The UCAC4 is the best star catalogue for stars to Mag(R)=16. It's error varies between 15 and 100 mas depending of the magnitude. (http://arxiv.org/abs/1212.6182), but if the stars you are using is bright, you can use Tycho-2 Catalogue.

Thanks Altair, yes I want to go to R~13-14, so UCAC4 is good. Thanks for the reference. I can't access www.usno.navy.mil from here for some or other reason.

UCAC4 is available from vizier.u-strasbg.fr. If you need the positions of many stars, you should be able to do a batch query.

Thanks Paul found it there. You are not perhaps the Paul Barret who worked at SAAO in the 1980s?

UCAC4 is good, you can use also 2MASS :)

Thanks, yes 2MASS is good, have been looking at it.

L.C. welcome :)

Altair Gomes Js is right. It really depends on your task. UCAC4 is the best astrometric calibrator for relatively large FOVs (10 arcmins and more) in the case of target magnitude is within 10 - 16 mag. For more faint objects astrometric data (stellar positions) form SDSS or another suitable modern sky survey is not bad solution.

Thanks Maxim, will have a look at SDSS.

Hi,

for automatic queries to several catalogs (including UCAC4) and to much more information store in CDS, I would suggest to use the "cdsclient":

http://cdsarc.u-strasbg.fr/doc/cdsclient.html

Cheers!

Thanks Jesús , will have a look at it.

We've been using from the early UCAC to UCAC4 for proper motion measurements. Note that it is a merged catalog, in the sense that some entries are replaced with values taken from other measurements if they were considered "better". For out latest work, we use PPMXL for its sensitivity and accurate proper motion data.

Thanks Wen-Ping, for my application proper motion accuracy is very important, I see that proper motions are absolute in the ICRF.

Yes, PPMXL turns out very useful. As you probably know already, the catalog (also merged) includes 2MASS magnitudes for bright sources.

This question is critical for those of us who observe occultations of stars by asteroids. Before ESA's HIPPARCOS mission, special efforts were needed to obtain astrometry that was good enough to predict these events. With the subsequent catalogs that are ultimately based on HIPPARCOS results for their reference frame, our work has blossomed, but as we move farther from the 1991 mean HIPPARCOS epoch, the errors in proper motions are accumulating and limiting what we can do. The best catalogs are FK6 and HIP2, but of course they have relatively few stars. For the large number of fainter stars, we use UCAC4 (and UCAC2 before that), but also check PPMX and PPMXL for differences for individual stars, and sometimes we need to use those other catalogs. 2MASS is not accurate enough for our work.

David Dunham, International Occultation Timing Association

I should add that we also check TYCHO2, but its proper motions are suffering, the updates with more recent observations provided by UCAC4 give the latter catalog an advantage, we find in our work.

David Dunham

Hi David, UCAC4 is indeed useful. It is limited to about 16 mag, so OK for occultation work, I suppose. We use PPMXL for its fainter limit (20 or so). I should add that Pan-STARRS will eventually (in a year or so) produce decent astrometry for the entire sky north of DEC -30, reaching 22 mag or slightly fainter.

Hi David and Wen-Ping, I have just attended the IVS2014 meeting in Shanghai, China and there was a presentation on Gaia and the expected results. I hope that the Gaia project achieves their objectives and that the time series will be long enough to obtain reliable proper motions. I have sort of gravitated to UCAC4 for my application. I am doing a light bending experiment (GTR test) during the March 2015 total solar eclipse, so need accurate position and proper motions for the star field surrounding the Sun at the time of the eclipse. Detected stars will probably be limited to magnitude 10-11, accurate proper motions are very important for the test.

Yes, Gaia will certainly be a game changer for astrometry. Yes, we hope they observe long enough to determine good proper motions. In any case, those proper motions might be refined by comparing with the 1991 mean epoch HIPPARCOS/TYCHO observations for the approximately 2 million stars that were observed by HIPPARCOS.

Markiyan S. Chubey Pulkovo Observatory

Dear colleagues, your answers and discussion are highly professional. Nevertheless I think that the definite answer on the question must be fitted to the target of research. Surely, all we use the best realisation, as the FK6, HIPPARCOS, TYCHO, UCAC4, PPM and also the USNO-B2. But all catalogues of this serie have their individual features and problems. Appearance of the GAIA-catalogue is waited only at the 2018--2020. Probably that will be the most perfect professional realization. The main problem will be the bright star environment solution,

Personal greeting to Dr David Dunham! Any sucsesses to his very interest idea and program for observations of occultations of stars by asteroids.

Thanks Markiyan, yes true, these catalogues all have unique aspects. Accuracy in proper motion is my main requirement. This is needed for a light deflection measurement during the 2015 total solar eclipse.

Fine, Ludwig! Proper motions problem is the most labour-consuming in the builting and construction of the reference frame. It will demand the repetition of the GAIA scanning at the epoch near to 2030th. And the big wave of theoretical works must gush in the atentive analisys of the zero-point control and dynamic movement determination. Only after that works, our follovers will get the faultless astrometric catalogue with acceptable photometric data.

Hi. How about use the XPM catalogues? The XPM catalogue is the combined data from the 2MASS and USNO-A2.0 catalogues in order to derive the absolute proper motions of about 314 million stars and added photometry data from the GSC2.3 catalog.

You can load the XPM catalog http://astrodata.univer.kharkov.ua/catalogs/XPM/

If you use small fields (less square degree ) you can create query from different catalogues, including XPM, 2MASS (PSC), UCAC2,3,4, SPM4, GSC2.3, PPMXL, TYCHO2, HIP2 and other.

http://astrodata.univer.kharkov.ua/astrometry/db/

Best regards, Vladimir.

Thanks Vladimir, I will have a look at the XPM catalogues, great tool, will use it for catalogue queries.

I have found that for extended objects, even in the Magellanic Clouds, XPM, 2MASS, UCAC4 and GSC2.3 are quite adequate. For general positioning, SuperCOSMOS images are still extremely useful (depending on the wavelength you want to check). Gaia will make a huge contribution when preparing future observations on 8-m + telescopes...especially where small diameter fibres are employed.

Thanks Warren, the SuperCOSMOS website is very useful, and having scans of photographic Schmidt survey plates available makes planning easy.

Hi David,

When you say that "2MASS is not accurate enough for our work", what is it about 2MASS that is the limiting factor? Is the epoch of the 2MASS observations too far back with respect to imprecise proper motions in the intervening period?

I started using the 2MASS point source catalogue in the early 2000s for astrometric recalibration of the GSC-derived WCS in the headers of HST frames, which were up to 1.5 arcsec in error. The most important thing about 2MASS for me was its consistency, with typical error of order 0.1 arcsec (although I encountered much larger errors than that for blended stars in more crowded fields). Perhaps I should now be looking at alternatives, like Vladimir's XPM catalogues? What would people here recommend for high precision, with a limiting magnitude similar to 2MASS...sounds like there's a consensus around UCAC4?

Until the initial GAIA catalogue is release in a few years time, UCAC4 is recommended.

Thanks, Paul. UCAC4 it is, so!

It really depends on the band and magnitude range you're interested in and whether you require completeness. Tycho-2, UCAC4, and USNO B2 are all good modern optical catalogs, but are complete in different magnitude ranges, although in a few more years they will all be superseded by the Gaia results. In the near IR there is 2MASS. See http://www.usno.navy.mil/USNO/astrometry/information/catalog-info .

I have also settled on UCAC4. Once we get to GAIA, we will have to start figuring out 'spacetime curvature seeing' problems due to micro lensing. That is going to get interesting.

As you mention, you want to use astrometric purposes in that case USNO-B1.0 is an all-sky catalog that presents positions, proper motions, magnitudes in various optical passbands that may be useful for you. But not the USNO-B2 which may not good!

If we want to use USNO-B1 catalog for astrometric purposes we need understand that not all stars have proper motion (select COUNT(*) from USNOB1 where MuRA =0 and MuDE =0) Result = 750 425 671 Total count = 1 045 175 762.

The choice between one or another catalog does not seem direct. In my opinion all these catalogs are globally good or very good but locally they can be bad or even give false proper motions, mainly to the fainter stars (V>12). So, I think the best to refine your research is: use the various quality flags given in these catalogs; compare the proper motions in the various available catalogs and eliminate those that are disparate; if it is possible, calculate the proper motion yourself in a artisanal manner taking positions in the various catalogs;

It seems to me that the more consistent astrometric catalog, thinking about proper motions, is the SPM4. But if we also take into account the completeness the UCAC4 seems to be the more appropriate.

Yes, I agree, it is a bit difficult, it would be nice to have some sort of comparison somewhere, summarizing the advantages/disadvantages, and perhaps some proper motion evaluation. Mostly, I think we blindly trust the catalogues, but I am sure the USNO work is very reliable, so I am latching on to UCAC4.

Ludwig makes some good points. Indeed, the fact that the original question had to be asked (and received so many, often disparate answers) goes to the heart of the matter - as catalogs proliferate, which one can you really trust, globally and locally? It's like the old problem again of "pick a standard...any standard" - https://xkcd.com/927/

It would be nice to collate and merge them all together to assess how good they individually are. (I know that this has been done to a limited extent - some catalogs like the UCACs and XPM are essentially meta-catalogs from a number of sources). But as Gaia approaches, would all that effort be considered a waste?

It may be worth to take a look at the article about a very limited work (R. Teixeira et al. - Astrometric Catalogs: Be Careful! ) in the site:

http://www.astroscu.unam.mx/~rmaa/rmsc43_frameset.html

Regards

In this paper presents the short analysis of positions and proper motions stars of XPM catalog with UCAC2, UCAC3, SPM2, SPM4, PPMXL and others.

https://www.researchgate.net/publication/229878394_The_XPM_catalogue_as_a_realization_of_the_ICRS_in_optical_and_nearinfrared_ranges_of_wavelengths?ev=prf_pub

Article The XPM catalogue as a realization of the ICRS in optical an...

Thanks Vladimir, good paper!

Received the UCAC4 catalogue on CCD yesterday, even has some C code to access the files that I can include in my telescope driving software...thanks USNO!

Hi all. Having worked on the construction of SPM4, I can attest that it is not a trivial task to materialize a good reference frame everywhere. A reference catalogue can be globally well tied to the ICRS yet have local systematics. I do recommend SPM4 for the southern hemisphere and UCAC4 for the northern one, and I tell you, even though both catalogs used the same first epoch material for the southern hemisphere, there are localized systematic differences, although small, between the two. I do also recommend to avoid using 2MASS or anything with 2MASS for astrometric purposes, it is not  an astrometric catalog and it was not intended for that, it suffers from horrible systematics that can be corrected but there is always the chance to leave uncorrected stuff behind. All astrometric catalogs, as good as they can be, degrade with magnitude, and to have a sense of how good a data is, individually, it must have errors estimate of some kind. Sadly, XPM lacks that, for example. Be aware of false/null data in the USNOs catalogs, many stars have "zero" or worst, quantized (2,4,6,8, ...)  proper motions. Finally  I will take the chance to let you know that we will be precisely talking about this at the upcoming VI ADeLA meeting in Santiago de Chile in Sep/Oct 2014. Best regards. :)

http://adela2014.das.uchile.cl/index.php?id=program

I advise you to compare the proper motions from various catalogs and taking those whose values are more consistent. 

See for example: Ducourant et al. 

Astronomy & Astrophysics, Volume 563, id.A121, 15 pp.

and 

V Reunión de Astronomía Dinámica en Latinoamérica - Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) Vol. 43, pp. 55-58 (2014)

Best Regards,

Rama

I'm not a specialist in astrometry, just using these catalogs for offset guide stars for IR work.  I've read Rama Teixeira's paper that he cited, and it's very instructive and useful as a quantitative answer or qualification to the question.  Teixeira et al describe high-precision CCD transit astrometry (4 mas/y) & >10 year baseline on galactic bulge window fields, compared to PPMXL, UCAC4 & SPM4 using ~10^4 stars in common.  In plots of their p.m. results vs. the catalog entries, if there were perfect agreement the points would be on a y=x line (slope 1).  But many of the fainter stars (V>~12) are definitely spread vertically!   This indicates that even for e.g. UCAC4 stars V>12, you might get a more accurate p.m. value and/or current epoch position by just assuming p.m. = 0, rather than using the UCAC4 catalog p.m. value.  (The SPM4 comparison fares better in this regard).  So as Dunham, Teixeira and others advise, check for other independent values available, look for any consensus.  If you're looking at V>12 with |pm| < 50 mas/y, and no good cross-checks available, may be better to just assume pm = 0.

n.b. in the pdf of Teixeira's paper, in some of the plots the points for brighter stars (V

Thanks Allan, very useful information!

Hi Katherine, thanks for the info on the SPM4 catalogue. Please report back to us on the outcomes of the VI ADeLA meeting in Santiago de Chile.

In Ducourant et al. 2014 we have looked for the consensual proper motion and was just this that allows us to obtain a convergence in our trace back and so the kinematic age. 

Gaia Data Release 1 (DR1) provides more accurate position, and proper motions for the ~2 M stars in the combined Gaia-Tycho brighter-star (m

I like to add the HSOY (Hot Stuff for One Year) catalogue providing precise astrometry and proper motions for 583'001'653 objects based on PPMXL and Gaia DR1. Fills the gap between DR1 and DR2. Typical formal errors at mean epoch in proper motion are below 1 mas/yr for objects brighter than 10 mag, and about 5 mas/yr at the faint end (about 20 mag). South of -30 degrees, astrometry is significantly worse. HSOY also contains, where available, USNO-B, Gaia, and 2MASS photometry. See Altmann et al. (2017).

https://arxiv.org/abs/1701.02629

Hi all. The PMA catalogue is the combination of positions from Gaia DR1 and 2MASS for more than 421 million objects. 

http://cdsarc.u-strasbg.fr/viz-bin/Cat?cat=I/341&menu=on

The best now is UCAC5, based on a re-reduction of the UCAC CCD observations with TGAS data. It is quite dense, but maybe not as comprehensive as PMA.

Thanks David

More info and downloads are available at https://gaia.aip.de/cms/data/ucac5/

Hi Ludwig,

if you need a specialized catalog you can query the catalog database:

http://vizier.u-strasbg.fr/viz-bin/VizieR

Best regards

Jens

UCAC4 serves the purpose. online GAIA DR1 catalog is also available. Other catalogs like URAT-1/UCAC5 are here

Visit link: http://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mission=irsa&submit=Select&projshort=USNO