Astro Session: October 12, 2018
Wide-field of the Wizard Nebula surrounding the open star cluster NGC 7380 in the constellation Cepheus, about 7,200 lightyears aways from us. I reduced the saturation so that you hardly notice the differences in the RGB mix, mostly R and B because this is a bi-color set with Ha and OIII. I think I prefer this reduced color or even a completely desaturated (grayscale) version. There are so many stars in this image and I'm not a fan of the off-color red and blue stars you get with narrowband. Also in this shot, I particular like the dark band at the top left. These "dark fog" or dark nebula regions consist of interstellar gas and dust that absorb the light from surrounding stars, and the constellation Cepheus has some famous dark cloudy areas, B 174, 150, and several around IC 1396. (16 x 300 second exposures in Ha and OIII, Atik 414EX mono CCD, Astronomik 12nm Ha, OIII filters, William Optics ZS61 + WO Flat F6A f/4.7, CEM25P EQ mount, Orion OAG + ZWO ASI120MM-Mini guide cam, Stellarmate OS (INDI/KStars/Ekos) running on Raspberry Pi 3b+).
Posted October 12, 2018
Small Refractor Mods: August 25, 2018
There were several high-quality 60mm apochromatic refractors that entered the market last year. They were pitched as portable wide-field scopes, and also marketed here in the US for the solar eclipse last summer. Starting around $450 USD, these little refractors, like the William Optics ZenithStar 61 sold out quickly. I didn’t get a chance to purchase one until May of this year.
The ZS61 has a 360mm focal length at f/5.9, synthetic fluorite objective lens--FPL-53, which has some amazing optical properties. It’s a great scope, with a solid focuser. But there’s an easy modification that will make it even better. I found one thing when I added the imaging train--here’s my narrowband setup, with an Atik414EX monochrome CCD, a ZWO filter wheel with 5 filters, hydrogen-alpha, oxygen3, sulfur2, clear, and a near IR 685nm longpass. With the field flattener this ends up around 3.2 pounds or 1.45kg. These scopes--I keep saying these scopes because there are several varieties of the same basic components, a few of them with the same focuser, focal length, and aperture, differing--as far as I can tell--only with the hardware, knobs, lens caps.
Anyway, the first thing you probably want to do with these is strengthen the scope’s connection to the dovetail bar. The stock version comes with this clamshell ring and shoe, and if you’re going to do anything other than some light visual astronomy, you will want to backup the stock ring with another. I found that when I added the camera, filter wheel, and guider, the whole system had a slight flex to it if I lifted or pushed down with the camera. At first I thought it was the focuser and was a bit bummed about that, but then I noticed it was the whole scope moving, and it all relied on this rather slender ring and shoe. The focuser itself is very smooth and very solid. It’s a dual-speed rack-and-pinion type, and so you may want to adjust some of the tension screws depending on the load you’re planning to add--a DSLR or more, but out of the box, this focuser along with FPL-53 glass makes this scope worth considering for your wider-field work.
To remove that flexure in the system, I bought a ZWO 78mm Holder Ring for ASI Cooled Cameras to see if it would work. The tube’s diameter is around 76mm, and with a delrin shim or something similar, the 78mm inside diameter of the ZWO ring worked almost perfectly. The one gap--literally--was with the two shoes of each ring. The stock William Optics one is ¼” (6.35mm) taller than the ZWO ring. Easy solution: I went to my favorite aluminum supplier (you have one, right? See the links below) and bought a set of stock aluminum pieces, 2” x 3” x ¼”, then drilled, and stacked it with the dual ring setup. Now the whole system is perfectly rigid with two strong foundations.
The other advantage of going with the ZWO holder ring are the risers with the threaded holes on the top and bottom. I added one of these SmallRig cheese grater mounting plates on the top--you should always have one or two of these on hand for bolting things together. They’re tough, anodized aluminum, and full of threaded holes of varying sizes. I use these on the ZS61 and my William Optics GT81 to connect the control hardware and power--usually a Raspberry Pi3b and 12v battery pack. What’s nice is I can use a couple hexcap screws to quickly add or remove all devices from one scope to the other.
So, there you have it. An easy way to build more rigidity into a nearly perfect portable wide-field setup. Let me know if you have questions, or a better way to accomplish this. I added some links below for the components I used.
https://www.highpointscientific.com/zwo-78mm-holder-ring-for-asi-cooled-cameras-ringd-78
https://www.amazon.com/dp/B019C2ZM8Q
For aluminum: Stoners Tools and Raw Materials
https://www.ebay.com/str/stonerstoolsandrawmaterials
Ebay listing for the 2” x 3” x ¼” aluminum bar stock:
https://www.ebay.com/itm/281291003556
Posted August 25, 2018
Astro Automation: August 19, 2018
Running a distributed INDI-based astro-imaging setup
This sounds grander than it is, but it’s not incorrect. And INDI makes it easy, with distributed processing built into the protocol, so that once you have your devices plugged into some number of machines (e.g., Raspberry Pi's) and you establish a chain of priority--who's calling who, there's no difference in the way any app (like Ekos) interacts with the INDI-based system, whether it's a single computer or a group of computers.
My main reason for dividing instances of the INDI server across two Raspberry Pi's is to separate my iOptron CEM25P mount from the rest of the hardware (CCD, filter wheel, focuser, guide camera). I want to run the telescope-based components over wifi, with a dedicated battery pack, so there are no cables running from the mount to...anything. Everything is attached to the scope, including the rechargeable battery. And everything is controlled from my Macbook Pro over wifi. The problem to solve, which started me down the chained INDI server path, was to exclude the Go2Nova 8408 hand-controller from the mix. The iOptron mount passes all slewing and guiding commands (and everything else) through the controller over serial. I don't know if this is unique to iOptron mounts, but I don't have to do this with my Orion Atlas EQ-G; the serial cable from the computer plugs directly into the mount, without having the SynScan controller in the middle. Here’s the general idea with the CEM25P: in order to control the mount from any command software using INDI or ASCOM you connect the Go2Nova controller to the mount as usual, and then run a serial cable (RS232 -> RJ9) cable from the controller to your computer, in this case, a Raspberry Pi3B+ mounted on the telescope. This is fine if you don’t mind running cables to and from your scope, cameras, focuser, filter wheel--for power and data. This is how I’ve run things on this mount for the last year or so.
What changed? I’ve been looking at the StellarMate gadget for a while now, and Jasem’s presentation on the Astro Imaging Channel (https://youtu.be/XkgwY_KsBjc) tipped me toward checking it out. He did a great overview of single-board computers in astro automation, with particular focus on Raspberry Pi's and the Atom-based Windows machines that have become popular. My goals with astrophotography have also changed over the last couple years; I've been moving more toward portability and automation, minimizing setup time, and using smaller refractors and lightweight but accurate EQ mounts. (Another general reason to go with StellarMate OS is it works great with the faster Rasp Pi 3B+. Just purchase the OS on stellarmate.com, download, flash an SD card, and you’re good to go).
Here's a diagram that shows one of my astro device setups. I spent the day getting this going, but haven't been able to get out under the stars with this yet. So far I've tested out the startup process several times, and successfully used all the connected equipment--slewing in KStars, taking a dozen exposures with the main CCD and guide camera, testing the focusing system. Everything worked well, but I think the final test will be guiding. I don't expect any problems, but that's the one connection that relies on one INDI server talking to another without any complications.
Any downsides to this setup? I don’t see any with the system distribution side of things. The only critique of chaining INDI servers I’ve read is about potential inefficiency and network latency, but I don’t see a problem here. Correct me if I’m wrong, but network speeds, even over a slow-ish wifi connection, are still going to be astronomically faster than the serial communication rates we use--9600 bits/sec to control a telescope mount, for instance. Even for guiding, where you need response times in seconds, latency shouldn't be a problem. With these inexpensive Raspberry Pi’s that can support 5.0 GHz wifi with speeds in the hundreds of millions of bits/sec, one second is still a long time.
I have only done some preliminary testing on the power side of this setup, with a boost converter (DC step-up) to maintain a fairly constant 12vdc output for the devices, and with a load the battery and converter can handle. I'm also looking at mounting a separate battery dedicated to dew control, and again it's about maintaining voltage and current.
Some helpful links, including Jasem’s distributed INDI tutorial:
http://indilib.org/support/tutorials/159-indi-on-multiple-devices.html
http://indilib.org/forum/wish-list/811-connecting-ekos-to-multiple-indi-servers.html
Here’s an overview of the settings I'm using:
All three systems--primary pi, secondary pi, Macbook Pro--are running over the Stellarmate Wifi hotspot. The secondary Pi (astro-ieq) has a static IP of 10.250.250.105
Secondary Pi: astro-ieq
Connect through USB to Serial to the iOptron Go2Nova 8404 controller and CEM25P
Run this command:
indiserver -m 100 -v indi_ieq_telescope
Primary Pi: stellarmate
Connect USB to: Atik CCD, ZWO guide camera, ZWO Filter Wheel, Moonlite-protocol focuser, and the remote connection you just started on the Secondary Pi: iOptron CEM25 on astro-ieq
Add a hostname to /etc/hosts that identifies the Secondary Pi
10.250.250.105 astro-ieq
Run this command:
indiserver -m 100 -v indi_atik_ccd indi_moonlite_focus indi_asi_ccd indi_asi_wheel "iEQ"@astro-ieq:7624
I don't think you need to sudo these commands, but I did in my tests. The "iEQ" designates the device ID for the iOptron CEM25 series of mounts. This parameter "iEQ"@astro-ieq:7624 tells the INDI server to connect to the "iEQ" device (iOptron mount) on astro-ieq (the secondary pi) through port 7624 (default INDI port). The tip from Jasem's tutorial (link above) on chaining multiple Raspberry Pi's together is to run indiserver -m 100 -vv indi_ieq_telescope first to get the verbose output and grab the device IDs. That's how I found the ID "iEQ", which works for several iOptron mounts, including the CEM25P and iEQ30.
Main computer
I have a Macbook Pro running Ubuntu Mate 16.04 in a Parallels VM. From here I setup a remote mode profile for the Stellarmate Primary Pi, which is running on 10.250.250.1. From the main computer's point of view--my point of view--there's nothing different about any of the operations in Ekos. That is the advantage of using the underlying INDI protocol, which supports distributed components at a deep level. After startup, you just do your imaging runs like you always do: polar alignment, create or manage your sequence queue, schedule new sequences. Everything just works!
Here are three shots of my working multi-node setup, showing the primary Pi (running StellarMate OS). The aluminum box on the top is a Raspberry Pi 3B+, with all four telescope-mounted components plugged in: Atik 414EX mono CCD, ZWO filter wheel, ZWO ASI120MM mini guide camera, and Moonlite-protocol focuser (not in view, other side of the scope. This is a new DIY focuser and controller I'm also testing out, which uses an Arduino Nano, 28BYJ-48 stepper motor, and ULN2003 motor driver board). The black box beneath the Raspberry Pi is a 6000mAh Li-ion battery with 12vdc out (https://www.amazon.com/dp/B00ME3ZH7C), along with a 5vdc USB power port. I run the Pi off the USB port, and the Atik camera off the 12v line, with a step up (boost) converter between to make sure we keep a steady 12v. You see that cable hanging down by the camera? That's the power line. I disconnected it before I took the pics because I'm measuring the boost converter for a 3d-printed case. For the system test I just velcro'd the PC board to the battery pack.
Close-up of the boost converter I used my testing so far, the XL6009 DC-DC step-up power converter https://www.amazon.com/dp/B06XWSV89D. I put this inline between the battery and the camera's 12v connector. The problem I'm solving is the battery pack will drop voltage over time as the batteries discharge, and I'm willing to trade-off amperage in order to keep the voltage stable at 12v along that curve. Again, this is a test, so we'll see how this works out. My concern with real-world use is how much the camera draws for TEC (thermoelectric cooling) when I'm maintaining a sensor temperature at -20C? I still have to figure this out and see what I need to do for power to support this.
This next pic shows the secondary Pi, the black box velcro'd to the back of the iOptron CEM25P hand controller. The RJ-11 line from the conroller plugs into the mount, the RJ-9 (4-pin serial -> USB) cable plugs into the secondary Pi. For now I'm testing this off AC power, but for portability I will also run this side off of a battery pack.
Another shot (from the top) showing the Pi running Stellarmate, with the four telescope-mounted devices using all the USB ports.
Here's a tip for you: if you're not actually doing any debugging, turn off debug on the Options tab in the INDI control panel for all your devices or you’re going to see a bunch of dialogues with commands sent to devices, status codes, and other fun stuff.
Posted August 19, 2018
Astro Session: July 18, 2018
Here's NGC 281 ("Pacman Nebula") in the Hubble Palette (SII, Ha, OIII -> RGB). NGC 281 is an emission nebula, about 9,200 lightyears away in the constellation Cassiopeia. I re-stacked and reprocessed some hydrogen-alpha, oxygen-3, and sulphur-2 image data I shot several months ago, and I'm happier with this latest result than I was then. It's called the Pacman Nebula because it sort of looks like the classic video game character. (6 x 1200 second exposures in Ha, 5 x 1200 sec OIII & SII with 16 dark frames, Atik 414EX mono CCD, Astronomik 12nm Ha, OIII, SII, William Optics GT81, CEM25P EQ mount, WO 50mm guidescope with ZWO ASI120S-MM guide cam, INDI/KStars/Ekos observatory control).
Posted July 18, 2018
Astro Session: July 9, 2018
I recently bought the William Optics FLAT 6A II, and finally made it out under the stars to take some sub-exposures. I paired it with my GT-81 and ZWO ASI071MC color CMOS camera. The FLAT 6A II is a 0.8x reducer/field flattener; it's adjustable for different focal lengths, and so far, with my limited use, it appears to be quite a leap over the old William Optics F6-A I've used for a few years. The ASI071 has an APS-C sized sensor, and anyone with a large sensor astro camera or DSLR knows if you don't want field curvature with your refractor you need some sort of flattener. The FLAT6AII design makes it easy to dial in the correct distance for the scope you're using. The old reducer/flattener worked, but I had to test out a dozen different flattener to sensor distances, and still had to do some cropping and processing to fix the corners. This new FLAT 6AII provides a fairly flat field across the entire view. Equipment: William Optics GT-81 + FLAT 6A II 0.8x reducer f/4.7, ZWO ASI071MC-Cool color CMOS camera - gain 0 offset 8, ZWO ASI120MM-S Guide Cam + 130mm guide scope.
Testing:
With the GT81 and ASI071 I get a 3.54° x 2.35° field of view, and I can capture some big chunks of the night sky. Here are three from the last two nights: [1] the Pelican Nebula (IC 5070) and the edge of the North America Nebula (NGC7000) at the bottom, [2] IC 1396 nebula with the Elephant's Trunk at the top and the Garnet Star bottom left, and [3] M31, our galactic neighbor, the Andromeda Galaxy.
Pelican Nebula image info: ZWOASI071MC 39 x 240 second color subs stacked in DSS, processed in PSCC2018
IC 1396 region image info: ZWOASI071MC 21 x 300 second color subs stacked in DSS, processed in PSCC2018
The Andromeda Galaxy. The last time I photographed Andromeda (M31) was 2015, maybe fall of 2014? It's been a while. I was using a DSLR--that was the only camera I had, and I had it on a terribly-used Celestron CG-5 equatorial mount with some aftermarket RA/DEC motors. By "terribly-used" I mean you could drive a truck through the gear backlash. Even so, I still managed to get some decent 30-second exposures of Andromeda, Orion Nebula, and other big bright targets in the sky. Well, I'm back with our galactic neighbor, and with much better gear: 192 x 120-second sub-exposures stacked in DSS, processed in PSCC2018, ZWO ASI071MC camera at -10C, William Optics GT81 APO, iOptron CEM25P EQ mount.
Posted July 9, 2018
Astro Session: July 7, 2018
Our galactic neighborhood, looking toward the center, with 13 stacked 15 second exposures, Nikon D750, Rokinon 10mm f/2.8 lens. What's crazy is this is with a decent DSLR camera, lens, a tripod, and some free image stacking software (DSS). I did the stretching in Photoshop CC--"stretching" is when you adjust contrast, intensity values, to bring out the features of whatever you're shooting--in this case the north end of the Milky Way Galaxy, our home. Let me point out some interesting features: starting at the left, that vivid red star is the "Garnet Star" (Mu Cephei), and that's right next to some cool nebulosity that includes the Elephant's Trunk Nebula (IC 1396), a little ways along, you see that blocky reddish region? That's the North America Nebula (NGC 7000) with the star Deneb (19th brightest star in the night sky). Deneb forms the northernmost (leftmost in this shot) point of the famous "Summer Triangle". The other two points are Vega, the 5th brightest star in the night sky (to the right and above the Milky Way core in this shot), and Altair (12th brightest) a little more to the right and below the Milky Way core. Moving along the galaxy to that bright region on the bottom side of the core, about halfway between Altair and the powerlines--if you really zoom in, you'll see the Wild Duck Cluster (M11). Now look just left of where the powerlines cross, those grayish-pink cloudy areas? That's where you will find the Eagle Nebula (Messier 16, NGC 6611) and the Swan Nebula (M17). That bright point of light in the middle of the powerlines is the planet Saturn, which is moving along the ecliptic and right now it's in a pretty good place for viewing. Just right of that are a few more cloudy areas. That's where you would look for the Lagoon Nebula (M8, NGC 6523) and Trifid Nebula (M20, NGC 6514). Somewhere along the Milky Way--this is where you will mostly likely find me focusing my telescope all the through the summer and fall. I almost see this shot as a map of places to visit from afar, and the cool thing is you really don't need to setup the astro gear for this. You can create your own galaxy map, as long as your camera can handle long exposures (not that long, only 15 seconds) and you have it on a tripod with a remote shutter control. And this is only part of the sky from where I'm standing on our little planet! Another way to put this image in perspective is here in the northern hemisphere, around 43° latitude, I don't have enough of a view south (blocked by hills and trees) to see Sagittarius A*, which marks the center of our galaxy, and this far north there's a sky full of other galaxies, a large section of our own galaxy, nebulae, and other deep space objects that I can't ever see from here--that I would have to travel below the equator to see. Some day!
Posted July 7, 2018
Astro Session: July 3, 2018
The Dumbbell Nebula (M27, NGC 6853), also called the Apple Core, is a planetary nebula in the constellation Vulpecula. I setup the AstroTech with 1350mm focal length, paired with the Atik 414EX mono CCD. This gives me .98" / pixel resolution and oversampling, but still managed to get some detail out of the nebula. (Imaging info: 63 x 90 second subs in OIII, 96 x 60 sec. subs of Ha. + 20 dark frames stacked in Nebulosity, processing in PSCC2018. Equipment: AstroTech AT6RC f/9 Ritchey-Chrétien, Atik 414EX mono CCD, 7nm Optolong 2" Ha filter, 8.5nm Baader 2" OIII filter, Orion Atlas EQ-G Mount, ZWO ASI120MM-S Guide Cam + WO 50/200mm guide scope)
Posted July 3, 2018
Astro Session: June 30, 2018
The Eagle Nebula (Messier 16, NGC 6611, Star Queen Nebula) is an open star cluster and emission nebula in the constellation Serpens, about 7000 lightyears away from us. Imaging Info: 96 x 240 sec. Ha + 42 x 240 sec. OIII frames stacked in DSS, processed in PSCC2018. These frames were taken over several nights. You can see the numbers are a bit unbalanced, but the clouds moved in during the OIII sequence last night, and there was nothing I could do. I went ahead and stacked and processed them as they are. I'll probably come back to this one in the future with more oxygen-3 (and maybe sulphur-2) to achieve something like the actual proportional levels of light from the nebula across these bandpasses. Equipment: William Optics ZS61, Atik 414EX mono CCD, 12nm Astronomik Ha filter, 12nm Astronomik OIII filter, CEM25P EQ Mount, ZWO ASI120MM-S Guide Cam + Orion TOAG, INDI/KStars/Ekos control software. Location: Stratham, New Hampshire, Bortle: 4, SQM: 20.62 https://www.astrobin.com/353803
