EQ5 Dual Axis ST-4 Guideport Mod

[badgerchap]

For the second time this year, I have found myself modifying the motor drive handset from my EQ5 mount, so this time I thought I'd share the process in the hope that it might help someone in their own endeavours. Also, it shows someone thinking of the project just how simple it really is! This post was initially written for my blog, so please forgive me whereever I seem a little patronising. I don't intend to try to teach anyone how to suck eggs! However, there are a number of pictures on the blog which may offer a more complete explanation of the process.

You will need:

• A small Phillips (cross-head) screwdriver - preferably a few millimeters will do.
  
• A soldering iron,
  
• Solder,
  
• Either the 'ST-4 Conversion Kit' which can be purchased from Opticstar (in the U.K.) or Shoestring Astronomy (in the U.S.). Alternatively, you can by any 6 core wire with an RJ12 connector - more on that shortly.
  
• An EQ4 / 5 Dual Axis motor control handset.
  
• Either an ASCOM compatible guide camera with ST-4 port or any other suitable guidecam / webcam and a GPUSB* guideport interface, also available from the above suppliers.
  
• Autoguiding software. I use PHD, which is free, but there are others available.
  
• About an hour of spare time.
  

*Please note: The GPUSB interface is only necessary if your camera does not have an ST-4 port. In cases of cameras with this socket, for example the QHY5, the camera itself acts as the interface between the guiding software and the handset.

This guide concerns the dual axis handset that we use to track the sky as the earth rotates. This is fine for your first foray into astrophotography, but due to a number of factors it will not allow you to take exposures much longer than a minute.

The ST-4 cable: if you're ordering from one of the suppliers above, this will indeed be called an ST-4 cable. However, if you wish, as I did, to purchase one of these from any other (non-astronomy) supplier, it may go by a different name. It will then be known as an RJ12 6P6C cable, the 6 referring to the 6 wires running through it. Be careful not to confuse this with the RJ11 which has only 4wires, and some others have only 2.

Be sure to check that your cables either use the same configuration as used here (White - Brown - Red - Green - Yellow - Blue from left to right with the release clip of the connector facing towards you), or that you can familiarise yourself with the configuration of your cable in order to match the correct cables to the correct soldering joints. Incorrect wiring could lead to damage of your equipment.

Whilst we're on the subject I must point out that this modification is in no way recommended by myself or any of the suppliers of manufacturers involved - you undertake this at your own risk, and any warranties will be invalid.

Right, with the warnings done and tossed hastily to the side, provided you have all you need, it's time to begin!

STEP 1: Remove the buttons

Gently prise off the four buttons with a screwdriver. Use 2 screwdrivers if possible to avoid breaking the buttons. Lay the buttons to one side.

Step 2: Removing the top cover:

Unscrew the four screws at each corner of the handset...

...and the two screws which attach the power socket to the main box.

Then, the handset cover should come cleanly off.

Don't be afraid of what you see if you're unfamiliar with electronics - you can ignore 99% of everything that's in here. Just be careful not to touch anything you don't have to - particularly the chip on the lower board (which you'll see in a moment).

Step 3: Open up some access.

Loosen and remove the two screws that fix the top board to the bottom board.

The top board now lifts away revealing the bottom board, which is the part that the hand controller uses to communicate with the mount. Note the large chip which I mentioned earlier. Be careful to have as little contact with this board as possible.

There are three small screws holding the bottom board in place - remove these also.

Step 4: The Cable grip.

Now the cable grip - we will need to remove this in order to lay our new cable underneath it after soldering. It is most convenient to undo this grip now, so as not to hamper yourself later on.

Ensure that the power socket is dislodged from its nook, being careful of the delicate wires that connect it to the main board. These are fragile and can break if tugged on.

Gently pull the main board away from its housing and turn over. You will see two bolts which hold the cable grip in place. Remove them.

Step 5: Hole boring

You can either chose to drill a hole, or cut a slot into the outer casing of the handset. The hole may be neater, but I found that a slot makes everything more flexible. Also, if you choose a hole MAKE SURE YOU PUSH YOUR NEW CABLE THROUGH THE HOLE BEFORE SOLDERING! Otherwise you'll find yourself having to redo the job after you do it! I only mention this because it's a mistake I have made myself! D'oh!

Step 6: Time to solder!

First, cut back the white (Pin 1) wire. This is unused by the handset. It is important not to have this hanging loose within the handset, as it may cause short circuiting or unpredictable behaviour.

Solder the wires into the follwing configurations. If you are a better solderer than me, which is very likely, your end result may look a tad tidier than this!

Now that you have your wires soldered in place, it's importand to test the operation of the unit. Carefully plug the unit in. Be EXTREMELY careful not to touch any exposed wires or contacts at this point. There is a risk of electric shock. Carefully press each button, and ensure that this causes the green L.E.D. to turn red. If you have a stepper motor from your mount to hand, you can always plug this in to ensure that the buttons are doing what they're supposed to. Personally, I check the functionality of the unit after every step from here on. It's easy to break off a solder joint or get a short circuit, so a quick check is a good idea.

Step 7: Put 'er back together!

First, put the three ST-4 cables beneath the cable grip and fasten it firmly. This is important as a loose grip will lead to broken solder joints in the future. A firm hold keeps everything together!

Slot the main board back into place and attach with three of the small screws. Use one more of these to reattach the lower side of the power socket.

Reattach the upper board with the two short, fat screws...

...and then replace the outer cover using the four long screws to hold it into place.

Use the remaining small screw to firmly attach the power socket, clip-press the buttons back into place, and you've completed your ST-4 Guideport modification!

PLEASE NOTE: The EQ5 is not the ideal mount for astrophotography, and it will only enable a low payload capacity to be used. I would suggest considering the use of a so-called 'finder-guider' rather than a dedicated guidescope, as these keep the weight to a minimum. If you do wish to use larger scopes with larger guiders, filter wheels and other equipment, you should consider upgrading to a sturdier mount. Of the more affordable mounts, consensus often favours the EQ6 and NEQ6 mounts, or their equivalents, which have served many successful amatuer astrophotographers well. The HEQ5 should really be seen as the minimum, and those taking on the EQ5 are either just slightly mad, or enjoy a challenge. Having said that, many people have made excellent use of this great mount. It remains to be seen if I manage to do so also!

Please also note that I accept no responsibility for any damage to your equipment during this process. I personally am notorious for breaking things and being a general bodge-artist (yes, that was the polite version), so my instructions should not be followed by anybody at any time!

[David Smith]

A very clear, detailed write up.

[Oily]

Very informative,did mine a few weeks back and as Badger has said it's pretty easy to do

[badgerchap]

Glad to hear it went well Oily

[nephilim]

Thanks for posting B.chap, I'm planning on doing the mod shortly aswell, i've been looking at Marks (Quatermasses) blog for direction & he's also been personally helpful but its always good to have more than one guide so to speak & it also means that if I run into any trouble i'll have another person to annoy with questions (Make that '2' more @ Olly )

Steve

[nephilim]

Btw, do you have any advice regarding the problems i've heard about with the hand controller shorting out as thats the only thing thats really worrying me.Thanks.

[badgerchap]

This happened to me (hence this was my second mod this year!) so I know how frustrating this is. The only thing I can say is to be sure your power supply delivers a steady 6v. A decent power supply should be regulated, but in the case of cheaper supplies you may get fluctuations in supply voltage which might cause a burn out. Of course you could solve the whole problem by buying an EQ5 goto upgrade. This has a wider tolerance of input values (11-15v) and obviously already has an ST-4 port, on top of the goto. Shame it costs £300!

[Oily]

Thanks for posting B.chap, I'm planning on doing the mod shortly aswell, i've been looking at Marks (Quatermasses) blog for direction & he's also been personally helpful but its always good to have more than one guide so to speak & it also means that if I run into any trouble i'll have another person to annoy with questions (Make that '2' more @ Olly )

Steve

Any time Steve It will be good to share ideas/tips along the way too if you want?

[JamesF]

I have on occasion thought that it might not be that hard to unsolder the leads from the power connector and insert a voltage regulator between the two. I think the ST4 conversion kit uses opto-isolators, so in combination that seems like a reasonable level of protection given that a number of people have complained about handset failures after similar conversions.

James

[Oily]

I use a selectable power supply with mine and set it to 4.5V,I've checked the output voltage which reads 5V and it powers the controller fine.By the way,If I select 6V the output is 7V

[JamesF]

If it's not a regulated power supply it's not at all uncommon to find the output voltage is a fair bit higher when measured open circuit than when the supply is under load. Makes me quite nervous about using unregulated supplies.

James

[Oily]

If it's not a regulated power supply it's not at all uncommon to find the output voltage is a fair bit higher when measured open circuit than when the supply is under load. Makes me quite nervous about using unregulated supplies.

James

Just had a look now and it's a universal regulator power supply so I should be ok with that

[badgerchap]

I have on occasion thought that it might not be that hard to unsolder the leads from the power connector and insert a voltage regulator between the two. I think the ST4 conversion kit uses opto-isolators, so in combination that seems like a reasonable level of protection given that a number of people have complained about handset failures after similar conversions.

James

It's a little disappointing they don't come with regulators already built in. It'd hardly be asking a lot considering the unit retails for nearly £100 and the most expensive component (the IC) can be bought for less than than £2 for 1!

[Quatermass]

Hi Chaps...Just coming in a bit late on this thread but I have burned out several of these control units' now on my 3rd burned out one and what has been said about a regulated voltage makes the most sense for the burn out issues.

I have been fiddling about with my 3rd one and I have two power sources, one is the battery's in the battery pack supplied, the other is a universal adapter that has a selection of voltages on it including the choice of 6 volt.

It was this adapter that I used when outside instead of battery's and it may be the cause of the burn outs I am not sure.

However this evening I swapped over the chip from the older control pad and was given a glimmer of hope.

Putting in the adapter on 6 volts gives me a green light but no motor activity at first then I pulled it, out switched off and put it back in again.

This time no green light but the motors where humming away?? Confused I tried the battery pack instead and although they are not fully charged up battery's when I plugged the standard battery pack in the motor turned for a few seconds then stopped??

I am not electrician but could this mean that the unit is not dead yet? Normally on my conversion handset the light would stay red when it burned out the fact that this one is actually green suggests it may be savable.

But truth be known, I have just about head it with these units they seem to be very unstable and not at all built for outside use in the damp and cold.

I am going to send them off to Oily for a look having had a natter with him this week to see if he can have any joy as I am not good at electrical stuff in the mean time if any one has one of these control pads that works and wants to sell it please let me know as I can do no imaging until its sorted and I don't have a 100 quid spare to buy all the kit for a 4th time, I have more motors and battery packs then I need now why on earth don't sky watcher sell spare parts for these kits it would certainly be a big help. If your out in the damp and cold every night imaging you need to know that your kit is not going to let you down and these control pads are simply not up to the job in my opinion.

The voltage adapter stats

Input is 230~50hz 9w

Output is 3,4.5,6,7.5,9 and 12

It says its a regulated power supply.

[JamesF]

I have more motors and battery packs then I need now why on earth don't sky watcher sell spare parts for these kits it would certainly be a big help. If your out in the damp and cold every night imaging you need to know that your kit is not going to let you down and these control pads are simply not up to the job in my opinion.

Stick the motors in the classifieds? Someone might want a spare or two, or to replace a DEC motor with a broken connector (seems to be a common failing) and it would help offset the cost of a new handset if that's the way it has to be. Otherwise perhaps the AstroEQ mod is the way to go for the future?

James

[Quatermass]

Yes James oily was telling me about this AstroEQ mod I like the idea of it turning my scope into a go to scope as well as running the tracking for me so may well go that way just waiting to see how Oily gets on with it but it sounds more reliable then the control pads at the moment. I will be out side in a mo looking for metorites as I cant do any imaging yet.

[badgerchap]

Quarter mass I thought you ended up getting an HEQ5?

I was lucky enough to be permanently loaned an NEQ6, but I still use the EQ5 for wide field stuff. Funny thing is that now it's not my main mount, it's been behaving itself wonderfully. Typical!

Typed inexpertly from my phone

[JamesF]

Quarter mass I thought you ended up getting an HEQ5?

I thought so too, but in the light of Mark's comments in this thread I assumed I must have been mistaken. I'm sure there was someone who had a guided EQ5 who eventually caved in and bought a HEQ5 in the last year or so though.

James

[badgerchap]

I thought so too, but in the light of Mark's comments in this thread I assumed I must have been mistaken. I'm sure there was someone who had a guided EQ5 who eventually caved in and bought a HEQ5 in the last year or so though.

James

Well with regards to Quatermass' and my own issues, and those of others, I think you have to be a bit masochistic to persist with the EQ5! I know the move upwards is costly, but then when handsets are £100 a go.....

Typed inexpertly from my phone

[JamesF]

Well with regards to Quatermass' and my own issues, and those of others, I think you have to be a bit masochistic to persist with the EQ5! I know the move upwards is costly, but then when handsets are £100 a go.....

Yes, it would help if there were spare handsets available, or if they were a little better engineered to start with. I guess it wouldn't be hard to solder a 6V regulator across the wires in the box oneself given the skill with a soldering iron. I don't know if a simple bridge rectifier might also be incorporated to protect against reversed-polarity connections -- it's not something I've thought of before.

James

[badgerchap]

Yes, it would help if there were spare handsets available, or if they were a little better engineered to start with. I guess it wouldn't be hard to solder a 6V regulator across the wires in the box oneself given the skill with a soldering iron. I don't know if a simple bridge rectifier might also be incorporated to protect against reversed-polarity connections -- it's not something I've thought of before.

James

Reversed polarity hasn't given me a problem so far. My adaptation has a removable terminal which routinely falls out and so in the dark I often get the polarity wrong. Never caused an issue, save for temporary inactivity.

Agreed though, initial manufacturing should be better at the price. I'm rather surprised no one in the UK has made a cheaper alternative.

Typed inexpertly from my phone

[Oily]

I've been doing a little reading on this,QM says the chip could be at fault as he switched one and it started working again.You can buy the chip for £4.50 and a reader/programmer for a tenner.Just waiting hear back from the guy who sells the reader to see if it can program this type of chip

[JamesF]

I've been doing a little reading on this,QM says the chip could be at fault as he switched one and it started working again.You can buy the chip for £4.50 and a reader/programmer for a tenner.Just waiting hear back from the guy who sells the reader to see if it can program this type of chip

That would be really handy. My gut feeling is that the only difference between the EQ3-2 and EQ5 handsets is the programming of that microcontroller to account for the different gear ratios, though there's a trimmer pot somewhere as far as I recall that may also be set differently.

James

[Oily]

Well the guy selling the chips doesn't know what reader/programmer to use with the chips,unbelievable !!

[JamesF]

It seems it's one of the 80C51 microcontroller family. There seem to be a few programmers for the 89C51 series, but I can't find any that mention the 87C51 at the moment.

James