MnAstro Forums

This reminds me of another cartoon I saw about 25 years ago. A young couple in a convertible are parked at a vista overlooking a large city in the valley below. The young woman looks up and exclaims, “OH WOW! The sky is sooo clear tonight! There must be dozens of stars out.”

It is not quantitative, but you can use a CD disc as a low quality diffraction grating to visually see the spectrum produced by a light source. LED’s usually produce monochromatic light (i.e. a single color). White LED’s either employ multiple smaller LED’s to get the components of white or else a s...

I too wish it was standard, not daylight saving, that was being made permanent. Regarding Dick's progressive adjustment, there is an added complication for anyone who needs to make international calls. As an example, the lab I used to work in had a sister lab in Sweden. When making calls to our Swed...

If you saw the movie the The Gods Must Be crazy you have seen with your own eyes the accuracy of this. After spending most of the movie trying unsuccessfully to find the edge of the world, the bushman Xi was beginning to think maybe the edge did not exist and then suddenly there it was! And when you...

I eventually found that 90+ % of my viewing was done with just two eyepieces that yielded 44X and 127X magnification (an Orion 2” Q70 and a Nagler 1.25” respectively). Using a barlow lens for the remaining few % is not too onerous. I echo Merle’s advice to consider paying the blackmail up front for ...

You might also click on Quick Links in the upper left of the forum screen and do a search of past posts using terms like dew, heater, etc. I found putting a shower cap over the base of my Dob helps delay fogging of the primary mirror by preventing ground level air from getting through the gap betwee...

A circle 300 meters wide (984 feet) has an area of 760,852 square feet. This is approximately equal to the flight decks of 3 aircraft carriers or the total exterior area of one of the old Twin Towers (before 9/11). That is quite some area to tilt. It would have to be very massively constructed to no...

I had to agree with the two people who said it looked like Santa's sleigh. That was my first impression as well. However, I think the cluster of helium balloons explanation is more likely.

(The link shows a video clip taken with a Hα telescope of something transiting the sun.)

I went to the real estate site zillow.com and looked for homes in Eden Prairie that are about $1.5M. The house in the article is at 10618 Sonoma Ridge. It even shows the exact same photo as in the Star Trib article. I looked at Google Earth. That street is at the top of a hill, but looking at the st...

Sky & Telescope magazine netted 166 hits.

Occasionally the parks have nocturnal visitors worse than party seekers. Thankfully the police patrols help keep the drug dealers, et al. from frequenting the parks more than they already do. The only time I was ever stopped was in Virginia. I had just finished observing in a wild life area and was ...

The main dish is 1000 feet in diameter. 100 feet is only 10% of that. It is a hard to tell for sure from this photo, but it looks like the missing section is a lot more than 10% of the diameter.

The Wikipedia article has a lengthy section on funding concerns over the last 20 years. I wonder how much this affected inspections and maintenance? It will also no doubt affect decisions about repairs.
https://en.wikipedia.org/wiki/Arecibo_Observatory

If I am envisioning your request correctly I think what you want is basically an armillary sphere or rather an armillary hemisphere. Check out the Wikipedia article on Armillary Sphere and then go over the Wikimedia Commons and check out pictures of armillary spheres and let me know if that gives yo...

I went to Amazon.com and typed in Planetarium. There were many desktop projectors. About 5 screens in there was one called Sayok Portable Inflatable Planetarium Projection Dome Tent for School with Air Blower and PVC Floor Mat It was about the size of a 2 person dome tent, but at $1400 is probably t...

A worked example on eyepiece usage. My first telescope was a Dob with a 10 inch (254 mm) diameter mirror. The focal length of the mirror was 45 inches (1143 mm), so the f ratio was 4.5. I found I could do most of my viewing with just 3 eyepieces a. 9 mm Nagler (apparent field of view 82°, fits into ...

What is the best scope depends in part on what you want to look at. Viewing the moon and planets generally does not require much light gathering capability, so you could go with a smaller diameter scope. If you want to view faint objects (e.g. most galaxies) you want as big a mirror as possible. The...

Does the light have a light sensor to automatically switch it off during the day? If so, it is probably on top. If it were on the bottom it would probably sense the light and shut itself off. You might rig up a can with a LED light inside and use a pole or a drone to set it over the sensor to fool i...

The NASA tool has a distance scale. I looked at a moderately small crater in one of the mare. It was almost the size of Lake Mille Lacs (≈ 16 miles x 12 miles). For comparison, the Barringer crater in Arizona is only about 4,000 feet on diameter and it is estimated that the meteor that created it im...

Knowledge of contingency plans may have been one factor, but I still think they were a brave bunch of guys. We have all seen old films of our post-World War II rocketry program in which rocket after rocket corkscrewed around until crashing or simply exploded on the launch pad. That was not that long...

Interesting. Other links: https://en.wikipedia.org/wiki/Hemolithin http://astrobiology.com/2020/02/hemolithin-a-meteoritic-protein-containing-iron-and-lithium.html The link you sent says “The hemolithin protein found by the researchers was a small one, and was made up mostly of glycine, and amino ac...

The article said the design is patented, so I visited the U.S. Patent & Trademark Office website (www.uspto.gov). Unfortunately when I typed in the names in the article I did not get any hits that sounded specifically like a telescope. Tom Milster is listed as the inventor in several patents rel...

Regarding mining the moon for basic building materials, our current needs would only affect a tiny part of the lunar surface. For example, the Stanford Torus (a 1 mile diameter space station proposed by NASA back in 1975) would weigh about 10,000,000 tons (including radiation shielding). This could ...

The basic idea is that average distance includes both nearest and farthest distances and all points inbetween. I can see where that might yield a closer average for Mercury than for Venus. Having said that, the graphics in the Youtube video should be taken with a grain of salt. In the middle of the ...

Note that I said light and heat. Heat could encompass both rapid changes due to elevated temperature or slow changes at room temperature, such as in a dark drawer. Another possibility are pH changes. Many triphenyl methane dyes can be used as pH indicators (materials that change color with changes i...