Project and Study Updates

I haven't posted here for a while, so here are a few updates on what I've been working on:

Stargazing and astronomy studies have been a big one. Details on that are pretty well covered by my Star Log gemlog.

I've also been studying Dr. Jason Lisle's interesting book "The Physics of Einstein: Black holes, time travel, distant starlight, E=mc²". I've been studing through the formulas given, working out some contrived examples with a calculator.

I've also been learning how to grow salt crystals, and most recently epsom salt crystals, with the help of an old book I checked out from the UAF library. I had a lot of difficulties in learning how prepare saturated solutions, and figuring out what growth procedures to use. But I did manage to grow a medium-sized solid crystal yesterday. I hope to post some photos tonight using a digital microscope I got for Christmas.

As far as electronics, I lost interest in projects I was working on, and so I hadn't been doing anything for a while. Recently though I had an idea to play around with vector graphics, using an old Tektronix 620 Monitor that a friend loaned to me. It is like an old phosophor oscilloscope, but one that only does XY mode, where you have to provide both signals. My working plan is to use two MCP4725 DACs, controlled by an Rpi Pico, to provide the XY signals, in order to draw vector gfx on the screen. During the lunch break today I was able to successfully set the voltage level on one of the DACs, so I think I'm making good progress. The MCP4725 is driven by commands over an I²C bus, and thankfully my last project was to put together a working I²C interface for Mecrisp Stellaris Forth, running on the Pico, which I had been using to drive the Trellis keypad.

My inspiration is to display a night sky projection on the Tektronix monitor, with graded levels of brightness for the different stars. Unfortunately the computer monitors commonly used today are incapable of producing various levels of brightness at any given point on the screen. Rather, they can only simulate brightness levels by using different shades of color/greyscale, or by drawing bright objects larger than dim ones. This is why Stellarium images don't look the same as the real night sky. Stars in the sky are all point sources, that is, they all look the same size, but they vary in brightness. (There is also some varying atmospheric glow effect around each star.) But Stellarium just draws them as large or small circles, since that is all the computer monitor can do. But with a vector display, like a phospher XY monitor, you can keep the beam steered on a particular point for as long as you want to get a desired brightness level.

The aircraft simulator at my workplace used to have a CRT-based graphics system, but it was replaced with a modern projector-based system. In the old system, the runway graphics were drawn in raster mode, but the runway lights were drawn in a separate vector cycle, and so the runway lights appeared very bright on the screen. It was a difficult system to maintain, but the glowing runway lights were pretty cool.