Orion Skies

Expert

Longer exposures, bigger targets than the frame, and doing the stacking yourself.

60 seconds in EQ mode

60 srecommended in EQ
120 sthe most
15 sthe most in Alt-Az

Four times the light in every frame and far fewer frames to stack. It wants good polar alignment: a small error that is nothing in 15 seconds shows in 60.

On one 53 minute run the field still turned 1.7 degrees, about 1.4 degrees an hour, from a little polar alignment error. That is 0.02 degrees inside one 60 second frame, nothing at all, so it is no reason to avoid 60 seconds.

Trailing in one directionIf the stars smear the same way across the whole frame, it is tracking, not the lens. A lens fault changes direction across the field. One target trailing is not a reason to give up 60 seconds: on the same night the others were fine.

The EQ stop, and the flip

In EQ mode the Dwarf has two habits that look like faults and are not.

  • It stops an hour and a half before the target is due south. The app says "obstacle" or "cloudy, redo" on a clear sky. Two runs, the Wizard and the California Nebula, both stopped at exactly 1.5 hours before due south. So start a target within an hour and a half of due south, or after it has passed.
  • It flips when the target crosses due south. Every frame after the flip is turned about 180 degrees. A stacker that only looks for small turns throws them all away. On one night that was 370 good frames called lost.

Mosaics: targets bigger than the frame

2.93 x 1.65degrees, tele frame
about 47 x 26degrees, wide

Work the target's size against the frame. The North America Nebula is about 2.0 by 1.7 degrees, so it nearly fills the tele frame and a sliver clips. The Heart, the California and M31 are bigger, so they want a 2 view mosaic. The wide lens is for constellations and the Milky Way, not a nebula: a nebula would be a smudge in it.

Stacking on a PC

  • Keep the FITS files. Stacking the JPEGs hits a ceiling; the FITS files hold far more.
  • AutoStakkert cannot see the Dwarf's frames. It wants a numbered sequence and the Dwarf names its files by time, so it reads a folder of hundreds as one or two frames. The fix: copy them into a fresh folder with numbered names. It changes nothing in the originals.
  • The stack comes out grey. That is normal: the colour is put back afterwards.
  • If the picture looked better on the Dwarf's screen, believe your eyes. On one run the processing was fitting the "background" right through the nebula and taking it away. Removing only a flat level and a slight tilt brought it back.
  • Frames from several nights stack together when the framing, exposure and gain match. Take darks each night, at the end.

Hit something else? Problems and fixes, or ask on the owners' wall.