Hubble Optics 14 inch Dobsonian - Part 2: The SiTech GoTo system

J. Christopher Westland

About Me

• Location: Vacation home (snow bird) in Phoenix AZ, permanent home in Wrigleyville, Chicago, IL

• Experience: 30 years, give or take

• Telescopes: Hubble Optics 10” CDK, Hubble Optics 14” Dob, Orion 120ED, Meade SCT 8“, Lunt 50mm Double Stack H-alpha,  GM100HPS (on order), Losmandy G-11 and Skywatcher AZ-GTi mounts

• Biases: Maximum aperture, maximum portability, minimum set-up; otherwise I consider myself to be rational and prudent.

Introduction

This is the second in the set of reviews about my Hubble Optics 14” Dobsonian, where I relate the performance of the installed GoTo system. I completed adding the Hubble Optics / SiTech GoTo system to my Hubble Optics 14” f/4.6 dob, but did encounter a bit of a learning curve on this, one which I’d like to share with anyone planning on upgrading any Dob to full GoTo. The final product is beautiful, full-featured and competitive (at least for visual work) with other mount systems that I have experienced. It’s all flat-packed and shipped out and Tong forwards the boxes to you; I don’t think he has production in the US. I have no idea about his volumes, but I’d guess they might be like Dave Kriege’s, with 100-200 telescopes in the supply chain at any time.

Price, Order Time and Competitive Alternatives

Order time: (~3 month lead time)

•             SiTech/SkySafari GoTo System: $1,995

•             Wireless Handpad: $350

•             Bluetooth Serial Adapter: $129

•             12V Battery Holder: $30

•             12V to 24V DC converter: $40

•             (shipping cost: $55 surface / $95 air)

•             Total: $2599

Dave Kriege’s Obsession 15” f/4.2 UC is probably the closest equivalent on the market to the HO 14” f/4.6. It comes with the ServoCat closed-loop servo system pre-installed with similar capabilities:

•             Scope: $5,995 + ~$1200 ( shipping / crating )

•             ServoCAT GoTo drive with Argo Navis DSC: $3,195

•             Wireless hand pad is $299

•             Total ~ $10.7K Weight: ~65 lbs

HO 14” f/4.6 Premium Ultra Light Dobsonian Telescope:

•             Scope: $1,995

•             SiTech GoTo System (motors are identical to ServoCat): $2599

•             Total ~ $4.6K Weight ~40 lbs

So the HO14” is ~40% of the Obsession price. Dave Kriege does the Obsession install, and I know having owned one of his scopes in the past, he does a great job of QC.

HO 14 with SiTech system installed

Technology, Installation and My Experience

I have been very pleased with the portability and performance of my HO 14” Dob, and decided to install HO’s GoTo system for the telescope. Hubble Optic’s system is the same one that SiTech sells (https://www.siderealtechnology.com/) but with hardware customized for the Hubble Optics Dobsonian scopes. Dobsonian telescope owners have two main DIY options for adding GoTo drives to their scopes:

1.          SiTech’s system (http://www.siderealtechnology.com)

2.          ServoCAT’s system (https://www.stellarcat.com)

I’ve had a number of CN members ask me about my SiTech GoTo drive installation on my Hubble Optics 14” Dobsonian. As there did not seem to be other reviews on the SiTech system, I thought a report on my experience would generally be of interest to Dobsonian owners who are thinking of adding GoTo drives to their telescopes. Dan Gray, the owner of SiTech has been available for help by phone and was very generous helping me with his time and expertise. He is reachable on the Sitechservo forum and the Sitech forum itself is quite active: https://groups.io/g/Sitechservo

SiTech battery and 24vdc converter

The HO site promises a fast install, but I suspected that this might be over-optimistic, as the HO scopes generally require a bit of adjustment and modification. They are like a Steinway piano; out-of-the box, they need care and attention and a lot of little adjustments, but after that are superb. I had some troubles getting the cable drive system installed, and part of this had to do with placement on the HO14 frame. But once these were worked out, I was sold on the cable system, as it is smooth and exceptionally quiet, as are the servos on both Alt and Az axes.

In particular (I want to emphasize this) the HO Dobs will work well as non-GoTo scopes without too much work. But structure needs to be finely squared up for the SiTech goto system to work reliably; much more so than with just a push-to operation. I squared the structure up by adding washers at various points along the altitude bearings. This was a trial and error process that took the better part of a week of adjusting and testing.

One significant problem with the HO GoTo system as well as any other Dobsonian GoTo system that uses an altitude bearing cable, is alignment of the cable. These systems have an advantage in accuracy, quietness and reliability; but the altitude drive cable which pulls the bearing up and down tends to slip off the bearing if your structure is not squared. I added a Delron guide at the front of the altitude bearing to make sure the cable stays put.

Installed SiTech control and communication hardware

The system is very quiet when slewing or tracking (as opposed to most GoTo systems which make gear mesh sounds on slewing). Slewing can be made very fast, and everything is fully programmable.

All of the electronics work right out of the box, and the mounting hardware is precise and sturdy. The servo motors exhibit much more robust operation if you power them at 24 volts. You can see from the picture of the rear of the base that a 12vdc batter sits on a bespoke holder, and I pump it to 24vdc. The 24vdc system uses a buck-boost transformer to pull the 12vdc battery up to 24vdc (I bought mine from HO, but you can get these off Amazon)

Topview SiTech control and communication hardware

Wired and Wireless Hand Controllers

SiTech cable drive for altitude bearing

Cable drive tensioner

I’m particularly impressed with the wireless hand controller which operates at 465 MHz (like garage door openers and key fobs so there is no interference from 2.4GHz devices). Computer communication is managed through Bluetooth (appropriately named for the Viking King Harald “Bluetooth” Gormsson and abbreviated with his runic crest) and shows up as COM4 on my Surface laptop. Encoder and motor specifications are set up with a configuration utility, ServoConfig1.3, that is available on SiTech’s site. ServoConfig lets you set parameters and read and write them to the servo controller hardware.

Hand controller and receiver

Getting the computer interface right also involved a learning curve and trial and error that I’m still managing. There is a very extensive ecosystem of ASCOM software, including a number of planetarium programs that will work with the HO GoTo Dobs. In the extreme, you can install a field de-rotator and (theoretically) use the scope for astrophotography. As I have no such aspirations for my Dob, I’ll leave that to the SiTech community.

You really need to be on a Windows computer, because all of the ASCOM software is written in Visual Basic, C# or (theoretically) any of the other .NET languages. There is an ASCOM telescope communication interface from SiTech called SiTechExe (.exe) that HAS TO BE started first. It has a lot of features in a very tiny window. You should master SiTechExe before moving on to any other planetarium software, as planetarium software does not communicate with your GoTo system, rather SiTechExe feeds information from the scope to the planetarium program. All this is non-obvious, seems complicated, but actually works quite well. And you would be hard pressed to find any other GoTo software that provides the sheer number of features, accuracy, and control that SiTechExe does; partly due to the breadth of the ASCOM ecosystem.

This brings me to the planetarium programs. The HO site suggests four programs that work with SiTech’s hardware and software:

•             Earth Centered Universe (ECU)

•             TheSky™

•             Cartes du Ciel

•             MegaStar

Apparently SkySafari 6 (which I like) no longer works with ASCOM (even with the SkyFi hardware). ECU and MegaStar, though supported, seem out-of-date and unattractive to me. TheSky is a pretty expensive subscription option. Cartes du Ciel is free, and has an attractive design, so is the obvious choice of planetarium software. I also looked a Starry Night Pro, which is not mentioned on HO’s site, but supports ASCOM interface, and has an attractive, feature rich interface. In fact, once you have SiTechExe up and running, it reliably connects with Starry Night Pro, and is a good choice for the HO/SiTech GoTo interface. I can use my Surface as a tablet, to track, select and GoTo objects to observe; combined with the handpad (which doesn’t interfere with the Bluetooth COM4 port on the Surface) I have a truly optimal wireless interface design.

That said, I still give the edge to Cartes du Ciel, as I think the interface is better than Starry Night. Additionally it is free, and I like the fact that Carte du Ciel’s author Patrick Chevalley is actively supporting the Linux community (my main computing O/S is Ubuntu). Cartes du Ciel has the best interface. It has a clean image of the sky, reminiscent of paper sky atlases, which makes identification and navigation easy. It is able to access most of the SiTech features, and works flawlessly.

Starry Night Pro was actually a disappointment, but perhaps I’m somehow missing something about its interface or connectivity. The interface initially looked good, and there seem to be lots of ‘educational’ features and in the end, the graphics make navigation more difficult, response is spotty, and telescope control seems an afterthought. SkySafari is better, but for my purposes, is hampered by not having access to the telescope encoders. Thus tracking and position are very inaccurate, because of drive slippage.

The SiTech hardware goes on and off pretty easily; it does add complexity (a large part of it being in the software setup). The interesting thing about the SiTech GoTo system is how fast you can slew the scope (with 24vdc power). I could see that this could track satellites - whether you could keep up with the eyepiece is another matter.

All told, the end result is worth the time invested in getting the HO/SiTech system together. The hardware is high quality and the software provides me with more flexibility and control than I could ever get with an ‘off-the-rack’ GoTo system. On the other hand, I know from owning an Obsession 20”, where assembly is minimal out of the box, that there is still a lot of fiddling around, collimation, adjustment of weights, and so forth that just comes with owning a large Dobsonian. I think it comes with the territory, and once you get a system in place and know your equipment, it’s part of your habit. An added benefit of knowing how to tweak the finer points of your system is that you can handle problems in imaging, QC or enhancements like focuser control yourself.