"it ROCKS! It's simple, small, and interfaces to Cartes du Ciel. What more can you ask for?"
- Astronomy author
Rod Mollise.

This document was last updated Aug. 25, 2015. The latest version of this document is on-line at faq.rtgui.com/ .
Copyright 2005-15 by Robert Sheaffer.

1. What is RTGUI (RTGUI+S)? How can I run it?

RTGUI is a very small, very fast astronomy program for Windows whose main purpose is to help you select objects that are visible right now, or at some specific time. (It does a lot of other stuff, too.) You can select objects by their common names or by catalog IDs, by object type, by constellation, magnitude, or elevation, to observe right now, or you can print a list of matching objects to observe later. You can also have the program suggest objects for you. Click one button, and you get an "instant Skychart" of the selected object. Click another button, and your Goto telescope goes straight to that object. And did I mention that it's free?

RTGUI will run on any version of Microsoft Windows, on any kind of Desktop, Laptop, or Tablet PC, so long as it is running a standard version of Windows (for example, Windows 8.1, not "Windows RT" or "Windows CE"). The user interface of Version 10 of RTGUI has been enhanced to make it easier to use on Windows Tablets. All buttons and fields on the main form have been enlarged, and all its functions can be invoked by typing a single character, displayed on the key. For example, you can invoke the "GoTo" function by typing "g", or by clicking on the GoTo button using a mouse or a stylus. Fields on the smaller secondary forms (for example, Catalog Select) have been almost doubled in size.

The home page for RTGUI is at http://www.rtgui.com .

2. What does the name mean?

RT means that by default it is a Real-Time program. It reads the Windows clock, and continuously updates object positions as the time advances. (Of course, you can set it to non-real times, too. Then the time does not update.) It gets your Time Zone from Windows.

GUI means that it has a Graphic User Interface (mouse or stylus controlled).

+S means that Scripting capability has been added.

3. How do I find out which objects can be seen in my telescope right now?

Several ways to do this. The easiest is to just press Best of the Sky to have RTGUI suggest the most interesting objects for viewing, based on your location, telescope size, sky conditions, and the time. First the well-placed popular "eye candy" objects will be suggested, such as Saturn, the Orion Nebula, the Andromeda Galaxy, or Albireo. Then you will get a longer list of selected Messier objects, NGC and IC objects, and finally double stars. You can move forward and backward along the chain as much as you like, you can save it to a file, and view or print it as a list. This will be useful for selecting objects to show the public at star parties.

You can also search by constellation, and/or by object type. If you see Orion standing high in the sky, just do a Simple Search on the name Orion. RTGUI will give you every deep-sky object in that constellation potentially visible in your telescope, one at a time, starting with the Messier objects, then the NGCs and ICs. That might be a lot of objects. Press Next Match when you want to go on.You can also back up to the Previous Match, and save or print these matches.

The Search Wizard makes it easy to refine your searches. Maybe you want to find galaxies in a particular constellation, or all well-placed galaxies in any constellation. The Search Wizard will locate the kind of objects that you tell it you want to see, and will select only the ones that you should be able to see right now, based upon your telescope size, and whether you are at a rural, suburban, or urban site. You can also specify a magnitude limit cutoff, for example, don't show objects fainter than magnitude 10. The data in RTGUI's NGC/IC catalogs has been uniquely updated with the latest and most accurate data available, giving much more accurate object searches (see RTGUI's NGC/IC Updates .). This data isn't available in any other program.

4. I have the name of an object I want to see. How do I find it?

You just press Simple Search, and enter the name of the object. In the default catalog full.rtg you can find all of the following names: M31; Polaris; DoubleDouble; Gam Vir; DoubleCluster; NGC 7009; IC 434; LagoonNebula; HR 2491; 61 Cyg; CarbonStar. This unusually rich search capability is made possible by the fact that each object in the RTGUI catalogs can have up to five names. M1, CrabNebula, and NGC 1952 all refer to the same object. That object will also turn up in searches for Taurus or Planetary. Double stars can be found by the label Dbl, and will be followed by information about their separation and magnitude. Over 2,500 double stars are listed in the default catalog, searchable by name or by constellation. Not sure if an object you've heard about is in there? Try it! You'll be surprised how many different kinds of names and objects can be found. RTGUI is not like most astronomy programs, where you have to search for this in this list and that in that list. For observers using typical amateur telescopes, probably 99% of the extrasolar objects you'll ever observe can be found in full.rtg, usually under several different names.

Each name is a maximum of 12 characters; you only need to type enough letters to get a unique match (for example, dumb will suffice to find the Dumbbell Nebula). Searches are not case sensitive, and spaces are ignored. Constellation names are fully spelled out for Deep Sky objects, up to 12 letters; stars have a 3-char constellation abbreviation, usually preceeded by a 3-char Greek letter abbreviation (Alp Cma), or a number (87 Tau). You can use the wildcard character * at the beginning or in the middle of a name (for example, *Cnc will match all stars in Cancer; when the second search name is set to Dbl, this matches all double stars in Cancer.). You don't need to use a wildcard at the end of the name because substrings matching the first part of the name are automatically accepted (which you can disable by putting a space at the end, for example to distinguish Sagitta from Sagittarius). Some names will match many objects (Example: galaxy ), you can just keep hitting Next Match. But you don't need to remember all this, because the Search Wizard will set up correct searches for you.

5. Does RTGUI draw Sky Charts?

No. But if you have installed the free program Skychart (Cartes du Ciel, Version 3.2 or higher), you can click the Skychart button to get an instant sky chart centered on the selected object. Skycharts is an extremely sophisticated, full-featured astronomical charting program. I use it a lot, and recommend it highly. And did I mention it's free?

6. How do I change the Catalog / the Time / the Location / etc. in RTGUI?

Generally, to change something in RTGUI you click a button, or type the character shortcut displayed on the button. Then up pops something, and you follow the directions. You'll also see Tool Tips when you place the mouse over a field. Of course some fields can't be changed, because they're derived from other data.

7. How does RTGUI know where I am? How does it know what telescope I'm using?

It doesn't - you have to tell it. Your location and all configuration options are stored in a small configuration file named rtgui.hom. When you first unpack that file, it has my location in it, not yours. You click on the latitude and longitude buttons to change them. If you have a hand-held GPS, RTGUI can read your location from that - click load. Or if your telescope has a GPS, it can also read that - again click load. After your location is established, don't forget to click save. If you observe at different locations (doesn't everyone?), you'll probably want to save several different location files under different names, and load them as appropriate.

The first time you run RTGUI, it will nag you to tell it what Goto telescope you're using (if any), and what Com port it is connected to. You should also tell it what size telescope you're using, so it knows what default magnitude limits to set for its searches, and whether your observing site is rural, suburban, or urban. You'll want to save this information, too, unless you want to keep getting nagged each time.

8. Can RTGUI find Solar System objects?

Of course. To locate the Sun, Moon, or one of the major planets, just find its name on the scroll bar at the bottom right, and click, or type the numeric shortcut character for that object. It gives you the constellation name for all solar system objects' positions.

It's easy to locate comets and asteroids. Just click on Get Comet/Asteroid, and enter the name of the object you want to observe. RTGUI uses the internet to contact the Minor Planet Ephemeris Service at Harvard, and loads 60 days' worth of positions for that object. (Click on Visible Comets/Asteroids to find out what objects can currently be seen.) The appropriate RA and Dec is automatically loaded each time the object is requested. Even if you take your computer out to a remote observing site with no internet connection, you will still have precise positions for the next 60 days, for as many comets and asteroids as you care to observe.

9. What Other Catalogs does RTGUI have?

In addition to the default full catalog, some others are:

Messier Marathon catalog, for the once-a-year attempt to see all 110 messier objects in the same night. Contains the objects in the order you need to see them, for northern and southern observers.

Herschel 400 catalog - Catalog of selected Deep-Sky Objects, 400 entries

WDS catalog, Washington Double Stars. 84,468 entries.

PPM catalog - Positions and Proper Motions, a standard star catalog with 468,861 entries, containing the entire SAO and HD star catalogs as subsets.

GCVS catalog - General Catalog of Variable Stars, 38,624 entries

GCPD catalog - General Catalog of Photometric Data, 152,000 entries

These catalogs are found either on the home page for RTGUI, or in the Files section of the Yahoo group. Of these auxiliary catalogs, probably only the first two will be useful for most observers. The others are primarily useful for special observing projects.

10. What is Scripting?

Scripting is the capability to accept command-line parameters, allowing RTGUI to be controlled by other software, instead of by the GUI interface. This makes it possible to have RTGUI+S perform completely unattended many automated tasks, such as positioning your telescope to Saturn at exactly 3 AM, then moving to Venus at 4 AM, etc. You can even write elaborate scripts in Visual Basic, Java, Delphi, or some other scripting language to position the telescope for imaging, sky surveys, or other repetitive tasks. See the document ScriptingRTGUI.htm

11. What else does RTGUI do?

It adjusts for precession, and for atmospheric refraction. It can download object positions from your Goto scope. It can upload your location to a Meade scope that doesn't have a GPS. It allows you to specify object positions, and to add them to catalogs. It can set the "night vision" palette for itself, and other programs. It tells you an object's Rise, Set and Transit times, and continuously updates the altitude and azimuth. It can tell you the Julian Date.

If you want to know everything it does, you'll have to read the program documentation, RTGUI.htm . You might also want to read or join the Yahoo Group for RTGUI, which has information on using the program, as well as user-created catalogs, scripts, and utilities not available anywhere else.

12. Is it true that the Program Documentation file RTGUI.htm is too long?

Probably. But I didn't want to leave anything out.

Please report to me any comments you might have on RTGUI, or any problems you may find with it.

Robert Sheaffer
Lakeside, California

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