Mobile astrophotography will never be the same again.
Peter Dunsby (Cederberg Observatory)
Every once an a while a new product hits the market that changes everything. For more than five years I have been driving out to remote dark sky locations with an EQ6-R mount. Don’t get me wrong, this is an extremely capable mount, but it is heavy, it requires counterweights and I’m not getting any younger. Heavy lifting was starting to become a pain!
In 2022, ZWO launched the AM5 strain wave gear mount. Small lightweight and beautifully engineered, this mount can be operated without counterweights up to a payload of about 13kg and with the optional counterweight bar and counterweight, up to around 20kg. The following review represents my first impressions of this mount and is based on two nights of use under the dark skies of the Cederberg Mountains. In a few months time I will write a more in-depth article on my experiences with this mount.
The key advantages that strain wave gears offer over standard worm gears are that they do not suffer from any measurable backlash and very little periodic error. Each mount comes with a PE test report and in my case the reported maximum and minimum values were 7.4 and 1.8 arc seconds respectively. There is also no need to balance the rig in RA, although care must be taken to position the telescope at the balance point on the DEC axis to avoid it from tilting forwards or backwards.
The mount comes with an optional lightweight carbon fibre tripod. Initially I was concerned that it would not be sturdy enough, but for payloads up to around 10kg, I found that it provides more than enough support and stability. For those who would like to mount larger telescopes, like a RASA 8 or Edge HD 800, I would advise using a standard aluminium EQ6 tripod (or similar) with an adapter that will take the AM5 mount head – see Astroblender’s excellent video on the subject for an in-depth discussion on how to do this properly.
The AM5 accepts both Vixen and Losmandy style dovetails, with the tension knobs located on the right hand side of the mount head. The power switch is can be found on the left (the same side as the ZWO logo). On the back, you will find the altitude and azimuth knobs. I must say that making fine adjustments during polar alignment was an absolute pleasure and a testament to the superb quality of the machining of these parts. According to the ASIAIR, the polar alignment was one of the most precise I had ever achieved out in the field and this was done in no more than 5 minutes. The main ports (USB, guider and hand controller ) are located at the front of the mount head, together with the main power in port. On each side of the base of the mount, there are bubble levels. Using a spirit level, I found these to be properly calibrated to give a precise measure of how level the mount was.
Although the AM5 can be controlled via a laptop (using NINA or SGPro, with the appropriate ASCOM drivers) and powered using an external 12-14V power supply, I chose to use an ASIAIR Plus to both power and control the mount and telescope equipment. This all worked seamlessly and without any issues. The ASIAIR was powered using a Titan 600 lithium ion battery.
An important difference between the AM5 mount and other goto equatorial mounts is that it cannot be slewed manually. This is due to the strain wave gear design and takes a bit of getting used to. Consequently it is important to put the mount in the home or park position after completing an imaging session and turning everything off. This can be done automatically using the control software of the ASIAIR (or using NINA on your laptop). The hand controller can be used to slew the mount around if you plan to use it for visual astronomy sessions.
Imaging with the AM5
On the first two nights of use I used the AM5 with my Teleskop Service 94EDPH, paired with the ASI2600MC Pro. Auto-guiding was managed using a ZWO OAG together with the ASI120MM mini guide camera. Autofocus was achieved using the ZWO EAF. As mentioned earlier, everything was powered and controlled using the ASIAIR Plus, which was positioned on a plate above the telescope.
I chose two broadband targets to image: The Sculptor Galaxy (NGC 253) and the Witch Head Nebula (IC 2118). Guiding was excellent on both occasions, with an out of the box average RMS of 0.56”. The AM5 seems to prefer short guide exposures of 1s or less. Both images turned out great, despite there bing a bit of high cloud on the first night. IC 2118 deserves some more time and I will be returning to this target on my next trip up to the Cederberg.
The AM5 is one of the easiest mounts to use that I have encountered in five years of astrophotography and on the two nights I used it, my guiding results were among the best I’ve had out in the field. The fact that the AM5 is so light makes it a pleasure to set up. Being able to lift the entire rig without having to break ones back is a major selling point of this mount and forgetting counterweights when packing for a trip is no longer a something you need to worry about! Finally the AM5 offers excellent value for the price point. In comparison to other mounts in its class, it delivers outstanding performance and reliability without burning a sizeable hole in your pocket. With its combination of advanced features, ease of use, and reasonable price, it stands out as an excellent option for both beginner and seasoned astrophotographers. From now on my EQ6-R will remain in my home observatory and it will be the AM5 that joins me on road trips to the dark skies of the Cederberg.