Archive for the 'Stellar Mapping' Category

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[Stellar Mapping] Historical Datasets (Yale & Gliese3)

As part of this weekend’s update to my Stellar Mapping page (more details about that will be in the next post), I’ve decided to move the Historical datasets (Yale and Gliese3) onto a blog post since they’re no longer accurate and probably aren’t being used much anyway (there’s a link from the Stellar Mapping page to this blog post). So, here they are!

Historical Datasets

Historical databases should not be considered “accurate” by modern standards, and have been largely superseded by the ones listed in the “Accurate Datasets” section. The full Yale and Gliese catalogues have been clipped at 300 ly from Sol.

Yale Trigonometric Parallaxes, Fourth Edition: The Yale catalogue (a.k.a the General Catalogue of Trigonometric Parallaxes, or GCTP) is a historical dataset that was one of the most accurate near star catalogues before Hipparcos, with parallax measurements taken from the ground-based observations. It includes many fainter stars that are not in the Hipparcos catalogue, but the distance accuracy is much lower. It also include many stars that are in the Hipparcos catalogue, but because of the lower accuracy they are somewhat shifted from their Hipparcos-derived positions – the difference increases with distance from Sol. However, the Yale catalogue does include Spectral data for most stars. As such, the Yale and Hipparcos catalogues should NOT be combined.

Source: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=I/238A/picat.
Number of star systems: 6,051
Distance range: 22.8 – 300 lightyears from Sol.
Accuracy: Positional data are less accurate than Hipparcos, but spectral data is included. Physical data are not accurate. All stars are listed as single stars.

 

Gliese Nearby Stars, Preliminary 3rd Version: The Gliese catalogue is one of the “classic” historical star catalogues – it was updated in 1991, and includes all stars known at the time within 25 pc of Sol, and a few that are further out. It has low accuracy, but again includes some of the dimmer stars that Hipparcos does not include. The 2300AD star map is apparently based on the 2nd version of this catalogue.

Source: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=V/70A.
Number of star systems: 3,667
Distance range: 22.8 – 300 lightyears from Sol.
Accuracy: Positional data are less accurate than Hipparcos, but spectral data is included. Physical data are not accurate. All stars are listed as single stars.

[Stellar Mapping] Extended Hipparcos dataset added!

I’ve now replaced the New Reduction Hipparcos data with the new Extended Hipparcos (HIPX) dataset published in 2012 by Anderson & Francis (see this paper for all the details). The HIPX dataset expands the original dataset to include luminosities, spectral types and much more useful astronomical data from a variety of sources, making this the definitive source of information about these stars! The searchable online HIPX catalogue is located at http://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=+V/137A/XHIP.

The HIPX data replaces the New Reduction Hipparcos data on this website – Astrosynthesis and Galactic XYZ data have both been updated! In most cases the HIPX XYZ data is identical to the New Reduction Hipparcos XYZs, but issues with the parallaxes for some of the multiple systems in the New Reduction data led to significant inaccuracies there – in those cases, the parallaxes were reverted back to the original Hipparcos parallax data (again, refer to the XHIP paper for further explanation).

The XHIP data includes more star names (including common/arabic names), which are also presented here. However, note that Gliese numbers higher than 3000 have been removed for ease of reference. Technically these numbers aren’t “Gliese numbers”, they’re “NN” or “Wo(oley)” numbers. Because this could cause confusion, I decided to remove them instead of editing them all, but this isn’t a huge loss since the stars can still be tracked using their HIP numbers or other names.

If you’ve been using the New Reduction data, then be sure to head over to my Stellar Mapping page to download the new Extended Hipparcos dataset!

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In other news, my Stellar Mapping page now has the Atomic Rockets Seal of Approval! This is Winchell Chung’s way of saying that he likes my work, and I’m very happy about that because I’ve been a fan of his Atomic Rockets website pretty much since it first appeared online (it’s a great resource for any SF fan)! His 3D Starmaps site is also one of the main inspirations for my own stellar mapping efforts! Thanks, Winchell! 🙂

[Stellar Mapping] CTIOPI dataset added, Stellar Mapping page reorganised!

I have now added the CTIOPI (Cerro Tololo Interamerican Observatory Parallax Investigation) dataset to my Stellar Mapping page! CTIOPI is another dataset from the RECONS group, aimed at locating red, white, and brown dwarfs that are within 25pc of Sol – it adds 164 stars that are mostly contained within 300 ly of Sol. However, it only covers (roughly) the southern sky as viewed from Earth, so only about half of the volume around Sol contains stars from this dataset – that said, the distribution of CTIOPI stars could be used as a guideline for adding fictional stars in the rest of the volume.

CTIOPI dataset, looking corewards.

I have also edited the DENSE dataset to remove all the stars that were duplicated in CTIOPI and HIPPARCOS datasets – the most accurate data has been retained (the original DENSE dataset is no longer available here, though I may make it available again in a later blog update). The CTIOPI dataset has also been edited somewhat to remove duplicates (none of the CTIOPI stars have HIP numbers though, though it does include one star – HIP 3856 – that is missing from the Hipparcos dataset). All CTIOPI entries within 22.7 lightyears have also been removed to avoid overlap with RECONS.

This means that there should now be no duplicated stars at all if the RECONS, DENSE, CTIOPI and HIPPARCOS datasets are used together, so the combined dataset is now about as accurate as it can be. Full details of these edits can be found in the “CTIOPI-DENSE merging details” section in the Astrosynthesis.txt and Galactic.txt files contained in the new RECONS-DENSE-CTIOPI.zip file available from Section 2 of the Stellar Mapping page.

I’ve also updated and reorganised the Stellar Mapping page to (hopefully) make it easier to decide which datasets to use. If you have already downloaded the DENSE dataset then you should download it again to make sure you have the latest version!

[Stellar Mapping] The 2300AD Near Star Map

The 2300AD Near Star Map

The 2300AD RPG – originally published by Game Designer’s Workshop in 1988 – presented an excellent gritty, realistic near-future hard sci-fi setting with lots of exploration, mystery, and interesting aliens. It’s also about to be republished by Mongoose Publishing as a setting for their version of the Traveller RPG!

One of 2300AD’s most interesting features is that the setting is built around a realistic (for the 1980s) Near Star List based on the Gliese Catalogue (2nd Version). FTL travel in 2300AD has a maximum range of 7.7 lightyears, resulting in the creation of “Arms” that extend from Sol to connect only the stars that are within this range of eachother (this limit can potentially be extended to 11.55 ly using Stutterwarp tugs, but this is expensive and uncommon).

There are three of these Arms, each colonised by a different political power in the setting – the French Arm, the Chinese Arm, and the American Arm. The French Arm stretches “upwards” from Sol towards Galactic North, ending at the orange giant star Arcturus. The American and Chinese Arms share the same beginning, but split off so that the American Arm heads Coreward/Spinward while the Chinese Arm sprawls around the (galactic) southern part of the solar neighbourhood.

Unfortunately the Near Star List (NSL) has not been updated for the new version of 2300AD. A lot of stars have been discovered in the solar neighbourhood since the late 1980s (as shown on my Stellar Mapping page), and the locations and distances of existing stars have been greatly refined since then too – so how does the updated stellar data affect the Arms?
Continue reading ‘[Stellar Mapping] The 2300AD Near Star Map’

[Stellar Mapping] RECONS list updated!

Oops! Gliese 667 slipped through the cracks and wasn’t included in any of the original stellar datasets on my Stellar Mapping page! This is slightly embarrassing since it’s a bit famous for having planets around it! It was within 22.8 ly from Sol, but for some reason wasn’t on the RECONS list – and because it was so close it wasn’t included in the Hipparcos dataset either.

I’ve now added Gliese 667 to the RECONS CSV files, so if you’ve already downloaded the RECONS data, you’ll need to download the new version so you can include Gliese 667! (I only found it because I was checking the stars on the American Arm for 2300AD!). There shouldn’t be any other missing stars there – I checked the border between RECONS and HIP and couldn’t find any other HIP stars within 22.8 ly that weren’t already on the RECONS list.

[Stellar Mapping] How to make your own stellar database!

Looks like my new Stellar Mapping page has been well received so far – thanks to everyone who has shown an interest in it, I hope you’re finding it useful!

In this article I’m going to show you how to make your own stellar database, with the same tools I used to construct the ones I presented on my mapping page. For this exercise we’ll be relying on something called VizieR, which is a huge online database of thousands of star catalogues. You’ll need to have a basic understanding astronomy to make the most out of this, but it’s not that tricky.

Let’s say you want to make a database of stars in a corridor between Sol and the famous Pleiades star cluster (if you’re familiar with the 2300AD RPG, this is essentially the path the Bayern took to the Pleiades). We’ll be using the Hipparcos star catalogue, since it has the most accurate parallax measurements (from which we can derive distances).

Continue reading ‘[Stellar Mapping] How to make your own stellar database!’

Website Update: Stellar Mapping page updated!

My new Stellar Mapping page is finally online! This is a complete rewrite of my previous “Realistic Astrography” page, and now includes Equatorial to Galactic co-ordinate conversion files, the complete RECONS (2012) and DENSE star lists, as well as all the data from the Hipparcos, Gliese 3, and Yale catalogues for stars out to 300ly from Sol! And the Further Stars list is also in there too 🙂

RECONS-coreward

RECONS dataset, looking towards the galactic core.

The focus has moved away from Traveller and its hex map format (I realised that I was taking accurate data and then making it inaccurate by forcing it into hex map format, so I’ve dropped that completely) and moved towards raw data and Astrosynthesis, but this will still be very useful for anyone interested in using realistic data for the stars near Sol.

You can check it out at http://evildrganymede.net/wp/rpgs/stellar-mapping/

I’ll be writing some articles in the coming weeks to expand this – this will include how to use the Vizier stellar databases, and what this means for the 2300AD RPG!

Website update: Further Stars List uploaded!

EDIT: This has been superseded by my new Stellar Mapping page!

I’ve finally added the “Further Star List” to my Realistic Near-Sol Astrography webpage – it’s an excel file containing accurate locations of a selection of major stars (including Vega, Deneb, 51 Pegasi, Spica, Bellatrix and Algol) that are more than 10pc from Sol.

The format is a bit raw (and I’m not entirely sure why I selected those specific stars to list!). The dark red X/Y/Z columns show the distances in each direction (Sol is the origin, +X is Coreward, +Y is Spinward, +Z is “above” Sol). If you have trouble interpreting it, let me know!

You can doublecheck the stars too – you can use the Convert spreadsheet in Section 1 of the mapping page to convert the RA/Dec of any stars into X/Y/Z coordinates. If you have astronomy software like Celestia, open it up and activate the Galactic Grid and rotate it so that you’re facing 0° latitude and 0° longitude – you’re now looking directly along the +X axis. Turn to look at 0° Lat, 90° Lon and you’re looking directly along the +Y axis. Look at the Galactic north pole, and you’re looking directly along the +Z axis. You should be able to find your stars using this (e.g. Aldebaran is pretty much directly along the -X direction, and down a bit on the Z axis. Look towards 180° Lon direction and -20° Lat, and there it is!).

I’ve been sitting on this for six and a half years (!!) and finally decided that I’m never going to draw hexmaps showing these stars, so I may as well just release the data and let other people figure it out! Enjoy! 🙂

The link is at http://evildrganymede.net/wp/rpgs/stellar-mapping/.