My New Favourite mount: ZWO AM5
The best astrophotography mount on the market: powerful, portable and accurate. And I’m not saying this due to some sponsorship deal – I don’t even own an AM5. My mate Andrew Abbott lent me his for my astro trip to the Canary Islands.
ZWO AM5 is $2k in the USA
The ZWO AM5 looks a bit scary to those of us used to traditional worm drive astrophotography mounts
- No clutches – so you can’t move it without power
- No polar scope – so you have to polar align it electronically
- Poor tracking without guiding – so you need a computer to run guiding software.
And yet it is brilliant. The main reason its brilliant is because when you’ve got it polar aligned and when you’ve got it guiding the AM5 counteracts the earth’s rotation to an accuracy of about 0.6arc seconds. WOW WOW WOW WOW WOW. And that’s all us astrophotgraphy nerds want. Well, ok we want it to be relatively painless to set up too… and it is.
Why is guiding accuracy so important
The accurate guiding allowed me to get this – the sharpest picture I have taken of M33. In fact it’s the sharpest picture I have ever seen shot with an 8 inch newt (on a Tuesday by someone with biscuit in their name🤣) – but seriously it is VERY sharp thx to the AM5’s incredible guiding and my incredible home built scope betty – which will feature in the next video so I’m not showing you the fully processed image of M33 here).
The box far right show extra galactic nebulosity in the Triangulum galaxy which is 2.5 million light years away – and I haven’t even sharpened the image yet! That’s what 2 hours of guiding at 0.5arcseconds RMS can buy you and that’s why this is my new favourite mount! The image was shot with 3minute and 9 minute exposures. More details in my next video!
The next most important reason that the AM5 is brilliant is because it SO LIGHT. Just 5kg. Obviously this makes it incredibly portable but also makes the AM5 less of a faff to set up .
Talking of less faff to set up the AM5 doesn’t want you to balance the mount. In fact with less than 10kg payload you don’t need counterweights at all – which is awesome.
One potential bit of faff is polar aligning.
The AM5 doesn’t have a polar scope. Now us nerds are all doing supersonically accurate electronic polar aligning with software like sharpcap or ASIAIR which although it doesn’t require a polar scope I do use a polar scope to get a rough polar alignment before beginning my computer assisted alignment. So I thought that the lack of a polar scope would be a potential problem. Turns out it isn’t. To explain why I want to talk about the hand controller.
The simple handcontroller has two buttons and a joystick. The joystick moves the mount in RA and Dec. This is essential as it is impossible to move the mount by hand. You can only move this mount with the motors as there is no clutch. I don’t like the fact that I can’t move this mount without power and yet a mount exclusively driven by motors does have an advantage. Remember the two buttons. One starts and stops the mount tracking, the other button parks the mount in the home position. And this button is far more accurate than trying to align a regular mount to the home position by hand. In the home position the AM5 points the telescope at celestial north – very near the pole star. Because the AM5’s home position is so accurate to get a rough polar alignment all I have to do is press the home button and then adjust the tripod’s longditude and azimuth settings so that the telescope has the pole star in its field of view. A rough polar alignment like this is a good enough starting point for the electronically assisted polar alignment routines. I use sharpcap. I expect many AM5 users will be using the ASiaair.
I’s also like to mention that the simplicity of the hand controller is something to be applauded. All a mount really has to do is counteract the rotation of the earth… and this handcontraller has a button for that. In contrast skywatchers horribly outdated hand controller requires about 30 separate buttons taps to get the mount to track at the siderial rate.
Harmonic drives (aka strain wave gears) have been used by robots manufacturers for a few years. Unlike traditional worm gears gears used in regular astrophotography mounts which rely on accurate balancing with counterweights to get the most out of the relatively weedy motors, harmonic drives seem to be quite happy pushing against a significant load. So you don’t need to balance them accurately – in fact if your telescope and camera set up weighs less than 10kg and your tripod is sturdy then you don’t really need a counter weight at all. The main advantage of harmonic drives is that they theoretically have no backlash and this probably explains the terrific guiding accuracy. The downside is that they are more expensive but their cost is coming down and at $2k I’d say this mount is such a leap forward that its worth it.
One word of warning. The AM5 doesn’t like tracking past the meridian. After a few minutes it will shut down. So be careful. Make sure NINA – or whatever capture software you’re using – is set to meridian flip as soon as the object you’re imaging reaches the meridian.
When I’m imaging at 3am in the morning I want a mount that just works. And this mount does. Not only that its consistently better at guiding than any other mount I have ever used including my Avalon Linear Fast Reverse. It’s also way lighter and less hassle to set up. If you do astrophotography this is the mount you want.