What magnification for planetary work?

[David55]

What magnifications do people use for planetary work? I have an 80mm refractor in which I can see Saturn's rings (but not Cassini) and 2 bands on Jupiter (but not the spot) . However, both planets still seem to be the size of a pea held at arm's length at about x100- far too little to make out any real detail.

I'm about to buy an 8" reflector, mainly for extra aperture to see DSO's better, but would be interested to know what magnification levels you experienced planetary astronomers use.

[Mr Spock]

For an 8" I'd expect x200 to be ideal. I generally reckon the best magnification for pulling out detail without losing contrast on most nights is x1 per mm of aperture. So for my C925 I mostly settle on x235

[John]

The aperture of your scope combined with seeing conditions limit the useful magnification you can use. With an 80mm scope that limit is around 150x unless it is of the short tube variety when 100x is about top whack.

WIth my 102mm refractor I find 150x - 190x a useful range. With my 120mm refractor that becomes 180x - 250x and with my 12" dobsonian 200x - 300x.

But poor seeing conditions will reduce the above quite substantially and, at the end of the day, that will be the limiting factor.

The planets may be huge objects but they are a heck of a long way away so you sort of get used to a smallish image scale when viewing them - they are never going to fill the field of view !.

Personally I prefer a crisp, sharp contrasty image at a slightly lower magnification to a larger but mushier one.

[Moonshane]

I agree with the above comments. I use between 120-150x on almost every occasion, 150-200x on many occasions and 200-300x on scarce occasions for planets. with practice and 'staring' it's surprising the detail you can tease out of planets. get in 'the zone' and watch for a prolonged period and eventually you see more and your brain sort of 'collates the data'.

[Schorhr]

Not that experienced with planets, but 200x works well often, on a 8" you can go up to 400x on real good conditions (probably rare). On bright On objects some more is even tollerable then twice the aperture in millimeters.

But I totaly agree, a sharp image is much nicer then a wobbly blurry view.

On the small h130p 260x works nicely once in a while but already is depending on transparency and conditions so I am happy I got a few eyepieces to magnify high. Though I would not spend a whole lot as the eyepiece will not come to use often.

A 26gbp, 6mm 66deg eyepiece will give you 200 on a 8"/1200mm telescope, and a 13-15gbp acrhomatic barlow could give you the max. reccomended magnification if the conditions are good (even though a barlow will somewhat decrease the quality). If you don't want a budget eyepiece you could get an aditional planetary 3.2mm for ~35-40gbp (50deg afov ), or Hyperion eyepieces (70deg afov)

Of course a 10gbp Plössl would work too, but 6,5mm or even 4mm will require you to get so close it will bump the telescope and your eyelashes brush against the lens.

If you want to invest a little more you could get a astrozoom and a planetary or better eyepiece to have a nice wide angle zoom for a good price! (for example a 8mm planetary will turn into a ~7-4mm zoom or something along those numbers).

[bingevader]

Yep, we were out Sunday night and the 11mm EP was plenty and gave the crispest image of Saturn, the 6mm was too much on that occasion.

So the 100x (ish) EP was "better" than the 200x EP on that specific night.

Having said that, from my back garden, I use the 6mm more often than not on planets.

Cheers

[umadog]

The 8" will provide vastly better planetary views. At 200x things look quite a lot livelier than 100x. Not only are you gaining magnification (you will now be at two peas rather than one pea) but you're also gaining exit pupil size, so the views you get will look brighter and the colours clearer. The great red spot is readily apparent in an 8", although right now it looks more like a great salmon-pink spot. Just keep in mind that 200x is only twice the magnification that you can get now. Don't expect miracles but do expect a significant improvement.

[David55]

Many thanks for the prompt advice. It looks as if, with an 8" dob, it will be the seeing that limits magnification rather than the telescope, which I think is the case with my 80mm f5 and that I'll be able to get up to at least x200 to give me 2-pea sized planetary views.

[jabberwocky]

I've used x240 on my 8" dob but x171 more often, really need to get a 6mm ep to give me x200 though as that would be ideal.

[rwilkey]

I used 150x on Sunday night with my 100/900mm refractor on Saturn, looked very good, with WO SPL 6mm, also looked good with 11mm ES/80 series at 81x.

[LukeSkywatcher]

I use about 200x with my 8" SCT on most clear nights. That's a 10mm EP with the scope. I have also used 254x (8mm EP). It depends a lot on local conditions. I have to say though that even on the best night, i wouldn't go over the 254x with my scope. When i used my 90mm refractor, 125x was about as far as i pushed it.

[glowjet]

You might also find that taking your equipment to a dark site may improve matters, especially if you are wanting to chase the faint fuzzies

John.