Barlow test

The most common problem with cheap glues is the actual crooked glue itself, which gives a traffic light output (transverse chromatism). The problem can be seen by both the (artificial) star and the displaced Newton rings. The ring test is faster and should be done this way: take a green laser pointer with a diffuser (matte plastic or a couple of cloths) and by tilting the pointer, find the position where the rings are visible. It is advisable to do this in a dark room because the rings are quite faint. Normal barlow will have the rings in the center. On the left the normal, on the right the curved glue:

However, you can try to use the latter as an ADC by turning it to a position where it reduces atmospheric dispersion.

Simply weather station on Arduino

Simply weather station on Arduino + BME280 + OLED. Graphs of temperature, pressure and humidity.

The latest version of the sketch is — using the u8g2 library, which supports many displays. In particular: SSD1306, SH1106, HX1230. The library is installed through the arduino environment, Sketch->Connect Library->Manage Libraries. The bme280 library is installed from the same place - a variant from Tyler Glenn.

The assembly is elementary - since the display and the sensor work via I2C, just connect the SDA pins to pin A4 of the arduino, SCK (SCL) to A5, Vin to the 3.3V supply and Gnd to ground.