observing hints and tips
star hopping
Coming soon!
how to find the andromeda
This is a useful link to two very good star hops to the Andromeda Galaxy, M31
Guide to planetary observing
Published: 22nd May 2015
Author: Stuart Davis
Please make yourselves comfortable, this could take some time 😉😉
I thought it worthwhile putting together some information for the new starters on observing the planets and how to get the best views. I hope this is of some use.
Despite their physical size, planets actually appear very small in the sky and so need relatively high magnifications to see the detail.
There are a number of factors which affect the views seen.
1) The distance from Earth. This might sound obvious but as planets orbit the sun, the distances can change significantly, along with their apparent size in the sky. Mars is a fine example. It can vary from approximately 35 million miles to 250 million miles away. At its smallest it is around 3.5 arc seconds and very disappointing to view. At its closest it is around 20 arc seconds, back in 2003 it was 25 arc seconds across. At these sizes, and under good conditions the detail visible on Mars can be stunning.
The best time to view planets is at what is called Opposition. This relates to the fact that it is opposite the sun in the sky, is visible all night and is at its highest point at 00.00 Universal time (Midnight or 1am GMT), and is roughly at its closest approach to the earth so appears at its largest. Dates for each planet's next opposition can be found in the various planetarium programs and apps, or just a Google search will do the trick.
2) The planet's altitude above the horizon makes a big difference to the detail visible. When low down (say below 20 degrees), you are viewing through many hundreds of miles of atmosphere and the turbulence and dimming effect really reduces what you can see. At opposition, planets are at their highest for the year so you are looking through less of the atmosphere and the views will be clearer.
Unfortunately Saturn is very poorly positioned currently, at or below 20 degrees, it won't improve for a number of years. Some years ago it was far higher and the views were magnificent.
3) Seeing conditions. The atmosphere changes constantly, and depending upon things like temperature and the position of the jet stream, it can range from excellent to plain awful. Views are best when the jet stream is not overhead.
During a hot day, the land heats up and releases that heat after sunset. This makes the atmosphere turbulent due to the convection currents. The best time to observe is after this heat has dissipated, often one or two o'clock in the morning is best (unfortunately) as by then everything has calmed down. It is a lovely, peaceful time to be observing, but can get a little chilly and don't get scared by any noisy hedgehogs!
It is always best to try to observe away from buildings and not set up on Tarmac or concrete. These all give off heat at night causing convection currents which spoil the views. Observing over houses is often impossible to avoid, but central heating flues can really kill the views. Look for times when the planets are in the gaps between houses and the views will improve. Observing from a grass field over unbuilt up land or better still the sea or a lake will give best results.
Conditions change from night to night and from second to second. Sometimes you will look through the scope and think something is wrong with it because the views are bad and there is no detail. Watch for a while, and if nothing improves keep trying on other nights until you catch one with good seeing.
One of my big bugbears is when people just take a quick look and say, oh that's nice, and walk away unsatisfied. Often it is worth spending an hour or two just looking at a single planet. At very least spend a few minutes rather than seconds. The longer you look, the more you see. Every now and then the atmosphere will clear and you will see stunning detail. Over time, your eye and brain work together to build up a picture of what is there and more detail reveals itself. A quick glance at Jupiter might reveal the two main bands. Spend an hour or so and you will see festoons, dark barges, finer bands, the polar regions and possibly a shadow transit of one of the moons or the Great Red Spot. Get comfortable, maybe use a seat, and look!
The second of my bugbears is focussing! I have dual speed, fine focusers on my scopes for a reason. That is because very small changes in focus really help to show the planetary detail. If you get to look through someone's scope, don't be afraid of changing the focus, they will expect you to. The chances of your eyes being the same as theirs are pretty remote, and you will not see the best image unless you tweak the focus, so please do!!
4) Scope cooling. All scopes need time to acclimatise to the ambient temperature outside, particularly if brought out from a warm house into the cold. This can vary between 20 minutes to an hour or two depending upon the type of scope. In general refractors need least, Newtonians the next, and closed tube scopes such as SCT's and Maks the most. Until properly cooled, high power views will be poor and will suffer from thermal currents in the telescope tube. You can see this easily by looking at a de-focused star.
5) Telescope collimation. This is the aligning of the optics/mirrors and like cooling makes a big difference to the views and detail you see. In general refractors are the lowest maintenance, rarely if ever needing aligning. Maks are also fairly robust from this perspective. SCTs and Newtonians should be regularly checked and once understood it is a simple procedure to align the optics. It is nothing to be scared of and well worth learning how to do.
6) The last point which specifically relates to Jupiter and to a lesser degree Saturn, is understanding what is on view at the time you are observing. There are a number of applications such as Stellarium, Skysafari, JupiterMoons and SaturnMoons which tell you the position of the various moons, and for Jupiter when you can expect to see the GRS or shadow transits which are great to watch.
Useful magnifications vary with the planet being viewed aswell as the size and quality of scope being used but here is a guide for a good scope under decent conditions:
Venus
Very bright and using high mags helps reduce the glare. Up to x200 is useful. There is little or no detail to be seen on Venus, but it's phase changes nicely over time from its current 'half moon' through to a larger, very fine crescent which is lovely to see.
Mars
A tricky customer but at opposition and under good conditions x200 to x250 is needed to reveal the detail such as the polar caps, frosting, clouds and dark surface markings.
Jupiter
There is plenty to see on Jupiter and it is a very dynamic planet, the atmosphere changes constantly. Many features are low contrast however so x130 to x180 is often best.
Saturn
This is generally a higher contrast target, particularly the rings and shadows plus the Cassini division. Surface markings are visible but generally are lower contrast. x180 to x220 works well for Saturn.
Neptune and Uranus are visible in amateur scopes but not particularly rewarding targets. The best you will see at high mags are tiny disks, bluish for Neptune and greeny-blue for Uranus. The hard part is finding them, goto obviously helps!
If you have got this far, you have definitely got the patience and stamina to be an excellent planetary observer 😉. I hope this is useful and helps you understand how to see more detail and generally to enjoy observing the planets.
Please do ask if you have any questions.
Stu
Author: Stuart Davis
Please make yourselves comfortable, this could take some time 😉😉
I thought it worthwhile putting together some information for the new starters on observing the planets and how to get the best views. I hope this is of some use.
Despite their physical size, planets actually appear very small in the sky and so need relatively high magnifications to see the detail.
There are a number of factors which affect the views seen.
1) The distance from Earth. This might sound obvious but as planets orbit the sun, the distances can change significantly, along with their apparent size in the sky. Mars is a fine example. It can vary from approximately 35 million miles to 250 million miles away. At its smallest it is around 3.5 arc seconds and very disappointing to view. At its closest it is around 20 arc seconds, back in 2003 it was 25 arc seconds across. At these sizes, and under good conditions the detail visible on Mars can be stunning.
The best time to view planets is at what is called Opposition. This relates to the fact that it is opposite the sun in the sky, is visible all night and is at its highest point at 00.00 Universal time (Midnight or 1am GMT), and is roughly at its closest approach to the earth so appears at its largest. Dates for each planet's next opposition can be found in the various planetarium programs and apps, or just a Google search will do the trick.
2) The planet's altitude above the horizon makes a big difference to the detail visible. When low down (say below 20 degrees), you are viewing through many hundreds of miles of atmosphere and the turbulence and dimming effect really reduces what you can see. At opposition, planets are at their highest for the year so you are looking through less of the atmosphere and the views will be clearer.
Unfortunately Saturn is very poorly positioned currently, at or below 20 degrees, it won't improve for a number of years. Some years ago it was far higher and the views were magnificent.
3) Seeing conditions. The atmosphere changes constantly, and depending upon things like temperature and the position of the jet stream, it can range from excellent to plain awful. Views are best when the jet stream is not overhead.
During a hot day, the land heats up and releases that heat after sunset. This makes the atmosphere turbulent due to the convection currents. The best time to observe is after this heat has dissipated, often one or two o'clock in the morning is best (unfortunately) as by then everything has calmed down. It is a lovely, peaceful time to be observing, but can get a little chilly and don't get scared by any noisy hedgehogs!
It is always best to try to observe away from buildings and not set up on Tarmac or concrete. These all give off heat at night causing convection currents which spoil the views. Observing over houses is often impossible to avoid, but central heating flues can really kill the views. Look for times when the planets are in the gaps between houses and the views will improve. Observing from a grass field over unbuilt up land or better still the sea or a lake will give best results.
Conditions change from night to night and from second to second. Sometimes you will look through the scope and think something is wrong with it because the views are bad and there is no detail. Watch for a while, and if nothing improves keep trying on other nights until you catch one with good seeing.
One of my big bugbears is when people just take a quick look and say, oh that's nice, and walk away unsatisfied. Often it is worth spending an hour or two just looking at a single planet. At very least spend a few minutes rather than seconds. The longer you look, the more you see. Every now and then the atmosphere will clear and you will see stunning detail. Over time, your eye and brain work together to build up a picture of what is there and more detail reveals itself. A quick glance at Jupiter might reveal the two main bands. Spend an hour or so and you will see festoons, dark barges, finer bands, the polar regions and possibly a shadow transit of one of the moons or the Great Red Spot. Get comfortable, maybe use a seat, and look!
The second of my bugbears is focussing! I have dual speed, fine focusers on my scopes for a reason. That is because very small changes in focus really help to show the planetary detail. If you get to look through someone's scope, don't be afraid of changing the focus, they will expect you to. The chances of your eyes being the same as theirs are pretty remote, and you will not see the best image unless you tweak the focus, so please do!!
4) Scope cooling. All scopes need time to acclimatise to the ambient temperature outside, particularly if brought out from a warm house into the cold. This can vary between 20 minutes to an hour or two depending upon the type of scope. In general refractors need least, Newtonians the next, and closed tube scopes such as SCT's and Maks the most. Until properly cooled, high power views will be poor and will suffer from thermal currents in the telescope tube. You can see this easily by looking at a de-focused star.
5) Telescope collimation. This is the aligning of the optics/mirrors and like cooling makes a big difference to the views and detail you see. In general refractors are the lowest maintenance, rarely if ever needing aligning. Maks are also fairly robust from this perspective. SCTs and Newtonians should be regularly checked and once understood it is a simple procedure to align the optics. It is nothing to be scared of and well worth learning how to do.
6) The last point which specifically relates to Jupiter and to a lesser degree Saturn, is understanding what is on view at the time you are observing. There are a number of applications such as Stellarium, Skysafari, JupiterMoons and SaturnMoons which tell you the position of the various moons, and for Jupiter when you can expect to see the GRS or shadow transits which are great to watch.
Useful magnifications vary with the planet being viewed aswell as the size and quality of scope being used but here is a guide for a good scope under decent conditions:
Venus
Very bright and using high mags helps reduce the glare. Up to x200 is useful. There is little or no detail to be seen on Venus, but it's phase changes nicely over time from its current 'half moon' through to a larger, very fine crescent which is lovely to see.
Mars
A tricky customer but at opposition and under good conditions x200 to x250 is needed to reveal the detail such as the polar caps, frosting, clouds and dark surface markings.
Jupiter
There is plenty to see on Jupiter and it is a very dynamic planet, the atmosphere changes constantly. Many features are low contrast however so x130 to x180 is often best.
Saturn
This is generally a higher contrast target, particularly the rings and shadows plus the Cassini division. Surface markings are visible but generally are lower contrast. x180 to x220 works well for Saturn.
Neptune and Uranus are visible in amateur scopes but not particularly rewarding targets. The best you will see at high mags are tiny disks, bluish for Neptune and greeny-blue for Uranus. The hard part is finding them, goto obviously helps!
If you have got this far, you have definitely got the patience and stamina to be an excellent planetary observer 😉. I hope this is useful and helps you understand how to see more detail and generally to enjoy observing the planets.
Please do ask if you have any questions.
Stu