Astrobin EPOCH (J2000 or JNow)?


#1

Hello,

I always use reference images from Astrobin.com for the purpose of slewing to DSO (“Slew Now” ) and centering DSOs (“Center Now”). I am curious what EPOCH (J2000 or JNow) does it use when it fills in RA and Dec coordinates after running a plate solve? I use ANSVR Astrometry.net and it does not matter whether J2000 or JNow is set in ANSVR configuration, I always get the exact same coordinates for both EPOCHs.

Thanks,
Peter


#2

Elbrus returns J2000.


#3

Peter,
That’s a good question. I would assume the coordinates from Astrobin are J2000 since it uses Astrometry.net for the solves. I’ll have to verify this though.

Thanks,
Jared


#4

One way to tell would be to look at the coordinates that Astrobin returns for an object and compare them with something else that gives both JNow and J2000 coordinates for that object. It should be pretty obvious which are returned, the difference is currently about 11 arc minutes.


#5

I believe the coordinates returned from Astrobin is the center of the image, not necessary the coordinates of the object in the image. There are many images of same object at Astrobin but I am not sure if the coordinates will be the same if the object is not at the same exact location in the images.

This is a perfect example of NGC 3718 and it’s companion galaxy and neither galaxies are in the center of the image:

http://www.tamanti.it/Galaxies/NGC_3718.htm

That’s how I would want to frame if I were to image them and I hope Astrobin returns the RA/Dec coordinates from dead center of the image. The real question is whether Astrobin returns EPCOH of J2000 or JNow.

Correct me if I’m wrong.

Thanks,
Peter


#6

The position quoted on that web site is the J2000 coordinates of NGC 3718, not the centre of the image. It’s not from the AstroBin site though and can’t be imported into SGP, if you try SGP crashes.

If I take an image from Astrobin, such as this:
http://www.astrobin.com/126555/
and put it in SGP then I get the J2000 position 11:33:13, +53° 06’ 07", that’s the position of the centre of the image.

Chris


#7

Thanks Chris. I am at work and my company blocks Astrobin so I could not find samples of NGC 3718 there and provide Astrobin link so I had to search elsewhere.

So, it’s good to know that Astrobin returns J2000 to SGP.

Thanks,
Peter


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