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, 2023 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, 2023 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 March 18, 2023 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.

[Xilman]

 

This is (136472) Makemake which is a trans-Neptunian object over 52 AU from us --- markedly further than Pluto in other words. Magnitude 17.1 at the time of observation, 2023-01-21.

 

1380 seconds exposure in 45 subs.  All other details as above.

 

So good they named it twice.

 

[Xilman]

Doh!

I have nothing to declare but my incompetence.

2023-03-21 to be more accurate.  2023-03-21T02:00Z to be more precise (and more accurate, for that matter).

[Paul M]

43 minutes ago, Xilman said:

This is (136472) Makemake which is a trans-Neptunian object over 52 AU from us --- markedly further than Pluto in other words. Magnitude 17.1 at the time of observation, 2023-01-21.

Wow! A bright one! Easy, even

44 minutes ago, Xilman said:

2023-03-21 to be more accurate.  2023-03-21T02:00Z to be more precise (and more accurate, for that matter).

I always enjoy boring people with the distinction between precision and accuracy... 🤩

[Xilman]

2 hours ago, Paul M said:

I always enjoy boring people with the distinction between precision and accuracy... 🤩

Do you mean "I always like (boring people with the distinction)" or "I always like boring (people with the distinction)"?

That is, is "boring" a left or a right associative operator?

😉

 

[Paul M]

1 hour ago, Xilman said:

That is, is "boring" a left or a right associative operator?

😉

 

Oh, my head 🤣

I spend a *lot* of time with my two shift buddie. I know when I've overstepped the mark. I turn round and find that they have both left the room! 🤣

But seriously. The forecast for yesterday had been positive. I had a few faint targets in mind. Unfortunatley the sky hadn't seen the forecast! I didn't even get to set uo. It's looking like spring (galaxy season) will be a complete wipe out for me

[Xilman]

 

Another TNO lifted directly from the BAA Handbook table of these things.  This one is (136108) Haumea which was 50.1 AU away from us when imaged (2023-03-21T0300Z) and magnitude 17.3 according to the MPC ephemeris. A 1600 second exposure (less than half an hour) unfiltered on a 0.4m telescope was used but either a tenth of that time or sqrt(10) times that aperture --- which is around 5 inches --- would have been easily sufficient.

Given that I have seen images posted to SGL taken with a 80mm refractor which show 18th-magnitude objects in the Andromeda Galaxy  (so lots of background light to hide things), there really is no reason for imagers not to try for 17th-magnitude objects other than apathy or a lack of self-confidence. Agreed, visual observers of TNOs are likely limited to Pluto.

 

[Paul M]

I'll have a look at a couple of these later. They are in the area im concentrating on just now.

I'm currently pointing my 10" RC at the Cosmic Horseshoe, yeah, I know. the Moon is just a few degrees away and my chances are slim! But this might be my last clear night of the year...

[Paul M]

So I have at least one success from last night. Cosmic Horseshoe didn't go well. Just a bunch of noise.

My next object was TNO Makemake! 

I took 37 subs of 90 sec at gain 240 and -10C . i binned this 2x2 after the event. I was having an issue with my new guide scope. So a number os subs got dumped. This is  stack of 34 survivors.

All stacked and annotated with ASTAP.

I'm moderately chuffed at what I think is my furthest Solar System to date. Pluto-schmuto...

[Xilman]

 

For various reasons, (50000) Quaoar has always been a difficult object for me. It is fairly but not particularly bright these days (it is at V=18.8) but the real problem is that it lies in a very dense part of the Milky Way and 19th magnitude or brighter stars are only a few seconds of arc apart in that region. The TNO does move, but slowly, and you have to pick the right time to find it when it lies in a relatively clear spot. The image above is my first clear detection. It is around 13 arcs from the bright 16.1 magnitude star and about 3 arcsec from the nearer of the pair of ~19 magnitude stars.

Unfortunately I screwed up. Although 50 minutes of subs were taken it turned out that  for most of them the Peltier cooler was switched off and so all those subs were useless. The 29 usable subs, totalling 820 seconds, were stacked on Quaoar so the stars are slightly trailed. All subs taken by an unfiltered SX814 camera cooled to -10C and attached to a 0.4m Dilworth telescope. Imaging began at 2023-08-17T20:55.

The right hand pane shows the DSS field with the ephemeris position of Quaoar marked with a purple cross. The limiting magnitude in that image is about g=20.5.

 

[Xilman]

Hmm, just noticed something. Has anyone else? Look at the line of fairly bright stars at the 7 o'clock direction from Quaoar. There are four in my image but only three in the DSS2.

Checking the Gaia DR3 shows more information.  The "missing" star is Gaia DR3 4103983023994688768 which appears to be extremely red.  Its BP, G and RP magnitudes are 21.1, 16.16 and 14.43.  It is so faint in the blue that Gaia gives error bounds of 0.25 magnitudes whereas the others are good to 0.01 and 0.03 respectively.

 

Edited August 19, 2023 by Xilman
Add 2nd para.

[Paul M]

I finally got a suboptimal chance to try for (229762) Gǃkúnǁʼhòmdímà   I shortened it's name to Gunk in my subs...

Anyway, here I present another episode in my ocassional series; "Not..."

This is Not Gǃkúnǁʼhòmdímà. Close but no cigar. 31 x 300 sec with the RC250 + 0.8x flattener/reducer ASI071MC Pro. The moon was a few days after full, 01/12/23, so the sky was marginal at best for tracking down a mag 19+ TNO.

My image goes down to 19.1 but I don't think I got it. A close up of the indicated loaction shows a pixel or 2 above the noise just on the r/h edge of the box but I think it's noise. I referenced DSS images to confirm all other objects in the field.

Close crop of the area of interest. 

Not Gǃkúnǁʼhòmdímà on this Moonlit ocassion.

 

 

Edited December 2, 2023 by Paul M

[Xilman]

Paul: when was your image taken? The best I can determine from what you have posted is close to 2023-12-01T00:00Z.  My estimate is from the file name, part of the path being 11-30 and another being 12-01.

At that  time the TNO's position was 05:21:31.3 +03:57:07 according to the MPC, which is a long way outside that image. As near as I can make it, by using astrometry.net for putting a WCS on the image, the bounding box of your image is (05:22:25, +03:45:20) (05:23:04. +04:12:00).  That is, the Declination covers the range but the RA is too far east.

If, on the other hand, that box does indeed correspond to the position of (229762) your image must have been taken on November 14th or 15th.

 

[Paul M]

My subs ran between 01:19 and 03:58 on  01/12/2023

I got the position from SkySafari using a central time (not that it matters over the span of the subs) 02:07 giving: RA= 05:22:46.12  DEC = +03:58:32.2, which is where the box is. 

It seems that I didn't verify my coordinates with MPC or any other source. Looking at Stellarium it gives coords much closer to those you give from MPC and had I used them the target would have been in the field.

It's a definite miss, but if the camera had been rotated 90 deg then !Gunk would have just made it into the frame, waiting for you to correctly identify it! I just know it would have been there....

Oh well, a lesson learned. But SkySafari has been reliable in the past. 

 

 

[Paul M]

I'll post this here for anyone wanting to have a go in the next 3 weeks

That might be me!

[Xilman]

3 hours ago, Paul M said:

My subs ran between 01:19 and 03:58 on  01/12/2023

I got the position from SkySafari using a central time (not that it matters over the span of the subs) 02:07 giving: RA= 05:22:46.12  DEC = +03:58:32.2, which is where the box is. 

It seems that I didn't verify my coordinates with MPC or any other source. Looking at Stellarium it gives coords much closer to those you give from MPC and had I used them the target would have been in the field.

It's a definite miss, but if the camera had been rotated 90 deg then !Gunk would have just made it into the frame, waiting for you to correctly identify it! I just know it would have been there....

Oh well, a lesson learned. But SkySafari has been reliable in the past. 

 

 

You are very far from being the first to screw up in this fashion. I speak from experience 8-(

I didn't even have the excuse of a source providing me with a poor position when my first attempt to find AE And was half a degree away from its true position. That said, I did manage to image six globular clusters in M31 so the time wasn't entirely wasted.

It is always worth going to https://minorplanetcenter.net/iau/MPEph/MPEph.html or https://minorplanetcenter.net/iau/NatSats/NaturalSatellites.html, IMAO, depending on which you wish to observe,

Please try again. I am certain that you can find a goodly number of TNOs.

 

[Xilman]

4 hours ago, Paul M said:

My subs ran between 01:19 and 03:58 on  01/12/2023

I got the position from SkySafari using a central time (not that it matters over the span of the subs) 02:07 giving: RA= 05:22:46.12  DEC = +03:58:32.2, which is where the box is. 

It seems that I didn't verify my coordinates with MPC or any other source. Looking at Stellarium it gives coords much closer to those you give from MPC and had I used them the target would have been in the field.

It's a definite miss, but if the camera had been rotated 90 deg then !Gunk would have just made it into the frame, waiting for you to correctly identify it! I just know it would have been there....

Oh well, a lesson learned. But SkySafari has been reliable in the past. 

 

 

As Ronnie famously said, having learned it from, Mikhail Sergeyevich, "Trust but verify".