What do I do to upgrade my guiding performance?

Hey

I do not know the specifics about whether or not your focuser would be able to carry the extra weight of an OAG, that being said, it’s not super heavy. 

If you go with an OAG, you have several options. 
I have the ZWO OAG-L and the regular OAG with an added Helical focuser on. 
The latter was bought due to backfocus constraints in my imagetrain. 
You could also take a look at the PegasusAstro Indigo OAG - very slim design. 

You can without any issues use an OAG with a Comacorrector. I am currently doing exactly that. 

To get the focus right, your guidecam sensor needs to be exactly as far from the middle of the prism in the OAG as the sensor in your regular camera is from the prism. 
If you have a helical focuser, you could extend it half-way and drop you guidecam in there, and then do all the measurements to make sure you are within +/- 1mm from your focus, and then easily use the helical focuser to dial it in perfectly. 

If you choose to go with an OAG, you should definitely consider upgrading your guidecam to either an ASI220 or the ASI174. The latter has the biggest sensor and gather most light, as I understand it. I have the 120 and the 220 and I only use the 220 for my OAG. 
I can use the 120 with my regular guidescope when necessary. 

Look also for some of James Lambs youtube videos on OAG. They are really good.

andrea tasselli:

I would like a guiding accuracy of at least a constant 0.5 arcseconds or smaller.

Prepare to spend a lot more money on the mount, for starters. And then some...

Hahaha, true. 
Just prepare to spend a lot of money on anything and everything astrophoto 🤣
Whenever you pull on one end, money disappear on the other end 🤷‍♂️😃

I used an AVX for a couple of years.  I have always said it was the cheapest mount capable of "decent"  guidance, but 0.8 to 1.0 is about as good as it gets.

Starting with the cheapest modifications:

1. Focus your guidescope for each target.

2. Good polar alignment and balance , but keep the AVX pushing.  DO NOT  let it get ahead of the scope.  The AVX can wiggle back and forth on the cogs if you let it. Your guidance pulses should all be PUSHING.

3. Shoot shorter subs.  It only takes one of those AVX wiggles to ruin a 5 minute sub.

You probably do not have a flexture problem, so an OAG will not help.

The sweet-spot for your mount is probably about 120 to 300 seconds or less.  With a CMOS camera that is plenty of time time for most targets.
   
CS
David Redwine

And which dew heater for a 50mm guidescope? I want it powered by one of the ASIair's power out ports.

Maybe tune up your avx to reduce backlash/better gear mesh?

how long is your guide exposure?

i’m guessing it’s the mount and not the guide scope.

Sean Mc:
how long is your guide exposure?

1 second

Maybe I should just get the ZWO OAG with helical focuser? Maybe that will give me the best guiding? I already have all the adapters to make that work for me, and I think I wouldn't need a dew heater.

Also check to make sure your mount is level. Being off level will give it a lot of work to do, and I’m reading that the AVX doesn’t really like to have a payload over 12-15lbs for photography ¯\_(ツ)_/¯

Brian Puhl:
Ditch the AVX, get something a little better, I'd suggest an EQ6R at minimum.    You're probably not going to see much better performance from that mount.  Improving your sampling isn't going to do much.   I've had some nights as low as 0.2 on my EQ6s, and averaging around 0.4" rms most nights.   It's a solid performer with a proven track record.

0.2" is unbelievable; it must work like a dream! Imagine imaging galaxies with that type of guiding Wish I had gotten an EQ6R, instead of the AVX, but I was too dumb at the time to know any difference between the two.

I don't think I can ditch it. It's already strapped to a JMI dolly.

I might ditch the newt instead, but I want to go after galaxies...

Or, I had an idea, I could get a smaller newt that is more dedicated for astrophotography.

Getting a smaller Newt and an OAG would help me in my guiding performance, right? My secondary mirror is too small and my focuser is way too cheap, and my spider vanes are way too flimsy anyway; I don't even get the normal cross shape in my diffraction spikes, neither do I see enough color in my stars, and my star cores don't even look right; moreover, my setup is so heavy and big that it nearly falls on my face when I try to take it down a step that goes to my backyard; if I didn't have enough muscle, I think I would be crushed long ago...

Brian Puhl:

I might ditch the newt instead, but I want to go after galaxies...

Or, I had an idea, I could get a smaller newt that is more dedicated for astrophotography.

Getting a smaller Newt and an OAG would help me in my guiding performance, right? My secondary mirror is too small and my focuser is way too cheap, and my spider vanes are way too flimsy anyway; I don't even get the normal cross shape in my diffraction spikes, neither do I see enough color in my stars, and my star cores don't even look right; moreover, my setup is so heavy and big that it nearly falls on my face when I try to take it down a step that goes to my backyard; if I didn't have enough muscle, I think I would be crushed long ago...

I think I missed that part, running an 8" newt.    If you wanted to truly keep the mount.... I would suggest going to a smaller frac like the Meade Quad 70mm, or the newer version, the Orion 70mm Quad.     They're very sharp scopes for their size.  On top of that, they're light weight and won't succumb to the wind.  I had one and I kinda regret parting with it.  Sampling with your camera would put it at 2.2 arc seconds per pixel, which means you can have horrible guiding, up to 1.8" and it will still look sharp.  It was so nice to never care about the wind or seeing conditions. It just worked. 

My honest suggestion would still be to upgrade the mount though.   The mount is the most critical piece to success in astro.  With the backlash that AVX probably has, you'll have issues with anything bigger than the Meade Quad....   I have two EQ6s and even on their worst days, they're still perfect with my Esprit 100s.

I'll stay with the mount.

How about an FRA400 or an 80PHQ? How long do you think my exposures can be, for maximum sharpness, for those two?

Don’t put a barlow in your guide scope. The more stars the better. I really don’t think the guide setup is the problem, I think it’s your combination of mount and scope. 

Now, just out of curiousity, i was having issues with my am5 and narrowed it down to the rubber feet being too squishy and allowing the whole setup to oscillate. I replaced the rubber feet with the spikes and my guiding got WAY better.