Where did my mosaic go wrong?

Sequence Generator
1

Lined up the LEO Trip with NGC3593 for a 2 panel mosaic. Haven’t done any mosaic’s yet and I wanted some data to test with. I have a 20% overlap setup.

I have a ZWO 1600mm-cool and I’m using a ES127 (952mm) with a 3" ES reducer/ Flattener making it a roughly a 670ish mm

In the framing and mosaic wizard I setup the pixal size (4656x3520) with my scale at 1.16 ArcSec/Pixal (verified with Astrometry.net).

The two panels don’t overlap. I’ve verified this with Pixinsight and with Astrometry.net.

I’m guessing the “dirty” fix would be to increase the overlap a bit, maybe 25-35% would do it, but I’m wondering if I have a setting wrong someplace else? 20% seems like it should work to me.

After much fiddling I was able to use “WorldWide Telescope” (free) and Astrometry.Net to show how this worked out. Dropbox - File Deleted

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It looks from your dropbox link as though you did not have the rectangle in F&MW at the same rotation as your actual camera rotation.

Take a look at these two crudely drawn examples (They’re not exact, just whipped em up by hand to illustrate the point) :

Here’s what you might have drawn in F&MW. White dots are stars, red dots are the centers of the 2 frames.

If, as an example, your camera was rotated 45 degrees, then here’s exactly the same field, with the 2 frames rotated ~45 around those center dots

Can’t say for certain that’s what happened, but it’s my best guess.

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Could very well be. I do not have a rotator and have the “manual rotator” setup.

4

Camera rotation is most likely the problem. I have my ASI1600 oriented with the USB ports in the bottom position of the ES127 and the CEM60 in zero position. Come to find out that position is actually 90 degrees rotation of the field of view. I thought it was zero! Equatorial orientations are a bit confusing!! So the mosaic was setup with the incorrect rotation angle, and the captured frames did not overlap.

Verify, and double check the actual rotation angle of the camera field of view and redo the mosaic wizard. One thing I am still struggling with in the MFW is the panels get reordered depending on the rotation. So I’m not sure exactly what camera orientation the panels are representing. The issue is not knowing exactly where the top/bottom/left/right is on each panel in the MFW. If that information could be added, either on the panels themselves or in a legend, that would be very helpful to understand how the mosaic will be captured.

Ciao,
Mel

5

Thank you for your info graphic it took me longer to realize what was going on that it probably should have.

I need to get the manual rotator turned on.

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6

Yes. I finally got to a point where I felt like I had (almost) everything working. I was able to setup, connect everything up and start imaging and I did not hit a single hiccup. That is the first time since starting this hobby that has ever happened.

7

As mentioned, the rotation angle is the problem. When setting up a mosaic you need to be very close to the actual angle. You can do this one of 2 ways:

  • Use the current angle that the camera is set at. This means that when planning your mosaic you just take the current camera angle and leave it. Your camera angle dictates your mosaic. This means you almost certainly sacrifice framing unless you get lucky.
  • Adjust the camera angle to fit your mosaic. Best way is to use the manual rotator and the “Rotate Camera” option in the target drop down (just like “Center on Target” option, but for rotation). SGP will then solve an image and tell you how far and which direction to rotate the camera. Once you have done this SGP will take another image, solve and again compute the direction and amount of rotation needed.

When using the manual rotator I can get pretty darn close (about a degree or less if I’m lucky) within about 3 iterations.

Thanks,
Jared