Here's how to do a large mosaic


#1

It has been asked how to do a very large mosaic - see Framing & Mosaic Wizard for large mosaics but the question was not answered. Here is my contribution. It is for an all-sky mosaic.

I have coded it up and I have a sequence ready to go but we have a week of bad weather. Also there may be reasons why it won’t work and I’d like to know that!

I coded the problem in R and it generates an Astro Planner xml file for the targets which you can import. What it does is convert alt-az coordinates to equatorial as of a certain date and time. This particular version generates 90 targets which SGP 3.1.0.170 handles reasonably well (but I have had a few crashes).

Any feedback? Will this work - getting the images might be OK but stitching them might be tricky due to camera rotation?

# Generate equatorial coordinates for a panorama specified in alt-az coordinates

library(astrolibR)
library(XML)

latAuckland = -ten(36, 54, 0) # -36.90
lonAuckland = ten(174, 44, 0) # 174.73
julian = jdcnv(2019, 3, 11, 8) # yr, mn, day, hr UT

xml <- xmlTree("root")

for (alt in seq(0, 90, by = 20)) {
  for (az in seq(0, 340, by=20)) {
    xml$addTag("object", close=FALSE)
    name = paste0("AltAz", alt, "-", az)
    eq = hor2eq(alt, az, julian, lat=latAuckland, lon=lonAuckland)
    xml$addTag("name", name)
    xml$addTag("ra", eq$ra*24/360) # convert degrees to hours
    xml$addTag("dec", eq$dec)
    
    xml$closeTag() # "object"
  }
}

saveXML(xml, file="mydata1.xml", encoding = "UTF-8", prefix = '<?xml version="1.0" encoding="UTF-8"?>\n')

#2

but stitching them might be tricky due to camera rotation?

You could always try Astro Pixel Processor - that’s brilliant at stitching mosaics seamlessly.


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