PHD2 Exposure Time

[Capella_Ben (Ben)]

Hi All,

Thought I'd share some observations.

PHD2 documentation says you should have a longer exposure time to overcome bad seeing. My observations do bear this out.

I have been recording my PHD2 findings for the last four months (using PHD2 Log Viewer). If I graph a scatter plot of Exposure Time (ms) and Total Error (RMS Arc Minutes) I get:



As you can see going up to 3 to 3.5 seconds does make a difference!

Hopefully this will help someone who is starting out with guiding.

BTW: I have a 200mm F5 scope and I use an off axis guider.

[xelasnave]

I have only run phd a couple of times and so far can only get acceptable results at half or one second...half being best it seems.
And have agressivness at 30 for RA and less or zip for Dec.
I have many others mount issues to sort out so I did not expect much until after another pull down.
I am only using a finder guider and as yet only guided on 8 inch f5 ...the auto guide via finder scope was is to go on my 80mm ..
I hope I can get mine working like yours in time.
Thanks for posting your experience I for one greatly appreciate you doing so.
Alex

[luka]

Ben, interesting and nice work which also shows the variation in seeing from night to night.

However, I would say that 2.5s, 3.0s and 3.5s are within the margins of error of each other. More data is needed to be conclusive as the night-to-night variation in seeing is very significant, just look at the spread of points at 3 seconds. As an example, from the graph one could even try to argue that 2.5 seconds is better than 3 seconds.

Also, probably the final results will also depend on the location, some places will generally have better seeing than the others.

Having said that, the trend for shorter exposure times is very clearly demonstrated

[Capella_Ben (Ben)]

Luka,

I agree more data would be better. Will keep logging.


Xelasnave,

I started out with half second as well, but after re-balancing my scope and changing cameras, I'm much happier at the 2-3 second.

Really good polar alignment always helps! :-)

Good luck.