u/SillyEngineer

I'm a solar chicken. I'm reluctant to look through a telescope pointed at the Sun regardless of how well the filter is fixed to the FRONT of the telescope. However, I wanted to share this super fun solar reflector that is not only cheap, but it magnifies. It needs a small piece of mirror and a ball. A billiard ball works great.

Materials:

1. Small chunk of mirror (ideally with the reflective layer on the FRONT)
2. Double-sided tape
3. A billiard ball
4. A roll of electrical tape or PVC coupler to act as a seat

Summary:
The reflection of the Sun off the mirror focuses a nice large image of the Sun on a dark wall in your garage or shed.

Tips:

1. Tape the mirror to the ball. Set it in the seat, approximately 30 feet away from the garage wall. Aim it at the dark wall in your garage or shed.
2. You can use a larger mirror (brighter image) if you have 80 to 100 feet to work with. Otherwise, mask off a 3/8" by 3/8" section of mirror with tape.

During the 2024 total eclipse, I built three and aimed them all at the same paper (photos included here).

Here's a tutorial video that shows you all the steps:
https://youtu.be/WwLBqhds2F0

If you have an older telescope, especially one from before the 1990's, check whether it came with small threaded filters that screw directly into the eyepiece. They often came with two of them. One was marked MOON and the other was marked SUN. The Moon one works great to reduce the glare of a full Moon.

It's the SUN filters that are so dangerous. These are the Lawn Darts of the astronomy hobby, if the Lawn Darts had sharpened hypodermic needles at the front.

The original concept was this: Your telescope captures the sunlight and focuses it on the dark SUN filter that is screwed into the eyepiece at the back of the telescope. You place your delicate eye up to the eyepiece, only a few inches from the searingly hot SUN filter.

As long as the glass didn't crack, you were fine. Unfortunately... they cracked a lot. Like, a whole lot. Sometimes they even shattered. This would instantly expose your retina to the full blinding light of a 3 or 4 inch magnifying glass, instantly causing solar retinopathy and likely blindness.

If you have one of these SUN filters, it is recommended that you smash & trash them so that nobody can ever accidently try them out.

I tested an old threaded solar filter while recording it with a camera. It reached 326 degrees Fahrenheit and in less than 12 seconds after installation, the filter cracked from the heat buildup and suddenly allowed bright sunlight through.

If curious, the recorded demonstration is at the start of this video: https://youtu.be/rtyLH5fBaJE

Safe Alternatives:

1. Solar Eclipse Glasses (by themselves, NOT in combination with telescopes, binoculars, or cameras).
2. Front-mounted solar filters specifically designed for your telescope. These stop 99.999% of the light energy before it even has a chance to enter your telescope.

Summary:
Solar filters for telescopes should go on the front of the telescope, before the sunlight is concentrated. Never put a solar filter at the eyepiece end. If you have one of these old threaded SUN filters, smash it & trash it.

Have a safe and exciting solar eclipse experience!

Why YSK: There's a surprisingly large number of dangerous threaded SUN filters littered throughout the basements and closets of the world.

If you have an older telescope, especially one from before the 1990's, check whether it came with small threaded filters that screw directly into the eyepiece. They often came with two of them. One was marked MOON and the other was marked SUN. The Moon one works great to reduce the glare of a full Moon.

It's the SUN filters that are so dangerous. These are the Lawn Darts of the astronomy hobby, if the Lawn Darts had sharpened hypodermic needles at the front.

The original concept was this: Your telescope captures the sunlight and focuses it on the dark SUN filter that is screwed into the eyepiece at the back of the telescope. You place your delicate eye up to the eyepiece, only a few inches from the searingly hot SUN filter.

As long as the glass didn't crack, you were fine. Unfortunately... they cracked a lot. Like, a whole lot. Sometimes they even shattered. This would instantly expose your retina to the full blinding light of a 3 or 4 inch magnifying glass, instantly causing solar retinopathy and likely blindness.

If you have one of these SUN filters, it is recommended that you smash & trash them so that nobody can ever accidently try them out.

I tested an old threaded solar filter while recording it with a camera. It reached 326 degrees Fahrenheit and in less than 12 seconds after installation, the filter cracked from the heat buildup and suddenly allowed bright sunlight through.

*** If curious, the demonstration is at the start of this video: https://youtu.be/rtyLH5fBaJE

Safe Alternatives:

1. Solar Eclipse Glasses (by themselves, NOT in combination with telescopes, binoculars, or cameras).
2. Front-mounted solar filters specifically designed for your telescope. These stop 99.999% of the light energy before it even has a chance to enter your telescope.

Summary:
Solar filters for telescopes should go on the front of the telescope, before the sunlight is concentrated. Never put a solar filter at the eyepiece end. If you have one of these old threaded SUN filters, smash & trash it.

Have a safe and exciting solar eclipse experience!

I bought a few pairs of eclipse glasses over the years. One was clearly defective (it let through way too much light).

That made me wonder: would a defective pair still block UV light?

I assumed the answer was probably no, but I decided to try a simple experiment.

Ingredients:

1. Good eclipse glasses
2. Suspect/Defective eclipse glasses
3. UV-sensitive color changing beads

Method:

1. I used three small plastic cups and filled them each with color-changing UV sensitive beads.
2. I wrapped the outside with metal tape to block light from the outside.
3. I covered two of them with solar eclipse glasses.
4. I exposed them to direct sunlight for several minutes.

Results:
Surprisingly, the UV beads didn't show any color change through either pair of glasses.

This suggests that my defective pair was still blocking the UV that these beads respond to, even though it failed the visible light test.

The experiment (and my bizarrely edited video) is captured here:
https://youtu.be/NearkopsWh4

Counterfeit and incorrectly manufactured eclipse glasses have been a recurring problem before major eclipses.

In 2024, I bought a pair of eclipse glasses that looked legitimate, but when I tried them indoors I realized something was wrong: I could see ordinary objects like ceiling fans and other details through them. That sent me down a rabbit hole learning how these filters are supposed to work, and how the ISO 12312-2 standard came about.

Three quick checks:

1. Look for markings indicating compliance with ISO 12312-2. This is not a guarantee of safety, but it's a good first sign.
2. Try them indoors first. You should not be able to see normal objects or room details through properly rated eclipse glasses. Check out some light bulb tests in action here: https://youtu.be/Q8aYrD32aAM
3. Check the manufacturer. The American Astronomical Society maintains a list of reputable eclipse glasses suppliers.

After I made a demonstration video (link above) about these tips in 2024, the ISO Project Leader for the standard found it and left a comment saying it presented one of the easiest ways for people to check their eclipse glasses. That was very kind of him, and I was grateful for the feedback.

References/Sources:

• American Astronomical Society - Solar Eclipse Eye Safety / Reputable Suppliers: https://eclipse.aas.org/eye-safety/viewers-filters
• NASA - Eclipse Eye Safety: https://science.nasa.gov/eclipses/safety/

Why YSK: Because counterfeit and incorrectly manufactured eclipse glasses have been a recurring problem before major eclipses.

In 2024, I bought a pair of eclipse glasses that looked legitimate, but when I tried them indoors I realized something was wrong: I could see ordinary objects like ceiling fans and other details through them. That sent me down a rabbit hole learning how these filters are supposed to work, and how the ISO 12312-2 standard came about.

Three quick checks:

1. Look for markings indicating compliance with ISO 12312-2. This is not a guarantee of safety, but it's a good first sign.
2. Try them indoors first (the light bulb test). You should not be able to see normal objects or room details through properly rated eclipse glasses. Seeing the filament of a very bright light bulb can be normal. Check out some light bulb tests in action here: https://youtu.be/Q8aYrD32aAM
3. Check the manufacturer. The American Astronomical Society maintains a list of reputable eclipse glasses suppliers.

After I made a demonstration video (link above) about these tips in 2024, the ISO Project Leader for the standard found it and left a comment saying it presented one of the easiest ways for people to check their eclipse glasses. That was very kind of him, and I was grateful for the feedback.

Sources/Citations:

• American Astronomical Society - Solar Eclipse Eye Safety / Reputable Suppliers: https://eclipse.aas.org/eye-safety/viewers-filters
• NASA - Eclipse Eye Safety: https://science.nasa.gov/eclipses/safety/

As the August 12 total solar eclipse approaches, I wanted to share a story. In 2024 I bought a set of solar eclipse glasses and found that the Sun looked way too bright for comfort. By chance I tried them on inside, and I could see light bulbs, ceiling fans, etc. I was pretty sure that wasn't supposed to happen.

That sent me down a rabbit hole researching how to tell whether the eclipse glasses were safe or not. I found three simple checks that anyone can do:

1) Check the markings: Legit eclipse glasses should have printed information indicating compliance with the ISO 12312-2 standard. This is not a guarantee, but it shows they did their homework.

2) Try them indoors first: You should not be able to see ordinary objects or details in the room through properly rated eclipse glasses. It's normal to see the filament from a bright incandescent bulb or a really bright LED light. Check out some light bulb tests in action here: https://youtu.be/Q8aYrD32aAM

3) Check the manufacturer: The American Astronomical Society keeps a list of vetted solar eclipse glasses makers.

After I made a demonstration video (linked above) about these tips in 2024, the ISO Project Leader for the standard found it and left a comment saying it presented one of the easiest ways for people to check their eclipse glasses. That was very kind of him, and I was grateful for the feedback.

As the August 12 total solar eclipse heats up, I have a story. In 2024 I bought a set of solar eclipse glasses and found that the Sun looked way too bright. So I tried them on inside, and I could see light bulbs, ceiling fans, etc. I learned that some manufacturers were likely selling defective units, so I did a deep dive to come up with three ways to check your solar eclipse glasses. They are as follows:

1. Real eclipse glasses should have printed text that says they are compliant with ISO 12312-2.
2. Inside your home, you shouldn't be able to see any light fixtures aside from the small filament.
3. Your manufacturer should be listed on the AAS dot org website under the list of approved manufacturers.

If you'd like to see more demonstrations of how much light should be let through, here's a compressed summary video:
https://youtu.be/Q8aYrD32aAM

The image from wide field-of-view eyepieces is pretty spectacular. I compared a group of 20mm eyepieces (same magnification) and tried to capture them with my smartphone camera. You can see the limited disk size of the Huygens and Plossl. The Explore Scientific 100 degree was wall-to-wall, so much so that the camera couldn't capture the actual edges. The myth about it being a "port hole view" is true. This is true in even milder fov's like the 82 degree eyepieces, but the 100 degree units are really cool.

Some highlights:

1. The wide-angle eyepieces work great in 8 inch Dobsonians.
2. If your focal ratio is less than f6, you start to see the "coma effect" and need to start considering using a coma corrector.
3. Using a Barlow doesn't impact the apparent field-of-view (that I could tell)
4. The "port hole effect" is real.

If you'd like to see the more in-depth review, here is the link: https://youtu.be/GxNcIblrY3w

I've used the AstroHopper smartphone app for finding sky objects for a while now. I've recently found the simplest solution for mounting it to the telescope is just to set it on top of your Telrad (it's flat). It requires it to be centrally mounted on the telescope tube, but this works great. If you're worried about it falling off, just rubber band it to the Telrad body.

I got a great deal on a used 8 inch Dobsonian. The only downside was serious water damage, all the missing parts, and a mirror that looked like something evil happened on it. This gross telescope sat in a very nice townhouse living room for years (according to the seller). At some point in time, a bird expired in it, leaving residue (see photos). I thought the mirror was trashed, which is the most expensive part of a telescope. The outside of the telescope had some type of moist purple goo on it when I bought it, but it eventually dried clear.

This little fixit project ballooned into a major restoration project. So I ended up doing the following:

1. A professional slow cleaning of the mirror.

2. Fabricated an entire new lower disk for the mount (and learned that contact cement will melt vinyl shelf paper).

3. Installed a new eyepiece holder and re-purposed two used eyepieces.

4. Installed a new viewfinder.

5. De-rusted the bolts and painted over with black epoxy paint.

6. I added handles and a smartphone platform since new hobbyists use their phones to guide telescopes these days.

The entire project spanned a couple of months, but probably took about 25 hours total. For anybody who is morbidly curious, I compressed this entire project into a video: https://youtu.be/X8C1ZFAqI1I

The mirror cleaned up really well and this telescope works like a dream now.

I restore wrecked telescopes as a hobby. This gross example sat in the sellers townhouse for years before I picked it up. At least that's what he told me. A bird of some type had crawled in and passed away on the large telescope mirror, leaving bad residue behind. I thought the mirror was trashed, which is the most expensive part of a telescope. The outside of the telescope had some type of moist purple goo on it when I bought it, but it eventually dried clear.

It was missing a lot of parts and the mount had a lot of water damage. So I ended up doing the following:

1. A professional slow cleaning of the mirror.
2. Fabricated an entire new lower disk for the mount (and learned that contact cement will melt vinyl shelf paper).
3. Installed a new eyepiece holder and repurposed two used eyepieces.
4. Installed a new viewfinder
5. Painted the corrosion over with flat black.
6. I added handles and a smartphone platform since new hobbyists use their phones to guide telescopes these days.

The entire project spanned a couple of months, but probably took about 25 hours total, including repairs research. For anybody who is morbidly curious, I compressed this entire project into a video: https://youtu.be/X8C1ZFAqI1I