PHD2 guiding, is this good enough?

[Marko of Oz]

My guiding seems to work ok but that doesn't mean I understand what the numbers mean.

Does this screenshot represent reasonable guiding bearing in mind I'm not shooting for perfection?

I'm imaging with the gear in my signature if that's important to know.

cheers

Mark

[g__day]

Yes your guiding is pretty decent!

The Root Mean Square of your total guiding error is +/- 1.14 arc seconds (so if I recall correctly that means on a normal distribution 68% (+/- 2 sigmas) of all adjustments fall within this range. I have seen rigs twice as good or bad still produce great results.

So your pixel movement involved in that RMS measurement is 0.28 pixels - which to mee seems pretty good - and a simple division shows each pixl therefore sees 4 arc seconds.

[Startrek]

In general terms folk should be aiming to guide around or preferably below the image scale of your rig , however this is not always achievable due to your equipment and seeing conditions.

For Example ( your rig )
RC6 telescope , focal length 1370mm @f9 ( assuming you haven’t reduced your focal length)
Canon 700D pixel size 4.3 uM

Image Scale (P) Formula
P= ( camera pixel size in microns x 206.3 )/ telescope focal length in mm
P is Expressed in arc sec per pixel

Image Scale P = 4.3 x 206.3 / 1370

P = 887 / 1370

P = 0.65 arc sec per pixel

Therefore at your image scale you should be aiming for 0.65 arc sec total rms guiding , minimum ( preferably less)

I owned a HEQ5 mount for a number of years and imaged at only 900mm FL with my 6” Newt , my guiding was generally around 0.80 to 1.00 arc sec total on good seeing nights and above 1.00 arc sec on average to poor seeing nights.

You really can’t evaluate your guiding based on one nights session , conditions change so much
Ive had nights with my EQ6-R pro mount where my guiding was 0.45 to 0.55 arc sec total and on another night a month later it’s been 0.75 to 0.90 arc sec total (and that’s with the mount being tuned by myself with Dec backlash at 900ms )
See how your guiding runs over at least 2 months or 4 to 6 sessions.

Another thing to watch is your Dec and Ra values , generally they should be fairly close to each other ( within say 20% )

At your focal length of 1370mm and not knowing your sky conditions, your guiding numbers are not too bad but no reason why they can’t be improved with either mount’s adjustments, re balancing and favourable sky conditions

Why not try the Guiding Assistant ( found under Tools tab at top ) to evaluate your guiding. Andy and Bruce, the developers from PHD2 always advise folk to get a bench mark when guiding and this tool is a good starting point.

Check your Polar alignment too, PHD2 can guide your mount with a PA error of up to 10 arc min but I wouldn’t recommend that larger error , it only introduces image shift into your session. Around 3 to 5 arc min error is adequate for PHD2. Some folk sweat over sub arc min PA error but it’s not required with PHD2

Here’s a good tutorial from PHD2 which is definitely worth a read

https://openphdguiding.org/Analyzing_PHD2_Guide_Logs.pdf

Good luck and clear skies

Martin

[Marko of Oz]

Thanks for that info, that's great.

cheers

Mark