Happy 20th anniversary, Hubble!

By Phil Plait | April 23, 2010 7:00 am

 

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Hubble doesn’t use lenses. Sorta.

hst_mirror_610

Even today, 19 years after Hubble’s launch, it’s not all that uncommon to hear a newscaster refer to “Hubble’s lens”. I once heard it used by an announcer on a science show produced by the Space Telescope Science Institute, the agency that runs Hubble!

The thing is, Hubble doesn’t use a lens. It has a mirror.

Galileo used a telescope with a lens, as did everyone up until Isaac Newton. He was the genius who figured out that a properly shaped mirror could focus light as well, and has advantages over a lens: mirrors need only be ground on one side (lenses have two), and mirrors can be made larger than lenses because they can be supported all across their back side, while lenses must be supported around their circumference, where the glass is thinnest and most vulnerable.

Over a certain size, lenses are simply impractical, so mirrors are used. Hubble’s primary mirror is 2.4 meters across, about 8 feet. Although it’s the biggest mirror for astronomy ever lofted into space, it’s considered small by ground-based standards; many telescopes today have mirrors 4 or more meters across. The mammoth twin Keck ‘scopes in Hawaii have mirrors made of segments that total 10 meters across each!

It turns out the cameras on board Hubble use mirrors too. Why? Glass absorbs light. Not much, maybe 2% of the incident light, but that adds up. A lens has two surfaces, each of which reflect a little bit of light, so you lose more through a lens than with a mirror. Also, mirrors can be made to reflect light of different colors about the same, but lenses bend light at different colors differently. So all in all, doing it with mirrors makes a lot more sense.

However, there are lenses on board: they are used in the Fine Guidance Sensors, small telescopes that track stars with incredible accuracy and help keep Hubble locked onto to its targets.

I could not find any other lenses used on the entire observatory. I read the instrument guides and asked several people who work with Hubble, and no one knew of any either. It’s possible they exist and I missed them, but the point is lenses are a very rare commodity on the ‘scope.

 

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CATEGORIZED UNDER: 10 Things, Astronomy, NASA, Pretty pictures

Comments (57)

  1. Dave H

    Story Musgrave came to Western Connecticut State University yesterday and I was lucky enough take part in a small Q+A luncheon with him. What an accomplished guy. Space really changed his life. He talked about how there are some things that dogs can simply never understand and that it’s very possible tha humans have the same limitations when it comes to understanding our universe.

  2. Douglas Troy

    It’s still a great a read Phil. Gotta love the Hubble and everything it’s allowed us to see and learn.

  3. Stargazer

    Beautiful picture! Isn’t it amazing to think that our civilisation is capable of doing something like that? And it’s just the beginning.

  4. Stargazer:

    And it’s just the beginning.

    Hopefully.

    On the other hand, there are people who still don’t understand. There was a letter to the editor in the local newspaper last week from someone saying that eliminating the “useless except for a few scientists” space program, we would “save” billions of dollars which could be used to create many thousands of jobs (I forget what jobs he was suggesting).

  5. Messier Tidy Upper

    HAPPY BIRTHDAY HUBBLE! :-)

    Actually there are two anniversary days for Hubble’s 20th anniversary :

    It was launched aboard the Space Shuttle ‘Discovery’ 24th April 1990 as you said -but it was actually deployed from the Shuttle on the 25th of April 1990.

    Then again, you could say the HST had a third special “start up” anniversary day – May 20th 1990 when it took its first ever image which was of NCG 3532 in Carina. Sadly, it was then that folks got the bad news of its spherical aberration being found.

    In case you’re wondering, NCG 3532 – Hubbles first target – is also known as the “Wishing Well” cluster is an open cluster 1,350 ly distant, containing approx. 150 stars of 7th magnitude & fainter. Mimosa (Beta Crucis) & Delcrux (Delta Crucis) in the Southern Cross roughly point to NCG 3532 and it lies between the Southern Cross constellation and larger but fainter “False Cross” asterism with X Carinae the nearest star and Eta Carinae & its famous nebula not too far away along with a bunch of other nearby deep sky objects. (3372, 3293 &I.2581.)

    (Sources : Ridpath, Ian & Tirion, Wil, ‘Collins Guide to Stars & Planets’, Collins, 2007 & Bakich, Michael E. (editor), ‘Hubble’s Greatest Pictures’, Kalmbach, 2008.)

  6. Stargazer

    #4

    Well, the space programme creates tens of thousands of jobs too, and that’s not even the main reason we have space programmes (plural for other countries). In my view it’s worth it in so many more ways than that. To increase our knowledge and understanding of this universe, to widen our horizons, to explore and do basic research. Of course, it also benefits us directly, through GPS, Earth observation, weather forecasts, climate research, etc.

  7. FC

    I’m almost positive you did this series before. Did you change the 10 items?

  8. Max

    Phil — you did it. I have worked on Hubble for the whole 20-year mission, and I was SO SURE there was nothing YOU could tell ME about it that I don’t already know. I would have authoritatively denied any suggestion that Hubble ever observed the Sun — nope, simply not possible. I would have been wrong. I know Glenn too, and can’t believe I never heard about this. Your legend continues to grow…

  9. Jeeves

    Point 6 illustrates what I think is a misconception that most people (not on this blog, obviously) have about telescopes. I think if you ask “the man in the street” what the primary function is of a telescope he’ll tell you it’s to “zoom in on” or “enlarge” an object, just like a pair of binoculars. People generally don’t know that many astronomical objects are big enough that you’d easily be able to see them, or see them in more detail if they gave off more light. I’m thinking of M31 or the nebulas in and around Orion. Those are surprisingly large but simply too dark to see with our poor, daylight-attuned eyes. And that’s why you need a telescope.

    Maybe an item for a future “10 things you didn’t know about telescopes”?

  10. Messier Tidy Upper

    Thinking of HSTs early drama and the huge shock and embarrassing disappointment it first appeared to be – before Hubble was fixed by shuttle astronauts reminds me :

    Curiously enough both Apollo and Hubble perhaps the two most successful NASA programs experienced major and severe early problems that had many thinking they were lemons in the beginning only to come back with astonishing success later.

    For instance in the book of ‘Apollo 13′ (also having its anniversary this year btw. but from 1970 & so 40th) Jim Lovell & his co-writer Jeffrey Kluger note :

    “The Apollo spacecraft, by even the most charitable estimations, was turning out to be an Edsel. Actually, among the astronauts it was thought of as worse than an Edsel. An Edsel is a clunker, but an essentially harmless clunker. Apollo was downright dangerous. Earlier in the development and testing of the craft, the nozzle of the ship’s giant engine – the one that would have to function perfectly to place the moonship in lunar orbit and blast it on its way home again – shattered like a teacup when engineers tried to fire it. During a splashdown test, the heat shield of the craft, had split open causing the command module to sink like a $ 35 million anvil to the bottom of a factory test pool. The environmental control system had already logged 200 individual failures; the spacecraft as a whole had accumulated roughly 20,000. During one checkout run at the manufacturing plant, a disgusted Gus Grissom walked away from the command module after leaving a lemon perched atop it.
    -Page 13, Apollo 13 Jim Lovell & Jeffrey Kluger, Coronet Books 1995.

    Moreover, that was before the Apollo 1 fire which killed astronauts Gus Grissom, Roger Chafee and Ed White.

    It would have been easy to abandon Apollo altogther after that. Just as it would’ve been easy to write off Hubble after the spherical aberration blunder.

    But thank FSM we didn’t – imagine what we would have missed out on. Imagine what we may be missing out on now with Obama cancelling Constellation which also seems to be widely critiscised and off to a troubled start just as Apollo & the HST once were.

    It was right to persist with Hubble & with the Apollo program.
    I think it shows that it would be the right course of action to persist with Constellation too. If we don’t build it and try to get it to work we’ll never know if it too could overcome its early mishaps and difficulties and really accomplish amazing, beautiful, marvellous things.

    Per aspera ad astra – through difficulties to the stars

    That’s the NASA tradition – not giving up halfway or 70 % of the way through because things are hard. We do these things precisely because they are hard as JFK would say.

    Or to end with Gus Grissom’s words :

    “The conquest of space is worth the risk of life.”
    - Virgil “Gus” Grissom, Mercury astronaut killed in the ‘Apollo 1’ fire.

  11. Gary Ansorge

    1. Dave H

    “it’s very possible tha humans have the same limitations when it comes to understanding our universe.”

    I forget who it was who said “It’s not that the universe is so strange and mysterious that is weird. What’s really strange is how we are able to understand so much about it.”

    ,,,or words to that effect.

    Just as we can never actually PROVE anything true (w/o an infinite number of tests), so too we can never know if we’ve reached OUR intellectual limits to understanding. For that to occur, we’d have to have some other intellect greater than our own to point out our limitations and even then we might still not “get it”, just as some might never get the point of a joke even after it’s explained to them.

    My dogs “see” the world with senses I don’t have. I sometimes wonder if they pity my obtuseness, for their world is full of scents I may never know(at least, directly).

    Since we have no such greater intellect to call upon(yet), we’ll just have to keep on trucking.

    I’m all for THAT. The really cool thing about reality is that we have so many puzzles to work on. I hope they never end(if they did, ennui might be the least of our problems).

    GAry 7

  12. QuietDesperation

    Thing You Didn’t Know #11: The Hubble has gone rogue, so the X-37B was launched today to hunt Hubble down and “retire” it.

  13. Messier Tidy Upper

    BA I asked you this one once before* & maybe you didn’t see it then but I would really love to get your answer to this question Hubble -history-wise :

    The BA : “I never used WFPC2 for any published work, but right after launch it was used to look at Supernova 1987A, an object I studied for my PhD. I had made some predictions based on our earlier, fuzzier images, and WFPC2 confirmed several of them.”

    Please, could you please elaborate on this – which predictions did you make & how were they confirmed? Tell us more please if you can. Ideally summarised & without too much maths. (My personal weak area.)

    ———-

    * On this thread : http://blogs.discovermagazine.com/badastronomy/2009/11/25/mr-hubble-goes-to-washington/

    comment # 14 if anyone’s wondering.

    ——–

    @ # 13 QuietDesperation : The Hubble Space Observatory is a replicant now? ;-)

    Roy Batty : “I’ve seen things you people wouldn’t believe: Attack ships on fire off the shoulder of Orion; I’ve watched c-beams glitter in the dark near the Tannhauser Gate. All those moments will be lost in time; like tears in rain. Time to die.”

    Love that movie.

    http://en.wikipedia.org/wiki/Blade_Runner

    PS. Surprised the BA hasn’t posted yet on the awesome new solar images (video? & photos) from the Solar Dynamics Observatory which were on Aussie TV yesterday and in some of our newspapers today.

  14. Pi-needles

    @12. Gary Ansorge:

    Just as we can never actually PROVE anything true (w/o an infinite number of tests),

    Mathematics the exception you forgot there? ;-)

  15. Cindy

    Max,

    You just had to work with the right people. I worked at ST ScI 20 years ago and my officemate worked on WFPC and I remember the discussion about the UV flood and if they should do it, and when, etc.

    I know all of the things this year, but last year I didn’t know that FOS is at the Air & Space Museum. Got to get there one of these days and give it a big hug.

  16. Gary Ansorge

    14. Messier Tidy Upper

    ” Ideally summarised & without too much maths. (My personal weak area.)”

    I recall Warner von Braun lamenting that he had the same problem but, since he couldn’t do the work he wanted to do w/o math, he applied himself to learning how to USE math(as opposed to intuitively understanding it) and managed to pull a B average in his math classes. Few humans are “real” mathematicians. My favorite physics professor(Dr. Wolfgang Rindler) told me he was working on his PhD in math when he discovered(ok, had to ADMIT) he was not a real mathematician, so he changed his major to physics. When I asked him what he meant by “real”, he said “A real mathematician understands math intuitively. He just knew how to USE math.” Which is how he taught differential equations. As a mechanical tool. Just learn the five most basic methods of solution(perfect squares, by parts, etc), turn the crank and out come your answers. You don’t have to understand how those methods were derived in order to use them.

    Which is not to say it’s easy. As Edison said, 98% of genius is just a LOT of hard work.

    Gary 7

  17. Chris A.

    @Pi-needles (#15):

    “>Just as we can never actually PROVE anything true (w/o an infinite number of tests),

    Mathematics the exception you forgot there? ;-)

    Gödel notwithstanding…

  18. mike burkhart

    I think Hubble has been a suscess. I find in some way Hubble has a lot in comon with Skylab :Both were damaged when they were launched ,everyone said they were a failre,they were repared in space, and were a big sucess afterwards.By the way I’m fan of Blade Runner and I’m wondering if we will have nexus 6 replacuts by 2018 .

  19. RMcbride

    From what I understand the plans are to let the Hubble telescope crash into the pacific in five years. Why not make a relatively small investment and tow it to one of the points of stable gravity (legrange) between the earth moon system?

  20. Gary Ansorge

    15. Pi-needles and 18. Chris A.

    “Mathematics the exception you forgot there? ”

    Actually I ignored math proofs. I was thinking of theories of the nature of physical reality. THEY can never be proven true w/o an infinite number of tests, which is why the SciMethod is so powerful. Just ONE test can show it’s not true(or, at least, only an approximation), which saves a WHOLE lot of time.

    In a previous post(long ago and ,,,), one poster pointed out that the Greeks developed the SciMethod a millennia before that crazy Persian(who’s name escapes me now) but they never adopted it as the basis of their science. Had they done so, we’d likely all be speaking Greek today(but they DID have great math proofs. Unfortunately, math proofs do not necessarily have any pertinence to this universe).

    Bummer! I think I’d have enjoyed worshipping in the temple of Athena(or was it Aphrodite?).

    GAry 7

  21. NerdBusters

    I was thrilled that Hubble got its overhaul and hopefully at least another decade of life. This orbiting observatory is priceless; a national treasure. We’d better have some means of retrieving it soon, because I for one would cry to know it was left in a decaying orbit to be burned up in our atmosphere. As Indiana Jones would say, “It belongs in a museum!”

  22. Since this was one of the last photos to be taken of Hubble by a human-weilded camera, I thought it deserved some extra care: http://www.nasa.gov/multimedia/imagegallery/image_feature_1369.html

    I cleaned up the internal reflections and bumped up the dynamic range, and the result is here: http://img38.imageshack.us/img38/4545/hubblefarewell.jpg

    Happy birthday, Hubble!

  23. You say the moon’s moving too fast to image accurately — I know that it’s possible to slew the telescope to track moving objects; that’s how MGS gets those spectacular pictures of Phobos, for example.

    So there must be some reason why this can’t be done with Hubble. What?

    Possible reasons I can think of:

    - too much thruster fuel required (does it use thrusters for attitude adjustement?)

    - can’t make observations while rotating due to vibration from the reaction wheels (does it use reaction wheels for attitude adjustment?)

    - too much structural distortion at the slew rates required (Hubble is big, and moving quickly centrifugal force will act on its components… beyond a certain rate this might damage instrument calibration. What’s the maximum safe slew rate?)

    - too scary (‘you want to *spin* the telescope? Are you nuts?’)

    Do any of these come close?

  24. Gary Ansorge

    23. David Given

    Our moons orbital velocity is 1.022 km/sec, so if you’re focused on something 200 meters across, you’ve got about a fifth of a second to observe it before it passes by, which is another way of saying, spin baby spin(way too fast for Hubble to rotate. It’s designed to hold a stationary position for long periods, not spin like a DeadHead).

    Gary 7

  25. Rob Davidoff

    Phil,

    Always love reading your stuff, even when it’s old material (as long as it’s awesome old material like this). Your initial analysis of the 2011 budget proposal was part of why I looked closely at the actual material instead of just getting information second hand, and thus why I’m so excited about where space could be by the time I hope to be working on it.

    By the way, how are you enjoying your present? I’ve been awaiting news on what you ended up doing with it, but was starting to give up hope of any news.

    Rob Davidoff

  26. DaveS

    I’m curious as to why they’re even talking about retiring it in five or ten years. Surely the science it can support isn’t exhausted. I mean, if they can keep using the Hale Telescope (built in 1949) to do science, surely they can find a use for the Hubble.

    Even if it would require more refurbishment in ten years, where’s the optimism about the future of orbital manned spaceflight, and how cheap and accessible it’s going to be?

    They’re talking about the James Webb Space Telescope replacing it. But when the Hale telescope breaks something, do they decommission it just because the Keck is bigger? And the JWST is going to be so far away, in solar L2, that refurbishment isn’t going to be possible for a LONG time, if ever. So unlike the Hubble, JWST is sort of a one-shot.

    It just seems to me that the Hubble will still be a pretty unique resource ten or fifteen years from now. And 20 or 30 years from now, when JWST has malfunctioned and is useless, we could still be repairing the Hubble.

  27. Steve A

    @20. RMcbride

    Actually, the five years you mention (four years now) is what they think it’s going to last, as a conservative estimate. If it continues past 2014, then they will. But, if there are failures, it’s better to have a planned decommissioning into the ocean instead of a Skylab near-disaster or worse. It also could be moved into a “graveyard” orbit like other satellites.

  28. Radwaste

    On a sadder note, someone just called in to a program about Hubble on PRI and asked if Heaven looked like what Hubble photographs showed. She was concerned about the use of “false color” to emphasize celestial features. She was serious.

  29. pontoppi

    @26. DaveS

    You should consider that a manned servicing mission to Hubble costs the same or even more than simply building a new Hubble from scratch and launching it in an unmanned vehicle. Like the ISS, the manned Hubble servicing missions were done more to demonstrate the capability to do complex repairs in orbit than for efficiency or cost reasons. The latest servicing mission cost in excess of $1 billion. In comparison, the Spitzer Space Telescope (the most recent of the great NASA observatories) cost about $700 million. JWST is projected to cost $2.4 billion until launch, but that’s of course a 6.5m mirror, compared to Hubble’s 2.4m. There will likely be something even bigger after JWST (plans are underway). The current climate is just to go 100% robotic and disposable, and that makes financial sense. I completely agree that the continued existence of a Hubble-sized space telescope could yield a lot of good science, but it is apparently hard to argue to Congress to ‘do more of the same’.

  30. locke

    @ 29 pontoppi Very well said! In all the glorification of Hubble, it’s easy to forget that not only is Hubble the most successful scientific instrument ever built, it’s also by far the most expensive, more so than even the LHC. Total costs over it’s lifetime have to be in the $10-20 billion range, far more than all the other great observatories combined.

  31. The Hubble definitely belongs in a museum, it’s a piece of history and possibly the most important scientific instrument ever built.

    I for one remember the sheer astonishment of realising that such a tiny patch of sky contained so many galaxies, when the Hubble Deep Field was unveiled in the mid 90′s. Not to mention the rest of the glorious images taken from Earth’s orbit.

    ….NerdBusters—”We’d better have some means of retrieving it soon, because I for one would cry to know it was left in a decaying orbit to be burned up in our atmosphere. As Indiana Jones would say, “It belongs in a museum!…..”

    The Hubble actually has a ring like device fitted to it’s bulkhead so it can be retrieved from space with “soft capture”. I hope they go for this method when the time comes !

    Here’s my own personal acclaim to the Hubble Space Telescope, with hopefully years of jaw dropping images and science to come http://astronomycentral.co.uk/the-hubble-telescope-two-decades-of-discovery

  32. Brian Too

    Let’s not forget that, besides all the great science, Hubble has been a public relations success story. The general public knows the name, considers it to be a success and a ‘good thing’ generally.

    That translates into willingness to fund that program and others like it.

    It also helps, in an odd way, that the program nearly failed and then recovered. It leads the public to believe that NASA nearly failed and then recovered. That’s a positive story to tell and fits nicely into a narrative of flawed people and institutions with redemption available if you work hard, have good people, and expend sufficient resources.

  33. ND

    What are the possibilities of bringing the HST back to earth with some sort of robotic retrieval system? Reentry would be rough on a telescope and so would landing but if the HST is to be ditched maybe someone out there might give it a try.

    The shuttle is the only vehicle that I know of that’s capable of returning the HST. Well I’m assuming that it can land with the weight of something like the hubble in cargo.

  34. ND

    pontoppi,

    Thanks for putting up those cost numbers for unmanned launches of new hubbles vs manned repair&upgrade missions. I’ve always thought given the amount of parts replaced on the HST and the cost of the shuttle manned missions sending up new hubbles once in a while made sense. Maybe without the shuttle an unservicable hubble could have had a 3 m mirror. The HST had to fit into the shuttle bay after all.

  35. Cindy

    Plans to bring Hubble back to Earth via the shuttle were already scrapped by the time it was launched 20 years ago.

    Hubble is in low-Earth orbit and therefore is in just enough atmosphere to cause drag. Every servicing mission has lifted it up to a higher orbit. Without some way of lifting it up to a higher orbit, it will eventually get too low and then will fall to Earth. I don’t know off-hand how long that will be, but I’m guessing under 10 years.

  36. #32
    >The Hubble definitely belongs in a museum, it’s a piece of history and possibly the most >important scientific instrument ever built.

    I don’t think that you can really justify that statement. The HST has produced some very pretty images – the deep field is awesome – but it has only filled in detail. It has not produced any scientific paradigm changes.

    I would argue that 1.5″ telescope in the hands of Galileo was a far more important instrument. Or the Michaelson-Morley interferometer. Or Hertz’ spark-gap receiver. Ot Jansky’s radio telescope. Those really did lead to paradigm changes.

  37. Ryan Jensen

    If Hubble has been orbiting Earth for 20 years, how much less time has it spent orbiting, from its perspective? I’m talking Relativity here, but have no idea how to do the math. Obviously Hubble is orbiting faster than an observer on Earth, so it should have spent “less time” up there, in its frame of reference.

  38. #37
    >>The Hubble definitely belongs in a museum, it’s a piece of history and possibly the most >>important scientific instrument ever built.

    >I don’t think that you can really justify that statement. The HST has produced some very >pretty images – the deep field is awesome – but it has only filled in detail. It has not >produced any scientific paradigm changes.

    But not just pretty images Dave, there is very real science behind them…

    The Hubble helped astronomers come up with an age for the universe, the suggestion of dark energy for a reason why the universe in accelerating in it’s expansion, evidence that supermassive black holes inhabit the centre of galaxies, images of solar systems in formation, and that proto-planetary disks around young stars is common, that star formation was at a high rate in the early universe, the first detection of the atmosphere of an extra solar planet, that gamma ray bursts eminate from extremely distant galaxies…

    It must be one of the most important scientific intrument ever built, at the very least. It’s up there with the best of them !!

  39. “One of the most important scientific instruments ever built”. Certainly in the top 100. And, as an astronomy ( albeit of the radio persuasion) I am very impressed by the science that has come out of it. But has it added any more to our knowledge of the universe than the Hale telescope did in the ’50s?

    Indeed the work done by Hubble and Humanson, discovering external galaxies and evidence for the Big Bang, at Mt Wilson is far more significant than anything observed by the HST. That did lead to a real change in the way we thought of the Universe.

    But it is a lovely bit of kit :-)

  40. Bob_In_Wales

    (Silly on.) Hubble should be easy to retrieve for a museum as it is only a hoax that it is in space. Look at the photograph. No stars. Obviously a bad paintshop job. (Silly off.)

  41. Mike

    Great read. I’m one of those new readers you were talking about in the beginning of the article, haha.

    Just saw you spoke at Caltech recently, you should’ve posted about it beforehand! I would’ve +1ed your audience.

    Anyways, great blog. Gotta love space.

  42. Floyd

    #10: I have an inexpensive 4.5 inch Celestron Newtonian telescope that I have used for hours to look at the sky. It’s amazing how much I can see just looking at M42 in Orion’s “sword,” and the objects around it. Hubble pictures are cool, but there’s nothing like looking at an astronomical object that you’ve found yourself.

  43. Dude, you used ‘serendipitously’ in a journal article abstract! WIN…

  44. Doug

    Phil: I, too, worked on Hubble in the early days. I believe I got all of your 10 things, but to be fair, I would not have known about the FOS being on the ground except that I read it in YOUR blog previously!

  45. Tim

    Phil,

    It’s not true that you have to show a need to get an archive account at STScI. Anyone can register. And in fact, to retrieve non-proprietary data you don’t need an account at all. Just give “anonymous” as your username and your email for the password (so we know where to send the completion message). As you say, the format is probably not appropriate for the casual Photoshop crowd, but it’s available. As for the load, a few gigabytes isn’t going to hurt us much. We’re currently handling about 100-200 GB/day.

    But if it’s cool pictures you want without the reduction hassle, the Hubble Legacy Archive has plenty (http://hla.stsci.edu/). Try searching on “M51″ and then click the “Images” tab. ;)

  46. Chris

    A fascinating read, but as a European astronomer I feel the need to point out that Herschel’s 3.5 m primary mirror makes a mockery of Hubble’s puny 2.4 m effort. And we get almost 2% of Hubble’s resolution! Whoop whoop, etc.

  47. In October of 1997, Hubble was pointed at the Large Magellanic Cloud, a small galaxy that orbits the Milky Way.

    That’s most likely NOT the case, Phil; the SMC and LMC are just passing by for the first time and are almost certainly not bound to the Milky Way. See here:

    http://adsabs.harvard.edu/cgi-bin/bib_query?2007PhDT……..16K

    Cheers,

    —JL Galache
    Minor Planet Center

  48. Pete Jackson

    “So really, the only — and best — way to see the Apollo artifacts is to go back to the Moon.”

    Well that’s the best way of course, but, as you have in fact posted (I’m only commenting here for the sake of those who are new to your blog), the Lunar Reconnaissance Orbiter has, since 2011, taken pictures of many, if not all, of the Apollo artifacts even including the tracks made by the astronauts’ footprints.

  49. Sanjay

    Happy Birthday Hubble!

    When will you fly over my town on a cloudless night?
    I wait …

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