Arisa explains Catadioptrics

After the discussion in my A few late Christmas shots thread, Arisa decided that it was up to her to come on here and explain for everyone how it works. It's also an opportunity for her to show off her new labcoat.

 

DSC01935SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: Hello there everyone. In case you are not familiar with me, I am Nakano Arisa, "Resident Scientific Genius"™ of the Nightmare household. It took our Cat-Father a very long time to find me a suitable lab coat, but I am quite smitten with it. It looks good on me, no?

 

DSC01936SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: Enough about that for now. The reason I am here today is to explain the workings of Catadioptric lenses, with the assistance of the Cat's super-high tech Sony α99 and this Minolta 500 AF REFLEX lens. Catadioptric is use to describe a combined optical system that uses both "dioptrics" or lenses, and "catoptrics" or curved mirrors.

 

DSC01940SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: The first two things you'll notice when looking into this lens is this black circle in the center of the front element, and that you may see your reflection inside the lens. The reflection is caused by the surface of the primary mirror. The black circle is the combined secondary mirror and aperture correction lens assembly.

 

DSC01937SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: Light entering the front of the lens is reflected by the primary mirror onto the secondary mirror, which in turn reflects the light into the lens aperture and into the camera (or in the case of a telescope, into your eye). Because of the doughnut shaped primary lens, the lens produces somewhat defined doughnut shapes in out of focus areas of images. Some people are not particularly fond of the effect, but it's so scientific that I just can't get enough of it!

 

DSC01941SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: The construction of this type of lens allows for long focal length lenses to be constructed in a much smaller, lighter weight form than a plain refractive lens. In fact, this lens does not even weigh 1lb! By comparison, a refractive 500mm usually weighs in at an arm breaking 10-16lbs!!! The Minolta example presented here is unique among similar type lenses in that it's the only Catadioptric lens that actually has Auto-focus capability.

 

DSC01944SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: It's really quite the interesting subject, no?

 

DSC01945SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: This subject has me all hot and bothered, how about you?

 

DSC01950SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: I just love technical talk about amazing equipment. Don't you?

 

DSC01958SLT-A77V35mm F220130116 by Visual Cacophony, on Flickr

Arisa: I hope you enjoyed this presentation as much as I enjoyed making it. I should probably get off of the Cat's camera now before he decides he wants to use it for something.

Wait.... there was a camera and lens in this story? I didn't see it....

 

All I know is that she had me at hello:

 

 

 

I really have no idea what she was talking about tho, I just know she's a wonderful model for that lingerie.

 

 

 

Billy

Wait.... there was a camera and lens in this story? I didn't see it....

 

All I know is that she had me at hello:

 

 

 

I really have no idea what she was talking about tho, I just know she's a wonderful model for that lingerie.

 

 

 

Billy

 

Too funny. She spent so much of the post sitting on the camera and lens that it's no wonder it's hard to understand her scientific ramblings.

Wow! That is awesome! The weight advantage seems immense. A log decrease is impressive. Do telescopes in space use this type of lens so they are lighter to send up into space? What advantages are associated with long focal lengths? How does such a complex lens manage to have autofocus? Autofocus is based on contrast, right? I really don't know much about how it works. Does the camera only focus on the center of the photo to establish focus? That is so interesting it produces doughnut shapes in the out of focus areas. Is that because the the combined secondary mirror and aperture correction lens assembly block the primary mirror and act as a doughnut hole? I think that is a perfect way to photograph Sabers.

 

Arisa is so lovely in (and out, kind of) that outfit! Lab coats always make things look so much more official looking. Technical discussions are so much fun. It is easy to get caught up in them. Please thank Arisa for presenting such fascinating information.

Boooooobies

 

Your Arisa is super pretty..!!

 

I haven't read any text, tho. I was all caught by the pics

anybody here understand wh tshe was saying because i dun

anybody here understand wh tshe was saying because i dun

 

I didn't understand what was being said either, but got lost when i saw the same picture as baldylox

 

Wow! That is awesome! The weight advantage seems immense. A log decrease is impressive. Do telescopes in space use this type of lens so they are lighter to send up into space? What advantages are associated with long focal lengths? How does such a complex lens manage to have autofocus? Autofocus is based on contrast, right? I really don't know much about how it works. Does the camera only focus on the center of the photo to establish focus? That is so interesting it produces doughnut shapes in the out of focus areas. Is that because the the combined secondary mirror and aperture correction lens assembly block the primary mirror and act as a doughnut hole? I think that is a perfect way to photograph Sabers.

 

Arisa is so lovely in (and out, kind of) that outfit! Lab coats always make things look so much more official looking. Technical discussions are so much fun. It is easy to get caught up in them. Please thank Arisa for presenting such fascinating information.

 

The Hubble telescope was set up this way, and I'm sure the more current ones are as well. Longer focal lengths allow the lens to see objects at longer distances.

The Minolta 500mm Auto-focus model moves the primary element assembly to focus, utilizing a geared mechanism that is coupled to the camera's in-body screw-drive motor.

The doughnut shapes are due to the doughnut shaped entrance of the light path. Haha, Sabers and their doughnuts...

 

Lab coats are awesome like that aren't they? I'm a fan of technical discussions as well, although it seems many of our friends here on theses forums couldn't quite make it past Arisa's physical charms. ;p

That is amazing that this system allows a telescope like the Hubble telescope to see that far into space. I heard the Hubble telescope is in trouble due to orbital decay and will someday re-enter earth's atmosphere. It is sad to hear since it has done so much for us...or at least those of us who like space.

 

There was something about the lens of your camera that made me think of telescopes. I suppose the scale in reference to Arisa is also suggestive of a telescope. Maybe Arisa can look at the stars in your camera lens. She would be a lovely astronomer.

 

I still think the innovations in optics are amazing. I use microscopes and cameras a lot here but I usually don't think about how they work. I love going down to the confocal microscope and hearing the director of the facility tell us about the details of how it works. In theory, he only has to help us establish settings on the software but he is always so nice to go into details about the different light path options and filter settings. I am glad he likes the equipment so much. It is great to have a job you like.

 

haha Yes, it seems that Arisa's outfit is quite distracting. I have a friend who said that he would love to have a teacher like Mitsuka from DearS and that way he would pay really good attention to lectures and make much better grades. I don't think it would work in practice though based on Arisa's experiment. Maybe she was trying to test how distracting she could be. I think the combination of her beauty and that awesome lens is great though.

maybe have virgin pick it up during one of their flights. drop at nasa to get the latest updates and gizmos and send it back up.

Arisa seems to have "problems" with keeping her clothes on, especially when she's having a technical discussion. A bit of an odd problem for a "scientific genius" to have? Maybe she can be talked into doing her next technical talk in her lab coat and underwear to start with so it doesn't become a strip show halfway through?

 

Satellites are regularly de-orbited at the ends of their life spans. I'm wondering what the plan is for the Hubble? It'd be sad for it to be gone.

The retirement of NASA's Space Shuttle fleet took place from March to July 2011.

 

Apparently, the problem is the Space Shuttle fleet is retired now. There isn't a shuttle to retrieve the telescope. It would have been nice to bring it back to earth intact after its long years of service.

 

I am hoping the retirement of NASA's Space Shuttle fleet means we get even cooler shuttles someday to take their place. Still it is sad to see such an amazing program end.

 

hmmm I think Arisa in just her lab coat and underwear will still be distracting.

The retirement of the shuttle program is a big hit to the space program indeed. Hopefully there is something to replace it soon. Although I'm sure that the last shuttle could make 1 last trip up there to pick up the Hubble if need be.

 

I don't think there's a way to get Arisa to keep her clothes on during something like this aside from having her do it away from home... Hell, she had her top unbuttoned/underwear showing when I took her to the Air and Space Museum in San Diego some months ago. She kept trying to fly every machine in there, even after I told her that they were display pieces.

 

DSC01321SLT-A77VDT 16-50mm F2.8 SSM20120804 by Visual Cacophony, on Flickr

haha But she is so cute half-dressed like that!

haha But she is so cute half-dressed like that!

 

 

I wholeheartedly agree with this.

 

 

 

Billy

haha But she is so cute half-dressed like that!

 

 

I wholeheartedly agree with this.

 

 

 

Billy

 

I agree as well, but nobody pays attention to what she's talking about then. ;p

I will still pay attention. I don't know anything about the topic but all kinds of technical things are really fun.

I will still pay attention. I don't know anything about the topic but all kinds of technical things are really fun.

 

Yay for one person who pays attention to Arisa when she talks.

Everyone else is too easily distracted by boobs. ;p

Can I ask her about the use of catadioptrics in lenses for photographing things or animals at long distances? Are they used for that purpose? Is it hard to photograph a deer that is far away using this kind of lens or it is good for things like that?

Satellites are regularly de-orbited at the ends of their life spans. I'm wondering what the plan is for the Hubble? It'd be sad for it to be gone.

 

Unfortunately it doesn't always happen at the ends of their lifespans either. A satellite's orbit often changes in small ways during its lifespan, due to gravitational effects, collisions with debris or malfunctions of its propulsion system. This can cause them to de-orbit and crash, kinda sucks when it happens in oh so many ways. Another little problem that sometimes occurs while a satellite is in operation is its radios can wander off their base frequencies, which causes problems with sending instructions to it and receiving information back.

 

Both of these are often repairable just from groundside programming, but the loss of the shuttle program definitely does hurt the ability to repair more significant defects.

 

(oops, radio geek hat apparently just appeared on my head XD)

Satellites are regularly de-orbited at the ends of their life spans. I'm wondering what the plan is for the Hubble? It'd be sad for it to be gone.

 

Unfortunately it doesn't always happen at the ends of their lifespans either. A satellite's orbit often changes in small ways during its lifespan, due to gravitational effects, collisions with debris or malfunctions of its propulsion system. This can cause them to de-orbit and crash, kinda sucks when it happens in oh so many ways. Another little problem that sometimes occurs while a satellite is in operation is its radios can wander off their base frequencies, which causes problems with sending instructions to it and receiving information back.

 

Both of these are often repairable just from groundside programming, but the loss of the shuttle program definitely does hurt the ability to repair more significant defects.

 

(oops, radio geek hat apparently just appeared on my head XD)

 

Hehe. I'm familiar with those instances as well. There's also that one instance of a satellite being shot out of the sky with a missile from a US Navy ship after control of it had been lost. I was stationed on that ship when we shot it down.

Oh, no! There are so many ways a satellite can have trouble. What causes the radios to wander off their base frequencies? That is amazing that this kind of thing can be repaired from groundside programming.

 

When satellites are shot down, it is to make sure they fall back to earth in small pieces instead of crashing down as a large chunk? Do they specifically shoot them down to land on water or unpopulated areas? Do satellites have black boxes with data that would be advantageous to retrieve?

Oh, no! There are so many ways a satellite can have trouble. What causes the radios to wander off their base frequencies? That is amazing that this kind of thing can be repaired from groundside programming.

 

When satellites are shot down, it is to make sure they fall back to earth in small pieces instead of crashing down as a large chunk? Do they specifically shoot them down to land on water or unpopulated areas? Do satellites have black boxes with data that would be advantageous to retrieve?

 

There were a couple reasons for shooting that one down. One: We didn't want the comms gear on it to fall into the wrong hands, and Two: it had about 1000lbs of Tetrazine fuel (extremely toxic) onboard and was most likely going to land in an inhabited area, killing a lot of people. Our missile shot directly struck the fuel tank, completely obliterating the satellite.

Oh, no! There are so many ways a satellite can have trouble. What causes the radios to wander off their base frequencies?

 

Well any radio has to be able to measure the frequencies on which it is broadcasting/receiving so that the operator (in this case a computer) knows that it is on the correct frequency. The problem is that this measurement, called a standard, must be constantly oscillating at the same frequency pretty much forever, and after a while it starts to drift, unless it has an external source to compare to.

 

Think of it as being like a clock (which it is, of a sort). Even the best clocks will lose or gain time if left long enough. Of course, when a clock loses time you just pick it up and change the time. This is hard to do with a lot of radios, and it compounds with a satellite. Generally, you don't 'fix' the change in frequency so much as you just measure it and compensate on your earth side radios, the same way you tune a radio station by tweaking the settings.

There were a couple reasons for shooting that one down. One: We didn't want the comms gear on it to fall into the wrong hands, and Two: it had about 1000lbs of Tetrazine fuel (extremely toxic) onboard and was most likely going to land in an inhabited area, killing a lot of people. Our missile shot directly struck the fuel tank, completely obliterating the satellite.

 

This a dramatic way to go down but I am glad it was successful. Those aromatic ring compounds can be really toxic.

 

Well any radio has to be able to measure the frequencies on which it is broadcasting/receiving so that the operator (in this case a computer) knows that it is on the correct frequency. The problem is that this measurement, called a standard, must be constantly oscillating at the same frequency pretty much forever, and after a while it starts to drift, unless it has an external source to compare to.

 

Think of it as being like a clock (which it is, of a sort). Even the best clocks will lose or gain time if left long enough. Of course, when a clock loses time you just pick it up and change the time. This is hard to do with a lot of radios, and it compounds with a satellite. Generally, you don't 'fix' the change in frequency so much as you just measure it and compensate on your earth side radios, the same way you tune a radio station by tweaking the settings.

 

That is a really fun idea. You can adjust the dial to communicate better with the satellite. It makes me think of those old movies and Twilight Zone episodes where the futuristic technology had dials and knobs and required much tuning.