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Very easy

Easy to use and stars are focused from test shoots to final capture.

Overall it’s a good quality tool. Because of the small apertures you are working with, use a very bright star so you can see the spikes. Also, get some step up/down rings so you can thread it to your lens, otherwise you are holding it in one hand, focusing with the other.

Tried out Focus Star Filter from MSM and its certainly a Filter to carry in your camera bag , Once you attach Filter too your Lens its certainly easy to focus with, once you align the star with the cross hatch, focus is completed , Well with the price.

Ordered the Bahtinov mask package for my astrophotography and the different size masks and adapters to accommodate various lens size is very convenient. No need to buy separate masks. Just by 1 and get the adaptor package and you’ll be seeing stars in no time —in focus too. Lol

It’s Pretty work well in Good Sky Condition with No Dust in the air and Twingkle Skars. Just like Introductions.
However, If you use “Slower” Lens over F2.8 You barely find stars with this Filter and Hard to judge it’s Focused. And Wider Lens is more difficult to use this Filter to find stars.
So If you use Wide Lens with Slow Apature in heavy Light pollution (and with more filters!), borrow it from your neighbor and test it works before Click order.

I had been struggling to get good focus with my camera lenses, the Bahtinov mask for my telescopes wasn't working as the plastic was too thick. This filter works with each lens I've tried it with on including 15-35mm, 24-105mm, and 70-210mm. It's a little tricky with the wide angle if your camera doesn't magnify enough but mine does and I get perfect focus every time.

I like the Easy Focus filter a lot, however because it is a screw in filter I have had to apply gaffer's tape to the focus ring to ensure focus doesn't move when removing the filter. If the ring was magnetic and the filter attached to it, there would be less chance of knocking focu off during removal.

After a number of attempts at 3D printing my own filter, the filter purchased from MSM should have been my first choice in the first place! The filter and reducing adapter to fit my prime lens works perfectly - the fringes are easy to see, thus making adjustments to focus equally easy.