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Ideal magnification for planetary viewing.

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Hey guys. Thought about  starting this thread. I feel like we all should inform eachother and newer members alike about the magngifications that can be achieved on planets,that provide the best sharpness/size ratio,depending on the scope and seeing. After this thread has grown a bit, i feel like this should be pinned,as to provide a little guide to newer members that are not experienced with planetary observing,as many will be fooled with the typical 50x per inch of aperture and get disappointed when they find that that image will be dim and blurry.

For my 8” F/6 Sky-Watcher Dob

For Saturn i like to use 150x in medium seeing and if i want something a bit bigger , switch to 240x ,which will give me a bigger,but blurrier image.iBut In good seeing, i found that 240x was very usable.When we have perfect conditions, i m certainly trying 300x.

Mars, isnt very big in the sky right now,so even at high magnifications like 300x it still appears as a small orange dot. For observing mars,I suggest waiting for it to reach opposition.It benifits hugely from it! However,this happens once every 2 years....But 5ere are other planets to keep you occupied until then, such as jupiter,saturn and   Venus.

For Venusi use 50-100-120 depending on its phase.

For  Jupiter, i like to use 150x, as it provides a very sharp image,with key features of the planet such as bands being very detailed.Waiting on my 6mm UWA Skywatcher to bring it to 200 and see how that plays out. Be careful! Don’t magnify jupiter too much, as it will loose much of its features and sharpness.

Neptune and Uranus: These two will not impress, but are certainly have a nice colour to them. Even ar high magnifications, such as 300x and 400x, they will look like small discs with color in them.Uranus will look be colored green and Neptune a fainter blue.

Mercury About mercury...Havent gotten the chance to observe it ,so the guys will have to inform you about that😅

Feel free to give your own opinions as to give members a wider source of information to help them observe better ! 

Cheers and clear skies.



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I think much depends on local seeing conditions. Often, transparent skies usually have poor seeing due to turbulence,  while good seeing with steady air can often be misty. Its on those steady, misty nights that high powers can be used to advantage. Generally speaking though, my personal feelings are that 180X is just about right for Jupiter and Saturn, and that over magnifying the image of either will offer no gain in detail. With Mars, due to its tiny apparent size and brilliance, higher magnifications can be used to advantage.Mars while at sub 5 arc seconds in diameter can benefit from 250X to 350X and more.The high power enlarges the tiny image scale to a useable disc size, while at the same time dimming the image which allows for fleeting glimpses of its subtle albedo features. Currently, while around 4.5 arc seconds diameter, I find 370X is just about right to give an image scale large enough to reveal subtle and fleeting detail. It is far from ideal but bright areas can usually be detected as the waves of turbulence subside momentarily, and also the subtle darker markings can jump in and out of view. Patience is the key at this size and power!

Venus likes higher powers as it gets closer to a crescent and Mercury like Mars needs powers high enough to create an image large enough to see a disc where albedo markings can be seen at times. 

As a rule of thumb I'd say use Magnifications as high as you can without softening the image. But when the disc size is too tiny to be seen, then power up until the disc is large enough to be useful. Then patiently study the blurry disc for a reasonable time before concluding there's nothing to be seen. 

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The magnifications that you are using seem well thought through to me and similar to the ones that I use with my scopes.

I do use very high magnifications on Uranus and Neptune but not to try and see disk details (although that would be nice !). I find the very high power helps pick out their faint moons. So far I've seen Triton at Neptune and Titania and Oberon at Uranus. I think 2 more Uranian moons are possible for me if I get a really dark sky and Uranus in a reasonable position.

With some practice and careful observing you should be able to see Triton with your 8" dob at high magnification. I find that the Cartes du Ciel software gives it's position quite accurately.

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I use a 15" f/4.5, and if seeing doesn't support my 8mm EP for 240x, I don't deem it a good night for observing planets.  I'm in the habit of checking the pesky jetstream forecast beforehand, and allowing several hours of active cooling for my mirrors.  On better nights, my 6mm is my choice ~320x for Jupiter, Mars, Saturn, Uranus and Neptune.  Very rarely I'll go higher with a Powermate.

With my 250px f/4.7 10" dob, I would use a binoviewer at ~208x for planets - which worked great too.  The 15" beats it even though mono;) I've some challenges reaching focus with the binoviewer in my 15", unfortunately. 

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