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Author Topic: AstroEQ Hardware and Software Choices  (Read 768 times)


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AstroEQ Hardware and Software Choices
« on: October 02, 2019, 07:29:06 »

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.)
Mount:  Choose "EQMOD ASCOM HEQ5/6" - this is what EQmod calls the mount
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 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


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!