This is the first of a series of articles. As I'm always experimenting and tuning my setup, I'm not sure how many more articles I'll be writing.
A few years ago I began to introduce myself to astrophotography. I had some fairly nice equipment back then: a SkyWatcher HEQ5 mount, a Meade ACF 8", guide scope and camera, a borrowed reflex, laptop, 12v car battery.
Although this is pretty much entry level equipment, barely sufficient to getting started, it had been already quite expensive (almost 2000€ just for scope and mount, even though the scope was second hand), bulky and heavy. I ended up barely using it, both because of a relatively steep learning curve and because I honestly was getting tired of carrying around 20/30KG of equipment with barely any tangible result.
Then a few things happened: the mount was stolen, I sold the optical tube, and ended up moving to London, where I embraced a new "astronomical philosophy": the lighter, the better.
I was also lucky that this was when some fancy new products like the Star Adventurer started to go "viral", which contributed to lower prices, good support, and good publicity as well, so it wasn't long until I got mine too.
Of course, the Star Adventurer is only half of the story: you also need optics, and some kind of camera. The Star Adventurer is often seen as the best pal to DSLR cameras, it can even trigger shooting using a specific cable, but what about other cameras, like CMOS/CCD astronomy cameras? I wanted to use a Mono camera with filter wheels, specifically an ASI 1600MM. This means you need to use a laptop to drive the camera, download the images (no SD Card slot there), rotate the filter wheel, etc. This might not seem a complicated addition, afterall everyone has a laptop, nowadays. The problem is that a laptop's battery, out in the cold nights, doesn't usually last long. You'd need to bring some sort of power source, like a 12V car battery (heavy, bulky equipment again). You might also want some table and chairs, as it's probably not a great idea to just leave a laptop on the wet grass while shooting.
Long story short, this is when a second "viral" world comes in handy: Single Board Computers, with its most famous example, the Raspberry Pi.
I'm now trying various alternative boards, but by far right now the Raspberry Pi (specifically the 3rd version) is the most reliable, the one I'm still actively using.
This is my typical setup/workflow:
The ASI camera and filter wheel are connected directly to the Raspberry Pi. The Raspberry is usually strapped nearby, either to the mount, on the counterweight, or on the scope tube. Being very lightweight, it doesn't really affect balancing, and it doesn't affect the mount load.
The Raspberry Pi is powered by a 20Ah power bank, the same you normally use to charge your mobile phone (I use the 20Ah version to get more "juice", since the Raspberry Pi, despite being a very low power device compared to a laptop, is still relatively power hungry).
For the software part, the Raspberry Pi runs an INDI server, and your client of choice to manage the imaging part. You can use KStars/Ekos, which is usually the best choice among INDI clients, and it's a very nice software indeed, but instead I'm developing my own scripts (which soon will become a webapp). You can have a look at my repo here: https://github.com/GuLinux/indi-lite-tools, but I'll be making a specific post later on. An easier, but less performant and more power consuming alternative, is to use a desktop version of Raspbian (or Ubuntu), and simply use VNC to remotely control your raspberry Pi.
Finally, you'll still need a laptop: pointing your target, adjusting the field of view, focusing, and exposure, they all need you to view what your camera is currently pointing. But here comes a little trick: you need a laptop only for these initial steps, which with pratice can last only 15/30 minutes. You won't need any large battery for your laptop, simply because you won't be using it for more than half an hour. And to get the images, you don't need to connect your laptop to the camera (and filter wheel), nor you need an ethernet cable from the Raspberry Pi to the to the laptop: the Raspberry Pi v3 has a builtin wifi interface, that can also act as an Access Point.
You can then simply connect your laptop to your Raspberry Pi Wifi, use KStars/Ekos to connect to the INDI server running on the Raspberry, and wirelessly get the images. Then, you will start the sequence on the Raspberry Pi itself, turn off your laptop, and... just enjoy the night sky :)
Or if it's particularly cold, and/or you're tired and want to rest, you can go inside (your house, your car, tent, or whatever), and wirelessly check on your sequence.
In summary, these are the advantages of this setup:
- Low power requirement (a large capacity mobile phone powerbank is more than enough to run it for multiple nights).
- Extremely lightweight, it's even possible to bring your astro equipment with you on a plane, effortlessly. Even the 20Ah power bank weights less than half a Kilogram.
- Hardware compatibility (INDI can support lots of devices).
- "Plugin friendly": a Raspberry Pi can be expanded with more hardware, both using the USB ports or GPIO. I tried connecting an RTC clock, an OLED display (showing current sequence progress), a buzzer to warn me if an error occured, a GPS module to get the exact coordinates, etc.
And the disadvantages:
- Setup can be very difficult for people not used to Linux command line (althought the VNC method described above is fairly easy). I'm working on a "provisioning script" that can easly setup the Raspberry Pi in just a couple of simple steps.
- Low transfer speed: the Raspberry Pi 3 still uses USB 2.0. With my setup, I usually have short exposures (under 60 seconds, sometimes even just 15 seconds), and the Raspberry takes up to 4 seconds to save an image, before shooting the next one. This means that a significant portion of the shooting time will be wasted waiting for image saving. Low USB speed also significantly increases Amp Glow. This is why I'm currently experimenting with some USB3 boards, instead of the raspberry.
Last saturday, after lots of garden testing and software checks, I've finally been able to drive to a dark place for a few deep sky shots.
The driving part itself was the most "scary", as I'm still new to driving in the "wrong side" of the road... Getting the hang of it, though..
I chose to go observing with the HantsAstro stargazing group.. they met in a quite dark site (at least for being not too far from London), and their website and facebook pages really did inspire me. I'm really glad I joined them, as it was a really pleasant evening, with lots of nice people.
My target for the evening was the center of the Cygnus constellation, between Deneb and Sadr. It's an area full of nebulae, perfect for a wide field lens. Technical data, together with stars and object names, can be found in the astrobin technical page.
This weekend weather in London was quite amazing: sunny, a bit too windy, but sky almost perfect. Seeing forecast was also encouraging, so on Friday evening I took a chance to shoot at Jupiter.
It was a bit of an unlucky evening: firstly I discovered that I forgot my red dot finder on, so the battery was totally drained. After struggling for a while trying to align my GoTo mount without it, I decided it was worth to leave the telescope alone for a few minutes (my garden is easly visible from the street... I didn't want to do it unless absolutely necessary) and got back inside to find new batteries.
After everything was aligned, and I was ready to observe and record my images, I noticed that the image wasn't exactly satisfying at the eyepiece. When I replaced the eyepiece with the camera, the very unfocused image revealed me why: some tree branches were in the way, and of course the image was deteriorated from the interference!
I looked around me to see if I could find a better spot to place my scope, but with no luck. I decided to try anyway, taking multiple shots, so maybe in some of them I might get an almost clear picture.
This is the best result I could get:
Of course, the difference with my previous shots taken with a bigger 200mm SC is pretty visible, but I think with better conditions this new telescope can do much more.
Since I made four sets of images, spanning a bit more than 40 minutes, I was also able to an animation showing Jupiter rotation:
- Celestron Nexstar SLT 127 Maksutov
- ZWO ASI 178mm with LRGB filters
- Software: my Planetary Imager for shooting, Autostakkert!2, Registax, Siril and GIMP for image processing.
Luminance channel: 4500 frames, best 20% used. R/G/B channels: 1000 frames, best 40% used.
I'm currently living in a house with a very nice backyard, right outside London. Still a lot of light pollution, but it can be manageable, and useful for testing my equipment before running to darker locations.
This was meant to be a (L)RGB shot, but light pollution and humidity made the blue and green channels pretty useless, while red channel produced quite good results
Last friday night the sky was finally very clear, so I made a few shots.
The brilliant Orion Nebula (M42) is very well defined, but also the Flame nebula (NGC 2024) is quite conspicuous on the left. And very close to the Flame nebula, a tiny Horsehead nebula can be spotted too.
For being just a test shot, I must say I'm very happy with the result, and can't wait for better conditions to try RGB.
This sunspot was particularly big, so I waited for the best moment to try and catch it.
Seeing wasn’t great, and my solar filter was a bit damaged, but the final image doesn’t look too bad anyway.
Unfortunately, this will be the last image for a while.
Just a few hours later, someone opened my car, and took away my HEQ5 mount, together with all my eyepieces and the camera I used for all my planetary shots.
I’ll also be relocating in a while, so I’ll wait a few months before buying a new setup.
If someone is interested, I’m selling my current main optical tube here: http://www.astrosell.it/annuncio.php?Id=70007
This was meant to be an improvement to the previous ISS shooting, since I tried to do it with a bigger telescope, but the low altitude and the very bad seeing did actually worsen the quality.
The shape of the Space Station is anyway clearly visible, as it passes in front of the Moon. It is dark, this time, because it already entered in Earth shadow. We could actually see it rising, bright as usual, and then slowly fade until it completely disappeared just a few seconds before crossing the Moon.
Technical details of the shot can be found on the pagina Youtube.
Mars is getting really close to 2016 opposition, the best in the last 10 years, since it’s very close to earth.
Weather in Milan wasn’t great these days, so me and Alessia tried to catch the first night offering a clear sky and a possibly good seeing.
We were pretty much lucky: seeing wasn’t the top, with mars being very low on the horizon, but it was good enough to get a proper look: we were able to distinguish a few major features, particularly when it began to rise a little bit over 20°.
I also took a few pictures, this is the best result, shown here with a Stellarium simulation for that day and hour.
We observed also Saturn, getting close to its own opposition too, although even lower in the horizon than Mars, and Jupiter, still quite high and bright in the sky.
At the eyepiece, it was impressive: the great read spot was particularly evident, and a satellite (we later identified it being Europa) was getting closer and closer to the planet disk.
When I started shooting with my camera it was already over Jupiter, and it’s visible as the bright spot in the left part of the planet.
Although the images are not as good as I was hoping, it was a very nice evening, we could finally have a good couple of hours doing astronomy, and it was a relief after a long time being unable to observe due to bad weather.
Last august I had the chance to see the International Space Station passing in front of the moon right from my home.
The ISS is clearly visible many nights, and depending on the user position on Earth, it might align with some object in the sky.
These days I was reorganizing my gallery, and I found the original video.
So, after reprocessing it a while, I decided to republish it.
The ISS is really fast: the video is slightly slowed down. I remember that during the transit I couldn’t see the station, and I waited a few minutes because I couldn’t know if the transit already happened or not: it was still daylight, and in the original frames is barely visible.
Only after watching the video I could finally notice that tiny dot passing right in front of the moon.
For this shot, I used my old Celestron Astromaster 130, in an alt-azimuth mount, and my QHY5L-IIm as shooting camera. I had to try following manually the moon, since I obviously had no motorized tracking.
I had to use the 130mm scope instead of my main 8″ scope because of the shorter focal length: this way I could shoot almost the whole moon, so I could be sure that I didn’t miss the ISS.
Spring is back, and here in Milan we finally had a few days (and nights) of very nice weather.
I also bought a new lightweight battery for my HEQ5 mount, instead of the usual heavy car battery I’ve been using until now, so I took a minimal setup and placed myself in a local park.
Seeing wasn’t perfect, but it was fine enough to shoot a few nice details of an almost full moon.
More importantly, Jupiter was at opposition a few weeks ago, so it’s still in a very favourable position.
After rediscovering Siril, a nice astronomical images preprocessing tool for GNU/Linux, I wanted to give another try at processing a few test images taken this summer.
It’s surely not a masterpieces, but I’m not too disappointed either by what I could make of them, given that it was just a basic attempt, with no more than half hour total shoot time.
Postrocessing was done using DarkTable.