I'm hoping for some clear skies tonight, enough to test out the #ZWOAM5 with my trusty William Optics GT81 and the ZWO ASI071 cooled color camera. It's a beautiful fall day out there right now, at quarter after 5pm, but I don't think this is going to last into the evening.
Just wanted to document the spacing and backfocus distance for the ZWO ASI1600MM-Pro with the electronic filter wheel and OAG. The William Optics SpaceCat 51 allows a maximum distance of 57.9mm to achieve minimum focus, so I like to be somewhere close to 50mm when everything is totaled up--and looking good:
I am using a fanless Windows 10 machine and a Pegasus Astro Pocket Powerbox to run my ZWO AM5 mount. Both of these are mounted to a SmallRig cheese plate with 3M Command Strips (I like these better than Velcro).
MeLE Quieter2Q Fanless Windows 10 PC with J4125 CPU, 8GB RSM 128GB Storage
Pegasus Pocket Powerbox
SmallRig Multi-Functional Cheese Plate
Sprig Cable Management Device
SVBONY Dovetail Base 32mm wide
Actually, I'm just taking pictures of my gear because the evening weather is foul. But if it was clear, this is what I would be using to capture the night sky.
If I'm calculating this correctly, the theoretical best performance for my particular ZWO AM5 mount with a maximum period error of 23.6" is 0.136 arc-second error for a 1 second guide duration. So, 0.136" error is what's possible with perfect seeing, no atmosphere, in Earth's orbit somewhere. Here on the ground, ZWO has specified that all AM5 mounts should perform with 0.5" to 0.8" total error or better, given average seeing and atmospheric disturbance. And that seems to be exactly what I am experiencing.
For a detailed walk-through of the periodic error report values and calculations see 10 things you need to know about the custom AM5’s PE Test Report provided by ZWO
The weather doesn't look like it's going to cooperate in the next four to five days, and at the same time, the moon is seriously imposing its reflective properties on the night sky. So, not the best time to try out a new filter—even a narrowband one. I recently bought the Optolong L-eXtreme dual-band filter, specifically for my ZWO ASI071 color camera, which has an APS-C sized sensor. The L-eXtreme filters out everything except two narrow (7nm) bands along the Oxygen III line and Hydrogen-alpha line. I am anxious to try this out with the 8" f/4 Newtonian on the Veil Nebula.
I have been imaging the night sky for eight years with five different EQ mounts, most of it from my backyard in New Hampshire, and I rarely experience guiding this precise. I have been out imaging three nights with the AM5 so far, with reasonably clear skies and average seeing—nothing spectacular. These are some of the lowest total RMS error numbers I have seen from my Bortle 4 to 5 backyard. We're going through a stretch of clouds and rain, but hoping for better weather toward the end of the week. I'll post more guiding results along with some PHD2 logs.
I nearly found out the hard way that the new ZWO AM5 mount is so compact that power and USB cables from the primary camera can easily loop over the altitude and azimuth adjustment knobs at the base and snag, something I never really thought about with a larger mount. This happened the other night, and I just managed to unhook them and continue imaging.
So, a little cable management was in order for the William Optics SpaceCat 51 on the ZWO AM5. The guide camera (silver camera on top) and the filter wheel plug into USB ports on the primary camera (ZWO ASI1600MM-Pro) at the back. Another USB cable runs from the autofocus (ZWO EAF), the red box under the scope. I end up with five cables leading down to the Pegasus Astro Powerbox and the fanless Windows 10 machine running the control software (NINA). What's new in these pics is the SmallRig Switching Plate (1598) and two of the SmallRig Spring Cable Clamps (MD2418). These are designed for cable management on cinema cameras, but work just as well for our gear.