Luke Korth

Space Calendar

Mon, 18 May 2026 00:00:00 -0400

A while back the New York Times shut down their space calendar, which I had subscribed to for years. It was a single curated calendar feed covering rocket launches, moon phases, eclipses, meteor showers and more. I couldn’t find a good replacement so I set out to build my own twist on it and wrote Space Calendar.

Space Calendar generates personalized ICS feeds you can subscribe to in Google Calendar, Apple Calendar, Outlook, or anything else that supports calendar subscriptions. You can pick what categories you want — launches, sky events, planetary events, space history anniversaries, and more — and get a URL to subscribe to. It includes the things you’d expect — moon phases, top meteor showers — but also includes local astronomy club events, recently discovered asteroids, and localized, up-to-date aurora forecasts.

Most of the geometric data is static. Moon phases and eclipses don’t change so they’re pre-computed from USNO and JPL data via a GitHub Actions workflow. Rocket launch schedules are temperamental, so they’re pulled from The Space Devs Launch Library and cached hourly. Aurora forecasts come from NOAA and refresh every few hours. All run at the edge on Cloudflare Workers.

You can set it up at space-calendar.lukekorth.com and the source is on GitHub. Ideas, requests, and contributions are welcome.

Getting an SSL Certificate

Mon, 09 Mar 2015 00:00:00 -0400

Two or three times a year I end up needing to update my expiring SSL certificates. Each time I have to look up the one or two commands I need and every time it takes two or three websites to find the right information so I’ve recorded it here for future reference and in the hopes that it helps someone else as well.

Generating a new CSR:

openssl req -new -newkey rsa:2048 -nodes -keyout example_com.key -out example_com.csr

OpenSSL will prompt you for the details of the certificate, they can be filled out in any level of detail you wish. The common name that is requested should match the domain the certificate will be used for; for wildcard certs the subdomain should be a star, for example *.example.com.

Once the CSR has been generated it should be submitted to the certificate authority. In return they will send your new certificate along with a copy of the intermediate and root certificates. The intermediate and root certificates will need to be chained or concatenated to your new certificate as follows:

cat example_com.crt intermediate_cert.crt root_cert.crt > ssl-cert.crt

Note: you may need to consult your certificate authority’s documentation to find which certificate is the intermediate and which is the root. For PositiveSSL through Comodo, purchased using NameCheap, my concatination was:

cat example_com.crt COMODORSADomainValidationSecureServerCA.crt COMODORSAAddTrustCA.crt AddTrustExternalCARoot.crt > ssl-cert.crt

You can now take the concatenated SSL certificate and your private key that was created during the CSR generation and use it with your web server of choice.

500px Embedding for Jekyll

Mon, 08 Dec 2014 00:00:00 -0500

Update

On June 15th, 2018 500px shut off their API. This plugin used the 500px API to retrieve information about a photo in order to render the embedded html and no longer functions without the API.

Original Post

From time to time I like to read through 500px ISO to look at the amazing photos and gather some inspiration. One of my favorite parts of 500px ISO is the overlay on the photos that allow you to vote and also link directly to the photo and photographer on 500px.

I recently realized 500px ISO was just using the embedded snippets built right into 500px. On 500px, right next to the sharing buttons, there is an embed button that provides a chunk of html and some javascript to embed a photo. Since I’d rather not copy the chunk of html for every photo I want to embed, I wrote jekyll-500px-embed to use on my website. jekyll-500px-embed is a Jekyll plugin that adds a 500px Liquid tag for use on your Jekyll powered website. The README details the setup required for the plugin, but once it’s setup you can simply pass the photo’s id to the 500px tag

{% 500px 89255597 %}

and when your site is built, it will produce the following

jekyll-500px-embed is available on GitHub. New features and pull requests are welcome.

Android 5.0 Breaks Dislock

Mon, 17 Nov 2014 00:00:00 -0500

Since the final release of Android Lollipop has started to roll out to devices in the last week or two many users of Dislock have noticed that it no longer removes the pin or password set on their device. I’ve spent a lot of time testing and trying a few workarounds, but the results are all the same, the removal of a pin, password or pattern has no effect until after a reboot. This breaks Dislock on Lollipop and most likely future versions of Android. Other apps like Dislock have also had the same problem. A few days ago I published an update to Dislock on the Play Store that restricts it to KitKat or older version of Android, specifically Dislock only supports API 14-19, Android 4.0 - 4.4.

It’s sad to see a breaking change in Android effectively kill an app that I’ve spent so much time and effort working on and supporting for close to two years now with many thousands of users. The user base of Dislock has a large majority on KitKat and on devices that will very soon receive over-the-air updates to Lollipop.

The light at the end of the tunnel for users is Lollipop has very similar features built into the OS now and they will be able to transition over to them when upgrading. It’s possible that this change was deliberate to prevent Dislock and apps like it from interfering with the now built in support.

Please feel free to comment or email me if you have further questions.

Photo Paper

Wed, 12 Nov 2014 00:00:00 -0500

Update

On June 15th, 2018 500px shut off their API. Photo Paper’s features rely on the 500px API and no longer function without access to the API.

Original Post

I’m a big fan of 500px, from time to time I post my photos there and I’ll happily spend hours looking through the amazing photos that others have posted. One day I was staring at the same boring wallpaper on my phone and I thought it would be really nice to have a live wallpaper that used photos from 500px. Unsurprisingly there are several in the Play Store ranging from really bad to pretty good. I gave them a try, but I wasn’t very happy with them. Several of them are freemium and most of the ones I’ve tried are live wallpapers and continuously use a lot of ram. It also bugged me that none of them were open source.

After thinking about if for a little while, I decided to develop my own app that automatically updates the wallpaper instead of being a live wallpaper. Using a few libraries it was very easy to develop in just a few hours time. Users of the app have a range of options for filtering the type of photos they would like to see as their wallpaper along with how frequently they should update. I’ve released Photo Paper to the Play Store and it is also open source on GitHub.

As always feel free to comment here, create an issue on GitHub or contribute with a pull request.

Astrophotography Workshop

Sun, 09 Nov 2014 00:00:00 -0500

At the end of August I had the chance to attend an astrophotography workshop by Sean Parker in North Lake Tahoe. This was my first time attending a photography workshop of any kind and I didn’t know quite what to expect.

After signing up Sean was very helpful and knowledgeable, recommending lenses and making sure I had all the gear I needed. I have tried my hand at astrophotography in the past and never had great results so I was looking forward to learning from such a talented photographer. When I arrived, Sean talked through everything I needed to know about setup, camera settings, shooting the night sky and milky way. Within 15 minutes I had my camera setup and was shooting. One of my best photos of the night came from the first few I took.

After spending some time learning how to shoot the milky way and take composite photos, Sean taught us about light painting with headlamps and other light sources. To finish up our shoot on the beach we did a series of self portraits, resulting in my favorite photo of the night.

For the second part of the night we drove up the mountain and setup to take star trails. We shot a few photos to get setup and then let our cameras do the work. I ended up shooting for 80 minutes and taking 191 photos. The work came later during post processing where I batch edited all the raws and then edited out all of the planes from each individual image. Once this was done I used StarStaX to combine all 191 photos into a single photo.

Almost as an after thought I decided to try a timelapse as well since I already had the photos and went through all the work to edit them. I’m pretty happy with the result having never done it before.

I attempted to shoot the following night as well, but the evening turned out to be very cloudy. The workshop couldn’t have gone better, Sean is an excellent teacher and a phenomenal photographer, he is more than happy to share the tools and techniques he has spent so much time finding and developing. I learned a great deal about photography and the night sky in general. If you’re at all interested in photography I highly recommend you take one of his workshops, I know I look forward to the next time I can attend one of Sean’s workshops. I also have a feeling I’m going to be spending a lot of money on gear in the future, I’m hooked.

Pebble Locker Renamed to Dislock

Fri, 31 Oct 2014 00:00:00 -0400

A week and a half ago I released an update to Pebble Locker that changed the name to Dislock. For eight months now Pebble Locker has supported many more devices than just Pebbles and it was past time for a new name. Another factor in the name change was Pebble changing their recommendations on how apps are named to make it clearer who is developing the apps.

Along with the rename comes more free features. Previously only Pebbles could be used with Pebble Locker for free, using other Bluetooth devices and WiFi networks required an in-app purchase. Now with Dislock the use of one Bluetooth device or WiFi network is free, using more than one trusted device requires an in-app purchase. It’s now easier for users to try Dislock for free and if they only need one device, continue to use it for free forever.

If you experience any issues with the update or have any requests, as always, feel free to use the in-app contact option to email me.

Pebble Developer Retreat 2014

Thu, 09 Oct 2014 00:00:00 -0400

Another year, another awesome Pebble Developer Retreat. The retreat this year was 4 days of talks on new features, making great looking images on a black and white display, pushing Pebbles to their limits by running OpenGL and writing directly to the framebuffer, a developer meetup, Pebbles talking directly to other devices over Bluetooth 4 Low Energy, a whole day of Pebble controlled robots playing soccer, how to get the best battery life possible and developers showing off what they’ve developed for Pebble. Over 100 developers from 14 countries were present.

The retreat started off with an introduction to the new APIs including the FrameBuffer API for advanced graphics and Background Workers for always on, background activity monitors. Pebble also announced a few new APIs they are working on that are coming soon, the Wake Up API allows apps to schedule a time when they should be brought to the foreground to run and Bluetooth Low Energy (LE) support for a central role.

A Pebble employee gave a talk on battery life, which remains one of Pebble’s key features, during the retreat and I found the stats shared to be very interesting. Running current firmware, a Pebble battery will last for

4 hours with the backlight on constantly
1 day when using a watch face with a 30fps animation
36 days when Bluetooth is turned off
14 days when using a watch face that updates every minute
12 days when using a watch face that updates every minute and a background app with accelerometer sampling at 100hz with 25 sample batches
9 days when using a watch face that updates every second

For those optimizing animations, Pebble also pointed out that the screen is drawn in rows so an animation that updates fewer rows per frame will results in better battery life.

Developers were given the chance to put the Bluetooth LE APIs to work on Saturday; an alpha firmware build with Bluetooth LE support was distributed, which allows Pebbles to act in a central role and talk to other peripheral Bluetooth LE devices. And of course what fun would these be without a challenge and a little bit of competition? The goal was to use Pebble’s Bluetooth LE support to talk to a microcontroller and remote control a soccer playing robot. Developers spent the day Saturday building robots and writing code to control them and the evening and night playing a highly competitive series of soccer games. The recording of the live stream is on YouTube. This was by far and away the most fun I’ve had at a retreat or conference.

The retreat was a great experience, meeting talented developers from around the world and seeing how quickly Pebble is iterating and adding new features that make the platform more useful than ever. Hats off to everyone at Pebble for their work organizing and running it.

Pebble Locker Adds Android Wear Support

Mon, 21 Jul 2014 00:00:00 -0400

Last week Pebble Locker added first class support for Android Wear allowing users to add their Android Wear devices as a trusted device and automatically lock and unlock their phones and tablets.

Pebble Locker uses the WearableListenerService to learn when Android Wears are connected and disconnected. The source code is available on GitHub

Pebble Locker Mentions

Sun, 11 May 2014 00:00:00 -0400

Pebble Locker made Android Central’s Apps of the Week list this week.

A few months ago Pebble Locker also made Paste Magazine’s Top 10 Must-Have Pebble Smartwatch Apps