If there's one thing that's caused me more head scratching than almost anything else in this hobby, it's guiding. It underpins everything: get it wrong and no amount of clever processing will rescue a night of elongated, egg-shaped stars. Over the last few years I've been steadily refining my technique to chip away at my tracking error, and in this post I want to share the five tips that have made the biggest difference for me, whether you're brand new to astrophotography or have been at it a while.
Before I get into them, a quick update. The UK weather has been relentless, with barely a clear night since the start of the year, so first light with my ASI 662MC planetary camera is still on hold (the Moon is now looking a better bet than the planets). I've not been completely idle though. I've been planning, ordering some new gear I'll reveal soon, and making life easier for future sessions: a 256GB SanDisk flash drive to replace the 64GB one in the ASIAIR, so I can image for several consecutive nights without offloading, plus a SanDisk external drive for storing all my original FITS files in case I ever want to reprocess them or add more data. Anyway, on with the tips.
Tip 1: Stay within your mount's payload capacity
Ask yourself honestly: is your payload too big for your mount? The mount's motor is doing all the work of tracking the night sky, and if you overload it past its imaging payload capacity, the weight will be tugging at it one way or the other all night. Your guiding ends up fighting the motor, everything becomes unstable, and you're left with bad frames to discard or elongated stars. The fix is simple enough: read the manufacturer's specifications for your mount and stay well within the imaging payload limit.
Tip 2: Take your time over polar alignment
Spend that extra bit of time at the start of the night getting polar aligned as accurately as you possibly can. Of all the tips here, this one makes one of the biggest differences. The more precise your polar alignment, the easier it is for your guiding software to track the sky, which means fewer errors and better images. A few extra minutes at the beginning pays dividends for the whole night.
Tip 3: Level and balance the mount properly
If you're anything like me and just want to get up and imaging as quickly as possible, you're probably cutting corners here. I know I have. Level the tripod first, ideally with the mount head off (I'll admit I don't always take it off, but you should, it's the proper way to do it). Once everything is level, put all of your gear on the mount, and I do mean all of it: guide camera, guide scope, ASIAIR, filter wheel, every last attachment. Balancing without the full kit on is a waste of time because it's not representative of what's actually there mid-session. The goal is to be able to pivot the telescope in any direction and have it basically stay put. Get that right and your mount stops fighting an uphill battle all night long.
Tip 4: Tune the guiding aggression (ASIAIR users)
This one gave me one of the biggest improvements I've noticed, and it's dead easy. I picked it up from another video (I can't remember whose, sadly, so I can't give them the credit they deserve). In the ASIAIR app, below the guiding graph, there are RA and Dec settings with plus and minus buttons and a percentage value. These control how aggressively corrections are applied. If your graph is bouncing up and down with big swings, constantly crossing the axis, you're probably over-correcting and should reduce the aggression. If the lines drift away and only gradually pull back, you're likely under-correcting and should bump the values up. Get it just right and the graph smooths out and hugs the axis, which means less guiding error. One caveat: this only works if you've done the previous steps first, otherwise the software is just trying to compensate for hardware problems.
Tip 5: Align your guide scope with your imaging scope
If you use a separate guide scope, spend a one-off bit of time making sure it points at the same spot as your main imaging telescope (and it really is one-off if they stay mounted together). I'll be honest, this is the most minor of the five. If your tracking is based on a completely different patch of sky to the one you're imaging, it's unlikely to cause massive issues, but for something so simple and easy to address it's worth getting right.
So those are my five tips. None of them are complicated, but together they've taken my guiding from a constant source of frustration to something I barely think about mid-session. If you'd like to see me talk through them properly, the video at the top of this post has the lot, and subscribing on YouTube means you won't miss whatever I get up to next. Clear skies!