Month: December 2016

news

Clean dust off a panasonic lx100 camera

Post author By admin
Post date December 24, 2016

The LX 100 camera is great compact 4/3 sensor camera. But it is prone to dust on the sensor which is likely pulled in by suction as it telescopes out.

Taking the camera apart is a chore, but I’ve read someone using a vacuum to apply suction to the lens assembly to pull out dust. Didn’t think much about it, but when I got dust on my sensor after 6 months, well. Had to try.

I turned it on and off twice to get the dust semi-airborne I hoped. Then turned on my vacuum cleaner and using the extension hose, i held it on the front side of the lens assembly then turned the camera off, which collapses the assemble and hopefully exerts positive air pressure. I repeated this 5 times. Then checked the camera using a white background. Poof, dust on sensor gone! Boy, was I surprised. I wanted to make an adaptor out of cardboard between the camera lens and the vacuum, but it wasn’t needed.

Tags dust, lx100, sensor

Finally measuring Earth using trigonometry

Post author By admin
Post date December 22, 2016

Eratosthenes measured the world using shadows cast in two different cities at the same time. I’ve been wanting to replicate it for over decade. Today I did. 5 volunteers from San Diego to Nashville all have the same style of pencil of the same length. Everyone is to measure the shadow on it at noon CST. Today only 2 could do it. From the data, I have computed the following:

circumference_earth – 32744.22 miles
> real_circumference_earth<-24901 miles

Error: 0.3149762

So a rough, but useful first attempt. The R code I’m using is:

#computing circumference of earth

library(dplyr)
library(tidyr)
library(ggplot2)
library(animation)
library(readr)
setwd("~/Copy/R/climate change/")

real_circumference_earth<-24901
data<-as.data.frame(read_delim("earth shadow data.csv", ","))
data<-data[,-1]
pencil<- 19.0
avg_data<-(colMeans(data))
str(data)
avg_data
angle_mt<-180-90-atan(pencil/avg_data[1])/(2*pi/360)
angle_tc<-180-90-atan(pencil/avg_data[2])/(2*pi/360)
net_angle_tc<-angle_tc-angle_mt
angle_mt
angle_ratio_to_tc<-360/abs(net_angle_tc)
distance_trevor<-651.0
earth_circ_per_tc<-distance_trevor*angle_ratio_to_tc
earth_circ_per_tc
err_per_tc<-(earth_circ_per_tc-real_circumference_earth)/real_circumference_earth*100
err_per_tc

Tags Eratosthenes, measuring earth

musings

Why Eratosthenes got it wrong.

Post author By admin
Post date December 22, 2016

Yep, Erathosthenes, that greek scholar who invented the leap year and measured the earth’s circumference, all in 200BC from Alexandria. I have discovered he systemically was set up to have errors based on his assumptions.

He was off by about 15%, and today I figured out part of why he was wrong. The premise is Erathosthenes read in a book about a well in what is now the town of Aswan. He read this well cast no shadow on a particular day of the year. If you look at the image on wikipedia, it shows the suns rays directly overhead. This is impossible as Aswan is north of the Tropic of Capricorn by 50 miles. It would be approximate, but not truly directly overhead at solar noon on the summer solstice. The sun can only be directly over head in the band south of the Tropic of Cancer to the Tropic of Capricorn.

news

Harvested 8 Arctic Frost Oranges

Post author By admin
Post date December 10, 2016

My little orange tree at Schick that I bought at the nursery with unripe oranges this spring, finally ripened up and I harvested 8 oranges off of it. Possibly ripened by thanksgiving. Definitely ripe on Dec 8. Plan on making some cuttings to ensure the plant lives in case it dies this winter. The other tree, at my house didn’t have oranges this year. Dunno if that is a function of 3″ of soil on a rocky slope, or the youth of the plant. The Schick property has far better soil.