Re: Alignment options
Posted by
karenacollins on
Dec 17, 2020; 9:03am
URL: http://astroimagej.170.s1.nabble.com/Alignment-options-tp1471p1472.html
Hi, if your images are already plate-solved, for time-series
photometry I prefer the option you mentioned "Use RA/Dec to locate
aperture positions". In general you can leave centroid enabled also
to fine tune each apertures location in each image. Avoiding
aligning the images retains the x,y centroid information in case
that's helpful for post processing, or to measure the
tracking/guiding performance of your observation. This approach also
avoids the extract step of aligning the images. If your images are
not plate-solved, then you can avoid the plate-solving process by
aligning with aperture, but this step is not needed in this case
either unless your tracking jumps by more than 1 aperture radius
from image to image.
Karen
On 12/16/2020 4:09 PM, 7170 [via
AstroImageJ] wrote:
Hi, I'm confused about which alignment option is best to use for
different scenarios.
I can see the following ways of doing an alignment:
(1) Align stack using WCS
(2) Align stack using apertures
(3) Align stack using image stabilizer
I do two types of work (a) double stars and measuring PA and
distance between pairs, and (b) photometry on variable stars
(plotting light curves over time).
For double stars I have always aligned the stack using option (2)
and then combined them into a single image using average. And for
variables I used to align using (2) and then plot the light curve
using apertures. But more recently have note done an alignment but
used "Use RA/Dec to locate aperture positions" instead.
I am however wondering if this is an optimal approach for both
types of work or not - what do people recommend? One thing I have
noticed is that option two does warp the image slightly - namely
the x and y pixel scale is usually slightly different after plate
solving, yet that is not the case with (1).
Thanks in advance.