Resolving power and auto-guiding accuracy - please help me before I drop in to the rabbit hole!

[paul]

I'm not sure if the comparison is meaningful but the Dawes limit for my scope is around 0.46 arcseconds. Under ideal conditions with perfect collimation I should be able to split binaries separated by that distance visually. (Not with my eyesight though🧐). I'm trying to relate that to the RMS of my auto-guiding. The fact that my mount can report as low as 0.2 suggests I haven't reached the limit yet of its performance.  I imagine I need an RMS in the region of 0.25 to get full benefits of my camera and scope combo (and probably a house move to a Peruvian mountain).

With my mount operating in the range 0.6 to 1.1 arcseconds RMS I'm wondering if its really worth pursuing lower RMS by tweaking - or is seeing always going to be against me and I should stop now before it becomes an obsessive rabbit hole I'll never get out of? I can feel a compulsion coming on....

 

 

 

 

 

[rwillits]

Hello Paul. If you have modest equipment as I do. "SkyWatcher" and use PHD2, or similar. I find doing a little trimming while guiding with the settings useful. Unlike the high-end equipment my kit will act a bit different following a target on the equator than near straight up. Watching the graph can be a bit mesmerizing, kills a some of the boredom. In a short time you will learn the difference between bad guiding and bad skies or bad flex if you pay attention. You will get to know your equipment and it is more fun.  🙂

Edited April 27, 2021 by rwillits

[TerryMcK]

If you are getting round stars then no need to go any further as you will be chasing your tail. I personally don’t stress too much about the guiding graphs or RMS values, in fact I turn off all the graphs. PHD2 shouldn't really need much tweaking in its “brain” settings and works well out of the box.

 

[paul]

On 4/28/2021 at 7:24 AM, TerryMcK said:

If you are getting round stars then no need to go any further as you will be chasing your tail. I personally don’t stress too much about the guiding graphs or RMS values, in fact I turn off all the graphs. PHD2 shouldn't really need much tweaking in its “brain” settings and works well out of the box.

 

You're probably right and I've been finding that careful processing gets the small stars. On the HEQ5 I have reached its performance limits but I figure the CEM can do better, just not sure I'll be able to see it with the seeing. I'm just trying not to leave any performance improvement on the table.

 

Tonight I tweaked the balance and found that the big scope hits tripod legs at certain angles, so I've loaded up some weight on the back end to push the ota forward in the rings. Now I find the weight can't be balanced by the single counter weight!  I've just ordered weight plates and quick release clamps with a 28mm bore to see if they will work- the official weights are pricey and seem never in stock. I figure since I only need a few kg I'd give the plates a go. I can put the plates at the far end and play balancing tunes with the official counter weight.  I'm also going to push the tripod post up yet another notch. Then I'll know if critical balancing is really needed. With the  counter weight imbalance tonight I had 0.8 rms which is not bad at all.

[paul]

On 4/27/2021 at 7:31 PM, rwillits said:

Hello Paul. If you have modest equipment as I do. "SkyWatcher" and use PHD2, or similar. I find doing a little trimming while guiding with the settings useful. Unlike the high-end equipment my kit will act a bit different following a target on the equator than near straight up. Watching the graph can be a bit mesmerizing, kills a some of the boredom. In a short time you will learn the difference between bad guiding and bad skies or bad flex if you pay attention. You will get to know your equipment and it is more fun.  🙂

That's a good observation,  I admit to not analysing the graphs seriously before or correlating them to the weather. I used the guiding  assistant for the first time after years of reading about. The tweaks it suggested made a visible difference. I'm recently back to the hobby after a few years of not having time for it and my commute. I've picked up some new toys and I'm having to relearn a few things.