Trans-Neptunian Objects.

[Xilman]

Starting this thread for the posting of images and discussion of trans-Neptunian objects such as plutinos, Kuiper Belt Objects (KBOs), Scattered Disc Objects (SDOs), Cubewanos and other such members of the zoo. A whole bunch are within range of amateur imaging and one, Pluto, can be see visually in, say, a 30cm reflector. The BAA Handbook contains a list of the brightest TNOs each year.

There appears not to be a sub-forum for these beasties and "planetary" appears to be the least inappropriate option. If the powers-that-be would like to create one and move this thread there ...

[Xilman]

 

To get things started, here is an image of (20000) Varuna taken on 2023-02-20. 177x30-second subs were taken with an unfiltered SX814 camera attached to a 40cm Dilworth. The subs were stacked on the stars because the KBO moved less than 5 arcsec during the observation. (Incidentally, that's an advantage of imaging TBOs because they move so slowly, even at opposition.) The position (08:42:04, +27:15:24), motion (3 arcsec / hour), predicted magnitude (V=20.3), distance (44.1 AU) , and so forth obtained from the MPC facility at https://minorplanetcenter.net/iau/MPEph/MPEph.html

Incidentally, most of the objects of comparable brightness to (20000) Varuna are background galaxies and not stars. Some can be seen to be elongated and/or diffuse in appearance.

[Paul M]

Fascinating subject Paul, we've discussed it a few times in the past and I just happened to to look at some of your other images of far-flung Solar System objects on your web pages a couple of days ago.

I hope to capture a few before spring gives way to summer.

[Xilman]

12 hours ago, Paul M said:

Fascinating subject Paul, we've discussed it a few times in the past and I just happened to to look at some of your other images of far-flung Solar System objects on your web pages a couple of days ago.

I hope to capture a few before spring gives way to summer.

If you check the BAA Handbook you will find a few close to or somewhat past opposition (so visible in the evening sky) and at a fairly northern declination.Over a year there appear to be 12 which reach mag 20.0 or brighter, which should be within range of a single night's observation with a 20cm or larger. This estimate is based on the facts that my 40cm has four times the collecting area and took 85 minutes to reach mag 20.3 with ease.

Good luck with your project and please display your achievements here.

Edited February 23 by Xilman
Fix typoo

[Xilman]

 

This is the magnificently named (229762) Gǃkúnǁʼhòmdímà.  It is a Scattered-Disk Object, meaning it orbits the sun in an eccentric (e=0.4843) and highly inclined (i=23.378 degrees) orbit.At the time of observations (2023-02-23) it was 40.95 AU from the earth and magnitude 19.8.  The image shows a very small trail of the SDO, which may be compared with the circular appearance of stars of similar brightness.

Technical details: 0.4m Dilworth, unfiltered SX814 CCD camera. 2790s exposure in 93 subs of 30s each.

 

(No I can't pronounce the name, despite having heard it spoken.  It will always be (229762) to me.)

Edited February 24 by Xilman
Fix Tyop

[Paul M]

3 hours ago, Xilman said:

This is the magnificently named (229762) Gǃkúnǁʼhòmdímà.

So I assumed that at least part of that name was a typo!

Not so. I'm currently using my Ubuntu lappy and KStars found it for me. Only got my Mak 127 to hand so I'll I'll give it a miss tonight!

For those itching to beat me to it, it's accessible in the early evenings. It has a different designation in the catalogue used KStars but I'm sure it's the same object!!

[Xilman]

 

This one is (90482) Orcus.  according to the MPC it was magnitude 19.1 and 48AU away from us at the time of observation.

Technical details: 5160s unfiltered exposure with a SX 814 Pro on a 0.4m Dilworth.  Mid exposure at 2023 Mar 15 - 00:35

Apologies for the poor tracking.  Deconvolution will remove that but will also require a round tuit which I don't presently have available.

At least one more TNO to come in the next few days, DV.

 

 

Edited Saturday at 22:32 by Xilman

[Paul M]

33 minutes ago, Xilman said:

This one is (90482) Orcus.  according to the MPC it was magnitude 19.1

Very well done again.

I just looked this one up. It culminates at about 24 deg in the late evening, down there in the "nonstellations" below Leo,  so very accessible logistically for me but my southern sky is my brightest so mag 19.1 is a bit of a push.

Right now my problem is cloud cover. It's been dreadful lately. My list of potential Trans Neptunian targets is currently infinitely larger than my list of successes.  Unless we're calling Pluto a TNO? Surely not...

[Xilman]

11 hours ago, Paul M said:

Unless we're calling Pluto a TNO? Surely not...

(134340) Pluto is undoubtedly a TNO. The largest by diameter and second by absolute magnitude because although (136199) Eris is a few kilometers smaller it has a markedly higer albedo.

If you would like to try for objects at higher declination, you may wish to consider (136472) Makemake and (136108) Haumea. Both are coming to opposition in the next month and both are 17th magnitude.