Review of Rigel Systems Wifi nSTEP Focus Controller on a Solar Telescope and a Mirror Lens

By Eric Loyd
@Astropotamus
http://astropotamus.com

Background

NOTE: While the specific unit I used was part of Dr Palmer's beta test for the ALPACA drivers, the product itself is the same as what is available on their web page, and you can purchase these from them directly.

Dr. Leon Palmer of Rigel Systems was looking for beta testers for their Wifi nSTEP Focus Controller for ALPACA.  I challenged him to let me test it on a Coronado SolarMax II 60mm DST Ha scope.  He took me up on the offer, and after a few back-and-forth emails on measurements, he nailed the mechanics first time out.  Here are the final pieces connected to the scope.  You're looking at the black gear ring, motor, and gear assembly on the visual end of the scope.

Everything else was so "right" out of the box that it took me much longer to find a day that wasn't rain and snow than it did to set it up and test!  So I tested the ALPACA connections inside.  If you don't know what ALPACA is, it's basically wifi ASCOM.  More on that at https://www.ascom-alpaca.org.

My Equipment

Telescope(s)

Coronado SolarMax II DST 60mm and a Rokinon 500mm/f8 catadioptric mirror lens on a Canon 450D

Computer

Intel i5-based Windows 10 Professional

Software

NINA, Sharpcap, and Firecapture.  Basically anything ASCOM compliant.

Installing Hardware

Straightforward installation, but the nylon screws that hold the focus tube in place are not long enough to go through the new focuser ring and the existing telescope focuser housing so I had to purchase two new 8x32 1" nylon screws.  I couldn't find any that had nice thumb screw ends so I went with simple nylon machine screws as you can see in the pictures.  I bought two of these screws from Lowes: (https://www.lowes.com/pd/Hillman-8-32-x-1-in-Slotted-Drive-Machine-Screws-2-Count/3013037 for $0.62 each.  Perfect.

Installing Software

1. As per instructions included, went to https://ascom-standards.org and downloaded the latest (AscomPlatform662.4195 as of the time of writing) ASCOM drivers.  They were already installed, but wanted to start from scratch so I uninstalled existing ones and installed new ones.

2.  Went to https://www.rigelsys.com, which is the new web site.  The old web site may still show up in the documentation (rigelsystems.com), so be sure you're on the right one.

3.   Next up was https://www.rigelsys.com/steppermotor.html, and clicking the wifi-nSTEP Manual link in the "Downloads" section at the bottom of this page pops up a PDF version of the install document.

4.   The documentation mentions "GCUSB_nSTEP1_Setup.exe" so I selected that one.  If you're running a second nSTEP motor, you'll need the nSTEP2 version.

5.    Ran the software and had to allow the exception through Microsoft Defender, as always.

6.  Using the USB cable included in the package, I plugged it into power (12V included cable, runs off approximately 2A) and into my computer.  It shows up as Silicon Labs CP210x USB to UART Bridge, and was assigned COM5.

Running the Software

I did a straight install without changing any of the installation defaults, and it took me a while to find the one named "GCUSB_nSTEP1_ROT" because I was looking for "nSTEP something."  Having found the right icon, I started it up and it ran without issues.

Getting Wifi Started

In order to get the Wifi connected, I had to make sure the switch was in "manual" mode.  If it was in USB mode, the access point would not show up.

·         Connected just fine the first time to the SSID

·         Web page came up quickly when I typed it in correctly!

·         Login as admin worked fine.

As I was using a phone to connect, I tried changing to using my work SSID

·         Received a confirmation (image attached with private information redacted)

·        

·         Logged back in to device to "Get Assigned IP" but just got a blank page at first.

o   Turns out that the page was somehow scrolled down and the text with the iP address was off the top of the screen.  All ended well with a proper IP.

o  

·         Connected to 192.168.1.143:80 and :8888 with no problems.

All told, wifi connection and configuration went well.  Next up – ALPACA.

AstroCat approves!

Alpaca Testing

NINA was able to connect to the Alpaca GCUSB without any issues!

Configuring

You have to configure the step rate from the "Configure this ASCOM device" page, not from within your software (in this case, NINA) directly.  This will take you to the focuser' internal web page to adjust stepper settings.

Note that the step rate is still pretty small, so the best bet is to loosen the spring-loaded screws that provide tension, manually adjust focus until it's close, and then re-engage the screws so that the motor can drive the gears.  Once you've done that, the very small movements needed for focusing can easily be done with just a few seconds of pulsing on the focus control motor.

Let's Take Some Pictures

After a few *weeks* of playing with this thing inside, I finally get a chance to get some pictures of the Sun using this device with the software controlling everything.  I was quite happy!

This was with an ASI432 using Sharpcap without any processing.  Sharpcap controlled the focus.

My Ha solar adventure is really just beginning, so I have a lot to learn about processing and pulling out some details, but with some simple work in GIMP to block out the central brightness, I was able to pull out these prominences in this almost eclipse-like image shot in the middle of September:

This was also with the ASI432 but the scope was tuned for proms rather than surface features.  I then blocked out the center in GIMP and stretched the proms a bit to create this faux eclipse picture.

Another Lens?

For my assistance, Dr Palmer asked if there were any other OTAs or lenses I wanted to try this thing with.  I decided to go "ridiculous" and chose my Rokinon 500m/f8 catadioptric mirror lens.  Partly because, combined with my Canon 450D it makes a perfect lunar combo, and partly because it has such a narrow range of good focus before it over focuses that I hate using it.  So it sits in the kit bag.  With the nSTEP, I thought, I could use the controller to nudge the focus without banging the entire rig on a tripod, and I'll use it more.

With a 110mm diameter, using a rubber ring gear wasn't going to work, so we went with a split-ring that clamps to the existing rubber focus ring.  This will rotate the lens around about 330 degrees of rotation. Since it's for astrophotography, we really only care about focusing near the infinity end of the spectrum.  Since the lens has a huge amount of its cylinder that rotates for focusing, with only a narrow section towards the camera end that doesn't, a 120mm telescope ring was used to hold the lens.  There is a T-mount connector to mount on the Canon, and the entire rig is on an upside-down Vixen mount screwed to a video head tripod.  The Canon is on an ADM double Vixen mount, which perfectly holds a different Bogen tripod head quick adapter.  Some day, I'll simplify the mounting, but for now, it works great!

I actually haven't had time to test this yet in the field, but I did a quick video to show how the focusing works and sounds.  It's silent.  You can see that at https://youtu.be/o62ZkkPfbL8.

Conclusions

Following Dr. Palmer's easy instructions had the equipment ready to go in no time.  Connection to the ALPACA wifi driver was trivially easy, and for the longest time, I thought I was doing something wrong because I was expecting it to fail.  Or, at least, to be more complicated.  It wasn't. 

When I finally did, the unit did everything it was supposed to do, without problem, without issue, without any troubleshooting of any sort, and worked with Sharpcap, Firecapture, and NINA (as expected).  I finally got to take some Ha shots of the Sun with it working in full automation mode, though I haven't yet done anything with the Canon and 500mm/f8 mirror lens.

All told, this makes my life significantly easier when doing Ha solar photography.  An electronically controlled focuser for the SolarMax make it so much easier to focus without having to deal with that crazy helical focuser and my aging eyes.  The computer can tell when something is in focus, so it can pulse the motor appropriately and get everything just right for me to take pictures instead of worrying about the gear.

With the ALPACA wifi-based drivers, that also means one less USB cable to connect.  Which means one less port needed, and thus maybe one less device overall (a USB hub) I need to add.  My laptop only has two USB connectors so if I'm doing solar, I'm likely using my laptop, and one of those ports connects to the camera and the other connects to the mount so without needing to connect to the focuser, I can ditch the USB hub that I used to have to need to get more ports.

Thanks so much, Dr. Palmer!  I can't wait for my next telescope, because one of your ALPACA focusers is going to go on it as well!

Eric Loyd
@astropotamus
http://astropotamus.com