OAG Cost for C8

Tony Gondola · Jun 12, 2026, 04:39 PM

People will tend to argue in favor of what works for them. Both approaches have pros and cons. Whenever I contemplate when I spend money in this hobby to first question I’ll ask myself is “will I see a difference in my images”. That’s really the bottom line for me. So, to that thought, are you currently having issues that you feel an OAG will solve? It will certainly help with weight and balance.

Are you seeing poor star roundness despite seeing good HFR or FWHM values?

Does the out of roundness or incidence of star trailing seem to get worse over time and does it suddenly appear at various times in a session. All of that would point to differential flexure taking place which is something an OAG would eliminate. If you don’t see those things and feel like star sizes are are what they should be then you wouldn’t benefit much from the upgrade.

I have noticed some subs can have oblong stars in the past but hard to say if that’s due to flexture or maybe just guiding errors, which have now improved a lot. It doesn't happen a ton though and can also be fixed with software. I really just don’t like the way my guide scope sits off center of my ota. I was thinking about getting a secondary rail to put on top of the ota but the lightest I could find was from Farpoint at 1.25 pounds, plus some extra hardware to attach my scope. An extra 1.5 pounds-ish is a big penalty to pay to center the scope. I wish I could get a more robust finder scope type bracket that had the right hole spacing so I could center it dead on the ota. But most seem designed for the finder scope screw spacing. I’m almost considering getting one of those orange the wider format rails then just chopping it down.

Tony Gondola · Jun 12, 2026, 05:39 PM

What guiding RMS numbers do you generate on a night of good seeing?

Around .76 to .85 on good nights. Mount is an eq-g. I’m basically really happy when it stays below 1

Tony Gondola · Jun 12, 2026, 06:24 PM

That’s a bit high but not out of the typical range seen for the mount. I’m not sure an OAG would improve that as you really seem to be “mount limited”. If I were to put money anywhere, it would be in that area.

Makes sense…. Definitely some work to do in that regard. I think it is capable of going lower. I’ve seen it get around 5 rms for some time then it sort of drifts up. Lots of balance and software things to try to improve this. I still haven't given phd2's predictive pec a fair shake.

Its extremely tempting to get a belt kit, or maybe just one of those kits with new gears. I’m fairly mechanically inclined but I just don’t know what “good" feels like with these mounts. Not having a frame of reference makes me very nervous that I could make things substantially worse for the benefit of maybe shaving a few arc seconds off my error. If there was still a service I could send my mount off to and get serviced, I would do it in a heartbeat.

Definitely tempting. I may just start saving up for something else. Once I get another mount i’ll be a little more comfortable experimenting with my non-daily driver. Couldnt hurt to have two big mounts. Would you recommend the pro? Sounds like the guiding numbers are good.

For my focal length, of around 1337 (after .63x reduction), my pixel scale is at .58. From what i’m reading, I should be guiding from 1/2 to 1/3 that level. But I know most mounts don’t hit that .2 or .3 rms range, and mine sure as heck never will. The demands for precision are astonishing, really.

I did listen to a very interesting talk from the creator of Metaguide and he had some thoughts on “chasing the seeing”. If I understood correctly, he was advocating for setting your mount to be as responsive as possible. Where a lot of resources suggest to use longer exposure lengths to minimize noisey star images, he seemed advocate to make your mount as responsive to change as possible. And eluded that other guiding software wasn’t built for that concept in mind. I’m curious to try it out, but I doubt my mount is tuned enough to react accurately or quickly enough to test that concept.