2023 DZ2

[Dennis]

Hi BMD

No worries, I enjoy getting outdoors and grabbing these images, that's the easy part.

The maths and orbital mechanics, I'll leave to Greg, ST4, Phil and yourself.

I identified stars down to mag 19.4 in the fully stacked images, who'd have thought this was possible from my Bortle6/7 skies.

Cheers

Dennis

[Dennis]

>snip

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Dennis, were you able to get any images a couple days later (March 25) when it was moving 4'/min and magnitude 11-12?

Hi BMD

No - Fri, Sat & Sun were all clouded out and raining, so I was so glad that the clouds cleared for a period on the Thursday 23/03/2023.

Cheers

Dennis

[Dennis]

I set up SkyTools 4 Visual for my Location, Date, Time, etc. and plotted the position of 2023 DZ2 and then took a screen capture and overlaid it on my image (using the bright stars) and it shows a 25 arcsec difference and slight time offset of the trail.

Here is the composite image. I measured the number of pixels using the Ruler Tool in PS CC and multiplied this by 0.357 arcs/pixel and got approx. 25 arcsecs.
 
Tak Mewlon 210 F11.5 with Tak x0.8 Reducer
Focal Length 2170mm at F10.3 (from plate solve).
QHY268M Pro BIN 1x1 (3.76 microns).
74 x 30 secs
Image Scale: 0.357 arcsec/px
UTC: 2023-03-23T09:46 to 2023-03-23T10:28
 
I’m not sure if I have made a mistake in one or more of the settings, as previously ST4 has been spot on for all NEO's that I have managed to record.?
 
Cheers
 
Dennis

   

[bigmasterdrago]

That's the way I'm always expecting it to work. I'm curious if you did the copy/paste of osculating elements (Horizons) or did as Phil suggested and do the MPC NEA Today download? I did the Horizons thing and it was near spot on best I could tell. However in the case of your March 25 image, I got the osculating elements for your image date the next day but for your date/time. Hope that makes sense.

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Dennis, I did notice a difference in the rock's trail length in this image. It appears longer than the image you posted earlier. This one seems to have the asteroids trail passing over the LEDA galaxy.

Looking closely at the image and overlay of the ST track, I'm guessing the total displacement error, considering time and offset, is ~2.5 arc minutes. Does that look about right? For me, the error is much smaller when using the osculating elements gathered from Horizons. At most, a few arc seconds.

[Dennis]

That's the way I'm always expecting it to work. I'm curious if you did the copy/paste of osculating elements (Horizons) or did as Phil suggested and do the MPC NEA Today download? I did the Horizons thing and it was near spot on best I could tell. However in the case of your March 25 image, I got the osculating elements for your image date the next day but for your date/time. Hope that makes sense.

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Dennis, I did notice a difference in the rock's trail length in this image. It appears longer than the image you posted earlier. This one seems to have the asteroids trail passing over the LEDA galaxy.

Looking closely at the image and overlay of the ST track, I'm guessing the total displacement error, considering time and offset, is ~2.5 arc minutes. Does that look about right? For me, the error is much smaller when using the osculating elements gathered from Horizons. At most, a few arc seconds.

Hi BMD

The overlaid composite image in that post (#33) was based on the download of the NEA's from the MPC ( downloaded 29/03/2023) in ST4.

This new image (attached) is a composite of the NEA download in ST4 using Astorb.dat (downloaded 30/03/2023) and shows a slightly different path.

I wouldn't put too much faith in the length of the image trail in my underlying images, as the Blend IF operation in PS CC to blend in the trail can sometimes add or subtract fainter pixels from the BG that are close in value to the path, depending on the settings.

Cheers

Dennis

   

[PMSchu]

Hi Dennis,

Do you download the MPC's NEAs at Today's Epoch file or the regular NEA file? The NEAs at Today's Epoch file is the one to use I think. Otherwise you may get the standard epoch that's currently 2023 Feb 25 0000 UT.

Phil S.

[Dennis]

Hi Dennis,

Do you download the MPC's NEAs at Today's Epoch file or the regular NEA file? The NEAs at Today's Epoch file is the one to use I think. Otherwise you may get the standard epoch that's currently 2023 Feb 25 0000 UT.

Phil S.

Hi Phil

It looks like Astorb.dat and the MPC NEA Today's Epoch produce quite different results?

I have attached the plots from Astorb.dat and MPC NEA Today's Epoch, with inserts showing the source data files used. I have also circled the date/time and location data.

Prior to this, I used the ST4 Function to delete all minor planets and then imported the NEA's again.

Cheers

Dennis

Astorb.data plot
   

MPC NEA Today's Epoch Plot
   

[bigmasterdrago]

I have no idea why ASTORB is closer.

Unfortunately, today is March 29. The elements from the MPC NEA Today will be far to out of date for SkyTools to use to make a plot for March 23 for a NEA as close as 2023 DZ2. Skytools would need to be able to plot the asteroids path with respect to the gravitational perturbations of both the Earth, Moon and Sun. It has no way to do that. Only 2-body (Sun-asteroid).

Try using these elements for the 10UT March 23 time frame:

2460026.916666667 = A.D. 2023-Mar-23 10:00:00.0000 TDB
EC= 5.412693910313859E-01 QR= 9.938098514947397E-01 IN= 8.192821214186695E-02
OM= 1.878509095935977E+02 W = 6.035004241916181E+00 Tp= 2460036.865521614440
N = 3.090905354830167E-01 MA= 3.569249030966974E+02 TA= 3.477779810230076E+02
A = 2.166434574159261E+00 AD= 3.339059296823782E+00 PR= 1.164707290171234E+03

Instructions are:
https://skyhound.com/forums/showthread.php?tid=2419

but you will simply edit those for 2023 DZ2 by pasting them in to the edit minor planet field. Make sure to insert the name, H and G since they will be blank.

[PMSchu]

Dennis,

You can see the epoch of the elements that SkyTools is using in the Object Info dialog at the bottom of the Orbit/Physical Data section. Note that the date shown is for the evening of the day of observation, but the elements in the MP database from MPC or Lowell are for midnight. If the OI lists the elements as 2023 Mar 29, the MP DB will show 2023 Mar 30 0000 UT. 

ST4v allows only one set of elements per 200 day interval, so unless you saved the MPC's NEA Today elements for 2023 Mar 23 there currently isn't a way to get them back using a file download. The MPC does maintain files of NEO elements for Today ±15 days, but ST4 doesn't support downloading those under user control currently. That would be a VERY niche functionality & probably not worth Greg's time to implement. The Log function does save a copy of MP elements for later use, but I'm not sure if that would work here either.

The plotted positions for the 2 sets of elements are so different that I can't see any overlaps to judge how far they're displaced.

We could use the trick that we used a few years ago to add addional element sets to 2023 DZ2. Edit the MP DB to add new MPs with designations 2023 DZ2a, 2023 DZ2b, etc with elements from HORIZONS with the desired epoch dates. ST4v used to accept MPs with these designations without any problems. That would show how the changing elements affect the predicted positions.

Phil S.

[bigmasterdrago]

Greg went to a lot of work to get SkyTools to use any element set (epoch) we want. Anytime. If you go to https://ssd.jpl.nasa.gov/horizons/app.html#/, make sure that the element type: is Osculating Orbital Elements, Choose your Target Body: 2023 DZ2, Coordinate Center: Sun, Time you want the element set for, and make sure #5 is set for your custom settings, Output Units: AU and Days. It will give you a set to edit into the MP edit box. Just do a simple copy and paste of the full output like I mentioned above and make sure to enter the name, H & G.

Save it, then go to that date and time for the position ephemeris and object that you edited. Run it for a period within a few hours of that epoch. If the rock is really close (<1LD) stay very close to the elements epoch time.

Here is a sample output for the small rock 2023 FY3 when it was less than 1.5LD away.    

Use the 1:00TDB time, not the one marked in blue (sample time only). You can paste it in, then run an ephem for that time and compare to the position output at Horizons.

My ephem in ST4v is only a few seconds off. Although it is a bit time consuming and condifluted to manage, it works very well for those stinking small close pass rocks.

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Just to show how precise or accurate ST4 can be with a lot of massaging and additional input, I ran the ephemeris for 2023 FY3 just now for the date very near the close pass (March 24 20:00CDT) when just 1.456751LD (559977.8Km) away from my yard. Compare those from ST4v and those from Horizons: