author
20Instructables293,070Views116CommentsChicago, ILJoined September 18th, 2014
I'm a professor of physics and astronomy at Northwestern University. I do a lot of hobbies, including amateur astronomy, woodworking, and Lego modeling among many others.

Achievements

100+ Comments Earned a bronze medal
10K+ Views Earned a bronze medal
Epilog Challenge 9
Contest Winner Runner Up in the Epilog Challenge 9
Big and Small Contest
Contest Winner Runner Up in the Big and Small Contest
Tiny Home Contest
Contest Winner Second Prize in the Tiny Home Contest
Audio Contest 2018
Contest Winner Runner Up in the Audio Contest 2018
Explore Science Contest
Contest Winner Second Prize in the Explore Science Contest
Homemade Gifts Contest 2017
Contest Winner Runner Up in the Homemade Gifts Contest 2017
Remix Contest
Contest Winner Runner Up in the Remix Contest
Gaming Contest
Contest Winner Second Prize in the Gaming Contest
Trash to Treasure
Contest Winner Grand Prize in the Trash to Treasure
Optics Contest
Contest Winner Grand Prize in the Optics Contest
Organization Contest
Contest Winner Runner Up in the Organization Contest
Show 11 More »
  • gravitino's entry Fountain Pen Chest is a winner in the Organization Contest contest 2 months ago
  • gravitino's entry The First Color Photograph is a winner in the Remix Contest contest 2 months ago
  • gravitino commented on gravitino's instructable Fountain Pen Chest2 months ago
    Fountain Pen Chest

    I'm glad you liked it! If you make one of your own, make sure to show us how it turns out!

    View Instructable »
  • gravitino commented on gravitino's instructable The First Color Photograph2 months ago
    The First Color Photograph

    That's awesome you've seen the original! Something historically I find interesting and don't know about is why it took several years between when Maxwell had the three color deduction and was able to try and do it experimentally?

    This is great. When I started this I had contemplated taking the pictures through the filters with my camera using the "monochrome" mode, but I hadn't found a satisfactory way to print the monochrome images out with just one color (red instead of black). If I could do that, it would be just a bit more like Maxwell did it. :-) Glad you enjoyed the instructable!

    Thanks! That is a great hint for finding some filters to work with! I will definitely see what I can find. I'm glad you enjoyed the instructable!

    View Instructable »
  • gravitino commented on gravitino's instructable The First Color Photograph2 months ago
    The First Color Photograph

    Thanks everyone who commented on the IR part of this story -- you are correct! In fact, modern solid-state sensors, like the one in your phone and DSLR, are also still IR sensitive. You don't get a lot of IR response because there is a filter that blocks the IR and only lets the visible light through. You can pull that filter out, or more to the point, replace it with one that only passes IR if you like (there is a an entire IR hobby community that does this). I've done this with some students with an off the shelf camera from a department store, and we flew two cameras side by side, one IR modified and one not, on a high altitude balloon. I include the images here side by side for you to see the differences. :-) Thanks for looking at the instructable, everyone!

    Thanks, glad you liked it!

    View Instructable »
  • gravitino's entry Fountain Pen Chest is a finalist in the Organization Contest contest 2 months ago
  • gravitino's entry The First Color Photograph is a finalist in the Remix Contest contest 2 months ago
  • gravitino's instructable The First Color Photograph's weekly stats: 2 months ago
    • The First Color Photograph
      326 views
      2 favorites
      2 comments
  • gravitino commented on gravitino's instructable Fountain Pen Chest2 months ago
    Fountain Pen Chest

    It's the same velvet through and through; I just called it flocking because that's what we call velvet we glue on the inside of telescopes! <shrug> As for the scissors, I agree. I was worried about cutting too close, and then as I laid the velvet down if it got off track the close cut edge would get away from the edge leaving it exposed. Since the wells are round, I didn't think I'd be able to glue the extra edge down without having big wrinkles of cloth. Any ideas there would be appreciated! :-)

    If you ever decide to do it, you can certainly do it on a smaller scale, making even one drawer. The molding idea might make a single drawer really quick and easy to build. :-)

    View Instructable »
  • gravitino's instructable Fountain Pen Chest's weekly stats: 2 months ago
    • Fountain Pen Chest
      3,766 views
      50 favorites
      16 comments
  • gravitino commented on gravitino's instructable Fountain Pen Chest2 months ago
    Fountain Pen Chest

    Thanks -- I'm glad you like it! The collection has been slowing growing since I was in college, but I've never had them all together in a nice display before. :-)

    View Instructable »
  • gravitino entered The First Color Photograph in the Remix Contest contest 2 months ago
  • gravitino commented on gravitino's instructable Fountain Pen Chest2 months ago
    Fountain Pen Chest

    Thanks, I'm glad you liked it!

    So I went and measured one of them and you are right, it is 3.1mm. However, in fraction mode my caliper calls this 1/8 in (the smallest fraction it will differentiate in display is 1/64; decimals are finer grades). But the difference between 3.1mm and 1/8" is just under 3/1000 in -- in general I would be surprised if that made a difference working with wood. Do you have experiences that suggest it does?

    View Instructable »
  • gravitino commented on gravitino's instructable The First Color Photograph2 months ago
    The First Color Photograph

    Thanks! I'm glad you liked it. I'm a physics professor, and I always thought this would be a good project for my students to learn about astronomical imaging. Now I have it written up! :-)

    View Instructable »
  • gravitino entered Fountain Pen Chest in the Organization Contest contest 2 months ago
  • gravitino commented on gravitino's instructable Fountain Pen Chest2 months ago
    Fountain Pen Chest

    Thanks -- I'm glad you like it! I was so happy that it turned out well. Though my collection perfectly fills it. I guess I'll have to follow the instructions now and build a second one. :-)

    Ooooo, that's a good idea to use moulding. I didn't even think of that! I'm going to have to make another box (see how this one is full?) for the future, so I may try that -- the routering was the most time consuming bit.Pens: Yes, I have 4 of those Star Wars pens. :-) I also have a few Retro51 roller balls, and those are on that bottom shelf -- I put Space Pen refills in them using the Parker converter end they come with. My favorite is the Smithsonian dino edition one. :-)Glad you liked the build! Let us know if you make one!

    It's so awesome to be able to see all of them and just pull one out when it strikes my fancy. I should have done this a long time ago! :-)

    View Instructable »
  • gravitino's instructable Winged Guitar Stand's weekly stats: 3 months ago
    • Winged Guitar Stand
      816 views
      2 favorites
      2 comments
  • gravitino commented on gravitino's instructable Winged Guitar Stand3 months ago
    Winged Guitar Stand

    I'm glad you liked it! We've both been very happy with the way it has turned out.

    View Instructable »
  • gravitino commented on gravitino's instructable Dymaxion Earth3 months ago
    Dymaxion Earth

    That is awesome! Just another reason why I should think about getting a laser cutter! :-D Also that link you found about projections is great -- I'll have to spend some time reading that.

    View Instructable »
  • gravitino entered Winged Guitar Stand in the Epilog X Contest contest 3 months ago
  • gravitino commented on gravitino's instructable Dymaxion Earth5 months ago
    Dymaxion Earth

    Ah, that's a cool idea, flattening it out into a piece of wall art! I could imagine that looking really nice in my study! :-)

    View Instructable »
  • gravitino's entry Dymaxion Earth is a winner in the Big and Small Contest contest 5 months ago
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    Telescope building is a great hobby. I hope you give it a try -- I do highly recommend the books I pointed to as a source of information and ideas to get you started. Glad you liked the instructable!

    View Instructable »
  • gravitino commented on gravitino's instructable Dymaxion Earth5 months ago
    Dymaxion Earth

    Thanks! I'm glad you enjoyed it!

    View Instructable »
  • gravitino's entry Dymaxion Earth is a finalist in the Big and Small Contest contest 5 months ago
  • gravitino commented on gravitino's instructable Dymaxion Earth5 months ago
    Dymaxion Earth

    I thought about doing that with magnets and facing screw heads to help hold it together on your table, but I found in testing that the magnets didn’t let go easily and it caused me to mess up other tiles I had laid down; so I opted to not have them “stick” to make playing with the tiles a bit easier. To make it work in 3D, you’d have to bevel the edges, I think. If you did that, then maybe in the 2D layout you’d still be able to slide them around? Hmmm... maybe worth trying a remix... :-). Glad you like the instructable!

    Most articles conflate the map being “accurate” with the fact that projecting onto the icosahedron facets means distortions are localized on each tile AND distortions are spread around and not concentrated in one place (e.g. like they are on a traditional Mercator projection, where the poles are highly distorted). It’s good to remember that all maps have deficiencies, even globes, and even the Dymaxion projection! But I’m glad you enjoyed the instructable. :-)

    View Instructable »
  • gravitino entered Dymaxion Earth in the Big and Small Contest contest 5 months ago
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    Cool! A friend of mine does radio astronomy with one of the old 6 foot diameter TV dishes. He does all sky maps by assembling them from "drift scans". What are you going to use for your receiver? There is a small but dedicated community of amateur radio astronomers out there.

    No, I've pushed my Dobsonians by hand for many years and am used to it at this point. As I noted in the last step, you can build an equatorial tracking table, but I haven't gone down that road yet. :-)

    View Instructable »
  • gravitino commented on gravitino's instructable Falling Sand Art Picture Repair5 months ago
    Falling Sand Art Picture Repair

    Hi Brotchie -- I don't know. I have a round one, and the access hole is a small circle in the middle of the frame (I attach a picture here). Is your frame integral to the piece, or just cosmetic? Maybe it is under the frame somewhere?

    View Instructable »
  • gravitino made the instructable Easy $5 Lightsabers5 months ago
    Easy $5 Lightsabers

    This was a great instructable! Made a set for my daughter for Christmas. She loved them! Great idea and great put together!

    View Instructable »
  • gravitino commented on gravitino's instructable Falling Sand Art Picture Repair6 months ago
    Falling Sand Art Picture Repair

    I'm glad you found it useful! I was just looking at mine and it is time to fix it again. I'm also glad I wrote it up so I know what to do now!

    View Instructable »
  • Wide Angle Reflex Finder for Amateur Astronomers

    Yay! I'm going to try and build one for my next scope project. I've never 3D printed before, so that will be new for me. My library has a print service, so I'm going to talk to them about it. I'll let you know how it turns out, and post here when i've done it. :-)

    View Instructable »
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    thank you! I'm glad you enjoyed it!

    I'm glad you enjoyed it! I added a new step with a few pictures of the Moon, which are all I have taken through Mariner (using my phone).

    I added a new step with a few pictures of the Moon, which are all I have taken through Mariner (using my phone). Most everything else is too hard to photograph with my phone, though you could upgrade the scope to be used for astrophotography.

    I added a new step with a few pictures of the Moon, which are all I have taken through Mariner (using my phone). I'm glad you liked the project!

    View Instructable »
    • Cosmos Mariner: a Large Aperture Dobsonian Telescope
      26,877 views
      257 favorites
      55 comments
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    Thanks! I'm glad you liked it.

    Thank you! I'm glad you enjoyed the instructable!

    It was definitely a lot more work than building the smaller one. As they get larger, it is harder to engineer them out of wood, though I do know of examples that are in the 36-inch range and made out of wood. A famous example is Tom Clark's "Yard Scope" (the mirror is a yard across!). https://www.cloudynights.com/gallery/image/22005-the-yard-scope-ii/

    Thanks! It was fun to build; hopefully it is all clear! The skies too (though not right now!). :-)

    View Instructable »
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    Yep, aperture fever is costly. :-( I don't have an instructable for Equinox because I built it so long ago, but the procedure is essentially the same outlined here, just scaled down to the size of the 12-inch mirror. You can do a scope like Equinox for probably less than $1000 -- the main cost is always the primary mirror. It looks like Agena Astro has 12-inch mirrors for $500. https://agenaastro.com/parts-accessories/mirrors-holders/primary-mirrors.html

    Wow! I never got to meet Dobson! I've heard a lot about him; it would have been fun to attend one of his classes!

    Thank you! It was fun, and it is fun to observe with too! Glad you enjoyed it!

    This was on the order of $10,000 when all was said and done (over half of that for the mirror). Motorizing is done easiest with an equatorial table; there are a couple of other comment threads below about that, but I just discovered last night there are a couple of nice Instructables about making equatorial tables. This one looks promising: https://www.instructables.com/id/Equatorial-Platform-for-the-North/

    View Instructable »
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    So you can make (or purchase) dual axis drives like you suggest, but operation is a bit more complicated because the two axes have to be driven simultaneously, but the rate and direction each one needs to drive at depends on where the scope is pointing in the sky. For instance, consider a star in the southeast sky. Viewed from above, the azimuth needs to rotate clockwise, and the atltitude bearing needs to lift the scope to track. For a star in the southwest sky, the azimuth again needs to rotate clockwise, but now the altitude bearings need to lower the scope. Systems like this usually need a central brain (computer) to figure out the right thing to do, and need to be alighned at startup. By contrast, an equatorial table preserves the elegance of the Dob bearings you note — the Dob si...

    see more »

    So you can make (or purchase) dual axis drives like you suggest, but operation is a bit more complicated because the two axes have to be driven simultaneously, but the rate and direction each one needs to drive at depends on where the scope is pointing in the sky. For instance, consider a star in the southeast sky. Viewed from above, the azimuth needs to rotate clockwise, and the atltitude bearing needs to lift the scope to track. For a star in the southwest sky, the azimuth again needs to rotate clockwise, but now the altitude bearings need to lower the scope. Systems like this usually need a central brain (computer) to figure out the right thing to do, and need to be alighned at startup. By contrast, an equatorial table preserves the elegance of the Dob bearings you note — the Dob sits on the table and still points using its altitude and azimuth bearings, but the table simple turns to track the stars. They are low and quite elegant. Here is a good example of one: http://www.reinervogel.net/index_e.html?/Plattform/Plattform_e.html

    View Instructable »
  • gravitino commented on gravitino's instructable Barncaster Electric Guitar6 months ago
    Barncaster Electric Guitar

    A standard telecaster body is just under 16-inches in the long dimension, and just over 12.75 inches in the short dimension. I cut my boards long (maybe 17-inches?), but only had 13-inch wide across the body after I glued the reclaimed panels together, so that was the tightest constraint. For the thickness, I planed everything before I glued it (step 6) to give me the thickness of 1-5/8 inches. Standard telecaster thickness is 1.75" according to blueprints, but many custom shops make them 1.5" (thickness of dimensional lumber). I had a cardboard template I was using to lay on the wood at each stage to make sure I had the grain I wanted in the right places and to make sure I had the full shape!

    View Instructable »
  • Wide Angle Reflex Finder for Amateur Astronomers

    This is really excellent. I always hack my Telrads and put a pulser in them, so it's great to see that built in. The wider rings will also be a great help, especially under moderately light polluted skies. I have a couple of questions:(1) What are the overall dimensions? I was wondering if my dew shield for my Telrad will fit this (I use the one from Astrosystems).(2) What do you do for the base? Does it fit in the standard Telrad base? It looks like you have a custom rail in step 6.Great build!

    View Instructable »
  • Cosmos Mariner: a Large Aperture Dobsonian Telescope

    I'm always glad to hear when people fix their telescopes! It means you'll get out under the stars more! :-) I'm glad you enjoyed the instructable.

    No, I'm a completely visual observer. I keep notes about what I see and sometimes make (crummy) sketches, but don't do any astrophotography through the telescope (I will sometimes hold my phone up and snap a pic of the Moon, but I don't have any I'm sure came from Mariner). However, the views are *STUNNING*. I long ago finished my Messier Catalog with my smaller scopes, but the amount of more detail that can be seen with Mariner is amazing (eg. spiral arms on galaxies!), so I'm slowing revisting things I've already seen before just to look at them again. :-) I'm glad you like the instructable!

    Thanks! I'm glad you enjoyed it. Clear skies!

    Good question. I don't have any tracking. I work between 60x and 120x normally, and things stay in the field for a minute or more. To track along you just give it a bit of a bump; after observing with Dobsonians for so long, it's quite natural to track along. The easiest way to add tracking is to build an "equatorial table" -- I've thought about it, but it would require having power in the field to drive the motor. I've been fine so far. :-)

    View Instructable »
    • Sonification of Gravitational Waves With Lego Mindstorms EV3
      3,077 views
      23 favorites
      3 comments
  • Sonification of Gravitational Waves With Lego Mindstorms EV3

    I'm glad you enjoyed the instructable! Yes, it is calculated directly from a physical model, though I've done some streamlining (mostly factoring out constants and setting them equal to 1, since the true physical numbers are tiny). I'll see if I can boil the basics down to a 1 page PDF and add it to the instructable. You can certainly do it in Matlab/Octave or other environment. Most of us do it in python or Mathematica. The event you speak of was the first LIGO detection (there is a link to the detection page in Step 1). For those interested, you can download all of the data from all of our events at the Gravitational-Wave Open Science Center: http://gw-openscience.orgYou will also find there: tutorials on analysis, explanations of the events, and audio for each of the events we've d...

    see more »

    I'm glad you enjoyed the instructable! Yes, it is calculated directly from a physical model, though I've done some streamlining (mostly factoring out constants and setting them equal to 1, since the true physical numbers are tiny). I'll see if I can boil the basics down to a 1 page PDF and add it to the instructable. You can certainly do it in Matlab/Octave or other environment. Most of us do it in python or Mathematica. The event you speak of was the first LIGO detection (there is a link to the detection page in Step 1). For those interested, you can download all of the data from all of our events at the Gravitational-Wave Open Science Center: http://gw-openscience.orgYou will also find there: tutorials on analysis, explanations of the events, and audio for each of the events we've detected that we make with our professional tools (that page is here: https://www.gw-openscience.org/audio/ ).Have fun!

    View Instructable »
  • gravitino's entry A Tiny Telescope Observatory is a winner in the Tiny Home Contest contest 8 months ago
  • gravitino commented on makeorbreakshop's instructable How to Make a Rubber Stamp8 months ago
    How to Make a Rubber Stamp

    Nice one. I've been thinking about doing this sort of fine scale carving with my xCarve but in some tests (trying to etch on anodized metal) I'm struggling with the right thing to do to get fine details, like around the "and" in your logo. So I have two questions: (1) The way you carved this with the V-big -- you did all the large areas with the V-point? So it just had to make a jillion passes? (2) You said you might do it with an end mill first -- would you have a separate pattern to do the large areas, then one like this for the fine patterns with the V-bit? Thanks! Nice instructable!

    View Instructable »
  • gravitino commented on gravitino's instructable A Tiny Telescope Observatory8 months ago
    A Tiny Telescope Observatory

    Yep, I built both my telescopes (the one in my profile pic, and the one in the observatory). They've been very dependable. :-) Glad you liked the build.

    View Instructable »
  • gravitino's entry A Tiny Telescope Observatory is a finalist in the Tiny Home Contest contest 8 months ago
  • gravitino commented on bcrocker1's instructable Truck Camper Platform/Bed8 months ago
    Truck Camper Platform/Bed

    This is great! I've been thinking about this in my Tundra to make camping quick and easy. I've been trying to find a high rise shell like the 122 you used. How much headroom do you have from the top of your rails to the top of the shell? Great build!

    View Instructable »
  • gravitino commented on gravitino's instructable A Tiny Telescope Observatory8 months ago
    A Tiny Telescope Observatory

    Thank you! I'm glad you enjoyed it!

    Lol! Of course, I never get much sleep if I'm out observing. :-) When I built this one, my wife said "There are worse things you could be doing!" I hope you build one -- if you do, make sure to show us the result here on Instructables!

    View Instructable »
  • gravitino's instructable A Tiny Telescope Observatory's weekly stats: 8 months ago
    • A Tiny Telescope Observatory
      8,212 views
      98 favorites
      32 comments
  • gravitino commented on gravitino's instructable A Tiny Telescope Observatory9 months ago
    A Tiny Telescope Observatory

    The lock is "to keep the honest people honest." With only single panel wood for construction, I decided there are any number of ways that someone could destructively get into the observatory if they really wanted to. Popping the roof is one, as you note, though it would be at the cost of destroying the overlapping ridge panel. It also would be difficult to get the telescope out that way, as you'd have to lift it over the wall!

    View Instructable »
  • gravitino commented on gravitino's instructable A Tiny Telescope Observatory9 months ago
    A Tiny Telescope Observatory

    Hi Stephen, I'm a completely visual observer, so I don't have the constraints of the photography crowd. IN practice, the floor is a bit over-built, and the observatory is so small there are seldom people walking around inside, so I get very little transfer from the floor to the scope. In the Note to MarkF147 below, I put a picture of another observatory I built where I put the Dob on a wooden pier (because people could walk around), and it worked just fine for visual work. If I was going to do photography, I would have done a pier, but didn't want to pour one. :-)

    That's a neat idea; I've never seen lift-off ends, though I have seen people fold the peak down (typically the south wall). In this case, given the light I have in the north and south, I'm not sure I needed to do that. But I'll put that idea down for the next observatory... :-)

    View Instructable »
  • gravitino commented on gravitino's instructable A Tiny Telescope Observatory9 months ago
    A Tiny Telescope Observatory

    My neighbors all know it's a scope and observatory. I think the lights get left on by habit or accident, and at midnight I don't think I should be knocking on doors! My improvised screen works pretty well for the times it happens. But you're absolutely right -- having an impromptu star party for your neighbors does wonders for relations. :-)

    Far and away the best thing to do would be to pour a pier for the Schmidt-Cassegraine -- that is not an uncommon practice in amateur observatories. You need to bury it past the frost line, make sure it is reinforced with mesh/rebar, and pour it to a convenient height for your needs. At the top, as you note, you'll have to put lugs in that will match a wedge or interface plate for your scope. The big deal there is the permanence, as you note. If you want to stick with your tripod, you can isolate it with a little more wood working. If you're doing photography with your scope, I think that is the right way to go. If you're just using your eyeballs though, the tripod is probably easier. I built another observatory where I did that for the Dob by building a platform in the center of the obs...

    see more »

    Far and away the best thing to do would be to pour a pier for the Schmidt-Cassegraine -- that is not an uncommon practice in amateur observatories. You need to bury it past the frost line, make sure it is reinforced with mesh/rebar, and pour it to a convenient height for your needs. At the top, as you note, you'll have to put lugs in that will match a wedge or interface plate for your scope. The big deal there is the permanence, as you note. If you want to stick with your tripod, you can isolate it with a little more wood working. If you're doing photography with your scope, I think that is the right way to go. If you're just using your eyeballs though, the tripod is probably easier. I built another observatory where I did that for the Dob by building a platform in the center of the observatory. I framed the floor joists around an open square, then built a mini frame of joists that sat in the square on its own footings that went to the ground. I put weather stripping around where the mini-frame and the main floor joists interfaced to keep critters and bugs out. It worked pretty well; you could probably do something similar with your tripod footing. I clipped together some old photos to show the framing, and the only shot I have that shows the footings.

    View Instructable »
  • More Activities