Lunar Parallax Demonstration Project

 LPDP - Parallax Results: Calculating Lunar Distance


01h20m 9th November 2003 Positional Maps

The diagrams below represent four images that were taken at 01h20m UT on the 9th of November 2003. The circle represents the Moon and the central cross, the position of the centre of the lunar disk at 01h20mUT.

A number of stars have been identified in the map (some positions are given at the bottom of the page): The final part of this project is the calculation of the distance to the Moon from the recorded observations. A number of the contributors have done their own calculations and worked out their own figures.

Rather than submit them here, the calculation will be left open for a while. Should any brave soul wish to submit their calculations and final value for the distance to the Moon, I will be happy to include the closest answer on this page.

Email your submissions to pete.lawrence@pbl33.co.uk with "PARALLAX" in the subject line.
 
 




Accuracy

It would be naive to assume that there were no errors in the processing procedure - there will be many. The parallax animations are pretty accurate in terms of position.

Inaccuracies will start to figure in the determination of the Moon's distance. So what are they likely to be?

Contributor timings
With the best will in the world, co-ordinating a number of images from people across the Earth to be taken at precisely the same time will be nearly impossible. Unless all contributors used atomic timing devices timing errors have to be assumed. However, I believe that the magnitude of these errors is small (plus or minus 5 seconds or an uncertainty of plus or minus 4 arcseconds in the position of the Moon due to timing).

Star positional accuracy
Some of the images had non-point stars. The degree of error here is small but still part of the error sum. In addition, my overlay technique require a degree of manual alignment for the overlay. I would estimate that the degree of error introduced by my alignment technique is of the same order of magnitude as that induced by the non-stellar star images. I would estimate the positional errors due to these effects to be in the order of plus or minus 18 arcseconds.

It should be pointed out that not all images exhibited non-point stars.

Marking accuracy
Although it looked pretty accurate to me, there is always an uncertainty as to the precise edge of the Moon. The edge of the Moon is not precisely smooth so the circle that was used to represent it cannot be assumed to follow it with 100% precision. I believe circle used to mark the Moon's disk (and hence the centre marker) is accurate to plus or minus 10 arcseconds.

Observer's position
Different observers report their latitude and longitude to different degrees of accuracy. Some calculate their position accurately from maps while others will gather them from public sources such as www.heavens-above.com which may not be precisely accurate (co-ordinates given will be for the nearest centre of population rather than the observer's observing site!). In addition, calculations should take into consideration the fact that no elevations have been quoted at this stage.

Measurement of the Moon's position from the maps provided
The very nature of measuring the Moons position from the graphics provided will be prone to error. How accurately can you measure something like this from a diagram?



Star Positional Data (refer to letters marked on upper map)
 
(A) Names and Catalog Numbers
Tycho catalog number: TYC 1224-346-1
Hipparcos number: HIP 13601
Henry Draper number: HD 18144
DM number: BD +15 0407
PPM number: PPM 118664
SAO number: SAO 93185

Tycho 2 Catalog Data

Equatorial coordinates (epoch J2000.0, ICRS)

RA: 02h 55m 17.4051s
Dec: +16° 18' 33.091"
 

(B) Names and Catalog Numbers
Tycho catalog number: TYC 1225-597-1
Hipparcos number: HIP 14098
Henry Draper number: HD 18783
DM number: BD +15 0425
PPM number: PPM 118760
SAO number: SAO 93243

Tycho 2 Catalog Data

Equatorial coordinates (epoch J2000.0, ICRS)

RA: 03h 01m 50.5909s
Dec: +16° 31' 04.948"
 

(C) Names and Catalog Numbers
Tycho catalog number: TYC 1224-1264-1
Hipparcos number: HIP 13509
Henry Draper number: HD 17996
DM number: BD +15 0401
PPM number: PPM 118645
SAO number: SAO 93170
WDS designation: HDS 370

Tycho 2 Catalog Data

Equatorial coordinates (epoch J2000.0, ICRS)

RA: 02h 53m 59.4361s
Dec: +16° 1' 13.568"
 

(D) Names and Catalog Numbers
Tycho catalog number: TYC 1224-967-1
PPM number: PPM 118643
SAO number: SAO 93168
Henry Draper number: HD 17997
DM number: BD +14 0485

Tycho 2 Catalog Data

Equatorial coordinates (epoch J2000.0, ICRS)

RA: 02h 53m 55.3679s
Dec: +15° 25' 37.486"
 

(E) Names and Catalog Numbers
Tycho catalog number: TYC 1224-1466-1
Hipparcos number: HIP 14048
Henry Draper number: HD 18717
DM number: BD +14 0502
PPM number: PPM 118749
SAO number: SAO 93235

Tycho 2 Catalog Data

Equatorial coordinates (epoch J2000.0, ICRS)

RA: 03h 00m 53.4622s
Dec: +15° 1' 52.240"



RA/Dec positions/map from SkyMap Pro


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