Get Better Guiding For Free

There are a ton of us out there who don’t have the money to go out and buy a $2000+ astrophotography mount and maybe are stuck to buying entry level mounts on the used market. That’s where I still am largely, I have a Celestron AVX I got almost half off MSRP. However, I currently get sub arcsecond guiding on it even without having opened it up for a hyper tune. The biggest difference has been PHD2’s multi star guiding system so far.


Before the update I was getting around 1.75-2.2″ of total RMS guiding. Not great, but fine for a wide field scope. This is largely due to mechanical imperfections in my mount, one of which being pretty significant gear play. This is essentially when the gears that move the mount have just a tiny bit of space between the teeth which results in inconsistent movement when they start turning. For a hobby that requires very precise movements, even a fraction of a millimeter can make a difference.

PHD2 settings, this is where you’ll go to enable multi star guiding, just click the brain at the bottom


After the multi star update, I simply checked the box in the PHD2 settings and it immediately began picking up 12 total stars. I reran my calibration and kept an eye on it, adjusting my aggressiveness settings depending on what I needed and eventually I settled in at 65-75 on DEC and around 45 on RA for a guiding accuracy of just under 1″. I generally bounced around from .75″ to 1.1″, but I think that largely had to do with wind. This resulted in noticeably more consistently shaped stars and less elongation overall. It also meant my exposures could be longer, but I found three minutes to be my sweet spot because I do get planes flying through my frames and random mechanical issues with my mount. Some people really like five minute exposures, but I think it’s simply too risky to spend five minutes on a frame and have to throw it out because of a gust of wind or a plane. Anyway though, my three minute exposures looked fantastic and my guiding is better than ever.

What This Means

Because of this update, my AVX has gotten a new lease on life and I’ve decided I could go a little longer with it before I really get to its limits. I think with careful calibration I could get this even better, but I don’t think I really have the patience for it. What you can take from this though is that if you also have an entry level mount with some suspect mechanicals, you could also greatly benefit from this update so give it a shot if you haven’t.


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