Should I upgrade my mount or my guiding camera?

If, as you say, your guiding is around 0.1 pixels, but also 0.85" rms, then your guiding scale must be 8-9"/pixel. If I'm correct then this is way to coarse for your imaging scale. Have considered an OAG solution where your guiding scale is closer to your imaging scale.
You try to aim for <0.5" guiding. Imo, this must be very close to what ordinary atmospheric conditions will allow (depending on your location, of course).
Optimizing guiding scale and tuning the mount, should improve your guiding results, but probably not as far as your goal. Nevertheless, that is where I would start.

cs,

Wim

Wim van Berlo:
If, as you say, your guiding is around 0.1 pixels, but also 0.85" rms, then your guiding scale must be 8-9"/pixel. If I'm correct then this is way to coarse for your imaging scale. Have considered an OAG solution where your guiding scale is closer to your imaging scale.
You try to aim for <0.5" guiding. Imo, this must be very close to what ordinary atmospheric conditions will allow (depending on your location, of course).
Optimizing guiding scale and tuning the mount, should improve your guiding results, but probably not as far as your goal. Nevertheless, that is where I would start.

cs,

Wim

Thank you!  I have decided to get a new guide camera which has a pixel size of 2.9u as opposed to my current one which has 5.2u.  This seemed like the easiest first step as I will still be keeping a relatively large FoV (and therefore potential number of target guide stars) compared to the OAG solution.

I cannot speak to your HEQ5 having never used it, but will say that it all starts with the mount. I use a 8" aperture 910 mm Newtonian myself and would never attempt to use it on a HEQ5 class mount. Heck, I wouldn't be comfortable using it on a GM811G! While your guiding RMS might be 0.85", what matters as much or more are sporadic short duration larger excursions that will ruin a sub. Good mounts will not just track more accurately but be able to respond much more quickly to guiding commands and will result in a lot more retained subs of higher quality. They are less sensitive to minor weight imbalances and are more likely to perform uniformly within their rated weights.

I agree with Andrea. If you're serious about the hobby, don't skimp on the mount. Upgrading mine was the best thing I did. It is a joy of watch it handle my Newtonian.

The best mount your finances can afford is the answer.

Personally, for a similar kind of money I'd go with a mount with about 40-50 kg load capacity.

Andy Wray:

would never attempt to use it on a HEQ5 class mount

I do agree with you that my HEQ5 Pro is overloaded with my gear.  I do end up throwing away 25% of my subs which is very frustrating.  The mount upgrade will happen this year;  now, which one should I choose?  EQ6 R Pro or something more exotic?  Any advice would be appreciated.

FWIW:  My total spend on hardware for this hobby has so far been less than £4,000  ($5,250), so I guess the maximum expenditure on a mount alone would need to be about the same.

I recently purchased the EQ6R pro, with guiding, and PEC, it is rock steady, it is well supported and has a fantastic following.  I am very happy with the mount.

Götz Golla:
What is the focal length of the guide scope ? It should be at least 1/3 of the main scope.

It's 162mm, so a bit shorter than it should be.

Andy Wray:
I have an HEQ5 Pro mount and a Skywatcher 200dps with coma corrector (That's an F4.5 906mm Newtonian effectively).  I guide them with an Orion Starshooter system.  I regularly get 0.85 arc secs RMS via this setup which is equivalent to the resolution of my ASI 1600MM camera which is 0.89 arc secs per pixel.  I feel like my mount and guiding should probably be at about 0.45 arc secs to get the best out of the camera/scope.  What should I do?  Look at a new mount or think about upgrading my guiding solution?  The guiding camera is managing to guide within about 0.1 pixels at the moment which I think is pretty phenominal.

Thoughts?

When you are shooting sub-arcsecond resolutions, the best thing you can do (aside from having a good mount) is to use an OAG. For that, it is recommended you use a very sensitive monochrome camera. My personal experience was the ZWO 120MM wouldn't cut it while the ZWO 290MM works just fine. I have yet to have any issues finding a guide star using the 290MM and an OAG with any setup. I am sure an equivelent camera from another dealer would work too.

For mount considerations, I think you will want something that carries at least 18-19 kg but the folks above are right; if you are going to be putting on a Newtonian that is almost 1m long then you will need something beefier that can handle the wind gusts. Something else to consider is how often you will be setting it up and taking it down. If that is a consideration, I know iOpteron usually has a pretty good mount weight to carrying capacity ratio.

Michael Ring:
Another quickfix would be to buy an off-axis guider as already mentioned above. If it fits, the new OAG-L from ZWO is quite nice. I also do own a HEQ-5 with Belt Mod, when I am not limited by seeing then guiding is in the range of 0.5"-0.6", with not so good seeing 0.8". Metaguider (alternative to PHD2) may improve those numbers but so far I did not yet manage to get it working reliably.

I know a guy (see here: https://www.astrobin.com/users/Cyrill/) that regulary uses his HEQ-5 for his 9.25" Celestron Edge HD and gets VERY sharp pictures at 1645mm focal length.

I also used my HEQ-5 once with my 9.25" and it also worked quite OK, but I prefer putting the heavy beast on the EQ6-R.

But as also said above, when you can afford it, get a bigger mount, this will pay off in many ways.

Michael

Remember, that EdgeHD is about half the length of the Newtonian Andy is using. That matters a lot!