NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Star photo plate solver
From: Peter Monta
Date: 2024 Jun 24, 17:35 +0000
From: Peter Monta
Date: 2024 Jun 24, 17:35 +0000
Hi Paul,
I experimented with images containing the Moon and some surrounding stars. A neutral-density filter suspended a meter or so in front of the DSLR's lens helped with glare, avoided saturation of the lunar image, and left most of the field of view clear for stars. Lunar positions were good to a few arcseconds. (I also used astrometry.net's "solve-field" tool, along with a custom lunar-limb-centroider.)
The software is here:
If there's interest, I could dig out the few hundred images taken with this system. This was during one of the wildfire events in northern California, so some images are slightly dim and yellow, but it didn't hurt positioning much except for a decrease in detected stars.
The images were well distributed around a lunar orbit, and I could see the stellar aberration very well (~20 arcseconds), which was a hoot.
Cheers,
Peter
On Wednesday, June 19th, 2024 at 10:15 AM, NavList Community <NavList@fer3.com> wrote:
Star photo plate solver
From: Paul Hirose
Date: 2024 Jun 18, 21:14 -0700I tried the astrometry.net online "plate solver" with one of my own DSLR photos. It got a solution in about one minute. I.e., it identified the RA / dec at image center, image scale, and orientation. This was my first time and I didn't want it to take too long, so I helped the software with approximate RA and dec. Note that most submissions to the site are much smaller fields, typically arc minutes rather than degrees. Constellation stick figures are not appended to such images. The photo was taken some years ago with a Nikon D90 and zoom lens set to about 24 mm (moderate wide angle), f/4.8 and 10 s exposure at ISO 1600. Slight trailing of stars is noticeable. The shot is toward the west in the evening and clearly the sky is not yet fully dark. The diagonal streak across the image is a contrail, and the "UFO" at bottom is the crossarm of a power pole. Despite not pushing the limit of the camera, the modestly priced lens, and the amount of light still in the sky, close examination of the Pleiades (just above the crossarm) shows stars well beyond what a naked eye can see under a dark sky. A plate solver could be useful for star identification in a photographic lunar distance measurement if the solver is not bothered by the Moon. However, I haven't tried that. https://nova.astrometry.net/user_images/10193987#annotated -- Paul Hirose sofajpl.com
