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© Croydon Astronomical Society 2012 Croydon, Surrey, England. Charity Registered in England and Wales No. 251560


Croydon Astronomical Society
est. 1956

Members of the society carry out observations at both the society observatory at Kenley as well as back gardens, in the local area of Croydon, nearby and other parts of the UK and abroad.

In addition to visual observing members can record their observations on a variety of instruments including cameras, both still and video. A recent activity (at least at Kenley) is using radio waves to detect meteors, and spectroscopy of bright stars using a diffraction grating.

Current favourable objects tonight. Rather than repeat identical information already in numerous other places, a selection of links below give information on what is visible in the night sky, right now and in the months to come, as well as general observing and amateur astronomy information. These links are reviewed regularly:

Sky Guide from Telescope House - January 2020


Solar System tonight - SkyLive

Astronomy calendar 2019 - SeaSky

Sky tonight - In the Sky

Sky tonight - Amazing Space

Sky tonight - Heavens Above

EarthSky - astronomy essentials - visible planets tonight

EarthSky - tonight

Sky Guide of the British Astronomical Association - regular

Sky this month - one minute astronomer

Sky this month - Skymap - monthly




Star atlas - identify and details - Skymap-org

Stars over Surrey - Brooklands radio - monthly






For daytime, the Sun


Sun in hydrogen-alpha - National Solar Observatory - live

Most if not all of these websites have much more interesting and useful information astronomically and are recommended to be explored.


Observing with the Society (highlights of current objects below)

Transit of Mercury, 9th May 2016

Transits of this planet occur far more frequently that those of Venus (the last two for Venus was 2004 and 2012 and the next is now 2017 and 2125). The next transit of Mercury is now fairly close, 9th May this year and we hope to open our observatory at Kenley to view this, Monday from midday towards sunset.

Transit of Venus, 6th June 2012

The European Southern Observatory has a page of information on both transits - they are intending to try to determine the size of the Earth’s Orbit from these measurements. This was used as the historic method of measuring the size of the Solar System but has now been superseded by radar measurements. It should still be interesting to see how accurate the measurements are.

Transit of Mercury, 7th May 2003

To aid planning your observations here in PDF format is a list of the altitude and azimuth of both the Sun and Mercury for the Transit for our Observatory at Kenley. Note that the Sun is very low around 6 degrees at First Contact. Also its azimuth is 70 degrees so you need a site with a clear north east horizon to get a good view or better still take a video. In both cases you must not look at the Sun directly or with any optical instruments unless you have taken proper precautions.


Telescopes for Astronomy

A wide variety of telescopes are available, from beginners to serious amateur astronomers and the choice can be bewildering, especially so for people new to astronomy and optical equipment. Whilst it’s true that all telescopes do essentially the same thing, after some experience and practice - and knowing more about each type of telescope - many people in hindsight would have bought something else. This is the case even with experienced observers, as they may specialise in a particular astronomical object. Often it can be a case of buying something bigger and or better (expense now justified), but the type and size of telescope is such that careful thought is required before even the first purchase.

It would be simple to list a few websites where good advice is given, instead the current advice would be to do a simple Internet search, say on: ‘choosing telescope’. The reason being that they are all good and very similar. It would otherwise be what would be done here anyway.

If you come across a good website do please mention (webmaster) and it will be listed here; thank you.


Mobile and tablet Apps

Mention must first be made of planispheres. These are card or plastic discs, available also from some bookshops, that show the visible sky above your horizon at any time of the night and night of the year. Easy to use, flat and lightweight, they are excellent for getting to know the names of the stars and constellations that you can actually see at the time.


One of the more advanced and sophisticated true astronomy apps, with a more straightforward and informative interface, SkEye introduces itself as an advanced planetarium that can also be used as a ‘Push To’ guide for telescope users. A particularly advanced feature is that it displays a continuous readout of the position of the centre of the screen, in both RA, Dec., and Alt, Az. Other features include a choice of which catalogue of objects to show, and variable brightness for different aspects of the screen. Despite the sophistication and wealth of features the view is practical and immediate from first use.

SkEye is available only for Android.



For those already with equipment, or looking for a particular telescope, or telescope-camera combination, these website provide online calculators where you enter simple measurements and it produces useful information. An example would be the field of view obtained with a telescope and/or camera combination:






For those with Dobsonian and other alt-az telescopes, knowing where to point the telescope is not obvious, but the following calculator converts a celestial co-ordinate from the RA and Dec to altitude and azimuth. RA and Dec are the celestial equivalents of terrestrial latitude and longitude:


Alternatively for those with an Android mobile handset there is SkEye, a planetarium type app which in addition to many features has a continuous readout of both RA and Dec and the Alt-Az equivalent. There is also the feature that it can be attached to your telescope and it tells you where to point it to find a particular object.


Observing Logs

Serious observers need to record their results so that they can be analysed later or for the less serious observers we need accurate notes to jog our memory:


Observing Projects

An excellent way to be motivated and involve fellow members is to think of and engage in an observing project. If anyone has something particular in mind please mention it via our forum croydonastro. Fellow members who would otherwise not engage would be willing to give advice. Your results can be presented at one of our society meetings if you so wish.

New projects or events will be added to the top of this list and some will be archived after the event.

More details of our observatory can be found here.

Members’ images are shown in the gallery.

To enable you to plan your observing sessions this website shows the twilight times for London.

The links above are good sources and those below may also be useful.

First, to enable you to plan your observing sessions this site shows the twilight times for London.


See the Moon phase at the top right of most of these webpages (you may have to click once or twice to confirm opening).


There are numerous websites and other sources that give very good indications, of which this is just one example:


Artificial satellites:

There are various websites and other sources that give very good indications, of which this is just one example, and particular visits can be selected from the list below the ‘Satellites’ section, which include the very bright ISS:


Deep Sky objects:

The links above give a good choice, and there are these two in particular:



Where is what and how to see it?

As these objects tend to be just below naked-eye visibility there is the extra problem of not being able to see the object to find, even when knowing the telescope is pointing close by.

There are a variety of solutions.

The original and always reliable and accurate is to use Circles, that is the calibrated coordinate scales found on many telescope mounts.

A more modern approach - this can be easier in use but requires time-consuming and involved setting up - is to use a Goto facility, found on most modern and advanced telescopes.

An even more modern approach is to use the observer’s existing mobile handset or tablet and the telescope communicates its position via wireless, Bluetooth and an App on the user’s device, and this may additionally make use of encoders on the telescope mount.

An also modern approach is simpler, cheaper but less precise, which may not be a problem once experience is gained, in using a planetarium type App, in that it shows what is in the sky where it is pointing and also has a Find/Search function. Most of these can be attached to the telescope for greater accuracy.


Highlights of current objects

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