5 replies to this topic

[jokrausdu]

Wondering if any atlases or books will be moving to a new epoch? If so, which ones?

 

With more and more people using digital atlases, will printed matter even come out for Epoch 2025 or 2050? (I still like using paper atlases.)

 

Sorry if this has already been discussed. Links to discussions would be welcomed.

[triplemon]

You can print yourself a chart or calculate positions using whatever epoch you want ... if no other publication publishes coordinates in the epoch you need for your chart - its a bit pointless.

 

Historically charts were made using B1900, B1950 and J2000. So odds are no one will care much about anything but J2050. I think adopting the next "standard" epoch is also usually slow. IIRC (and its a while since...) in the 80ies and even 90ies much still refered to B1950. I suspect folks might abolish changing epoch entirely, as for any precision telecope pointing you'll have to transform to current equinox, anyways. So there is really less and less benefit of using coordinates that are close to but not exactly current equinox.

 

The astrometry folks also have given up on adjusting anything to our solar system, actually even to our galaxy. All that unstable junk moves too much by todays precision standards ... They go by extra galactic radio sources and their ICRS system, essentially J2000, is fixed forever. Wait, 'currently foreseeable future".

Edited by triplemon, 21 November 2023 - 12:52 PM.

[beggarly]

http://faraday.uwyo....douts/51605.pdf Quote: "It is possible that in our lifetimes the International
Astronomical Union will initiate a switch to J2050.0 coordinates".

 

https://syrte.obspm....e_com8_ga06.pdf Quote: "But ICRS is permanently frozen, close (~23mas) to the J2000 mean equator and equinox. There will never be a change to J2050 (and we no longer have to say “ J2000” )."

 

ICRS: https://aa.usno.navy.mil/faq/ICRS_doc

https://en.wikipedia...ts_realizations

[Tony Flanders]

Why would you care? The sky looks just the same regardless of how the coordinate grid is oriented. Old atlases printed with 1950 coordinates are every bit as useful as one printed with 2000 coordinates.

[gmiller123456]

Why would you care? The sky looks just the same regardless of how the coordinate grid is oriented. Old atlases printed with 1950 coordinates are every bit as useful as one printed with 2000 coordinates.

If someone gives you the coordinates of an asteroid in J2000 coordinates, and you try to locate it using a B1900 chart, you're going to have a bad time.

The "old" system of tying the coorinate system to the equinox was done primarily to make celestial navigation easier. Since celestial navigation isn't used much now, there's no need to keep it tied to the equinox.

The new ICRS system was aligned to the J2000 system out of convinience. There is no mechanism or need to update it. Instead, computing power, and well define algorithms are relied on to produce "of date" coordinates when needed.

There really hasn't been enough time elapsed to tell if there would be a desireable reason to update it. Thousands of years from now a polar aligned scope could slew its RA axis and actually have more of a change in Dec than RA.

[yuzameh]

If someone gives you the coordinates of an asteroid in J2000 coordinates, and you try to locate it using a B1900 chart, you're going to have a bad time.

The "old" system of tying the coorinate system to the equinox was done primarily to make celestial navigation easier. Since celestial navigation isn't used much now, there's no need to keep it tied to the equinox.

The new ICRS system was aligned to the J2000 system out of convinience. There is no mechanism or need to update it. Instead, computing power, and well define algorithms are relied on to produce "of date" coordinates when needed.

There really hasn't been enough time elapsed to tell if there would be a desireable reason to update it. Thousands of years from now a polar aligned scope could slew its RA axis and actually have more of a change in Dec than RA.

Not only asteroids, but also transients, especially confirmation of faint ones, which need good astrometry for confirmation purposes.

 

Unfortunately my old planetary and charting software doesn't have an ICRS/ICRF option.

 

However, it DOES allow correction for epoch from 2000.0 using proper motions and as ICRS is equinox aligned to J2000.0, it is still viable.

 

It's no longer updated but has utility beyond any other I've ever seen or heard of, including customisation capabilities for personal use.  It can also show me epoch 1910 if I need it to, which I did yesterday.