AstroEQ and the EQ3-2 - early testing results

[Avocette]

Well, continuing good news!

There was some cloud last night but I set the cursor in CdC for Mars and the scope slewed for 8 minutes from the Home position and started siderial tracking. When there was a clearing in the cloud, there was the planet not far from the centre of the finderscope and it tracked quite well for an hour. Then I spotted Saturn, set the cursor in CdC on it and clicked 'slew'. The slew went via the NCP (presumably to avoid collisions between the tube and the tripod) so the whole operation took 15 minutes, nevertheless Saturn was in the finderscope FOV. Finally I clicked on Park to Home position in EQMOD and seven minutes later the scope was pointed at the NCP and the weights were vertically aligned.

Just as a suggestion, I think it would be good if the Mount Configuration table in AstroEQ Config had suitable default values for various 'standard' mounts including the EQ3-2 and EQ5 with the SW motor kits added. Clearly there needs to be a comprehensive table for those who've gone 'off-piste'. That'l be my next project phase when I replace the SW motors with NEMA 14 or 17 ones with a belt drive for the DEC axis and direct drive for the RA axis - should improve the slewing speed.

I now understand more fully why Steppenwolf is making a new Dob base to fit his redundant 250px Newtonian OTA. As he points out in the thread http://stargazerslounge.com/topic/217535-let-me-get-this-rightsteppenwolf-dobsonian/, in the time his GoTo mount found 2 DSOs at SGL9, John, an experienced Dob user, had found 15!

[TCWORLD]

The go-to values do get rounded - I am still trying to find a way of showing the actual value on the config screen (it gets calculated later at the moment). One of the key things that V7 brings is a greater range of go-to speeds (less rounding), so the values you get will be closer to the values you enter - with V6 it could sometimes (rarely) double the speed.

I'm thinking that in a near-future version of the utility I may have some default selections built in, so you can either choose a standard mount (e.g. EQ5, EQ3-2, etc.) to customise, or enter settings for a completely custom mount. I'm also trying to figure out how to get it to jump between text boxes using the tab key.

The skywatcher motors are painfully slow. With better motors it is possible to achieve up to 1200x the sidereal rate with AstroEQ.

[TCWORLD]

When you run V7 on a mount previously configured with V6, the axis settings will remain unchanged, but the go-to speed will be a completely obscure value the first time as the data being stored in the EEPROM for this setting is in a different format - the previous setting you had probably was more likely rounded to ~56 or ~60 (can't remember the exact value off the top of my head).

[Avocette]

Thanks Tom - I'll carry on now with the v7 confiuration which seems to be pretty stable from my recent experiments.

Following last night's success I've invested today in a Logitech F710 wireless GamePad so I've got full remote control of EQMOD when at the scope. I also have a Toucam Pro with firmware upgrade to SPC900 in waiting, so with SharpCap II installed I can start to do some planetary imaging weather permitting. Some further learning also in the dark art of accurate polar alignment!

[Avocette]

Further testing yesterday tracking the Sun and last night locating and tracking the planets went well!

I am concerned a bit over the heat of the motors (warm enough that the plastic motor cases are a loose fit and can slip off the motor/gearbox assemblies day or night). This seems to apply whether or not the mount has been in use for a long period.

And one thing is puzzling me - there's often a high pitched 'fizz' sound emanating from both motors at times when the mount is Parked or not tracking, and even after I've closed down CdC (and therefore EQMOD) but before I switch off the AstroEQ PSU. When I turn things on again, the fizz does not immediately start up again. However once the mount has slewed a distance, if I park it (stop tracking) most times the fizz is audible from both motors and when it's tracking the fizz can often be heard in the DEC motor.

I presume the fizz is caused by very short pulses from the stepper control board? I would have thought intuitively there should be no pulses at all.

Any ideas?  

[TCWORLD]

If the motors are too hot, the current limit needs adjusting. If you open up the AstroEQ box (2 screws on the back) there are two little purple circuit boards inside. On each there is a screw head in one corner which can be used to set the current limit. Turning anticlockwise will reduce the current - you should only need to turn then a few degrees.

The fizzing sound is normal. Stepper motors are always powered, even when not moving. When you first turn on the power before connecting EQMOD the motor drivers have not been initialised/enabled so it wont make a sound. As soon as EQMOD connects, the drivers are enabled and the sound starts. This is perfectly normal. It may sound different from the skywatcher handset, but that is simply due to the fact that AstroEQ has a PWM based stepper motor driver circuit which allows the 6V skywatcher motors to be driven at 12V without any problems - and will as a result also allow the motors to maintain torque at higher speeds. Its the PWM current limit that makes the fizz.

[Avocette]

Thanks for that.

One further phenomenon noted so far is that when tracking, the RA motor induces a resonance in the mount/scope combination, probably just an unfortunate function of the mass and solidity of the various elements, which manifests in a slight shake of the object viewed. This was first obvious using the webcam, pointed at Mars, which was wobbled into a short streak about two or three times its diameter. I then checked with an 8mm eyepiece and sure enough it was clearly there. I could damp the resonance down a bit by holding onto the flexible coupler between the motor and the RA worm gear shaft but not get rid of it completely.

Anyone else have experience of this sort of thing? Is it a common occurrence?

[TCWORLD]

It may be better if it were to be using 1/8th microstepping during low speed rather than 1/4. I am planning on adding the ability to select the level of microstepping in the next version of the software - so rather than just enabled or disabled there will be the option of 1/2,1/4,1/8th etc.

[Avocette]

I thought that with the SW motors we should not use microstepping?

[TCWORLD]

On the current version, no. On the next version, possibly yes. I'm looking in to it.

In fact in the current version, it uses 1/4 stepping if microstepping is disabled.

[RichM63]

Avocette, when I first installed AstroEQ the covers on my SW motors also fell off due to heat and I burnt my thumb.

Turning down the current by a small amount solved this.

Also have the 'fizz'.

Tom a suggestion, as it seems that folk with standard SW motors experience hot running, why not set the current slightly lower or include an instruction to do this on the provided reciept during installation?

It can be a little worrying when the motor cover suddenly flies off.

Will also be installing V7 this week. I'll get back.

Cheers,

Rich

[TCWORLD]

Rich, I have been setting it lower and lower each time, but it seems like there are two different sorts of motors, one of which requires a much lower current - the set I have don't even get noticeably warm at the current level I have been setting. I will take you up on your advice though and add instructions for setting the current limit with the parcels.

[RichM63]

Strange to be sure.

One thing, my hot set on the EQ5 were originally QM's/Mark, did he ever report a hot condition on his earlier AstroEQ? (don't know if he everused them BTW)

Just a thought.

Rich

[Avocette]

I have now reduced the current limits, as you suggested Tom, just a little, and I think the sound level has reduced and also the motor heating in idle mode. I haven't had chance to test for resonance when tracking but, again, less sound probably equates to lower level of mechanical 'chugging'.

I must congratulate you Tom and everyone else concerned - hardware, firmware and software designers - for an amazingly functional and versatile system. I'm busy adding sounds to EQMOD, and with an appropriately long flat (i.e. not coiled like a phone handset) cable to my SW 'auto' focuser I should be able to operate everything remotely (well 3m away) from the scope.

[Avocette]

I've been running the mount for an hour in the sunshine tracking the sun, monitoring the tracking precision using some sunspots viewed in my ToUcam Pro webcam. Tracking was pretty accurate but there was some oscillation/vibration/resonance clearly visiible. But my judgement is that it's quite a lot less than before and the noise from the motors and the heat generated even in the sunshine is definitely less than before. I shall now upgrade the config programme from v7.2 beta to v7.3. I've  been genning up on 'microstepping' (WikiPedia) and the article does suggest motor resonances can be reduced this way. I'll be interested in trying to learn some more.......  and as an independent later step may try a further reduction in the peak current limit in the stepper motor drivers. 

[Avocette]

Further good news! I updated my AstroEQ using v7.3 and ran the mount for six hours with the new default configuration for the EQ3-2.

I noticed that this included the 4 microsteps per step setting so I was keen to see what the impact would be on noise and vibration. I was very happy with the result - a significant reduction in audible noise when tracking and no sign of oscillation or resonances when webcam images are viewed on the laptop.

During this long session I regularly checked the motor temperatures and I think I'll leave well alone on the current limit now.

So a big thanks Tom - I'm very happy with my new AstroEQ v7.3 GoTo mount!