Website Help
Page last updated July 30, 2021

Why This Site Does Not Use https:// ("secure" encryption)
 Websites that ask you to enter any personal information are now supposed to be rewritten to accommodate SSL ("secure" encryption), to safeguard your information (e.g., your bank, or an online store). However, there is no place on this site that requires (or even allows) you to enter any information at all, so there is no point in my going to the trouble and expense required to switch from http:// to https:// encoding.

Finding Specific Topics On This Site
 To search for a topic on this site, enter before your search term (this should work for any browser). As for any Web search, pages added or revised since the site was last 'crawled' by your search engine may not be properly indexed.

Browser Caching
 Although I am always updating this site, it has more than a thousand pages, and only a few are modified in a typical week. Under such circumstances it is recommended that server-side browser caching be enabled, as that allows nearly instantaneous loading of recently viewed pages. However, it also means that changes made to pages you viewed within the last day or two may not be shown. If you are concerned about that possibility, click the refresh button to view the current version of the page (some browsers may require that you clear the browser cache first, but most do not).

Broken Links
 Many websites (especially government sites such as NASA and JPL) continually reorganize their structure, and in the process images or articles linked from this site either move to a new URL or are simply deleted, with the result that clicking on the link will not take you to its original target. If you find such a "broken" link, please do two things: (1) Copy the link location, go to the Internet Archive Wayback Machine (at and paste the link URL into their Web search box (in most cases checking one of their older copies of the target page will show the original target of my link). (2) Let me know about the problem, so I can either hunt down the original (if it still exists at a different location) or add the link to the Wayback Machine, myself.

Known Browser Issues
 There are many browsers in common use today. Different browsers, particularly those using the Android operating system commonly found on most tablets and smartphones, may display pages in different ways (for instance, Microsoft Edge does not always display tables properly). By and large this site is best viewed using Firefox, but some problems may crop up with any browser. This section addresses issues I am currently aware of, and efforts I am making (and you can try to make) to resolve these problems. If you are having problems with the site not discussed below, please feel free to contact me, so that I can try to address them.

(0) (Update of July 30, 2021) The animation of the Sun's movement in Mercury's sky does not display
 The animation of the Sun's apparent movement in the Mercurian sky "shown" on the page about The Rotation of Mercury no longer displays on any device that I am aware of, because the NASA site that provided it uses Shockwave Flash to display the animation, and Shockwave Flash is no longer supported by Adobe on any device. This problem has existed for several years on Android devices, and NASA has shown no interest in updating the animation, so the only way I know to fix it is to create an animation of my own. I have little objection to that, as there were several problems with the NASA version that I would like to fix; but the only method that will work on all devices will require a tremendous amount of work and time, so this problem, though very distressing, is near the bottom of my "to-do" list, and until this paragraph disappears all you can do is read the text that describes what the animation used to show. (Now that the problem is universal, instead of existing only on Android devices, I will try to post a far more detailed discussion of what the animation should have shown before the end of 2021; so it has been moved up a bit on my "to-do" list.)

(1) Greek Letter / Special Font Errors ("MOSTLY" FIXED):
 Special characters (such as the Greek letters used to designate stars' "Bayer designations") were originally displayed using the purportedly web-safe fonts, Symbol or Wingdings. However, I belatedly discovered that these fonts are not supported by most browsers. This means I have to search through the 1000+ pages on this site and replace all non-standard characters with special numerical codes to ensure that everything is properly displayed. The most critical problems involved were resolved by 2015, but problems with "degree" signs and similar "standard" characters not being properly displayed are being addressed only as I work on a given page, so it may be a while before they are all taken care of. If you notice any problems or apparent errors on a given page, please let me know, so I can address them as soon as possible).

(1a) Non-Standard Character Problems (USER-CONTROLLED BROWSER PROBLEM):
 Even some "standard" font characters may not display properly because the user's default character setting for their browser does not allow their display (this is part of the problem discussed in item (1)). The result is strange-looking characters inserted in various places, such as in non-English names or words with accented letters. As part of the 'fix' for font errors discussed in item (1) I am changing the code that tells your browser what character set it should use to properly display all characters, but if your browser default setting ignores that instruction, you may see strange or meaningless characters on some pages (particularly pages containing mathematical formulas). If you have deliberately set your browser to ignore the "normal" page preference for personal reasons (such as having difficulty reading English), there is nothing that can be done about that; but if that just happens to be the default setting and you haven't bothered to set it to allow the page to control its appearance, check the default font settings for your browser. You should be able to find a check-box that says something like "Allow pages to choose their own fonts" or a drop-down menu that says something like "Default Character Encoding". For the latter, set the default to Western (ISO-8859-1). That should take care of the problem.

(1b) Non-Standard Paragraph Indentations (NOW BEING DEALT WITH):
 Until recently I was unable to find a way to force indented paragraphs to have a consistent indent; but I have finally found a way to achieve that goal (as shown by the uniform indentation of the paragraphs on this page), and am gradually fixing the problem. It doesn't take long to do this for a single page, but with a thousand pages on this site, it may take years to finish the task. Once I am sure that has been done, this paragraph will be deleted.

(1c) Mobile Access Problems (USER-CONTROLLED PROBLEM):
 Because of their small size (compared to desktop or laptop screens) and multiple operating systems, tablets and smartphones may not properly display websites designed for laptops and desktop computers. A complete solution (used by most banks and businesses that have the money to throw at the problem) requires setting up a "duplicate" website that replaces the desktop website when viewed with mobile devices (this is why websites that could theoretically be viewed with a mobile browser are often available as "apps" specifically tailored to mobile devices), but that requires time and resources I do not have (since this is a non-profit educational site, its cost comes out of my pocket, even without paying someone to create a mobile app). I have tried various alterations to my "author" site (, but they didn't seem to solve the problem, so I've given up, save for writing the following paragraph.
One thing I've noticed on my family's tablets (a Kindle Fire and a Samsung Tab A) is that pages display better if used in landscape mode, and pretty well even if loaded in landscape mode, then rotated to portrait mode. So if you access this site with a mobile device, I'd recommend trying that "fix".

 I have tried to use "standard" text sizes wherever possible, but as for all web sites, some users will prefer larger or smaller "print". This can sometimes be adjusted with a View / Text Size submenu selection, but the most effective method for controlling text size is to use your browser's "Zoom" setting to make the entire page larger or smaller, and not just the text.

(3) Browser and System Updates (BUGS-A-MILLION):
 Most browsers and some operating systems are updated several times a year (Microsoft 10 is updated in some way almost every week, and does Java ever go even a week without an update?). The updates are almost always full of bugs requiring further updates as frequently as every few days. Pages that are properly displayed prior to an update may not display properly after an update. There is nothing that can be done about such things except to check the Web for complaints about such matters and suggestions for workarounds. (If you use a desktop or laptop computer you could try using another browser, but most mobile devices don't let you switch from their proprietary browser.)

 If printing a page (or using the Print Preview function) cuts off the right side of a page, try the suggestions below:
(Almost always works) (1) Select File / Print Preview / Scale / Shrink To Fit.
 (1a) Do the same thing but print to a PDF file, to make sure it "printed" properly, then print to paper.
 (2) For some tables browser adjustments may not be adequate to provide proper printed output. For some critical tables I have provided web-based and PDF versions; the web-based version may be used for online viewing but the PDF version should be used for printing. Your device/computer should include a PDF reader that allows you to print out the PDF version, but if it does not you can get a free download of Adobe Reader at the Adobe site, or a free PDF reader app at your device's app store.

Why Are Most Of The Pages On This Site Relatively Narrow?
 When I started this site most monitors had only 800 by 600 pixels, and I wanted visitors to the site to be able to read a full line of text without having to use a horizontal scrollbar, so the maximum width of most pages is set at 792 pixels. As time passed it became common for laptop and desktop monitors to have far greater pixel counts, particularly on newer "HD mode" screens (I often use monitors with more than 2000 pixel-widths), and as a result many websites now have far wider pages; but a substantial minority of my visitors now use mobile devices, which means their screens are smaller than ever. So rather than increase the page width I have decided to keep it at 792 pixels for all but a very limited number of pages specifically devoted to wide-field images.