Few words about me:From very childhood I loved computers, electronics, lasers, sulfuric acid and liquid nitrogen. I always wanted to be making microchips, UAVs and see nuclear explosion.
Now I am doing software engineering and in the spare time - some microelectronics and physics/chemistry experiments.
I live and work in Russia, Moscow.
ZnSe lenses for CO2 laser: plano-convex vs convexo-concaveSome time ago I've bought CO2 laser engraver from China. It had lots of issues, including bad lens, which supplier had to replace. I've chosen 102mm replacement lens that time. A month ago I noticed that price of 20mm ZnSe lenses on ebay dropped to 15$, so I ordered more suitable lens for my engraver with 51mm focal length. When it arrived I was pleased with quality of edges and coating, but was surprised to see that it is an convexo-concave lens instead of usual plano-convex type.
On the left - first bad lens, on the right - replacement sent by supplier and in the middle - this new one.
Is there any practical difference between plano-convex and convexo-concave lenses for CO2 laser focusing? Also, which way one should mount it? Let's try to figure it out...
Bitcoin conquers real worldRecently I was buying beamsplitters on ebay via Shipito - mail forwarding company in US. I noticed that they now accept payments in bitcoin and decided to try it out. It worked flawlessly, and due to lower bitcoin transaction fees comparing to Paypal/Visa I even got +4.3% extra. Needless to say that this operation was completely legal and all taxes will be paid by Shipito.
This is how bitcoin silently conquers real world. My package was received, sorted, stored, repackaged and sent oversees - all paid by bitcoin. At this stage government is no longer able to stop bitcoin economy - any attempt to do so will lead to all real-world-related operations being pushed overseas, as well as taxes for such operations.
445nm laser diode Nichia NDB7875So much time without new lasers... I had to stop this! Just received Nichia NDB7875 - 445nm laser diode with nominal power of 1.6W:
Through the window one can see laser itself and static discharge protection device (it looks like small cube):
Giant sunspot group on the SunI've though that last time I've seen big sunspot... But today there was just enormous sunspot group, largest since 1990, it's about 128'000 km wide.
Another step to the future - 4G/LTE in MoscowAll major mobile operators in Moscow already got their LTE frequencies in 800 and 2600Mhz bands, and already operating. Year ago I used Yota (they had the first operational LTE-Advanced network in the world) for temporary internet access, and now Beeline decided to put some real stress on the network and offered unmetered and free traffic on LTE till 15th of Jaunary. Ofcourse it was very hard to resist this, given that my phone already supported LTE. The only thing I needed to do was to update SIM card to a 4G-ready one.
Speeds appeared to be a big step forward compared to 3G and (especially) 2G. Apparently, there are still not many LTE-capable clients.
Worst case speeds are 20 mbit/sec (center of the city, in the building).
2 hour after enabling LTE - cable internet provider "2COM" decided to make "feeling of the future" even more palpable - they were cold-calling and promoting their new infrastructure where each client is getting 1 Gbit/s Ethernet cable, with maximum available Internet speeds of 500 Mbit/s (symmetrical, unmetered)... Unfortunately they had my old address, and in my current building they still had no equipment, so I will have to continue suffering with mere 100 Mbit/s Internet... I guess outstanding Internet access is probably one of the best perks of living in Moscow.
Finally some nice spots on the Sun to observe
Largest spot is greater than Earth...
UNIS tbm de Luxe typewriterDuring my childhood in the village I was learning to type on a typewriter. It was some electrical typewriter, "Yatran" if I recall it correctly.
Recently I accidentally got mechanical Yugoslavian UNIS "tbm de Luxe" typewriter in a leather case - it seems they were very popular in USSR back in 1960-80's.
It is quite hard to type on it as it requires to hit keys with much higher force.
So blind 10-finger typing is impossible without lots of extra physical exercises :-)
Also scored 3 last typewriter ribbons from local e-shop. These were made in Belarus in 2013. It's surprising that typewriter ribbon is still in production (BTW manufacturer guarantee that it is good for only 2 years since manufacturing). Probably typewriters are still in use in some government agencies (due to secrecy?)
On this photo it is still with old ink tape:
Sun photographyToday I bought Baader AstroSolar filter for sun observation - it reduces brightness by a factor of 100'000 (OD5).
The following photo was made by Sony 500mm/F8 lens and A77ii - my first semi-transparent mirror camera: finally I can observe the sun without fear of retina burn if something happens with the filter.
Exposure which allows to see the spots is 1/800 at ISO100/F8, without filter it would require exposure of 1/80'000'000 seconds - which is unrealistic. Full 14-bit resolution is needed to see the spots without excessive noise. In the future it might be beneficial to normalize sun brightness variation across the area - this should help with the spots close to the edges.
Sun is currently near maximum of it's activity - but on this photo we can only observe 3 tiny spots, that's abnormally low. During maximum activity total number of spots could reach 250 - this should be more spectacular.
I remember first time when I tried to observe sun ~7 years ago with 50mm/30x spyglass and floppy disk "filter". I made a fatal mistake then: i placed "filter" on the eyepiece side, and obviously sun immediately burned through it as soon as I found the sun. Luckily, it didn't get retina burn that time.
Flying Flight Design CTLSThis weekend I was flying on Flight Design CTLS. This is fully composite 2-seat small airplane, empty weight is just 326kg. This airplane costs about 200k euro, 1 hour of rental in the air club is ~200$. According to our approximate calculations it eats about 7 liters of gasoline (AI-95) per 100km of flight, some actually use it to travel across Russia.
On the video takeoff is at 3:45 , I am in control at 8:45 and landing at 11:45.
Among others flying same day my impression was the most neutral, apparently I am not going to be adrenaline addict. That was extremely interesting, but that's it. My interest was completely fulfilled.
I finally figured out that ailerons are much more useful than rudder. With ailerons you utilize maximum aerodynamic quality of the wings when changing direction of flight, while with rudder only fuselage is working, so you have aerodynamic quality of only 2-3 - this means you are loosing much more energy for the same rotation. It always felt unnatural that RC airplanes tend to use rudders for rotation, not ailerons.