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Cabling the mount - recommendations anyone?


DougAtDallington

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I've been astroimaging for about a year, and use a number of OTAs (refractor, SCT, Newt) for different tasks, and was wondering if anyone has tips or recommendations for mount cabling.

To accommodate the various OTAs and their accessories a cat's cradle of wires and cable has evolved, some cables not in use because they are used with a particular OTA,

I've even tried using spiral cable tidys but I'm worried that the bundled cables might be stiff enough to affect the mount operation.

For example, is it best to put as much as possible on the mount (USB hub, dew controller, etc) to minimize the cables to the mount?

Your thoughts would be appreciated.

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I have two waterproof enclosures. One each side of the telescope, fixed to telescope supports that I fabricated and are sandwiched between the telescope rings and the losmandy plate. The enclosures contain all the electronics for supply to ccd, rotator, focuser and dew heater controller. All the voltage DC/DC convertors and USB hubs are in the enclosures that need to be to reduce wiring to an absolute minimum. The only wires connected to the enclosures are two 12 volt power supplies and the supply USB from the computer. (CCD power supply is separate to everything else). These power supply wires are of silicon as it is the lowest stiffness I can find and stay that way well below freezing. I have just finished encasing the supply wires and USB in mesh protection. This protects the silicon (as it is easily damaged) and allows the cabling to basically glide over any mount contact whilst tracking.

The photo was taken a while ago before the wording was finished.

Derek

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I've got two rigs, a fixed obsy, and a smaller, portable rig. Both are wired slightly differently.

I basically, on both rigs, split the wiring into functional groups, ie, mount, scope, camera. Every group of cables is loomed in braided sleeving and tied off tightly:

http://www.ebay.co.uk/itm/Black-Braided-Cable-Sleeving-Sheathing-Auto-Wire-Harnessing-Marine-Electrics-/150899408011?var=450115825449&hash=item23224e3c8b:m:m3qi4dFX8H9VjqdGL6aFGCw

On the portable rig, cables from the camera and scope are dressed so they run back to the axis of the mount, to create as little drag as possible, then to a power and control box on the ground.

 This is how my QSI is cabled:

post-6754-0-31795200-1449564743_thumb.jp

In the obsy, the scope is much larger, a 16 inch Fork mounted Truss Newtonian, so there is room on the scope itself to mount kit. This is where the dew heater controller, USB hub,  power distribution, and focus electronics are mounted.

All cables are then routed through the fork mount back to PSUs and computer.

Hope this helps

Huw

  

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If you get neatness-itis (a malady to which I'm immune!!  :grin: ) be sure to colour code or otherwise identify your different USBs and power supplies because, when one goes belly-up, as it will, you will struggle to know what's what. It's a pain when trouble shooting if cables vanish into one end of a neatness tube and appear unidentifiable at the other...

I host a robotic shed. Tell me about it.

Olly

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I use a spiral cable tidy with mine, but I only have 4 cables to deal with. A black USB to the SXV-H9, a grey USB to the QHY5 a white USB to the mount and black power cable to the SXV-H9. I can sympathise with Olly. I have had to replace cables a couple of times and it's a right pain. For my portable widefield kit I just use little bits of double sided velcro to hold things together. 

In both cases, I route the cables but to the mount then off down to the floor where my USB hub and power supplies live, in a big sandwich box with a few holes drilled to poke the cable ends through.

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:grin:

If you get neatness-itis (a malady to which I'm immune!!  :grin: ) be sure to colour code or otherwise identify your different USBs and power supplies because

Olly

Thanks Olly! Guilty as charged  :grin:  :grin:

I have numbered, colour coded cable markers on all my USB cables. Makes rigging, fault finding and tearing down a piece of the proverbial.

http://www.bryant-unlimited.co.uk/E09C%200

I use these for work, so can 'redirect' a few for astro kit, not cheap, but there must be something similar in smaller quantities on ebay.

Huw

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Thank you all for your useful comments.

I have two waterproof enclosures. One each side of the telescope, fixed to telescope supports that I fabricated and are sandwiched between the telescope rings and the losmandy plate.

Derek, How did you fix the boxes to your scope's rings? Do you have a close-photo of that? And, is there any issue with the offset weight of the boxes making balancing difficult?


I basically, on both rigs, split the wiring into functional groups, ie, mount, scope, camera. Every group of cables is loomed in braided sleeving and tied off tightly:

http://www.ebay.co.uk/itm/Black-Braided-Cable-Sleeving-Sheathing-Auto-Wire-Harnessing-Marine-Electrics-/150899408011?var=450115825449&hash=item23224e3c8b:m:m3qi4dFX8H9VjqdGL6aFGCw

Huw, I like the neat snag-free effect of the braided sleeve, and grouping the cables. I'll see if I can adopt a similar scheme.

be sure to colour code or otherwise identify your different USBs and power supplies


I have numbered, colour coded cable markers on all my USB cables.

Olly and Huw; sage advice. I had been using self-adhesive address labels, but they get mangled easily and are prone to getting soggy with dew. So I've ordered some marker cable-ties for EBay to make a more permanent id for each cable. See http://www.ebay.co.uk/itm/321438721763?_trksid=p2060353.m2749.l2649&var=510302249910&ssPageName=STRK%3AMEBIDX%3AIT


My tip would be to keep power and USB cables seperate. They don't mix too well! Especially if they are wrapped around each other.

Ian; that's a good point. I'm an electronics engineer and had concerns about, say, the DC pulses in dew heater cables causing degradation of USB traffic in adjacent cables. But, so far, this hasn't been a problem. However, it is good engineering practice to keep information service cabling separate from power supply cabling so I'll re-route my cabling accordingly just to be sure.

Thanks again to all for your feedback.

I'll post a pic of the results of my labours in due course.

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Ian; that's a good point. I'm an electronics engineer and had concerns about, say, the DC pulses in dew heater cables causing degradation of USB traffic in adjacent cables. But, so far, this hasn't been a problem. However, it is good engineering practice to keep information service cabling separate from power supply cabling so I'll re-route my cabling accordingly just to be sure.

Hi

I used to get a lot of "snow" on my guide camera images (a Lodestar). That reduced dramatically when I seperated the power cables from the USB cables!

Cheers

Ian

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Hi Doug,

The boxes are almost identical one on each side of the scope and also almost identical weights, done on purpose. I made up aluminium support bars bent and machined as required. Two of them fit on top of the losmandy plate, sandwiched between it and the tube rings, one to support each end of the boxes.There are then aluminium spacers to raise the boxes so that the USB leads clear the mount when it is tracking. I just sprayed the fittings black to match the tube rings. At present everything is boxed up and put away, (I cannot do any imaging at home), but at the first chance I get I will photograph it and post on here for you.

It just means that there are fewer wires leading up to the scope from the mount, less objects to drag and catch.

Ian has made a good point about power and USB being separated, but the same can be accomplished by wrapping the USB in a net wiring shield and earthing one end. This shields the signals from power induced EM signals. Some good quality USB cables accomplish this by the cables having internal shielding and the outer metal of the USB connector being earthed. I spent several years working on electronic systems on board ships and shielding was invariably the answer.

Hope this is of some help.

Derek

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Hi Doug,

As I promised here are some close ups of the mount. It is so long since I altered the mountings I had forgotten that I eventually replaced the sandwiched construction as I wanted to space the scope rings differently so that I could alter the spacing but also that I could remove the rings without affecting the enclosure mounts.

I hope this helps you to make up your mind as to how you want to proceed.

I took a long time experimenting before I was satisfied. This is the third actual fabrication as I kept changing the design requirements. At first I only had one enclosure as the EQ8 was heavy on one side and that helped to balance the system.  But I found that the camera kept alarming and shutting down. This proved to be an overvoltage problem, so I fitted 12 volt DC/DC convertors to stabilise the voltage at a set level of 12.2 volts. That solved that problem. I also needed to introduce a 15 volt supply for a newly acquired rotator, so a Buck  convertor was fitted. Then a change from the EQ8 mount and  acquisition of a GM1000hps mount meant that I needed much better balancing. Using the present setup with two enclosures means I am now balanced within a few grams, between  each side of the scope.

One enclosure houses the two DC/DC stabilised supplies and two USB hubs, this isolates the rotator and focuser from the camera. It also has most of the USB connectors and power connectors fitted The other side enclosure has the Buck convertors (plus spare Buck)  and the on the outside the Dew Controller and Focus Controller.

The 12 volt supply from the batteries go to the Mount Legs distribution box and in it  is fitted a USB hub and Buck convertor to supply the mount with 24 volts. There are two separate batteries supplying the whole setup. One does the Mount and Dew Heaters. The other does everything else. So there are two separate supply cables to the mount using 6mm2 cable to reduce voltage drop. I just calculated the drop at 10 amps. Over about 8 metres its around 0.5 volts as opposed to 2.5mm2 being around 1.1 volts. Cable to the enclosures is 2.5mm2  as it needs to be supple and free moving (but its only about 1metre). Inside the enclosures I used 4mm2 wiring. All connectors are XLR type. But I have used different pin numbers, i.e. 3 pin 4pin etc up to 7 pin. That way you cannot plug the incorrect lead in to any socket. Especially in the dark!

On the jack plugs I am at present in the process of changing over to types that actually grip the centre pin. I have found over time that the original cheap one fitted on some equipment can be very loose and give poor reliability and are prone to falling out or disconnection. I use shielded USB but as yet may have to change to externally shielded  types, easily accomplished at a later date.

One note about batteries. I have tried lead acid liquid types and  Gel types. Gel is preferred for safe operation. Trouble is the very large drop off in supplied voltage under load and as the battery becomes depleted. I have moved over to LiFePo. These ensure the same output voltage over almost all of their supply from fully charged to almost depleted. They are prohibitively expensive, but should out last lead acid at least 5 to 6 times in terms of battery longevity. The first one I bought was from Tracer. Cost £650 for 40 Ah. Ouch :mad:

Tracer fitted a second connector as per my request after an initial screw up.  But then for other buyers they have proceeded to up the price from 650 to 750 then to a present whopping £850 for the exact same battery and case. It was just pure greed on their part! The base 40Ah LiFePo battery is still the same price on their website. The only difference is a change of plug socket from XLR to Speekon.        Speekon are cheeper!   I decided to make up my own next. I bought a Tracer 40Ah battery  and then purchased a Pelicase separately. Extra charger and two speekon plug sockets. Total cost well under £600 saving over  £260 for the exact same thing.

I am after long term reliability. I spent 24 years as a marine engineer and in the latter part working on Electronic Dynamic Positioning systems on a dive ship as well as more mundane deck and engine room wiring systems. With the Dynamic Positioning we had to get reliability as the sat divers lives were at stake. As I only get a few chances to image I do not want to waste time trying to get things working.

I hope some of this is of interest to you and may be useful. If you want any more information  please feel free to PM me.

Wonderful Hobby (Obsession) Eh! :p

Derek

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  • 2 months later...

Dear all,

Thanks for your helpful suggestions and useful information.

I promised I'd share the eventual configuration so here's three images of the setup currently in use. The 110 mm Starwave is being used for imaging in this configuration, with the Celestron 70 mm pressed into use as the guide scope.

There are effectively two wiring umbilicals; one from the pier to the RA part of the EQ8 mounts (carrying power, and USB 3.0 from the obsy PC to the hub on the RA axis of the mount), and one from there to the dual saddle on the DEC part of the mount (carrying power for the dew heaters, USB 3.0 x2 for the cameras and power for the Nightscape camera).

The bundled up excess of the USB and dew heater cables is a bit unsightly, but neither the electrons nor the photons seem to mind! :-)

Yes Ian and Derek, I was concerned about induced interferences but in the last two months of use I've experienced no problems at all.

And after removing both the EQ8 alt adjustment bar and the two az adjustment screws I've experienced no snags during slews or guided tracking.

Hoping this is of interest.

 

WP_20160223_18_43_04_Pro.jpg

WP_20160223_18_47_02_Pro.jpg

WP_20160223_18_46_23_Pro.jpg

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Not too different from my setup(s), either of which I will need to place onto the mount for an imaging session because the mount remains permanently on the pier. Because I'm imaging remotely with the scope out of direct sight I need to be quite sure the mount can perform unhindered meridian flips with nothing snagging, and that the cables do not pull on the OTA which would be detrimental to tracking performance. In each case the cable loom passes along the OTA and the first secure point is in the area of the puck (top of RA axis). A second support point is made at the South end of the RA shaft housing forming a loop with enough slack to allow the scope to point anywhere without pulling. Both these attachment points are made using a Velcro tab attached to a cable tie, that makes a secure connection yet allows some rotational movement. The refractor loom is contained within a zip-up sheath and works well, the ODK12 loom is a temporary arrangement (temporary because the final hardware config is not yet assembled and some of the cables are actually unused) which I feel is too stiff. This will be replaced with a sheath similar to the refractor soon. The strategy works well, I can operate the scopes remotely with impunity which always includes making many meridian flips during creation of an all-sky mount model.

 

DSC00716_zpsdbgieao5.jpg

DSC00846_zpsja3n0ckh.jpg

ChrisH

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Chris did you purchase the extra long cable connection to the mount from the 10Micron computer? 

I did not know about the zip covers, thanks will look into those.

Do you leave the mount out all the time? I could not do that her with mine, as it would disappear double quick!

Derek

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5 hours ago, Physopto said:

Chris did you purchase the extra long cable connection to the mount from the 10Micron computer? 

I did not know about the zip covers, thanks will look into those.

Do you leave the mount out all the time? I could not do that her with mine, as it would disappear double quick!

Derek

No, I didn't buy the long cable (if it's the one I think you're referring to it's an extortionate price anyway). The mount does stay outside, certain security features prevent it being easily removed from the pier and I think it's likely safer there than putting your faith in the usual type of observatory to keep it secure. It's well able to withstand any weather conditions under a couple of waterproof covers. and the control unit and hand controler are stored elsewhere. The 10Micron mount is a boat anchor without those and there is no chance of obtaining a replacement without going through 10Micron themselves.

ChrisH

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It's a lovely mount Chris. Looks a great and solid pier. Yes the price of the cable was what I was wondering about. I got a shock when I looked at buying the cable. Certainly not worth the price asked. I have the 1000 and love it so far. brilliant for taking to Star Parties as not too heavy. EQ8 nearly killed me getting it in and out of the car(each box 46kg).

Doug, looks a really solid setup. The EQ8 can handle a heck of a payload.

Derek

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Thanks, Chris, for the details of the cable cover - I'll look into that.

Quote

Doug, looks a really solid setup. The EQ8 can handle a heck of a payload.

Derek

Yes, I bought it to handle either my C10N newt + 110ED side-by-side or my C11SCT + 110ED side-by-side plus cameras, etc.

What's stopping me putting these OTAs on the mount at the moment is a search for a Vixen clamp that I can bolt on top of the 110ED rings to carry the 70 mm guide scope. I've not had much luck looking through the ADM website or anywhere else - would you guys be able to suggest a place to search?

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