Telescope Dovetail PC Mount for Celestron CGX GEM Mount

Here is my dovetail mounted mini PC mount plate with fused DC power distribution, for use when doing astrophotography, which I am currently using on my Celestron CGX GEM mount with my Celestron C925 OTA.

You can see the PC mount, fuse box and my associated cabling solution on YouTube at https://www.youtube.com/watch?v=HanCjVhxCfM and in some of my other videos.

The Celestron CGX mount has a declination head which occupies about 20.5cm on the telescope's dovetail, which is the spacing I have implemented between the two dovetail plates which then go onto the bosses on the PC and fusebox mount plate. If your mount has a bigger or smaller head, then you'll need to do some remodelling before you can make use of my design I'm afraid.

I have provided a version of the mount plate for my configuration, which accomodates an AWOW NYI3 mini PC and a six-way DC fuse box, which I use to power all of the devices I use when doing astrophotography from a single 12V 10A DC power supply, notably:

The CGX mount
RVO Dew Band
A3 Flats Panel
AWOW Mini PC
ZWO ASI294MC Pro

There's a spare fuse position for if I come up with anything else to add to my setup :-)

As well as the version specific to my setup, I've also included generic parts that don't include my 5.5mm barrel jack connections or my cable clamping parts, although those elements are here in seperate STL files if anyone wants to hack them to use for their own configuration.

I'll be uploading seperate instructables covering my cable management solution that goes alongside this mount plate, which keeps al of the cables neat and tidy and securely retained close to the mount's rotational axis, reducing any pull or load on the mount's motors.

One disadvantage of having a PC mount that utilises the telescope's dovetail, is that moving the 'scope on the mount in order to adjust declination balance is made more difficult. Therefore, I usually set up my tripod and mount, get it all levelled, then mount the telescope. I then attach the lightest set equipment I expect to be using during an astrophotography session to the 'scope, then balance it in declination. At that point I then add the PC and fuse box mount plate and do all my cabling. If I need to add more equipment to the back of the 'scope, I then use my adjustable declination counterweight to get my declination axis back into balance without having to move the dovetails position on the mount. You can find my adjustable counterweight solution here: https://www.instructables.com/Adjustable-Telescope-Declination-Counterweight-Wit/

Rather than having a load of long cables attached to the PC mount plate, I utilise a seperate cabling loom which I connect to the PC and DC fusebox, where each of the cables is just the right length to make a good connection to the other device.

Supplies

For a complete PC and DC distribution solution you'll need:

3D Printer Parts:
PC and Fuse Mount Plate.
Earthside and Starside dovetail mounts.
Splits pins, two off.
R-Clip Holders, two off.
Dew Band Controller Clip
Spring Steel R-Clips, two off. Mine are 14mm x 43mm.. Don't try to use the STL ones I have provided below!
Mini PC, I used an AWOW NYI3, but they are no longer available, although there are plenty of other similar PCs available.
6-Way Fuse Box. I used Amazon product B07GYTZF35.
5.5mm x 2.1mm (or 2.5mm) Barrel Plugs, with flying leads, three off.
5.5mm x 2.1mm (or 2.5mm) Barrel Jac, with flying leads, one off.
Red 7.8mm Ring Crimp Connectors (5.5mm hole), 12 off
Black Heatshrink Tubing, six pieces
Red Heatshink Tubing, six pieces
Spade Fuses appropriate to your devices. I use 2A, 3A and 5A.
Mounting bolts for mini PC, two off (or as many as needed), size as required.
Mounting bolts and nuts for fuse box, two off of each, size as required. I used M4 bolts and nuts.
Dew Band Controller

Step 1: PC and Fuse Box Mount Plate

I've provided my full version of this, as well as a generic one, with the bits that I've removed from the full version as seperate files.

The main plate is 215mm x 125mm, so you'll need a 3D printer that can print something that big. If your printer is smaller than that, you might be able to fit the plate on by positioning it on a diagonal, but if that still doesn't work, you'll need to split the plate into two halves, maybe using a dovetail-type joint, and then glue them together.

Check the hole size, location and spacing of the mounting holes on your mini PC, and adjust the holes in the mount plates as required to fit.

Check the hole size, location and spacing of the mounting holes on your fuse box, and adjust the holes in the mount plates as required to fit.

Layer Height: I printed mine at 0.2mm layer height, but you might get away with doing it at 0.3mm.

Material: PLA

Supports: As the bosses need to be a good fit in the dovetail supports, the holes in the bosses a good fit for the retaining split pins and the rubber band hooks have overhangs, I suggest that you use supports, either automatic, or add custom ones for the specific areas mentioned above. If you print my version, you shouldn't need supports for any of the 5.5mm barrel jack holders or the cable clamps.

Step 2: Dovetail Mounts

There are two dovetail mounts, one to slide over the the bottom end of the dovetail and one over the top end, with one having a globe on it for the Earth side and the other with a star on it for the skyward end of the dovetail. They should be a fairly tight fit on the dovetail.

Layer Height: I printed mine at 0.2mm layer height, but you might get away with doing it at 0.3mm.

Material: PLA

Supports: None Required

Step 3: Split Pins

You'll need to print two split pins, one for each boss on the PC mount plate.

Layer Height: I printed mine at 0.2mm layer height, but you might get away with doing it at 0.3mm.

Material: PLA

Supports: None Required

V2.1 Split Pin.stl
Download View in 3D

Step 4: R Clip Holders

Although these aren't strictly necessary, they make getting the R Clips, which hold the split pins in place securely, much easier to get in and out.

The longer one is for the R clip that goes through the skyward end of the PC mount plate split pin, and the shorter one for the Earth end.

Push the R clips into the slot in each of the two clamps, then slide the D-shaped retaining covers over the top. They should be a tight fit, but you can always glue them in place with super glue if required.

If your R Clips don't fit into the slots I've 'carved', then you might need to cusomise those. I have provided an STL file for an R clip which you can tweak, and then convert into a 'hole' to then use to cut out your version of an R-clip in the clip holders.

Layer Height: I printed mine at 0.2mm layer height, but you might get away with doing it at 0.3mm.

Material: PLA

Supports: I suggest that you print supports for the overhangs on the D-shaped clips, then carefully remove them before use.

Step 5: Dew Band Control Clip

You don't need to print this unless you're using a dew band, although you might need to customise it if your dew band controller is a different shape to mine.

Layer Height: I printed mine at 0.2mm layer height, but you might get away with doing it at 0.3mm.

Material: PLA

Supports: None required.

V1.1 Dew Band Clip.stl
Download View in 3D

Step 6: Initial Assembly Prior to Cabling

Mount your mini PC using the appropriate bolts. I used some spacer washers between the plate and the PC, to ensure that the plate doesn't flex when the bolts were tightened.
Mount your DC fuse box. I have mine oriented with the positive rail input being closest to the PC, but your fuse box might be different, in which case you'll have to sort your own wiring out!

Step 7: Wiring Explanation

How many fuses you need to utilise and which connections you need to make will depend on what equipment you've got and its DC power needs.

My rig has a single 12V 10A DC Power supply which is connected to the fuse box, with the Mini PC, Mount, Flats Panel, Dew Band and ASI Camera, all needing fused 12V DC, being supplied though connectors appropriate to their needs. If any of your kit needs anything other than 12V, then you're on your own ;-)

You need to choose 5.5mm (or other) connectors that are appropriate to your needs, and I made the decision that incoming power to the PC and fuse box would be a male jack, such as you get on laptop DC power supplies which connects to the female 5.5mm connector which then connects to the fuse box, with any outputs to devices being male jacks that power cables for devices will connect to.

The slots into which all of my cabling clips, are spaced so that the cables are a push fit, but are then retained by small overhangs in each cable clip. If your cables are different sizes to mine, then you might need to increase of decrease the spacing of each cable clip pair. The two rubber band hooks support the use of a rubber band to keep the DC input, DC to mount and the USB cable, which I have going from the mini PC to my CGX mount, securely in place. Given the tight fit of all my cables, I find that I don't use this any more, but I've left the hooks in place in case anybody else does need them.

Having resized any cable clips, I suggest that you put all of your 5.5mm connectors and their flying leads in place, and then split the paired flying leads and route them to where they need to go, using my pictures as a guide, then cut them to the right size to go to the appropriate positive or negative connectors on the fuse box. On my fuse box, the main positive and negative connectors are on each end, with all of the negative lines going to the end where the negative input is, and the inidividual positive leads going to each fuse position.

Having cut all of the flying leads to size for a good neat fit, I then thread red (+) or black (-) heat shrink onto the cable, strip the ends of each flying lead, then crimp on the ring connector, then I pull the heat shrink tubing back over the connector and shrink it into place with a heat gun, then take the bolt and washer out of the fuse box, stick the bolt through the ring connector and then screw it securely into place.

Step 8: Assembly Onto Your Mount

Once you've printed all of the 3D parts, mounted your PC and fuse box and done all of the wiring, you're ready to test the plate with your mount and telescope.

The first picture shows the PC and fusebox mount plate fully assembled, with the split pins and R clips in place. The second picture shows the pointy ends of the split pin, dovetail plate and the PC mount plate all aligned, with the R Clip securing them in place.

Set up your mount and get it level, then slide your 'scope onto the dovetail, then position it where it should be in order for it to be in balance in declination with your usual minimal camera configuration. I have two sets of marks on my dovetail for this, for when I will be utilising a dew shield and for when I am not using one, which makes setting up so much easier :-)
Rotate your mount so that the OTA is parallel with the gound, with the side you'll have the PC on uppermost.
Slide the Earth-side dovetail plate onto the bottom of your dovetail and all the way up to the edge of the declination head of the mount.
Slide the Star-side dovetail plate onto the top of your dovetail and all the way down to the edge of the declination head of the mount.
Connect the invidual cables in your cabling loom to the appropriate connectors on the mount plate and secure them into their respective cable clips, using the rubber band hooks if necessary. For my configuration I have a wiring loom with cables for DC input to the fusebox, DC power out to the mount, the USB connection to the mount's hand controller and an RJ12 flat cable which goes from the mount to my Celestron focuser and Celestron StarSense devices, with the latter not being attached to the mount plate.
Slip the bosses on each end of the mount plate into the holes in each of the dovetail plates, which might mean moving one slightly, then make sure that they are pushed tightly onto the plate, keeping it securely in place.
Connect your Dew Band to the dew band connector (if used)
Push a split pin through the hole in the centre of each boss to retain the plate on the two dovetail plates.
At this point the PC and DC fusebox will be hanging away from the 'scope, giving access to do any 'tidying' that may be required.
Rotate each of the split pins so that the pointy end on each aligns with the pointy end on the dovetail plate, then push an R clip partially though the small hole in each to keep them aligned. Do not push the R clip all the way though yet!
Lift the mount plate into place so the the pointy ends also align with the pointy ends of the split pin and dovetail plates, which will then ensure that the small holes in each are aligned, then push the R clip fully home, which will keep the PC and fuse box in place close to the 'scope, and will keep all of the cables secure.
Route your cabling loom down to the mount, hand controller and DC power supply (see my other instructable, at https://www.instructables.com/Celestron-CGX-Cabling-Solution/, for how to do this neatly).