Notes on PHD Guiding

  • Maximum RA guide pulse is 1000ms (1s). If PHD is not locking on to the star and it says "dur=1000" in the status bar, a better polar alignment is required.
  • RA hysteresis is used in a 2-term weighted moving average:
RA_dist = (1.0 - RA_hysteresis) * RA_dist + RA_hysteresis * last_guide



Auto-generating CoreData Classes

If you have a xcdatamodel file, open it, and using the menu: File > New File > Cocoa Class, you will see an extra item: Managed Object Class. This will autogenerate the required header and implementation files for your CoreData entities so you can use the convenience accessors instead of [setValue:forKey:]. Doing this will also update your data model so your entities won’t have NSManagedObject as their class. Instead their class is the corresponding generated class.

The thing is, you won’t see “Managed Object Class” item unless you have opened the xcdatamodel file and it is the front most window.

Naturally I discovered this by accident just as I was about to hand write the last CoreData model class.



My First Galaxies (Kinda)

I finally managed to find some galaxies last night. This has been something that has eluded me due to my location, inexperience, and frankly inadequate equipment. (You in the back! Stop snickering!)

Last night, with my Canon 1000D I caught the barest glimpses of M83 and NGC 5128, aka the Hamburger galaxy, aka Centaurus A. The pictures are below, all taken at ISO1600 and 30s exposure time.

This however doesn’t really count - I didn’t see it with my own eyes. This is not conceptually different to seeing (much better) pictures taken by Hubble and other telescopes.

Time to start saving up for a bigger telescope.