid" in nsc_dr1.meas corresponds to "id" in nsc_dr1.object. Both are string types (made necessary by the chosen format of the identifier), so you have to make sure to compare strings. For instance, this query:
result=qc.query("SELECT id,ra,dec from nsc_dr1.object LIMIT 10")
print(convert(result))
returns:
id ra dec
0 188514.24591 318.350687 -66.606197
1 188514.48667 318.350906 -66.606002
2 188514.24758 318.350792 -66.606248
3 188514.46029 318.351096 -66.605730
4 188514.19996 318.352374 -66.606638
5 188514.15704 318.348066 -66.600734
6 188514.25380 318.349318 -66.602292
7 188514.11898 318.350985 -66.599728
8 188514.15703 318.354688 -66.601013
9 188514.34215 318.356654 -66.601968
It does look, however, that id in nsc_dr1.object is indicated to be type char[1], I wonder if this is the cause of the problem. Will investigate.