xkcd on telescopes

xkcd on telescopes

Types of telescopes in homes up for sale:

99.999% Refractor

.001% Reflector

Usually it's a prism. Vampires don't reflect on mirrors because of the silver coating on the metal behind the glass so they would indeed reflect on prisms. That's also the reason why vampire hunters carry mirrors with them, instead of prisms.

Vampires don't reflect on mirrors because of the silver coating on the metal behind the glass

In all of my many years vampire hunting, not once did I think of this.

But that refractor won't be able to see space vampires either. The diagonal is clearly a mirror.

And if there is a reflector it's pointing towards the floor.

Is there a blindspot on reflector telescopes?

The downward facing dob.

Silver was anathema to most paranormal creatures in the olden days. Silvers association with purity counteracting and causing the dissolution of their corrupted physical forms.

This depends on how big your refractor is. If it's top big it could not fit to the bin.

Woah. Is this why we can't detect dark matter? It's just made of vampires and we don't know it.

How do you know it wasn't just space wasps?

One interesting property of reflectors, however, is the weird appearance of out-of-focus areas (Bokeh). Not relevant for telescopes, but if your you're using the reflector as a cheaper and lighter alternative for photography.

One interesting property of reflectors, however, is the (Bokeh). Not relevant for telescopes, but if your you're using the reflector as a cheaper and lighter alternative for photography.

It is a natural "antibiotic". People that build water cooling loops often include silver kill coils in the loop to prevent build up of mold and other microbial life. Picture here.

It is a natural "antibiotic". People that build water cooling loops often include silver kill coils in the loop to prevent build up of mold and other microbial life. .

This is incorrect (but gets upvoted by Reddit anyway). The amount of 100% illumination varies with the size of the secondary mirror (and therefore the percentage of the obstruction). Put a 5" secondary in front of a 6" primary mirror and you can see that you aren't going to get much of the primary 100% illuminated. That same thing is true, whatever the size of the obstruction, but below a certain percentage threshold it is not objectionable. - Good article on the subject.

A cottage I rented had a telescope, it was actually a reflector! A reflector with a wasp nest inside though.

So is garlic, actually. Vampires are harmful bacteria, it all makes sense!

Original Source

Mobile

Title: Telescopes: Refractor vs Reflector

Title-text: On the other hand, the refractor's limited light-gathering means it's unable to make out shadow people or the dark god Chernabog.

Comic Explanation

Stats: This comic has been referenced 8 times, representing 0.0055% of referenced xkcds.

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... are y'all talking about a microscope?

A Dobsonian reflector certainly gives you the most bang for buck.

Spend the rest on eyepieces!

Doesn't silver actually kill a fair number of little critters and germies, etc.?

What a useful superstition!

So what your saying is throw my refractor in the bin and get a reflector?

I thought only werewolves had an aversion to silver? I thought vampires were just vulnerable to wooden stakes and garlic?

No. Since all of the reflection surface gets all of the light, the result is that the image will be slightly dimmer, but not noticeably so.

Only at close distances.

Original Source

Mobile

Title: Telescopes: Refractor vs Reflector

Title-text: On the other hand, the refractor's limited light-gathering means it's unable to make out shadow people or the dark god Chernabog.

Comic Explanation

Stats: This comic has been referenced 4 times, representing 0.0027% of referenced xkcds.

xkcd.com | xkcd sub | Problems/Bugs? | Statistics | Stop Replying | Delete

It is how the linked picture was taken, but actual telescopes like you would buy in a hobby generally aren't used for terrestrial photography. I have used my 5in refractor as an 800mm lens, but it's obtuse and therefore pretty rare.

Lens companies used to make mirror lenses as a cheaper alternative to long focal length refractor lenses. One example:

http://nikkor.com/story/0013/

Is the consensus that I should get a reflector?

My pleasure

Just to clarify for everyone, the smaller mirror creates a part of the larger mirror that doesn't receive light. What OP meant was that each unobstructed portion of the larger mirror is capable of producing the whole image. This is due to the curvature/optics. It might sound hard to wrap your head around, but yes even a tiny square of the larger mirror is capable of producing the whole image. You take the sum over the whole larger mirror to get the final image. The net result of the smaller second mirror is a loss in brightness, but there is no blind spot. Sorry, I'm not disagreeing with you, just replying here for most visibility

cheaper and lighter alternative for photography

Could you please elaborate? I'm genuinely curious, does this mean that reflector telescopes are used for ground-based photography? Is that how the linked picture was taken?

So if I were a vampire, I could use a polished steel mirror? Just asking for a friend.

Thanks. I forgot I even wanted a telescope as a kid.

LMAO! I love how there is a [citation needed] tag for "vampires are widely believed to be made up"

So does that mean we can throw a bit of alcohol on them to kill them?

Holy shit, is that what holy water actually is?

Thanks /u/xkcd_transcriber love you!

This video

shows the view through a reflector going from way out of focus (large "donut") to perfect focus (diffraction spikes overlap). As you can see, the "dark hole" (shadow of the secondary mirror) disappears when everything is in focus. Visually, the star would appear as a point of light.

(If you're wondering, collimation means aligning the mirrors. You can tell this particular telescope was well collimated because the secondary mirror shadow is right in the middle of the large white image reflected off the primary mirror. The little dark notches along the edge are the shadows of the primary mirror clips.)

Have your mom call me. I'll help her out.

8" dobsonian reflector is the answer to 99% of "what telescope should I get?" threads

As a telescope owner since childhood (reflectors) it took me WAAAAY too long to get this.

If you click the link they've actually fixed it, it's different from the preview which still has the diagonal.