Die computer, die!

[Ags]

I had hoped that a TalentCell replacement for my old lead-acid powertank would make my AZ-GTi behave well, but despite clearly having more power (motor noise much louder), the mount still does its random slewing thing - in an hour observing session it zipped off sideways like an astronomical rabbit four times. Beyond frustrating when it is past midnight and time is limited.

I will try upgrading to the latest firmware, but I have no real hope this will help.

So I am going for the nuclear option. Computers are bad. I am looking at a simple EQ mount with clock drive. Limited in functionality, but presumably incapable of glitching on me? 

I don't like big kit, so I am thinking about an EQ3-2 carrying a small frac or a C6. The C6 would do planetary imaging and also lucky imaging of DSOs at F6.3 or F4 - so exposures of no more than 15 seconds. Because the EQ3 is electrically and mechanically simple I fancy trying some DIY like a belt mod. The mount head would go on my Berlebach Report 112 tripod.

I have never owned an EQ mount so any input is appreciated!

A final annoyance is the AZ-GTi is unsellable given its dodgy condition. I suppose I could use it as a door stop.

[ONIKKINEN]

I am continuing my rant about this class of mount here, and will do so in every thread i come across. The EQ3-2 (and EQM35) are a class of mount that is suitable for almost no-one. Its only 2 selling points are the price and the weight. When you factor in the heavier counterweights included in the EQ5 (a MUCH better mount, no comparison possible even) even the weights are very similar. I cannot recommend you buy these mounts if you wish to do long exposure astrophotography of any kind with any other than extreme low focal length systems, which the C6 is definitely not.

 

The design in the EQ3 is simple yes, but it is hardly improvable. The electronics and transmission are simple but not the main problem, and with good meshing of the gears these problems just go away, belt or no belt mod. The main culprit of the design is the weak, entirely bearingless design of both the RA and DEC axis and the quite sloppy tolerances of the worm gears themselves. You will NOT be able to remove backlash, especially from the DEC axis. There is a point where the mount starts to be very sticky and binds but you will still have backlash and play in the axis. Imaging with a C6 even at F4 will be dodgy at best, and you can forget about arcsecond accurate pixels. If you want to drop DSO imaging from the feature list, it might be a not so bad idea, but...

 

Spending just 200e more gets you the EQ5, which is a much better mount that can handle the C6 and other types of telescopes you may want to buy later. The next mount up the hierarchy would be the HEQ5 which is a bit more expensive, but will work with lots of telescopes with good success rates. Take it from someone who fell down the "affordable equipment" rabbithole, the weak mount is not worth the money and you will want to upgrade anyway. And if resale value is something you're worried about then its definitely not a good idea to buy the EQ3-2. Its just not a desireable mount.

[Ags]

I was considering the EQ5 as well. I have seen nice results with the EQ3, but I suppose there are some lucky good ones.

[Alien 13]

2 minutes ago, Ags said:

I was considering the EQ5 as well. I have seen nice results with the EQ3, but I suppose there are some lucky good ones.

Not lucky but good matching, a reduced 70 ish mm refractor will have a focal length of about 330 mm which would be my upper limit for an EQ3 allowing 1 min subs, of course when you go to lower focal lengths the sub length can go up even to four mins of more for the nifty fifty or similar.

Alan

[doublevodka]

I've seen somewhere that there is a firmware fix for that issue, so don't get too put off by the current issues, have a poke around the forum I know I've seen it somewhere.

I own an eq3-2 with RA motor (well a skyscan 2001, but it's exactly the same) and I really wouldn't recommend it for imaging, passable for visual but even then you're going to want to upgrade the tripod etc, meaning you're pretty much at eq5 prices already, but with a worse mount head

You could go manual eq5 with an RA motor, but for 200 odd quid more you can get the full goto version which will have a better resale value and more flexibility and the used market is slowly getting a bit more sensible if you didn't want to pay new prices

I feel your frustration though, there's nothing worse that malfunctioning kit to ruin a session 

[Ags]

I was hoping that it would work with very short subs, but I don't want to replace one hassle with another.

[Avocette]

@Ags Could you let us know which firmware you’re presently running in your AZ-GTi, which mode (AZ or EQ), whether you use an EQDirect cable or WiFi, and what software you’re driving it from (SynScan Pro App, RPi or PC)?
The fact that your change of power supply made an audible difference suggests you may have been running under voltage for much of the mount’s use, and you may well have a corrupted firmware. The intermittent movements you described sounded like typical issues with power supply, but there have been firmware versions which have had issues.

[doublevodka]

41 minutes ago, Ags said:

I was hoping that it would work with very short subs, but I don't want to replace one hassle with another.

Technically yes that probably would get you by, but it would be a frustrating compromise I'm sure. If your budget can stretch to it, then go bigger, you can never really overmount a scope, but you can certainly undermount! Hell I should know, have an 8 inch reflector on an eq3-2 😉

[Ags]

@Avocette I am updating to the latest firmware tonight. I didn't want to do it before I hade a solid solution for the power supply. I see on the CN thread "DEC Runaway" is a thing and it may be solved in the latest version so I will keep you posted.

As for the other details, I am always in AZ mode, controlling the mount over Wifi from Android. I do plan on trying EQ mode, but currently no wedge.

If that doesn't work, I am going for an EQ5 with belt mod, no goto.

[Avocette]

@Ags as usual it’s a process of elimination if there appear to be faults in a complex interactive hardware/firmware/software piece of equipment but the AZ-GTi is amazingly capable and does work very well for many (some people are saying it is the presently the best selling Sky-Watcher mount). I have operated mine successfully from the iPad App and via WiFi, although others have reported issues with the WiFi especially in locations where there are many WiFi networks competing for the same frequency spectrum and the AZ-GTi uses the ‘older’ 2.4GHz band only, which is very congested these days. 
The Dec axis runaway issue is a well documented problem in autoguiding in EQ mode with several of the AZ/EQ firmwares Sky-Watcher have offered over the last couple of years. Many of us have had to revert to good old v3.20 from 2019 until two days ago when v3.32 was made available. The Dec axis is the Alt axis in AZ mode, so that does seem to equate to your problem. But if you’re running an ‘old’ AZ-only firmware I haven’t heard of others having your specific issues. 

[Ags]

Firmware upgraded. Looks like it is clearing up - so hopefully I can test it out on Polaris tonight.

[Avocette]

Got my fingers crossed! Tonight I tuned my guiding error to a respectable 1 arc seconds so I am happy with v3.32….

[Ags]

There was a bit of fuzzy cloud and haze tonight so not promising conditions for imaging. But I shot some sequences around Polaris (most buggy part of the sky) and Deneb. Deneb was really tracked well without any glitches:

Moving on to Polaris, the mount tracked really badly as ever and raced off in AZ a couple of times. I think that the mount risks an AZ/DEC runaway every time it moves in that axis, and the frequent corrections for Polaris just mean more rolls of the dice.

However I did enjoy using the mount tonight. I kept things simple with a focal length of only around 330 mm. If my theory about the AZ/DEC runaway is correct, I can clear the problem up by using an EQ wedge and fooling the mount into thinking it is perfectly polar aligned.

[Ags]

Spent the weekend with the AZ-GTi in EQ mode and I had no DEC runaway events.  So hopefully this is a happy ending.