Subject: Autostar's SAO Star Catalog Sent: Thursday, November 1, 2001 17:43:45 From: DChantrill@aol.com Now that Dick Seymour has discovered which stars are included in the Autostar's list of 17,782 stars from the SAO Catalog, I believe I have determined how these stars were selected. The snippet Dick posted to the LX-90 group gave me some clues. First, I noticed that the magnitudes in the Autostar database did not agree with the SAO catalog. Upon examining those entries in the SAO catalog, I found a connection to the Autostar database: In the SAO Catalog, columns 68-73 contain the epoch of the original declination observation (EpDE2); in every case, the magnitude listed by Autostar is equivalent to the last three characters of the DE2 epoch. So if the epoch is listed as '1894.6', Autostar lists the magnitude as '4.6'. I'll bet that this was a typo in the program Meade used to extract the data -- instead of extracting the visual magnitude (Vmag) starting at column 81, they used the data starting at column 71 instead. Using a relatively simple algoritm, I have extracted a list from the 'SAO Star Catalog J2000' (ADC Catalog 1131A, http://adc.gsfc.nasa.gov/) that is practically identical to the Autostar SAO database. Here is the algorithm: Extract SAO number, RA and Dec (J2000), spectral type (SpType), photographic magnitude (Pmag), and visual magnitude (Vmag, but use columns 71-73 for Vmag as explained above) for each entry. Select entries where: ( Pmag is in the range from 4.4 to 6.5 ) OR ( Pmag == 99.9 [i.e., Pmag is not determined] AND ( Vmag is in the range from 4.4 to 6.4 OR Vmag == 6.5 and Dec > 0 [I suppose they eliminated the 6.5 mag stars in the Southern Hemisphere to shorten the list a bit.] ) ) That's all there is to it. I ended up with a database that is nearly identical to the Autostar SAO list, with the following slight discrepancies: (a) Most of the magnitudes match exactly, but those that differ are only a tenth of a magnitude off. (b) There are some slight discrepancies on some of the RA and Dec values; it could be that the positions in the Autostar database were calculated from B1950 positions precessed to epoch2000, whereas I simply extracted the J2000 values directly from the most recent catalog. (c) On a few entries, the spectral type do not match. These first three discrepancies make me believe that the Autostar list may have been extracted from an older version of the SAO list, or from another database (but I haven't found another database that includes the crucial EpDE2 column). (d) There are three entries in my list that are not in the Autostar list: 47433, 127420, and 227039 (the last one is marked as 'Deleted' in the catalog, but I have no idea about the other two). I will post this message to firstname.lastname@example.org, because my findings indicate some issues to be addressed: (a) Nearly all the magnitudes in the SAO list are wrong. (b) If the intent was to provide a bright star catalog (there are 17,402 stars in the SAO catalog that are mag 7.0 or brighter), this list fails miserably because 80% of the entries in the Autostar SAO list are actually dimmer than mag 7; most are dimmer than mag 8. (c) Autostar displays the same wrong distance value for all stars in the SAO list. Again, thanks go to Dick for sending me the Autostar list so I could do an exhaustive comparison with my list, and for opening up this issue in the first place. Clear skies, Dale Chantrill Vista, California
Subject: 18,737 Stars ... and more! Sent: Wednesday, November 7, 2001 18:46:07 From: email@example.com (Richard Seymour) OK... you've seen the 79 Alignment ("Named") stars.. you've seen the 943 "original" stars... you've seen the Constellation-sorted 17,788 SAO star list. Now, thanks to Gregory Pruden's (firstname.lastname@example.org) further efforts, there's an abstracted version of the Sky 2000 catalog, using the Autostar's SAO list as the guide to which 18,737 stars to include in the list. It is located at: velatron.com/dca/download/saobig.zip My contribution was merely the SAO list which is in the Autostar. He's spent a week or so hammering the data into something useful by using that list as an index, and by adding and formatting data from other lists. The zip file is 1 megabyte, and unpacks to 2.7 megabytes. Here's what's in there: Tab Delimited, First Row Contains Field Names, No Text Delimiter, CRLF Row Delimiter. Elements * [sao] [int] - SAO Number * [const] [char] - Constellation (computed from RA/DEC) * [StarName] [char] - Bayer Flamstead name * [Mag] [decimal] - Visual Observed Magnitude * [BV] [decimal] - BV Color Index * [MK] [varchar] - Morgan Keenan Spectral Type * [RA] [varchar] - Right Ascension (h,m,s) * [DE] [varchar] - Declination (h,m,s) * [Distance] [decimal] - Distance (computed from Parallax) * [DblSep] [decimal] - Separation of brightest and second brightest components for Multiple Systems * [DblPeriod] [decimal] - Orbital Period for Binaries * [DblPA] [int] - Position Angle for Binaries * [VarName] [varchar] - Variable Star Name * [VarType] [varchar] - Variable Star Type * [PmRa] [decimal] - Proper Motion RA * [PmDec] [decimal] - Proper Motion DEC * [ProperName] - Star Proper Name * [HIP] [int] - Hipparcos Catalogue Number * [IAU] [varchar] - International Astronomical Union number * [HD] [int] - Henry Draper Catalogue Number * [DM] [char] - Durchmusterung Identifier * [HR] [int] - Harvard Revised Number from the updated Bright Star Catalogue * [WDS] [varchar] - Washington Double Star Catalogue Number * [PPM] [int] - Catalogues of Position and Proper Motion Number * [SKY2K] [int] - Sky2000 Catalogue Number You can import this to Excel by starting Excel, and using the top line's File / Open... method to open the text (.txt) file. A Wizard will appear to walk you through the procedure... have fun --dick
Subject: The Lights in the Sky are (selected) stars... Sent: Thursday, November 8, 2001 17:55:41 From: email@example.com (Richard Seymour) The attached JPEG was created by Bob Rose using Carts du Ciel.And:
It shows an (almost) all-sky view.... and all of the white dots are the full 18,000 stars in the 22eR Autostar's SAO database. (the rest of the red/square/etc. objects are not Autostar related... Bob just forgot to kill the other displays of CdC.) Bob (firstname.lastname@example.org) gave me permission to post it to you for broader distribution. (improved versions may appear later) have fun --dick
Click for full size version
From: email@example.com (Bob Rose) I just finished a converting Dick and Gregory's Autostar-SAO database to a catalog for Carted du Ciel. Similar to what created the jpg, but this time the stars have the correct mag. In the jpg I made the stars with the same mag so I could get them to display at the same time. Anyhow, I need a place to post this file. Since it is the Autostar SAO catalog and The Mighty ETX site is the world best place to find all thing autostar I was hoping you might consider posting the CDC-autostar catalog at your site. Maybe this will start a trend and other will post the autostar-SAO catalog for other popular sky programs. Here is the file that contains the catalog (708K). Did you notice the "C" in the pattern of stars? Somebody at Meade might have a soft spot for Celestr... I had better not say it. I think this phenomenon with the "C" occurs because Meade mistakenly mistook the epoch of the original declination observation, for the magnitude. This was suggested to me by Mr. Dale Chantrill. This looks to be the case. I other words when Meade went through the SAO list and look for stars brighter than mag 5.0 all the stars cataloged in with a date of 1894.6 made the cut. With their selection software looking at the 4.6 part as the magnitude. If you check the autostar's mag. for the SAO stars they are mostly incorrect the magnitude that the autostar will display will more closely match the last few digits of the original date of the star. In light of this fact, my "Oliver Stone" type theory is probably incorrect. Still Celestron could have some fun with Meade over this. bob rose
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