Thursday, October 10, 2013

HEQ5 on steroids

HEQ5 equatorial mount is not top quality. It is build in China, often requires some adjustments when you receive it. But on the other hand the price is very acceptable, and you can start your astronomy adventure with not really astronomical investments. 
Due to its flaws many amateurs wanted to improve HEQ5 - mainly for astrophotography purposes. There are two popular modifications made for HEQ5 mount:

  1. replacing original Chinese bearings with some better ones made by more reputable companies (EZO, Timken, FAG)
  2. replacing original gears with belts and pulleys
The first modification I already made some time ago. Now the time has come for second one :) There are two types of belt mod kits - one changes original gear ratio so it can be controller only using laptop and EQMOD interface. Another type keeps the original ratio, so there is no limitations to future use of the mount. These second type requires some fancy small 9 tooth pulley and usually are a little bit more expensive. Me and few other astro amateurs have chosen belt mod kit manufactured in Rowan Astronomy company located in UK. This one keeps the original 9:47 gear ratio so it is transparent to any controller.
The kit has come well wrapped. It contains four pulleys, two belts, acrylic cover spacer, two steel pins for idlers and two idler rollers, three different allen keys and 6 head screws for cover. Additionally one can order pinion extractor to remove the pinion gear - I can recommend this tool. This gear sits tight on the motor shaft and is not so easy to remove.
There is also very detailed instruction provided for the whole process. It took me about one hour to replace the original gears with the belt kit mod. Un-twisting motor wires can take some significant amount of time.
Above there is declination motor with plate and two gears. The larger one will be replaced with idler roller. The good news is that there is no need to move the main worm gears, so you do not need to adjust it again. This worm gear adjustment process can be time consuming.
Stepper motor with pinion gear removed. The extractor did its job perfectly :)
New 9 tooth pulley on place and idler roller fixed to the plate.
Declination belt mod on place. Now the right ascension part to go.
Voila! All kit elements fit precisely and there is no more annoying noise during mount moves. Unfortunately weather forecast says that I will need to wait few days for real test :( 
There are few advantages when using belt mods:
  1. quiet mount work :)
  2. smoother guiding (especially important for the astrophotography with longer focal lengths like over 400mm)
  3. more regular periodic error correction (PEC) so it can be recorded now and can work better when making unguided photos
Some real life tests to come...
Clear skies!


  1. Widzę jak poszło ale przespałem temat i mój HEQ5 cały czas czeka.
    Czy zgłaszał się ktoś jeszcze do Ciebie, żeby drugą turę zamówienia zrobić ??
    Tadeusz - sp3occ

    1. Nikt bezpośrednio, ale w wątku już chyba dwie osoby też wykazały zainteresowanie. Myślę że za jakiś czas trzeba po prostu będzie zaproponować kolejną akcję i zobaczyć ile będzie chętnych.

  2. Thanks for the blog about the belt mod. I am proceeding with this mod myself very soon. You mentioned replacing the bearings. Which bearing did you replace? Astrobaby's website shows an overhaul of the HEQ5, but still uses existing bearings. Is there a noticeable improvement using replacement bearings? Other people have changed the worm & ring gear with precision replacements. I moderate a Yahoo group dedicated to the HEQ5 called HEQ5EquatorialMount, & my fellow members are very interested in anything that people do to improve the performance of their HEQ5.

  3. Hello Peter. I replaced all bearings - for these small worm bearings I used EZO replacement. Other large axis bearings have been replaced with TIMKEN and our local FLT bearings. At my mount the original bearings were in quite good shape, I found comments saying that the older the mount is the worse bearings have been used. After just a bearing replacement the improvement was not obvious, I got rid of guiding peaks after changing these horrible tooth gears with belt mod.

  4. Czy masz może jeszcze ten ściągacz? :) Zamówiłem sobie zestaw z Rowan Astronomy, ale zakładałem, że wszystkie potrzebne narzędzia będą dołączone -- niestety, ściągacz jest sprzedawany osobno.