EQ-Z – RA Housing and Shaft Assembly (Part 3)

Quick and final update for the RA assembly. I’ve already started working on Declination parts and hopefully I will start putting the Declination assembly together. The toughest part (the shaft) is done – I am anxious to have everything ready for when the optics get here.

But unfortunately, the winter is already here and I am not sure how fast I will be able to work on the observatory. The pier is done and I just completed the four footings. Next week-end I should be able to start working on the structure, finally.


Back to the mounting – I’ve finalized the RA assembly by installing the gear cover. This gives the mount a nice finishing touch. At this point I just need to do some final wiring for the motor and to install the motor/worm assembly… after which I could be tracking!


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CDK17 – Optics shipped!

My Optics are ready and are shipping! I should have them within 4 weeks. I received the final optical specs (namely spacing between the different elements) which will allow me to finalize the structure. I found that the front of the scope was a little too light so in order to avoid having to add counterweight to the front of the OTA, I had re-machined the front ring, made some changes to the CF tube ends/fittings and used thicker CF tubes. I was waiting on these final specs before I cut the tubes to length.

I am not an expert in Optical engineering, testing. I am not afraid to admit the test results below don’t talk to me too much. I will judge the quality when I start taking pictures and hopefully I will be happy!

First, here’s the Ronchi test:


Next is the Foucault test:


And here’s the data from the Foucault test:


I can’t wait for the first light – I’ve got quite a bit of work ahead of me, I need to get busy now!

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EQ-Z – RA Housing and Shaft Assembly (Part 2)

I was able to make more progress on the mounting this week.

I first finalized the clutch assembly. I needed to enlarge (actually deepen) the housings for the four dowel pins (which force the clutch assembly to be kept in rotation with the shaft – see last Part 1 for more details about this). The force picture shows the “captain wheel” screwed on the shaft compressing a large wave spring pushing on the friction plate increasing friction to the gear. I don’t expect to have to play with this “captain wheel” very often but in case I do have to loosen/tighten it, the rear gear cover has an easy access to it (I will show this in future blog entries).


Once this was done, I was ready to install the second bearing block. I made the tolerances a little more easy so that I wouldn’t have to put the whole RA shaft + first bearing block in the fridge. Greasing the shaft was enough and the bearing slid on it without much problem.


I then installed the first side panel which locks the two bearing blocks together. I made another short video showing the housing spinning around the shaft: http://www.youtube.com/watch?v=vrRT7599iZ8&feature=youtu.be


I didn’t take any picture of this but one thing I did before installing the second side panel was the installation of the AC to DC12V power supply. There is no easy access to it which hopefully won’t be a problem down the road. I’ve used these industrial power supplies for some time and I am not expecting problems, but still.


I was a little hesitant in pushing the assembly past this stage because, as is the RA housing + shaft is already incredibly heavy. But I really wanted to be able to adjust the bearing blocks (concentricity) and the bearings preloading plate so I decided to install the whole RA assembly on the base of the mount. The first picture shows the front (North) side.


And this is the South facing side of the EQ-Z.


And finally here’s a look through the RA shaft. It’s only through to get all of the cabling to run through the mount. No Polar Finder will be installed.


Note the Aluminum preloading plate. This part has two purposes: one is to preload the bearings (tapered roller bearings need a preload), and the other is to “host” the High Resolution Renishaw shaft encoder. I initially wanted the shaft encoder to be directly installed on the shaft but it was almost a last minute addition and it would have caused me to remake quite a few parts.


I am using a torque screwdriver to apply a very even torque on each of the six screws. I will be using a rotary dial indicator to ensure perfect concentricity between the shaft and the encoder.

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EQ-Z – RA Housing and Shaft Assembly (Part 1)

It’s been a while since my last progress on the equatorial mounting… But I am now officially started on the “serious” work: i.e. all of the heavy assembly work. So here’s what I have so far:

Although I haven’t made any of the DEC housing parts, I needed to at least have the housing back mating plate. This part attaches to the RA shaft itself. By design, it’s retained with 6 large M8 screws only accessible before the RA shaft is installed in its housing – so it had to be done before anything.

Next, I installed the front (the larger one of the two) tapered roller bearing. Because of the tight tolerance I am working with, sliding this bearing on the shaft required to bring the shaft to sub zero temperatures (-25 C) so that it would “shrink” enough for the bearing to slide on. It actually went really well – on the picture below you can see the “frosty” shaft and its front bearing. Also note the DEC back mating plate under the shaft.


While the shaft sit there for a couple of hours under the sun (and warming up), I assembled a bunch of RA housing parts including the left panel, front block, front panel, bottom plate and worm support plate. It’s getting heavy :)


Figuring the details of the assembly I found out it would be easier to have the front bearing block on the shaft instead of on the housing. Something about the 15.25″ gear that I sure don’t want to damage when handling it – that way I can keep the gear on the shaft tightened with its clutch and just slide it into the housing. On the picture below I installed the front bearing block (with the bearing outer ring installed in) on the shaft. Then added the Stainless Steel and Delrin washers part of the friction clutch.


I recorded a short video showing the bearing block spinning around the shaft. Nothing super exciting there haha: http://www.youtube.com/watch?v=e4Az1otffDQ

Then is definitely the toughest step of the assembly so far: assembly of the gear and its PTFE (self lubricating nylon material) sleeve bearing. This required 4 hands. There is absolutely no play and it’s spinning well. Not hard, not easy – I’m pretty happy about it! Since this is part of the slipping clutch, the shaft will spin inside the gear ONLY when the clutch is slipping. Note the white/grey liner in between the gear and the shaft this is the sleeve bearing. Since it’s a strip that I cut to size, there is about 4-5 mm gap in between the 2 ends.


Next is the second Delrin washer and the installation of four M3x8 dowel pins. These will force the whole clutch to spin with the shaft and preventing to loosen/tighten. Since I use a “captain wheel” that screws onto the shaft to compress the clutch spring, if the friction plates were not to spin for some reason when the shaft is spinning, then there would be a chance that frictions force may cause the “captain wheel” to turn relatively to the shaft which would effectively cause the clutch to tighten or loosen (most likely loosen).


And this is pretty much where I stopped – the friction plate that mates this Delrin washer needs to slight adjustments on the CNC which I will take care of this week. Then I will be able to finalize the clutch assembly and hopefully install the shaft + 2 bearing blocks into the RA housing. At this point the assembly will already be very heavy and I will probably have to wait until the observatory is completed to install this on the pier before I can start working on the Declination assembly.


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Antares to Rho Ophiuchi

June 1st, 8th and 15th 2013: This is my second light with the FSQ106EDX-III and I wanted to try to capture some nebulosity.  It also happened that I had been waiting to shoot this region of the skies for years. I didn’t want to work on mosaic just yet so I decided to frame that very colorful area between Antares and Rho Ophiuchi. It’s got several types of nebulae, a few globular clusters and so much dust!

Considering the size of the region I obviously chose to use the focal reducer which with this camera and scope give me a field of just about 5×3 degrees.

My godson was on vacation here for about 10 days so I decided to just go for this target for a few nights (three precisely!)  so that we could spend the time doing visual with his binoculars and Dan’s dob. Great times.

Then I’ve been very busy with the move that it literally took me over a month before I even touch the data.  My processing workflow has not changed much since my last picture. I did find a nice way to improve my stars with a much better stacking interpolation. I also have to mention that the data was pretty clean to the point that there was very little processing to do.


  • Date: June 1st, 8th, 15th 2013
  • Camera: Moravian Instruments G3-11000 (Sensor maintained at -25 C)
  • Exposures: ~ 10 hours of integration time (L: 600 s – 1×1, RGB: 300 s – 1×1)
  • Mount: Losmandy G11 Gemini 2
  • Imaging Telescope: Takahashi FSQ106EDX III @ f/3.6
  • Guiding: Borg 50 mm – Barlow 2x – SX Lodestar
  • Calibration: Darks, Flats, Dark Flats
  • Stacking: PixInsight 1.8
  • Final blending/processing: PixInsight 1.8
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New wide field setup

Last year my DSLR died. I could have bought another one and have it modified but I was already well into my 17″ CDK project and thought I should just get the CCD camera I had already chosen for the project. That brought a little bit of technical problems because neither my 8″ RC nor my AT10IN were remotely adapted for this large chip. I struggled finding a good coma corrector and adjusting it was just really tough. Then a not so good winter on top of a big project at my work.

Spring came in and I was a little less busy at work, I decided to just put my hands on a refractor that is well suited for full frame cameras so that I could spend more time imaging and less time tinkering. I went with the Takahashi FSQ106EDX-III. After 2 nights out with it I couldn’t be happier with the purchase. Both times I used the .73x focal reducer which makes it really fast and although it reduces the imaging circle close to the diagonal of my CCD sensor, the elongations in the corners are really minimal. The G11 is handling the whole setup just fine – a piece of cake compared to what it was with the 10″.

For guiding, I am still using the same setup I used on the 10″ Newtonian: a Borg 50mm with a 2x Barlow making it f/10 and SX Lodestar. The imaging scale of the guider is actually smaller than that of the main imaging gear combo (~ 4.8 arcsec/px). The only thing I am somewhat missing is the motorized focuser. I have already started looking at getting a Robofocus and I’ll probably do that soon, I am trying to find out if my Moonlite mini controller would work with it… Here’s a picture to help me wrap up this short description of my new wide field setup.


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EQ-Z – Motor Interface

Theoretically the Gemini-II controller could work with any brushed DC servo motor. There are some limitations to this. One is the maximum current that the IC built-in the Gemini-II controller can actually output (that limitation could probably be lifted by driving a power transistor connected to a power source with a greater current capacity). The other is the encoder type : it’s got to provide quadrature signals in the form of two channels typically: Ch. A and Ch. B. Most high end encoder would output Ch. A in the form of two separate signals: A high and A low, same thing for Ch. B and the Index (if available).

I originally thought that I would be able to just use the A high and B high signals directly to the Gemini-II controller. It didn’t work. Looking in details at the encoder datasheet, they recommend the use of a line receiver. I draw a simple 2-layer PCB to interface the 6-wire cable coming from Gemini-II (DIN type) to the motor (two 2.80mm quick disconnects) and the encoder (10-pin ribbon type). The line receiver I used is a AM26LS32 which has 4 independent lines for 4 different signals. Considering the short length of the ribbon cable and the location of the 2 motors, I decided to go with two interfaces, one for the RA motor and for the DEC motor. Below is an image of the PCB layout:


Next picture is the PCB before installing the components.


And finally the finished PCB:


Before, making the PCB I tested everything on a breadboard and hooked it up the Gemini-II controller. Here’s a short video showing the motors driving the worm everything being controlled by the Gemini-II controller: Motors in Action (Youtube)

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The Virgo Cluster

May 11th 2013: It’s been over 8 months since I was out imaging. Combination of bad weather and battles with equipment to get things straight convinced me to get an imaging scope that is adapted to my new full frame CCD camera. I am now back using a refractor. I went with the Takahashi FSQ106EDX III and its .73x reducer which combined with the Moravian Instruments G3-11000 gives a 5-degree wide frame. With the CDK17″ in the works I figured I’d happy with the Tak to work on wide field targets.

Other than for engineering and making a couple of adapters for this camera, the battle with equipment, collimation, and other excessive vignetting issues should be sorted out.

In many ways, this image is the actual first light for both the camera and the scope.

I wanted to shoot the Markarian’s chain when I had my AT65EDQ, but the wider field that gives the new equipment combination covers most of the Virgo Cluster so that’s what I went after. I could have framed it probably better especially considering that M100 is cut in half, but I’m overall happy with the results. With so many galaxies in the frame, I couldn’t resist and made a montage with some annotations.

I started with some Luminance (10mn at 1×1) before the meridian flip followed by some more Luminance… after 3.5 hours, I started alternating between each of the 3 color filters (5mn at 2×2) until… it was too low and polluted by horrible gradients. Out of practice a little there, I guess I got my maths wrong. I ended up with about 30-40 mn per color. At that point, I pulled the flatbox out and started shooting flats, I was a little anxious about this as I never took any flat with a CCD camera. It’s got a shutter and it typically needs 3-4 seconds minimum. These flats turned out to be decent. I had a good bunch of darks waiting for me at home to start processing.

Here’s the picture (click for full frame):


And here’s the montage with annotations:


  • Date: May 11th 2013
  • Camera: Moravian Instruments G3-11000 (Sensor maintained at -25 C)
  • Exposures: ~ 5 hours of integration time (L: 600 s – 1×1, RGB: 300 s – 2×2)
  • Mount: Losmandy G11 Gemini 2
  • Imaging Telescope: Takahashi FSQ106EDX III @ f/3.6
  • Guiding: Borg 50 mm – Barlow 2x – SX Lodestar
  • Calibration: Darks, Flats, Dark Flats
  • Stacking: PixInsight 1.8
  • Final blending/processing: PixInsight 1.8 and Adobe Photoshop CS6 for the Montage/Annotations
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EQ-Z – RA Shaft

After several months with no work on the mounting, I finally got back to it by working on the electronics that interfaces the motors to the Gemini-II controller. Meanwhile, I sent out one of the two big lathe jobs. None of the lathes I have access to were big enough for the job… I sent the 3D models and drawings to many shops and gave the job to the shop with the lowest bid. It’s funny (or not) the huge differences in price from a vendor to another.

I’ve just QC’ed the part and it’s spot on with my specifications. I’ll have this part anodized sometimes soon along with some other parts (RA and DEC covers for instance, probably some little parts like knobs too).

Next on the to-do list are all the parts for the RA housing (which is made of several thick milled aluminum plates) and the DEC housing. When that’s done, I will be able to start assembly most of the lower part of the mount. I can’t wait.


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EQ-Z – RA Bearing Blocks

I’ve started working on the Right Ascension housing which once assembled will be the single most massive part of the whole mounting. Two of the main parts of the RA housing are the Bearing Blocks. Each of these blocks host a large tapered roller bearing.

Front and Rear bearings are not exactly the same size (front bearing has a slightly bigger OD). I am using a SKF bearing to the front and a Timken to the rear. Both are made of two parts: the outer ring and the inner ring plus roller ring assembly.

Each bearing block was machined with tolerance of -0 ; +0.02 mm to guarantee a perfect fit between the block and the bearing outer ring. I still to use lubricating grease to ease the installation but no tool or force was required to slide them in.

It’s only when the RA shaft will be installed that the bearings will be locked in place. I will need to make and assemble parts for the housing and the shaft to complete that step.

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