[Placidus (Mike and Trish)]

Originally Posted by andyc

Was that using the NED? It's been on my list to tidy up an image of NGC1365 that has about a dozen quasars in the background. I located them a bit laboriously with NED and Sky-Map, but it was still pretty exciting to image a tiny speck of light that has a redshift of 3.17, from only 2 billion years after the Big Bang, and a co-moving distance of 21 billion light-years away, all from the backyard! NED is great because you can confirm you've identified the right speck, then get cosmological data if you want.

NED seems patchy on quasar distribution (??), or at least my selective searches around the few galaxies I've imaged, like M83, produced far fewer hits than NGC1365 - and I'd presume that the quasar distribution isn't that anisotropic!

Hi, Andy,

My further researches discovered:

https://.heasarc.gsfc.nasa.gov/W3Browse/all/milliquas.html

where you can enter the RA/Dec of the centre of your image and a search radius, and it produces a table. I found it easiest to save the "printer friendly" version. I then precessed the table from J2K to the current equinox, and plotted them along with the Tycho I star catalogue. I then used PhotoShop to superimpose the plot over the photo. Confident that there are packages out there to do all this, but it's part of the hobby for me to do all the maths myself.

As you said, the distribution of the sky that they have surveyed is extremely patchy. That's partly because you can't find quasars against the milky way background, so they've chosen very carefully where to look. But even round NGC 5792, they just happen to have surveyed the southern half of our image, and not the northern half !!!

Originally Posted by RickS

Interesting image, M&T, and good to see some unusual objects in the field!

Cheers,
Rick.

Thanks Rick.

Originally Posted by Bassnut

Thats a brilliant shot Mike n Trish, tack sharp and excellent star colour. Unusual and great to see other quasars in it. Deep indeed.

Thanks, Fred. I'm cobbling up the 35 quasar version for posting tomorrow.

Cheers,
Mike