Celestron – EclipSmart Safe Solar Eclipse Telescope and Camera Filter – Meets ISO 12312-2:2015(E) Standards – Works with Your Telescope, Spotting Scope, or DSLR Camera – Observe + Photograph Eclipses

I tested this filter out against a lot of other ones and while this one wasn't the best, it did have the virtue of being the most versatile. The ability to collapse or expand the opening to fit a lot of different telescope and camera lens sizes is very handy! And it has excellent design and construction for what is basically a paper-craft project with a bit of solar filter film super-glued to a bit of cardboard.The directions are a bit hard to follow because of the uneven drawing skills of whomever did the art, but once you have the idea, it's fairly easy to construct and get it into the proper configuration. The solar filter is obviously not H-alpha quality, so you won't see solar prominences, but I was able to make out sunspots without too much difficulty. The color balance of the filter is also fine, tinting the sun to the orange-red side of the spectrum, which reduces eye fatigue when keeping the sun under longer observation.This will work fine for the coming eclipse or for any other solar observation use!

I travelled to the US-Canada border with a few cameras and used this filter to capture the total eclipse on April 8, 2024. It's a square cardboard item, but the filter is professional grade, and I used it for two Nikon DSLRs and a Canon Pro HD video camera. Perfect results.

First, the filter works. However, the cardboard can accommodate up to 100mm outer-diameter lenses while the filter material itself is 60mm.I believe that while this makes no difference in terms of optical performance, it does present a challenge for those with lenses that are about 60mm or smaller. Bigger lenses will press against the cardboard at the back, but smaller lenses want to pierce the filter material. If you don't add a shim or press the filter against the lens, it will droop.One suggestion to Celestron: a total of 4 straps, one for every 90 degrees, should hug the lens under the rubber band, not just 2 that are 180 degrees apart. With 2, one degree of freedom is removed while the other is not constrained.Here's an analogy:While wearing sunglasses, try moving them side to side while someone presses against the parts that go behind your ears. This will pin them against your head (like the rubber band holding the strap). This movement won't be easy.Next, try raising them up and down while they are still pinned against your head behind your ears. This will be easier because they will pivot at the point at which they are pinned. If the glasses were also pinned to the top of your head and under your chin, then this too would not be as easy.Or, a shim of some kind could be included to center the lens.

I have an inexpensive (affordable, but not 'cheap') backpack telescope. I wanted something for it for sunspot gazing and this seems like a good option. Coming from Celestron, I'm confident in its design over unknown alternates. It comes in a flat pack, but is really easy to fold into shape and using the included straps to attach it to my scope. In use, it does block out a large amount of sunlight to make the sunspots viewable (I didn't have a camera attachment when I tried it, so I can't show it). Construction is basically heavier cardboard and coated paper filter and plastic velcro. Glass filters are more than 10x as expensive, so this option is good choice for me.NOTE: the instructions state this and I'll repeat it here: remove the spotting scope before pointing at the sun to avoid damaging it or anything behind it.

The description of the size is inaccurate and deceptive. It says will fit a 75 to 100 mm lens; that number describes the EXTERIOR diameter of the lens barrel over which the cardboard housing will fit. The actual solar filter is ONLY 60 mm diameter! I did not find this number in the item description.I tried the filter on a 70 - 300mm zoom DSLR lens. This lens has a glass aperture of 65mm and uses a 67mm filter. The filter worked just fine with this lens for solar photography. At 300mm, the image of the sun is only about 5mm on the sensor. I did not notice any vignetting.My primary lens for solar photography is a 1000mm, f/13 mirror reflector lens. I got some great images in 2017 of the eclipse, but had to be VERY careful as I had not properly prepared for solar filtering. I tried the Celestron EclipseSmart filter and actually got an image. However, it was obvious the filter blocked a significant area of the lens aperture; this darkened the image on an already slow lens by an unacceptable amount. A reflector lens has a large, flat glass in the front; in the center of the front is the secondary mirror that directs the light into the camera. On my lens, the front glass has an outer diameter of 85mm; the central, secondary mirror is 35mm. Normally, this leaves a ring opening of 25mm radius to admit light. (85/2 - 35/2 = 25mm). Using the 60mm Celestron filter leaves a ring aperture of only 12.5mm radius! (60/2 - 35/2 = 12.2mm). That is a reduction of 60.4% in aperture area (about one whole stop.)The filer comes packed flat and will be easy to take along, especially for the April 2024 eclipse. It has easy to use velcro to strap on the front of the lens barrel. I will keep this filter and use on my 300mm zoom. If you have a refractor telescope with a front glass up to about 65mm, this Celestron EclipseSmart filter should work fine. If have a large aperture reflector or Cassegrain telescope, I think you will be disappointed. I gave this only 3 stars not because of any fault of the design but because the description is incomplete and deceptive.

This isn't rocket science, it is a practical "tool" for solar eclipse viewing. It is marketed as a helpful appliance to view our sun daily. That is true. But I bought it for eclipses (or solar events) and it will work great.