Terrestrial photography with a telescope and DSLR

I setup my 8" Celstron Nexstar with f/6.3 focal reducer and Lumix GH1 to try out some "terrestrial" photography. I picked a public road in Redwood City, CA that has a good view and easy parking nearby. As far as I know this is a public sidewalk here.

Here is a shot with the GH1's stock lens at 14mm. The red squares indicate areas that I will image with the telescope.

Here's the stock lens zoomed all the way out to 140mm. This area is centered on the left red box in the first image.

This image was taken through the telescope and f/6.3 redcuer, so it is effectively 1260mm f/6.3.


This image was taken through the telescope at prime focus 2000mm f/10. Note that with the GH1 crop factor, the field of view here is comparable to 4000mm in standard 35mm SLR terms. Most of the blurriness is coming from air currents and haze. I will try again on a cool, overcast day, and I would expect better resolution. I am also eagerly awaiting my telescope remote-focus project to be completed. It's extremely difficult to achieve perfect focus while touching the telescope's focus knob, so it's possible this photo was taken slightly out of focus.



The distance is about 2.4 miles.



Here is a cluster of antenna across the Bay.

22 miles.

Here's another post of photos that I took many years ago with the same telescope and a Nikon 35mm film camera.
http://benkrasnow.blogspot.com/2009/09/telescope-magnification.html

I forgot that I even had an eyepiece projection adapter. I'll try it out next time, but I suspect the limiting factor will be air clarity not the telescope optics.

Web-controlled watering can and vortex tube

UPDATE: Code added at the bottom of this post.


This is an interactive art project that I have been building for an upcoming exhibition. The idea for a web-controlled watering can come from the first "iphone watering can" that I helped build with a friend for Maker Faire a couple years ago. Search the internet/youtube for "iphone watering can" for details.





This new version uses a different drive mechanism and a PD control loop to make the watering can track the desired position in realtime. The interface works with any webkit browser. My collaborator and I have discussed using the iphone or android accelerometers to achieve control through phone tilting. I'm not sure if the tilt data is available to the web browser, though, and we are trying to make the interface run on as many platforms as possible. Any ideas?

The siteplayer webserver is extremely old technology and has many problems, but does work. I would explore using a hacked WRT router in the future for similar projects.






HTML file from Siteplayer webserver:
http://www.magconcept.com/watering/can.htm.txt

SPI file from Siteplayer webserver (simply to establish a server response):
http://www.magconcept.com/watering/serial.spi

Arduino code to get serial data from webserver and effect the PID control loop
http://www.magconcept.com/watering/watering_can.pde

Youtube speed and partner program

I have a couple questions for anyone reading this:

1. Does ATT DSL suck? I live in the SF Bay Area, and the speed on youtube is often acceptible, but 720p sometimes has problems playing and even 480p sometimes has problems because of limited bandwidth. 1080p never works smoothly. I am fairly certain the the DSL link itself is not the problem because while a video is paused due to lack of data, I can go to other websites in other browser windows, or even run a DSL speed test and get decent speed. So, it seems that either youtube itself is slow, or ATT has a crappy connection to youtube servers, or is actively throttling bandwidth. Look at this (http://www.youtube.com/my_speed)

My ISP is AT&T, and I have 3 Mbit DSL. I am not sure why youtube doesn't have any view data for me personally. It might have something to do with firefox privacy settings or Adblock Plus. In any case, this looks really disappointing. It makes me want to sign up for Comcast. What are your thoughts?


2. Is the Youtube partner program (revenue sharing) worthwhile? After my last blog post ran on hackaday (attracting a couple thousand views to my video), youtube invited me to become a partner. At first I thought that I would definitely do it, but now I think I might pass. When I started to create an AdSense account, the signup page looked all messed up. At that point I realized Adblock Plus was preventing my browser from loading the css for the entire page. I think it would be a little hypocritical to force ads on other people, while I myself hate them with a passion. I am thinking the world has enough advertisements, and the amount of money that I could make from these videos is probably very small. Youtube will not disclose how much they pay, and after searching the net, I found that youtube partners are not allowed to tell other people how much they make or what the pricing structure is. How insecure is youtube that they don't want anyone to know how much money is to be made? If there were a lot to be made, surly they would want to advertise the fact?

Feel free to leave an anonymous comment.

Universal motor speed control by a microcontroller

I am showing a method of using a CdS photoresistor to control a standard triac dimmer circuit that is wired to an electric drill motor (a universal motor). The CdS photoresistor is driven by an LED that is controlled by a PWM pin an an arduino microcontroller. This system provides a very easy way to control 120V AC devices with a single PWM pin, and not use any timing code or worry about zero-crossing of the AC power since this is done intrinsically in the circuit. It also offers true electrical isolation between the AC line voltage and microcontroller.

Replacing a gas oven ignitor

My new house has a Thermador range with gas burners and gas oven. I've used it a couple times since moving into the house, but it has a strange problem. When using the oven to bake something, the flames will ignite, then sputter and flicker as the oven comes up to temperature. It seems to bake okay, but the noise from the flames doesn't sound normal. I checked the oven's manual to see if the thermostat has some sort of proportional control so that it tapers off the gas valve as the oven approaches the set temperature. It does not. The flames are supposed to ignite fully, then extinguish altogether.

I started reading about oven problems on the internet, and found a classic problem of searching for information with search engines: there are too many ways to describe a problem. I found people with gas ovens who saw flames that:

flickered
sputtered
fluttered
hiccuped
wavered
pulsed
pulsated
intermittently burned
burped
etc.

Anyway, it seems the root cause of any sort of flame problem is almost certainly the ignitor. This oven has a "hot surface ignitor", which is basically just a heating element that is positioned close to the burner. When the heating element is activated, it becomes hot enough to ignite the gas mixture coming out of the burner. Once the flame is ignited, the heat from the flame will keep the ignitor yellow-hot. As a safety feature, the oven is designed to only allow the gas valve to open when the ignitor is yellow-hot. If the ignitor cools down, the flame must have gone out, and the gas should be shut off. The oven determines the temperature of the ignitor by passing current through it. As the device heats up, it's resistance lowers and enough current flows to activate the gas valve. If the resistance becomes too high (because the ignitor cools down), the gas valve is shut. Ignitors apparently wear out just like light bulb filaments, and eventually their resistance slowly increases over years of use. Eventually, the resistance rises high enough so that the gas valve is just at the cusp of being activated. As the ignitor's resistance fluctuates just around the point where the valve is being switched, the flames will sputter and the oven will not heat as quickly as it should. As directed by troubleshooting guides on the 'net, I put an ammeter in line with the ignitor while the oven was running: 2.9A. It should be 3.2 to 3.6A.

I searched for genuine Thermador replacement parts, since I wanted to keep this oven in original condition. The Thermador website seems to require a registration just to browse for parts, and did not seem very end-user friendly. Forget that! I found some aftermarket ignitors sold by online appliance repair sites for about $80. Then, I found a general fits-all flat-style ignitor for $40. Then, I checked eBay and found a general flat ignitor for $13.50 plus $4 shipping. I figured that I would try it since it was so much cheaper than the rest it would be worth the gamble.
The new ignitor is below the old ignitor in this photo. They are very similar. The new part has two mounting wings, while the original had only one. The length of the stainless steel cage is identical, and the ceramic insulator is a little shorter on the new part.

I installed the new ignitor and the oven works perfectly. The gas snaps on, the flames are steady, then the flames snap off when the thermostat opens. Great!


Here's a shot of the ignitor near the burner tube.