AstroEQ Hardware and Software Choices

[johneta]

I thought I would layout what I did to complete my ASTROEQ upgrade.

I found there was a lot of different suggestions and opinions out there on what gear to use, and what software to use.
I personally found this very difficult to wade through, when I was struggling to understand what was involved and to take an educated guess at which setup would work well. Especially when a lot of suggestions in various threads trailed off into silence when the person didn't post on there completed project.
So maybe people would be interested in laying out their own Hardware and Software choices, and how successful they were.

Here's mine --
My setup
I started with a: Skywatcher EQ5 (which I had recently torn down, re-greased and tuned up)
Motor Drive on it was a dual axis motor Kit same as this one--- https://www.astroshop.eu/drive-motors/skywatcher-enhanced-dual-axis-motor-drive-for-eq5-mount/p,46068
I removed it and began the Astro EQ project ----

AstroEQ Hardware: 

Circuit Board: purchased Toms pre-made circuit board
Processor Chips (Pic and ATmega): purchased 2x Toms Pre-programmed processor chips ...... (available on his site)
All components on the circuit boards were purchased from element14. (I used a plastic box I had lying around)

Motor Drivers: DRV 8825 -cheap aliexpress copy of polulu board
(Current sense pots set to around 0.4v giving a current of around 0.8Amp)-Actually this surprised me when I measured the current setting I had when I was finished. I didn't realize it was a bit higher than the max rating of the motors, but it seems to work well and the motors don't get too hot.

Motors: 2 x https://www.aliexpress.com/item/32586088729.html?spm=a2g0s.9042311.0.0.9b374c4dJCkxfd

Manufacturer Part Number  17HS24-0644S
Step Angle                    1.8°
Step Accuracy               5%
Holding Torque            60Ncm(85oz.in)
Rated Current/phase    0.64A
Phase Resistance          15ohms
Voltage                         10V
Inductance                    32mH±20%(1KHz) (Inductance seems very high compared to Toms recommendation to choose a low
                                                                       inductance motor, but it worked well!)
Weight                           500g

Motor Pulley:  MXL 15tooth. Bore- 5mm(suits motor)  for 6mm wide belt
Worm Pulley:   MXL 40Tooth. Bore- 6mm(suits SW EQ5 mount's brass worm shaft)  for 6mm wide belt
Belt:  2 x MXL Belt, B66MXL, Closed-loop, 66 teeth, 6mm width ( this was a bit short to fit and the motor ended up very close to the body of the mount. Needed some filling and messing about, but ended up quite compact and neat. But I would probably prefer slightly longer next time - maybe a 71tooth belt. They are cheap enough to get a couple of different sizes to give yourself options.
Motor Bracket:   https://www.aliexpress.com/item/32960658308.html?spm=a2g0s.9042311.0.0.9b374c4dJCkxfd
a cheap right angle steel bracket which saved me having to bend my own. It fitted well and enabled a compact setup. I still needed a couple of other bits of Aluminium to mount brackets on.

Power supply for AstroEQ board:  12v
DRV 8825 Fast decay Modification: --NO! ( did not seem to be required).

Toms AstroEQ Config settings for my setup;
Firmware: Astroeq V4-DIY Board (Including DIY)
ST4 Rate: (x Sidereal): 0.95
Advanced HC Detect: Enabled
Motor Drive: DRV882x
ustep Gear Changing: Disabled
Motor Microstep Level: 32 ustep
RA Axis: Forward
Dec Axis : Backward (this depends on which way round you mount the motor)

Step angles etc, same for RA and DEC as below;
Motor Step Angle (o): 1.8
Motor Gear Ratio (:1); 2.666666666
Worm Gear Ratio (:1): 144
Goto(x Sidereal): 115

Hand Controller: XBOX cheap generic handset with USB cable -setup in EQMOD

EQMOD software. (Note you have to install Ascom on the PC as well)
EQMOD Main Settings;
Ascom PulseGuide  RA rate: x0.30
                                 DEC rate: x0.50
                                 Minimum Pulse width (msecs) : 20
                                 DEC backlash (msecs) : 0    (not used)

Guiding:  PHD2 
NOTE- I have measured my RA backlash at ~3 seconds and DEC backlash at ~ 7seconds(yuck!). Also Unguided Periodic Error is around -Tot. peak to peak 20 arc seconds. Its the best I can get out of the mount.
(Guide Scope;  300mm guide scope(old 75-300mm zoom camera lens) with a QHY5L II-M camera.)
Settings;
Mount:  Choose "EQMOD ASCOM HEQ5/6" - this is what EQmod calls the mount
Algorithms;
RA: 'Predictive PEC' -default settings except Minmo = 0.10
DEC: 'Resist Switch' Mostly around - aggressiveness 100 Minmo 0.16
Backlash Compensation: - OFF    PHD says to only use Backlash compensation if your mount's DEC backlash is 3secs and below
DEC guiding: Auto (works fine even with terrible backlash I have)
Max RA duration: 2500mSec
Max DEC duration: 4000mSec.

GOTO software;
'Stellarium'
'Stellarium Scope'-(this is to connect the mount [AstroEQ] to Stellarium)

Capture Software (I use a DSLR);
Astro Photography Tool  -- APT.

Polar align with Sharpcap. -(Cant recommend this highly enough!)

Telescope Orion 8" F3.9 Newtonian
Total payload on EQ5 ~ 11kg! -so way overloaded for imaging

END RESULT;

I get guiding total RMS of 0.7 - 0.9 arc seconds most of the time, which I'm very happy with, given my mount is overloaded.

Accurate GOTO's and reasonable GOTO speed.

Please share your own setup 🙂      ..  Also Thanks Tom for a great idea and the follow through to make it happen!
 

[astrosathya]

Hi John, Looks like I came acroos your writeup after 2 years, ha ha.

The motherboard on my HEQ5-PRO blew and I am planning to DIY the AstroEQ using Arduino Mega. I understand that you used Tom's board, but if you could kindly share pictures and your experiences in the past 2 years, i'd be grateful.

TIA. 

[johneta]

Hi Astrosathya, Sorry I only saw your post today. Do you still want any info.

Over the past 2 years it has operated well. I still get good guidance and generally no problems.

I looked at the Arduino Mega option too as I make a few things myself with Arduino. But it just didnt seem worth it. Tom's board works right off the bat.
You do have to be a little confident with electronics and soldering, but it is pretty straight forward.

The new setup just means my system is very reliable and I dont have to think about the Guidance or finding objects anymore. I can focus on the imaging.

[chemistorge]

Hi,

 

I built the AstroEq mega version, for pulleys I went with 60 and 15 tooth, the 60 tooth just fits on the eq5/old cg5 mount. This gives me a 0.7 arc secs per step using 1.8 deg 16 micro steps or 0.35 arc secs per step with 0.9 deg motor.

For motor drivers I stayed well away from drv882x and the a4988 drivers (too noisy). I initially went with tmc2100 drivers at 0.6 amps very smooth and quiet, they were pricy though at £10 per driver. I have recently built a second rig and used the more advanced tmc2208 drivers, much cheaper also (use A4988 16 micro steps in astroeq, they are pin compatible with a4988 in legacy mode). I have to put my ear near the motors when slewing to check they are running they are so quiet.

For software, I use a raspberry pi 4 with Astro berry using stars/Eros. It is excellent, the polar alignment routine in ekos gets me within 1 arc min of the pole in less than 5 mins. If you also include the guiding, focusing, cam control it is amazing. Also I can program a sequence and (if it is going to be dry all night) go to bed. 

 

Edited July 18, 2021 by chemistorge

[johneta]

Sounds good chemistorge. There are many ways to do it for sure.
Interesting about your controller being quiet.

My motors aren't quiet but it doesn't bother me.

[chemistorge]

I agree there are lots of ways to do things. I was worried about vibrations using the DRV88xx and A4988 drivers. I like ekos as all tools for imaging are there unlike windows where you have to have a separate mount control program to imaging and alignment if you want to stay with low cost options. Maybe I am biased as a Linux user for 20 odd years.

One thing I will say is you don’t need to buy a fancy all singing mount with go to if you are willing to do a bit of research, go to is now open source!

[dazzystar]

How did you guys work out which type of pulleys you needed?

[johneta]

On 02/03/2022 at 06:45, dazzystar said:

How did you guys work out which type of pulleys you needed?

Good question, I have forgotten 😔. I think that info is on the Toms AstroEQ website.
I think you basically have to know the worm gear ratio of your mount (search for model online usually works), and then do some calculations and guesses on how many motor revolutions it takes to spin the mount 1 revolution.

Im pretty sure I multiplied all that out and got a rough idea of the number of teeth on the pully I needed. But its not to critical as once you decide on the pully teeth number, and buy them, then you can input those actual numbers into Toms AstroEQ configuration software and it calculates the pulse rate to the motors to get the right speed.