There are a few more QSOs that could be added to this list, which was, with one exception, restricted to those QSOs with published V brighter than 16.0, and with brightness at or very near the highest observed for a given or greater z, including lensed sources- in short they would be just about the easiest to detect for their red-shift distance or beyond.
There are z~3 QSOs in the list that appear slightly brighter than their published V mags would indicate, owing to a flux peak blueward of the V passband, but within a couple hundred nm of the scotopic sensitivity peak, or right on top of it. Also, even hyperlumoinous QSOs are variable within a fraction of a magnitude or so, and their light-curves are not well constrained, so you may be granted a slight flux bonus if you happen to catch them near peak. Here are some additional sources that I think merit a mention:
S5 0014+813 z~3.36 V~16.5 SMBH Possibly the largest known, and a Blazar.. Try to catch it in outburst!
HS 0747+471 z~3.20 V~16.4* scotopic mag about 15.8-16.0 due to VERY strong, phased lya/NV emission feature (the peak of the "big blue bump"), similar to that of SBS 1425+606
CSO 38 z~2.62 V~16.0
HS 1103+6416 z~2.23 V~15.8
HS 1700+6416 z~2.72 V~16.1
HS 1626+6433 z~2.30 V~15.8
HI all; I though I'd add a newly discovered HLQSO to this list. This one is near record in several categories, including an estmated SMBH mass of ~27,000,0000,000 Suns and a bolometric (total) estimated luminosity of just over 10^15 Solar luminosity. The source name is 2MASS J13260399+7023462, V~16.1, z~2.89.
This source was identified using modern photometric template methods for deep QSO surveys; Multiple passbands across the visible and infrared (Pan-STARRS and WISE) are used (QSOS by their relative broad-band intensities are seen to show a color space "track" that differs -albeit only slightly- from most main sequence stars) and thus a candidate list is produced; the likeliest candidates (among millions) are then chosen for spectroscopic follow up, which remains the only way to firmly distinguish a "bright" QSO from the myriads of faint stars, and spectra is also needed to determine a QSO's red-shift.
At this stage of the game, the search for new QSOs and especially lensed QSOs is concentrated beyond z>5, (which no amateur can ever hope to see -due to Lyman-forest absorbtion of the extreme rest-frame UV emission, sought by science for its value in determining the structure of the early universe). So, new, optically bright QSO discoveries in the z=2-4 range have been few.
Among HLQSOs the majority were identified by Schmidt-prism surveys, and there are perhaps only a dozen or even less that remain yet to be identified. We don't yet know whether many (or all) of the sum of remaining HLQSOs may be hidden behind brighter foreground stars or Galactic dust in the disk of our own Galaxy; but it remains likely that at least a few are probably still just hiding in plain sight, Beyond the the halo or closer to the plain of the Milky Way, certainly not at all easy to spot among overwhelming numbers of faint, twinkling stars, yet quite visible and subject to possible confirmation.
For myself, it's good to know that even though a newly discovered ancient AGN as bright as One Thousand Quadrillion Suns may not even make the evening news anymore; -yet there are still teams of individuals working with an awesome array of tools and talent, cooperating to complete mankind's ongoing census of these extraordinary denizens of the Early Universe; Its neat that new ones are still to be found, and its great to have a really big dob, so I can go take a look.
The Discovery paper is fresh (June 2020); calculus-free, well worth a brief read:
Stay safe and Be well, Aight?
Edited by quazy4quasars, 11 August 2020 - 01:58 PM.