Guided EQ3-2 write up.

[stan26]

As suggested by other SGL members, here is a write up of how I setup my EQ3-2 for guided long exposure astrophotography.

When we talk about suitable mounts for long exposure AP and in particular what is the minimum requirement, in my experience most astrophotographers will suggest that the HEQ5 is the bare minimum for successful deep sky AP. Although there is valid reasoning behind this widely regarded rule of thumb, I do not totally agree that the HEQ5 mount is the bare minimum. I believe the EQ3-2 and EQ5 are very under rated mounts which are more than capable at deep sky AP even unguided. The budding imager needs to be realistic when using these lower end mounts. In particular keeping weight to a minimum, cleaning and re-greasing the internal moving parts and correct adjustment of the DEC and RA axis worm drives will greatly improve overall performance. I will try to cover all the important aspects in this write up to help others wanting to do AP on a tight budget with there EQ3 mounts……

(unfortunately I only took a few pictures along the way as at the time I didn’t plan on doing a write up. I will add links to relevant information as I go)

So forgetting guiding for a moment, we need to “tweak” the EQ3-2 to get the best out of it, and this applies to unguided EQ3’s as well. The first thing I did was strip it all down and degrease all the internal parts getting rid of all the cheap Chinese gunk they use at factory. Re greasing only the friction surfaces with high quality lithium based grease available from places like B&Q. The mount was then re assembled paying special attention to the tightening the RA and DEC main axis bolt/shaft. This is particularly important in DEC. Too tight and it will nip up and cause “stiction” resulting in jumpy movements from the motor drive. Too slack and the DEC head will be very sloppy. It needs to be somewhere in between, a matter of trial and error really.

JamesF on here has done a write up with pictures on his blog about stripping the DEC part of the mount. EQ3-2 Mount Tune-Up (Part One) | www.tanstaafl.co.uk

Unfortunately I can’t find any pics/guides on the net of stripping the EQ3’s RA axis. Its not difficult to take apart the RA section but it may not be immediately obvious how it actually comes apart. You need to remove the polar scope (if applicable) then remove the RA axis dial ring. This will expose a hole in the casing of which you can gain access to (3 I think) small allen grub screws. After slackening these grub screws you can then unscrew the main RA shaft. To do this you need a special tool. There are two small holes in the end of the RA shaft. (SEE FIG 1 BELOW) The tool inserts prongs into these hole to enable you to unscrew it. I simply used a pair of circlip pliers. Some people have used a piece of wood with 2 nails through it.

There is a write up on this on the EQ5 here on astronomy boys page. Its essentially the same design so will apply to the EQ3. Astronomy Boy: CG-5 Mount Improvements

After the mount has been re assembled with the new grease, we then need to tune the RA and DEC adjustment bolts. This again is all trial and error. I read many ways on the net of how to do this and neither really worked for me. I spent about 2hours tweaking these screws and somehow got it right in the end…but I couldn’t tell you how! The idea is to tighten the main outer allen bolts to take up the backlash in the wormdrive and the centre small allen screw is use to back off the adjustment so that the gears don’t bind. I removed the motor drives and bolted on the manual turn knobs to judge the adjustment needed by feel. The only real advice I can give on this is this…..Adjust the screws with the mount fully loaded (i.e scope/guide scope camera etc) all bolted on. The extra weight will make the backlash more obvious with the mount under load.

After a good drift alignment and correct balancing the EQ3-2 mount would now be ready for non-guided AP. I would expect up to 1min subs @ 500mmFL with a good alignment.

Now we talk about “GUIDING” with the EQ3-2……

Before we go straight into the required electronic/software side of things there is a mechanical modification we can do to help with backlash in the DEC axis. Even after the above tweaks there will still be some backlash in the gear driven system. I have made my own direct drive mod that does away with the gears and greatly reduces the backlash. (SEE FIG 2 BELOW)

This mod can be found here: http://stargazerslounge.com/diy-astronomer/172953-eq3-2-dec-axis-direct-drive-mod.html

Connecting mount to computer. We need to add a guide port to the hand controller. (SEE FIG 3 BELOW) I believe pro goto and or synscan versions of this mount already have an ST4 port…? But this write up is based on the basic dual axis motor upgrade which does not have any input port. The style of port that you will ideally want to add to your hand controller is as mentioned above an ST4 port. ST4 is a particular configuration of the wiring based on the RJ12 socket/cable. RJ12 is basically network cable, similar to phone line cable/connectors. ST4 is a standard de-facto format recognised by most astronomers and now manufacturures of astro equipment across the world, hense it’s the best option to use and the cable is cheap and can work realiably over long distances (unlike standard USB). To add an ST4 port to your HC is easy, but does require some soldering. Shoestring astronomy sells the EQ port mod kit for about £10. This is where I got mine from. There are some suppliers in the UK that also sell these kits. You can find some very good and clear instructions on how to solder the ST4 port into you HC here on shoestrings website: http://www.store.shoestringastronomy.com/eq_mod.pdf

There is also an excellent thread on here that covers this modification on an EQ5 (the same HC as EQ3-2) which has been done by Quatermass. http://stargazerslounge.com/diy-astronomer/172701-guiding-conversion-project-200p-eq5.html

This is a great thread full of information about guiding with cheaper mounts, a must read for anyone thinking about this sort of guiding…..

Interface.We now need a device to convert the commands from the PC/laptop into commands that the HC can understand. This is called an interface. There are two commonly used types of interface depending purely on personal preference and what ports are available on your computer, 1, Serial interface or 2, USB interface. Most people will use USB because all modern computers have USB. Serial port are now old hat but I prefer them because they are more realiable/robust. Luckily my old dell latitude laptop has the 25pin serial D port, so this is what I use. (SEE FIG 4 BELOW) These interface’s can be purchased from shoestring astro (and some UK suppliers). I purchased the shoestring asto GPINT-PT serial interface as seen here The Shoestring Astronomy Store - GPINT-PT

Both USB and Serial ports have an ST4 socket on them, so now we just need a length of ST4 (RJ12) cable to connect them to the ST4 port we added on the HC. ST4 can also be purchased from company’s like shoestring.

So…just to make sure you’re following me here: We have added an ST4 port to the HC (handcontroller), we run a length of ST4 style cable from the ST4 port on the HC to the interface (beit usb or serial) and the interface connects straight into the computer (beit laptop or PC) Got that..?

Now we have the mount connected to the computer we need to think about the guide scope, how we’re going to mount it and what guide camera are we going to use and how to connect that to the computer.

The Guide scope /mount (this is where DIY can help to keep costs down) You can use anything from a 50mm finder scope to a small refractor for guiding. As mentioned earlier with the EQ3-2 we need to keep that weight down so a 1000mm FL refractor as a guide scope isn’t going to do us any favours here. I have used a home made 60mm guide scope which I made from cutting down an old plastic F13 vixen refractor and removing one of the objective lenses. I also fitted a small 25mm finder to this. A lot of people use the standard 50mm finder scope. The is what Quatermass Is using and explains how to use it for guiding in his thread http://stargazerslounge.com/diy-astronomer/172701-guiding-conversion-project-200p-eq5.html The great thing with the finder guide scope is they already sit in an adjustable holder so you can move them to find a guide star. I had to make my own guide scope holder, but you can buy such devices from most astro shops, but this sort of gear can be expensive for what it is (IMO). As per pics, I made my guide scope rings from old metal kitchen utensil holders, then measured/drilled out 3 holes on each ring for the adjustment screws to go in and stuck some nuts on the inside using epoxy resin (strong stuff) and finished it off with a lick of black hammerite. I made a mounting rail using scrap metal from local tip, then I bolt this either to the top of my ST102 scope rings or to my new widefield rig I made. (SEE FIG 5 BELOW) Almost any type of optic tube can be used as a guide scope, just be sensible about size…..

The guide camera. I’m not going to talk about standalone guiders here for two reasons, 1, I don’t know much about them, 2, from what I have read and from Quatermass’s experience (as per his thread) they do not work well with dual axis stepper motors, because of the speed of the increments the motors operate at. For more info see his EQ5 conversion thread above.

There are a few options available to us here, but the main two options for a guide cam are 1, webcam 2, dedicated astro guide cam. Even second hand you’re going to be talking £100 + for a proper purpose built guide cam such as the QHY5. These are worth the money as they work very well and are generally more sensitive to aid in finding dimmer stars, and I suspect have a sensible FOV, but if like me your on a tight budget you options maybe limited to webcam, and this is what I use.

Not all webcams are effective for astro work, and the main component that dictates whether or not a particular model is worthy or not is the sensor chip. There are two types of sensor CCD & CMOS. Now the general rule of thumb here is CCD is best. Its more sensitive and (I think) better signal to noise. That said the latest CMOS cams have come along way and are now almost matching the performance in some respects. The main daddy’s when it comes to webcams are the Phillips SPC900/880’s. These are older generation CCD cameras fitted with the SONY CCD sensor. The problem is they are getting harder to come by these days and if you do find one they can be £50 +, quite hefty for a webcam. Thankfully there are other older generation CCD webcams out there that go for a fraction of the price and have similar performance to the Phillips.

Check out this SGL thread for alternative options to the SPC900’s

http://stargazerslounge.com/imaging-discussion/81143-alternative-philips-spc900nc.html

I managed to get a Logitech Quickcam Pro 4000 off ebay for around £10 delivered. This is the camera that I and Quatermass use as a guide cam. They don’t need modifying for long exposure, they work fine as they are, the beauty of the SONY CCD sensor chip!

To attach the camera to the scope/finder a bit of improvisation may be required. If you are using a telescope with a 1.25” focuser tube than your most simple option will be a 1.25” webcam nose piece. I believe these are around £15, and simply screw into the webcams focus tube and then slots into the telescopes drawtube. I went full DIY and used a tapered bottle cap with a hole drilled in the end to accommodate the webcams focus tube (by the way the lens of the webcam is removed). The cap was bonded to the telescopes drawtube (hot glue gun). I have cut out some fine slots across the cap so that when I push the webcam onto it the sharp inner edge round aperture clips into the slots and holds it in place securely, simple but effective. (SEE FIG 6,7 & 8 BELOW)

I then use a 5M USB repeater cable to connect the webcam to the laptop. (you cannot run standard USB longer than 5m reliably, it needs and active or repeater cable)

So apart from the software we have now covered all the main bits and pieces to guide with the EQ3-2.

* Tweaking the mount

* Modding the hand controller

* Choosing an interface

* Connecting the interface / hand controller / pc

* Guide scope

* Guide scope holder

* Guide cam

It still may seem all a bit confusing how all this fits together, so below is a drawing I have done, because some times pictures speak more than words……(large version added as tiff if you struggle to see it)

The Guide software: Once again we have a few options here but I will talk only about PHD developed by Craig starks of stark labs.

PHD = push here dummy!......It really is very simple software to use. I won’t go into great detail here because there is plenty of well written info about this programme all over the net coming from people who are a lot more experienced than me.

(IMPORTANT NOTE: ALWAYS RUN PHD AND CONNECT TO MOUNT BEFORE YOU SWITCH ON THE HAND CONTROLLER)

If using one of the shoestring interfaces before you fire up PHD or any other guiding software for the first time you can download a handy simple bit of software from shoestring called GPUSB check or GPINT check. This enables you to find the port on your pc that the interface is connected to and make sure its all functioning correctly by pressing the simple DEC and RA buttons to make sure the motors are reacting correctly.

Once you have found the correct port you simply start PHD and select the "MOUNT" tab, a then select the relevent port from the drop down list. You then come out of that menu and select the picture of the telescope at the bottom (connect to mount). Once this is done you can switch on the hand controller. To configure the guide cam you simply click on the picture of the camera, then select the type of camera fromthe list that pops up. (i.e windows wdm style webcam) if you are using an unmodded webcam like me. Once the cam is selected you can click the green arrow picture (loop) which will start the webcam looping images on the screen at the rate of 1second exposures. You now find the guide star on the screen, click on it then press the bullseye and your guiding!!

Its just a matter of tweaking the settings from here......

Hopefully I haven't missed anything important here, if I think of anything worth adding i will added in the thread....

I hope this helps people wanting to guide with the EQ3-2.....

Regards

Stan

GUIDE SETUP.tif

[JamesF]

Excellent write-up, Stan. I'm sure it will prove very useful to people who want to give imaging with an EQ3-2 a go.

James

[stan26]

Thanks James, a few more "figs" added now to help.....

Stan

[Rob L]

That's a great write-up Stan, very detailed and lots of great information. There's plenty in there that should benefit any eq3, eq5 owner.

Thanks for taking the time to do it

[Gonzo]

Nice write-up, thanks for this.

Can you explain the "(IMPORTANT NOTE: ALWAYS RUN PHD AND CONNECT TO MOUNT BEFORE YOU SWITCH ON THE HAND CONTROLLER)" please?

[badgers]

Unfortunately I can’t find any pics/guides on the net of stripping the EQ3’s RA axis.

Thanks again for this Stan.

I'm planning to do a full stripdown, tighten and regrease of my EQ3-2 to prepare it for guided imaging this weekend.

I'll take pictures of the RA axis part of the job to try and make it easier for others.

Badgers.

[badgers]

Components acquired so far:

* EQ3-2 Mount

* Skwatcher 150P f4 newt

* Skywatcher 9x50 guidescope with attached Logitech Quickcam Pro 4000

* GPUSB

* Shoestring Hand controller port mod

* Dual-axis motor (on order)

I'm planning to strip down the mount as described above.

My main worry about my proposed setup compared to yours is mainly stability.

Your setup is pier mounted, while mine will be on a tripod. The weight added to my setup with the guidescope and DSLR I think will put me at the limits of what the mount is designed for, although I can't find anything online that tells me what the EQ3-2 is designed to support.

Canon EOS40D body = 750g

9x50 FinderGuider with Logitech Quickcam = 350g

Skywatcher 150P OTA = 5kg.

Rings, dovetail and other gubbins = 1-2kg

Total: Somewhere between 7-8kg (need to weigh this properly on scales).

My other worry is that my guidescope is sat in the standard skywatcher finder bracket, so I worry about flexure issues.

Anyway, thanks again for the post and I'll report back how my own setup goes.

Badgers

[stan26]

Nice write-up, thanks for this.

Can you explain the "(IMPORTANT NOTE: ALWAYS RUN PHD AND CONNECT TO MOUNT BEFORE YOU SWITCH ON THE HAND CONTROLLER)" please?

Sorry Gonzo, I was meant to explain this.....

basically, if you connect up the the mount/pc without running PHD and "connecting to mount" first, the mount will go into a uncontrollable slew! i.e the RA motor will run at whatever the selected slew rate is on the HC. I don't know why this is but it caused me a few moments of tearing my hair out wondering what was going on.......

Stan

[stan26]

Components acquired so far:

* EQ3-2 Mount

* Skwatcher 150P f4 newt

* Skywatcher 9x50 guidescope with attached Logitech Quickcam Pro 4000

* GPUSB

* Shoestring Hand controller port mod

* Dual-axis motor (on order)

I'm planning to strip down the mount as described above.

My main worry about my proposed setup compared to yours is mainly stability.

Your setup is pier mounted, while mine will be on a tripod. The weight added to my setup with the guidescope and DSLR I think will put me at the limits of what the mount is designed for, although I can't find anything online that tells me what the EQ3-2 is designed to support.

Canon EOS40D body = 750g

9x50 FinderGuider with Logitech Quickcam = 350g

Skywatcher 150P OTA = 5kg.

Rings, dovetail and other gubbins = 1-2kg

Total: Somewhere between 7-8kg (need to weigh this properly on scales).

My other worry is that my guidescope is sat in the standard skywatcher finder bracket, so I worry about flexure issues.

Anyway, thanks again for the post and I'll report back how my own setup goes.

Badgers

Hi Badgers, yes you're probably pushing the upper limits of the EQ3-2 there, and the tri-pod isn't the best, but that said as long as theres no wind about you shouldn't have a problem. With your setup balance will be the critical factor, and remember you don't want precise even balance across the RA, just a tad heavier on the eastern side. Get the balance right and the EQ3-2 will work wonders all night long!

Flexture may become a problem for you, but I would have thought you should be OK. Flexture becomes more apparent with longer focal lengths. Even at 750mm FL I think you should be ok on a calm night. I can't really comment on the finder holder as I don't use one. I haven't encountered any flex issues yet......

Stan

[JamesF]

Could be worth putting some weight on the tray to stabilise the legs a bit.

James

[Gonzo]

thanks Stan for explaining

[Rob L]

Could be worth putting some weight on the tray to stabilise the legs a bit.

James

I only use a camera for widefield without a scope and I don't need both counterweights so I put one on the tray and it does help. I've heard a lot of people suggest hanging a bag of sand from the bottom.

Also, although it's a pain in the neck (literally) I don't extend the legs at all, this may not be possible depending on the telescope but this makes a massive difference to the stability of the tripod. The only downside to this is it does require a certain amount of crawling around on your hands and knees.

[JamesF]

How well did you do at getting the backlash out of the final drive on the DEC axis, Stan (between the worm and the DEC gear itself)?

With the scope and weights in place I can get mine down to the point where if I turn the axis one way and then go back I have about 35 degrees of rotation on the worm before the axis starts to turn, but if I go any tighter on the adjustment then the DEC motor starts to skip badly. I'm wondering if the motor is just getting a bit past it.

To measure movement in the DEC axis I've put a spirit level on the scope and wait for the bubble to move. To measure worm rotation I stuck a wire pointer to the worm axis with a bit of plasticine. If there are better ways to do this I'm happy to hear them.

James

[stan26]

How well did you do at getting the backlash out of the final drive on the DEC axis, Stan (between the worm and the DEC gear itself)?

With the scope and weights in place I can get mine down to the point where if I turn the axis one way and then go back I have about 35 degrees of rotation on the worm before the axis starts to turn, but if I go any tighter on the adjustment then the DEC motor starts to skip badly. I'm wondering if the motor is just getting a bit past it.

To measure movement in the DEC axis I've put a spirit level on the scope and wait for the bubble to move. To measure worm rotation I stuck a wire pointer to the worm axis with a bit of plasticine. If there are better ways to do this I'm happy to hear them.

James

Hi James, I never accurately measured the backlash when I adjusted mine. It took me about 4 attempts to get it right. On the final occasion I brought it indoors bolted to a wood plinth and adjusted it on the kitchen table loaded up with scope etc, I had a bottle of red with me at the time I sat the bottle right next to the star diag on the scope (about 1mm away) and watched for the gap to open and close as I turned the adjuster knob. I would say that 20-30 degress of play is what I had before my final attempt but after about 20mins of playing on the kitchen table I almost completely eliminated the backlash altogether, Its honestly almost instantaneous in changing direction, I couldn't believe it! Its not tight either, before I had it really tight to get rid of the BL, but now is quite loose and fairly consistently smooth around the gear. It takes approx 4-5 secs in manual mode PHD for the star move from south to north on 4x slew rate. Before I was clicking for nearly a minute before it would start to move!! Correct adjustment of the DEC axis bolt/shaft helps here as well. It can't be too tight. It sounds like during the processes of getting rid of the BL you have adjusted the worm so its bound up to tight to the DEC gear. It doesn't need to be tight (stiff to turn) its just finding that fine balance in the adjuster screws. If I could tell you how I done mine I would but I honestly don't know what order I done what in, randomly turning screws for 20mins whilst consuming the red stuff..........

Stan:)

[JamesF]

I'll try backing off the worm retaining nut then. Could be that once everything is reassembled that doesn't need to be as tight as would appear when the worm housing is separated from the DEC gear housing.

James

[badgers]

Well even though my motor is still not here, I finally tested my 9x50 guidescope with the logitech quick cam pro.

It took me an age to tweak the settings and get focus.

Is this about how it should look ? (see attachment)

I was wondering what settings the other quick cam pro 4000 people use (e.g. Stan and Quatermass), for gain, shutter, brightness, gamma etc.

Badgers

[badgers]

Thanks to this thread my mount is running silky smooth now!

I've posted my RA and DEC strip down walkthrough with images into a new thread.

I originally had it here, but it was kind of large and would make it hard for people to get to other useful info.

Full strip-down, cleaning, regreasing, adjustment and reassembly in this thread:

http://stargazerslounge.com/diy-astronomer/176641-eq3-2-strip-down.html

Thanks again Stan for making me brave enough to try this.

Badgers

[Gonzo]

This thread is getting better and better, 5 stars

[stan26]

Well done Badgers, very handy write up!

Stan

[badgers]

My motor is due to arrive tomorrow, woohoo

However the wobble from my EQ3-2 Aluminium tripod is pretty shocking and seems the achilles heel in my setup.

I'm going to spend some time tomorrow, filling up the legs with sand and putting something heavy hanging from the centre of the mount.

I'll try and quantify how much difference this makes observing something distant at high mag.

Badgers

[Gonzo]

However the wobble from my EQ3-2 Aluminium tripod is pretty shocking and seems the achilles heel in my setup.

search my posts and see how I've fixed the wobble

[badgers]

The downside of this cheap aluminium tripos was: VIBRATIONS!!!!

I had a hard time focusing on anything due to vibrations, you touch the focuser and it goes all wobbly...

Well not anymore, after reading many posts on many forums on how to improve a cheap aluminium tripod, I fixed mine by doing the following:

I filled up the bottom legs with fine sand, now the trick is that you do need to tap them with a rubber mallet after filling up the leg to compact the sand. Fill up more as needed.

I then used some expanding foam in the upper legs (messy job....).

Cost: just shy of £10

Results:

Vibrations are 99% gone, seriously gone. I can now focus with ease on objects. Night and day difference.

I still want to buy the anti-vibration rubber pads too and do the hanging heavy weight trick.

This one ?

That's very reassuring, I'll pop into B&Q on the way home and get a bag of sand.

So you pour sand in and compact it so its say 75% filling the cavity and fill the rest with expanding foam to seal it in ?

My current wobble is means it's taking 6-10 seconds for something like jupiter to settle down and be stable after a DEC/RA adjustment.

I'd imagine if I can get it down to 2-3 seconds that would be a result.

I've also got some pads for putting under furniture (see attachment). £40 seems like madness for the Celestron ones, but I'll see how these do.

Thanks Gonzo

[Gonzo]

not wanting to hi-jack this excellent thread, so I'll make it quick:

the down legs: filled with sand only (compacted)

the twin upper legs: expanding foam only

vibrations are gone and I really do mean gone.

Had a terrible time before, just touching the focuser on the megrez and it would vibrate like nuts, but now: nothing at all.

[badgers]

The down legs are the ones that make contact with the ground that sit between the two up legs on either side ?

Why the expanding foam ? does it increase rigidity ? I guess it can't weigh much.

PS: I'm sure Stan won't consider this a thread hijack, we asked him to start this thread off and seed it with his wisdom : ) but a lot of EQ3-2 peeps are going to want to beef up the tripod as well as the mount.

[Gonzo]

The down legs are the ones that make contact with the ground that sit between the two up legs on either side ?

that's correct

Why the expanding foam ? does it increase rigidity ? I guess it can't weigh much.

no particular reason really, it was a bit of a trial and error but it worked first time.