M 51 MCG -03-01-01 Bochum 15
NGC 2100 vdB 150 Ced 122
PGC 63008 PK 26-11.1 LBN 623
UGC 11670 Abell 347 ESO 350-23
The ACP "Slew or Sync (catalog)" window, as well as the Color Series form on ACP's web user interface, have a Search button. This displays another interface with which you can do powerful searches of the Deep Sky Catalog. The "Match pattern" box is where you enter your search specification. The power of the catalog search facility is in the construction of the match pattern. This simple form can do very sophisticated searches. First, let's look at the simplest way to use it:
The easiest way to search is to enter some part of the name into the "Match pattern" box and click Search. This will return any object whose name contains the characters you entered. For example, "M" will match all objects that contain the letter "M" or "m".
If you want to specify the starting characters of the name, prefix your pattern with an up-arrow. For example, "^M" will match all objects that begin with the letter "M". For just Messier objects, which begin with M and a space, enter "^M " (note the space after the M).
You can perform arbitrarily complex catalog searches with the use of regular expression match patterns. If you haven't encountered these before, they can be a bit intimidating. Play around with regular expressions a bit and you may find they will enhance your searching ability greatly. If you already know about regular expressions, you will immediately be able to use the full power of ACP's catalog searching facility.
The following table shows the meta-characters that can be used in regular expression searches of the ACP Deep Sky Catalog. Multi-line features are not available. You have already seen the use of the up-arrow to force beginning-of-text matching.
| Character | Description |
|---|---|
| \ | Marks the next character as either a special character or a literal. For example, "n" matches the character "n". "\b" matches a word boundary. The sequence "\\" matches "\" and "\(" matches "(". |
| ^ | Matches the beginning of input. |
| $ | Matches the end of input. |
| * | Matches the preceding character zero or more times. For example, "zo*" matches either "z" or "zoo". |
| + | Matches the preceding character one or more times. For example, "zo+" matches "zoo" but not "z". |
| ? | Matches the preceding character zero or one time. For example, "a?ve?" matches the "ve" in "never". |
| . | Matches any single character. |
| x|y | Matches either x or y. For example, "z|wood" matches "z" or "wood". "(z|w)oo" matches "zoo" or "wood". |
| {n} | n is a nonnegative integer. Matches exactly n times. For example, "o{2}" does not match the "o" in "Bob," but matches the first two o's in "foooood". |
| {n,} | n is a nonnegative integer. Matches at least n times. For example, "o{2,}" does not match the "o" in "Bob" and matches all the o's in "foooood." "o{1,}" is equivalent to "o+". "o{0,}" is equivalent to "o*". |
| {n,m} | m and n are nonnegative integers. Matches at least n and at most m times. For example, "o{1,3}" matches the first three o's in "fooooood." "o{0,1}" is equivalent to "o?". |
| [xyz] | A character set. Matches any one of the enclosed characters. For example, "[abc]" matches the "a" in "plain". |
| [^xyz] | A negative character set. Matches any character not enclosed. For example, "[^abc]" matches the "p" in "plain". |
| [a-z] | A range of characters. Matches any character in the specified range. For example, "[a-z]" matches any lowercase alphabetic character in the range "a" through "z". |
| [^m-z] | A negative range characters. Matches any character not in the specified range. For example, "[m-z]" matches any character not in the range "m" through "z". |
| \b | Matches a word boundary, that is, the position between a word and a space. For example, "er\b" matches the "er" in "never" but not the "er" in "verb". |
| \B | Matches a non-word boundary. "ea*r\B" matches the "ear" in "never early". |
| \d | Matches a digit character. Equivalent to [0-9]. |
| \D | Matches a non-digit character. Equivalent to [^0-9]. |
| \s | Matches any white space including space, tab, form-feed, etc. Equivalent to "[ \f\n\r\t\v]". |
| \S | Matches any nonwhite space character. Equivalent to "[^ \f\n\r\t\v]". |
| \w | Matches any word character including underscore. Equivalent to "[A-Za-z0-9_]". |
| \W | Matches any non-word character. Equivalent to "[^A-Za-z0-9_]". |