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Posts from the ‘Education’ Category

24
Feb

A View to the Infrared

With the huge popularity of smart cell phones has come the rise of the portable infrared camera. One can readily go to Amazon and slew through a series of miniature attachables for your phone, each with their features and abilities. This is a look at two widely accepted models by two companies: FLIR and Seek Thermal. As an educator, having an IR camera is a very cool way to SHOW students what seeing in different wavelengths is all about. Great strides have been made in astrophysics and other sciences due to our abilities to “see” in multiple wavelengths with some very cool tech. So lets look at these two units.


On the left is the Seek Thermal Compact model. This is available now for iPhone series, and will be coming to Android later this summer. Three models are available each with progressively more features/abilities and with increasing price tags. This unit comes in at $249 US. The more expensive they get, the better they are at resolution and frame rate. More can be seen for comparison at their site here: Seek Thermal Compact

On the right is the FLIR One unit for the iPhone. This is a Gen2 unit, as FLIR have a redesign out there for Gen3: a whole new look there, so you likely can find one of these Gen2 units out there for less money.

Cases: The case for the FLIR is not a case so much as a neck lanyard with a rubbery wrap for the camera. It’s difficult to get the camera out of the case, and your finger is likely to hit one of the lenses. The Seek unit has a very nice water proof case with a strong latch and foam insert.

Image Quality: both are fine for image quality given their tiny size. The thing about long wavelength IR is that resolution will suffer, period, unless you are able to fork out many hundreds for a pro level, stand-alone unit from FLIR often used by law enforcement or the military. You wouldn’t be reading this either 😉 The cool thing about the FLIR system is that it has two lenses: one takes images in IR the other in visual wavelengths. The system then does a edge find algorithm on the visual image and uses that to draw outlines in the IR image to accentuate the subject matter. This is a boon and a bust: it makes your subjects obvious. It also fools people unfamiliar with the system into thinking that these edge lines are part of the IR light being received. Nope. Some educational extra work is needed to make sure that people are not fooled.

The FLIR default image: note the edges drawn in by the software to make subjects more visible. This is a nice feature when using the unit to ID small features or plumbing issues in the basement 😉
This is the same subject though I placed a finger over the visual light lens to prevent it from generating an edge to the subject…. except at the far left of this image. The blurriness is typical of IR images.
Here is the same subject taken using the Seek system. No edges here.

Abilities: Both are pretty much equally capable. The abilities of the system (other than the edge drawing feature of the FLIR) are within the software. Seek’s software has the annoying feature of wanting you to join their Seek online group. This can be circumvented, but you have to do this every time you launch the app. Both allow different palettes. Both have spot measurement of temperatures. Both have temperature scales available with the palettes. Some examples for you to enjoy:

Spot temperature reading on the FLIR: looking at the wood of the basement door. Note the cooler air below the door.
Cooler portion of the same door where cool air is being pulled up into the house by the air circulation system in the house.
Can you find the hot cup of coffee in this busy kitchen?
We always know when the dog has been sleeping on the couch…. she leaves her thermal signature wherever she has been. This image had my thumb over the edge-making visual light lens.
Seek’s spot temp measurement of my hot Comcast set top box. The stereo amp is below the Set top unit…. yeah – that is one HOT set top. Shame on Comcast.
Same image but with the temp scale turned on. A nice feature.

Other oddities? Yes! The Seek Thermal systems have no internal battery, so…. it draws all its power from your iPhone and will eat up batteries pretty rapidly. Your phone will also heat up. The FLIR unit has an internal rechargeable battery. This requires a tiny USB plug wire for charging, time to charge, etc. Don’t lose that cable! The internal battery cannot be replaced, though I have had mine for years and have had no issues. Recharging is slow but it lasts a day. Pick your poison. Both units are pretty good given that they are small and limited in resolution. If you like the FLIR edge drawing ability, and its internal battery, then the choice is to go with FLIR. If you do not want/need that edge finding ability, then the Seek is a good choice. Just know that it will consume your phone’s battery for you.

27
Dec

Comatic Aberration and Chromatic Aberration

These two phrases are pretty much guaranteed to raise the blood pressure of optical aficionados: Comatic Aberration and Chromatic Aberration. There. Did your blood pressure go up? Then it is likely you have dealt with one or both of these issues before… and it is likely that you do not need to read further! For those looking around the internet for an example of these aberrations, seek no more!

Let us start with an image. This shot is of the December sky taken through a wide angle 20mm AFS Nikkor 1:1.8G ED lens on a Nikon D-810. The images were raw NEF files without any processing (except resize), either on board the camera or using software. Click on any image to see it in larger format.

Taurus and comet Wirtanen
Taurus and Comet Wirtanen

The image is a pretty typical night shot: 10 seconds focused at infinity and using 5000 ISO at f/2 (a little stopped down). The constellation Taurus is dominating the right side of the image. There is an airplane top-center moving to the lower left. If you follow the airplane’s future trail it leads to a faint greenish fuzzy object, Comet 46P/Wirtanen. This image is reduced in size…. but upon close, full-scale viewing, this image displays two of the common issues that astronomers and photographers aim to rid themselves of. Funny thing is that this lens gets fabulous reviews on sites like Amazon, and when I complained about these issues I was actually chastised! “Are you kidding? This is such a great lens!” Well, no. It’s not, and for the price, it really should perform a lot better. Add to this story the fact that the Nikkor 16mm fisheye actually is BETTER than this 20mm lens, and there you have an argument to not buy this 20mm lens. So, read on….

May I present to you comatic aberration:

comatic aberration in star images
Classic coma on the images of stars. These should be small round dots, not winged things….

This aberration is off to the sides of the image, off-the central axis. The further from the center, the worse this aberration gets. Some systems sprout seagull like wings from stars. This lens sprouts more than that. Ugly. The cause of this problem is in the optical design and is usually found in parabolic mirror systems like Newtonian reflectors. Alas, it also happens here in lens designs.

May I now present to you chromatic aberration:

Chromatic aberration in star image
An example of chromatic aberration: note the violet halo surrounding the bright star. The violet wavelengths focus at a different distance than all the rest. The fuzzy green object to the left is Comet Wirtanen.

Chromatic aberration has been the bane of the optical world for a long time, starting with those who first pointed telescopes up at the stars (i.e. those like Galileo, etc). A single lens acts very much like a prism in how it bends (refracts) light. The angle of refraction has to do with the light’s wavelength, so not all colors of light will come to focus at the same spot. This is usually handled with complex, multiple-lens systems like Petzval lens groupings using unique glass recipes than minimize chromatic aberration. Well, this lens? It suffers. When pointing at a bright white star, this lens gives an image very much like that of a simple two-lens refracting telescope, what is called an achromatic refractor. Well, they are notorious for having a violet to blue ring of light surrounding bright objects… and halos of blue around the moon and Jupiter. Not fun. Nope. This is why we have monstrously expensive systems like apochromats and Petzvals. We are talking expensive!

29
Nov

20-21 January 2019: Total Lunar Eclipse

We have a splendid opportunity to see a total lunar eclipse this January. It will be taking place late on a Sunday night into the early hours of Monday morning. That Monday is also Martin Luther King, Jr. Day here in the USA, so many schools will not have classes that day. Eclipse timings are given in the above graphic, in Universal Time.  Converting that to the various USA time zones: 

Event Pacific Mountain Central Eastern
Partial eclipse starts 7:34 pm 8:34 pm 9:34 pm 10:34 pm
Total eclipse starts 8:41 pm 9:41 pm 10:41 pm 11:41 pm
Total eclipse ends 9:43 pm 10:43 pm 11:43 pm 12:43 am
Partial eclipse ends 10:51 pm 11:51 pm 12:51 am 1:51 am

Usually the real eclipse visibility starts to take place late in the penumbral phase approaching the first contact of the umbra. If you have not seen a lunar eclipse before, it is quite a special event. The moon will appear to have a charcoal chunk missing from it as the eclipse progresses.  Deeper into the eclipse, the moon will take on a rusty red hue caused by the sunlight passing through the earth’s atmosphere before arriving at the moon. Telescopes are not required, as one can see the whole event easily with the eye. Binoculars and telescopes will offer a nice closeup view.  Photography of the event is a relatively simple affair. A good tripod and telephoto lens will work well with the moderate shutter speeds required.  Tracking is not needed.  An example of a series of photos I took of the last total lunar eclipse is below. The camera was a Nikon D7000 with 200mm telephoto on a tripod. Click for a larger image.

2
Sep

What is a Quindar Tone?

Ever watched footage of the Mercury, Gemini or Apollo space projects? When Houston talks to the astronauts, there is a beep, then some talking then another beep? Yep – those beeps are Quindar Tones. If you listen carefully, the tones are not the same pitch: there are two distinct tones, one at 2525Hz and the other at 2475Hz. They are both 250ms in length…. like these:

What are these tones for? What’s going on? Why the beeps?  Well, it all boils down to older technology. Back when they were shooting astronauts into space on top of missiles (some more controlled than others), eventually they got people into orbit. As astronauts orbited the Earth, they needed some way to talk to them, even when their space capsules were not within the line of sight of Mission Control in Houston, Texas. Communications centers and tracking stations were built around the world, each with the ability to talk directly to the space capsule as it orbited on by. Mission Control then had telephone lines to each of these stations around the world. These lines were dedicated lines, and expensive. The tones were used as a method to control when the remotely located transmitter was transmitting, and used the phone lines to send these remote control tones as audible beeps. Both tones originated at Mission Control…. like this:

  1. Mission control needs to say something to the astronauts in space. They push the push-to-talk switch.
  2. This send a 2525Hz intro tone to the system.
  3. The remote communications station receives the intro tone, and turns on the transmitter to the radio antenna aimed at the space capsule.
  4. Voice communications takes place.
  5. When done, Mission control releases the PTT switch, and the 2475Hz outro tone is sent, thus turning off the system. The remote transmitter is off.

An example for you is below. Note that the Quindar tones only take place just before and after Mission Control speaks. The astronauts do not initiate any of the tones. They make all radio calls into the “blind” so to speak, hoping that some ground tracking station is picking them up.

Now, you might wonder about the issues here. If an astronaut were to also talk at the same time, they might pick up a Quindar tone on their audio and retransmit it back to the ground and cause all sorts of troubles down on the Earth side of things. Yep – that was a problem(!) so engineers made their best effort to prevent the tones from even reaching the astronauts by placing a filter into the stream of all uplinked audio sent to the capsule. These filters were simple notch filters centered on the tone frequencies…. not perfect, by any means, but it worked, generally.

The name “Quindar”?  That came from the organization that invented the system, Quindar Electronics. You can visit their site at:  http://www.qeiinc.com/History.aspx  to see some of their excellent history.

What now?  Quindar tones were used from the early flights of Merucry through the Space Shuttle program. With new methods of telecommunications (i.e. fiber optics, satellite feeds, etc), sending command and control statements to remotely located transmitter sites is a lot easier. There is no need for audible tones these days.

 

 

23
Aug

Cleaning Time!

Every observatory needs basic maintenance, and those here at PEA are no different. I usually cringe at the thought, but cleaning is a part of the requirement… not that I dislike cleaning. I actually really find it meditative, and a clean observatory dome makes me smile. The cringe-feeling comes from the prospect of kicking up a ton of dust, pollen, cob webs, and such… all of which will have to come to rest some place: Hopefully not on any optics! EEEK! Scheduling the cleaning is a whole other game to play, as well. School ends in early June. A few weeks later, the summer school program begins, and then runs for 5 more weeks. Grass is growing and getting cut throughout June and summer, so, why clean if it’s going to get even more dusty and grassy and pollen-dusty…? So… I wait until the end of summer, when there is a cool, dry, sunny day, like today!

Step – one – cover the optics. Then cover the telescope tubes and mounts with trash bags. Open the dome and aperture.

Two – Vacuum the whole place from top to bottom. We have open studs, so there are a lot of nooks and crannies to work through.

Three – Damp wipe of surfaces, and then a scrub of the floor.

Four – wipe down the ladder and other step-stool devices used by observers throughout the year.

Five – wait for everything to be dry. A light breeze and sunny, dry weather help here. Today was a perfect day.

The result? A clean observatory with a bunch of displaced spiders and no more wasp nests. Webs are gone. Pollen and dust are gone. Happiness!

IMG_1947

A clean machine!