PHD2 help

[kosborn]

Tonight I managed a really good polar alignment but this is what my guiding graph looks like. It seems to plod along nicely but I get those big DEC spikes on both sides of the baseline. My total RMS error ranges from about 0.6" when good to over 1.1" when not. It is windy tonight - not sure if that has anything to do with it...?

Kevin

[AndrewJ]

Gday Kevin
Those big spikes line up with a guide direction change, so are probably just PHD2 applying your designated backlash correction.

Andrew

[traveller]

Hi Kevin,
Don't get too hang up on the RMS error, what you have is more than acceptable with your scope and camera setup in your signature.
So long as the stars are round, there's no need to lose sleep on the RMS error.
I regularly get 1-1.3" error and it doesn't affect the quality of images if I keep under 5 mins subs (which I do due to the LP and the sensitivity of the camera).
cheers
Bo

[kosborn]

Thanks for that. At 5 minute exposures I'm happy with the guiding. I tried 10 minute exposures a while ago (and would like to try again) but that didn't go well. I know there's lets of opinion about best exposure length vs gain and read noise but I still haven't got my head around that yet. In my simplistic way it seems to me that a longer exposure should get more detail in the faint areas - as long as bright areas aren't saturated and I've certainly seen some great shots from others with subs with very long exposures.

Kevin

[xelasnave]

Back in the past we seemed to go for one long exposure...manually guided so it was as much a test of endurance I guess.
I cant wait to get some long exposures in the bush with this nikon..remember my last camera was a 450 d canon ...and it worked great with long exposure so this one should be heaps better.
But I still cant get over what 30 shots get..for me two minuntes will be long exposure now...the longest I manually guided was fir one hour twenty minutes...and if not crazy to do it you were crazy after that time lini g up the cross hairs.
Alex

[kosborn]

I'm seriously impressed! Great stamina to manually guide for over an hour!

Kevin