Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A must for ETX90 astronomers.

This finder, a standard on the ETX125, is a must for the ETX90 if one plans on using it for astronomy. The straight thru finder is fine for birding, or other terrestrial viewing, but is akwardly placed for most astronomical observing, especially near the zenith (overhead). The tiny screw used to hold the finder can be difficult to replace. Then again, it is still only a 25mm finder.