This is not absolutely. But if there is, it is very useful. That all.
This is a must have for all who are using their telescopes to view the sun. You would think it easy to find the sun but it is a bit more difficult when you can't use your finder, Tel-rad, or laser pointer. Once you have this thing aligned it works every time.
I find this sun finder very easy to attach and use. This finder works great.
I put this on my Lunt scope and WHAT a BIG Differance !! I can spot the sun in just a few seconds ---easy to mount and Easy to use !!!