Filters for planetary viewing

[Planetesimal]

Given my current set-up, views of Jupiter tend to be quite washed out and lacking contrast, which I think is made worse due to the brightness of the planet. I've read that filters can be used to improve the contrast when observing planets. Would a neutral density / variable polarising moon filter do the trick, or should I be looking at something more specialised for planets (i.e. coloured filters).

Or should I just accept the limitations of my supplied EPs and get an 8mm BST?!

[Mr Spock]

Better eyepieces do help I've never found filters to be much help myself.

[Moonshane]

Jupiter (in fact any planet really) needs to be high enough to be away from the main impact of the atmosphere. The scope needs to be cooled and well collimated and on this basis assuming you can get to maybe 100x you will see a lot of detail on Jupiter. you do need to watch the planet for a while and get your focus spot on. this will allow you to take advantage of the fleeting moments of good seeing as the view sharpens maybe a few times a minute for a few seconds at a time. after a while you 'learn' how to look and then you'll start to tease more and more detail out. it all takes practice.

I do find that a Baader Neodymium filter enhances the contrast a little and reduces the glare a bit too.

[Moonshane]

looking at your kit, the 10mm should give good results in an f8 scope. better eyepieces are always good but there's often a lot more affects planetary viewing than eyepieces and filters. my 6" f11 dob needs a good hour to cool and I suspect yours will be similar.

[dweller25]

The Baader Neodymium filter is the only filter that has ever shown me a noticeable difference on the planets.

[crazyjedi]

I can only echo what has been said above.

Planetary filters can make no more than very subtle improvements, and the down side is that they impart an artificial colour to your view (depending on the filters colour and wratten number) which can be distracting.

Improved EP's are usually better investments than a box full of filters that (in most cases) end up gathering dust.

Perhaps the much vaunted BGO's or at more of a premium price the short FL Pentax XW's

[Planetesimal]

I keep my 'scope in the garage so it's reasonably close to outside temperature - I think about 30 mins is okay for cooling. My biggest problem at the moment may be the focusser. Now if I could only attach the SW auto focusser to the R&P I'd be set!

[Northern Soul man]

Hi Ya Planetesimal, the planets can be very rewarding in terms of detail, but you have to work at it!!!, wait till they rise high enough in the sky - have a look around to start with for other objects and then set yourself a chunk of time for Jupiter watch, she's really riding high in Taurus at the mo, probably the highest on the ecliptic for years - so the least amount of atmosphere will degrade your views. Your always battling against the atmosphere the unsteady air currents and turbulance are always a problem so be patient.

Certain filters help some but not others, our scopes have very highly reflective mirrors - when looking at really bright objects - like Jupiter - detail tends to be "overwhelmed" by light - keep at the ep and after time your eyes will begin to pick out better detail for a second or two, when the air/atmosphere steadies you will begin to notice "irregularities" in the equatorial belts (I say the equatorial belts because these tend to have the highest contrast) bumps and dips begin to appear to extend past the edges of these belts into the respective zones, transits of the moons are also nice to watch creep across Jupiter's disk, the more you look, the more detail pops into view, belts then begin "appear" at higher latitudes, so instead of 2 belts, 4 belts are seen in moments of better seeing.

The Great Red Spot is also a feature thats visible at certain times - here's a nice little program that helps you with transit times of the spot - http://www.skyandtel...pt/3304091.html - you can usually observe 30 or so minutes either side of the stated time - don't expect a Red Spot though - its very pale in colour, but the edges of the spot "spill" over and these edges tend to be easier to see than the actual spot.

Hope this helps a little - don't get me wrong - larger aperture scopes don't always show a better view than smaller aperture and detail in a 20" scope isn't TWICE the size as the detail in a 6" scope - the 6" will show more, on more nights than the 20", only a few nights of perfect seeing account only for a few nights each year - larger aperture scopes give you a much brighter view, allowing you to increase magnification to see fainter detail - but as said before increased magnification increases the turbulence and seeing conditions are worse.

Your never going to see the detail you see in photos from Hubble and even the planetary imagers take amazing shots to show a wealth of detail that will never be visible to the naked eye.

I like nothing more than sitting at the ep for hours on end looking at the same object in real time which is hundreds of millions of miles away.

Hope that helps and stick at it - the rewards will come.

[Planetesimal]

Do you reckon the BNF is worth the £49 quid asking price or would I be better off with a higher quality EP? I had heard the 10mm SW supplied should be ok on an F8 'scope like mine, but I'm wondering if I need to upgrade... I can't focus bright stars with it (they develop blobby "limbs" like little moving flames). You've all pretty much talked me out of the whole filter idea - maybe I need to do a star test and brave the Cheshire for the first time!

[Planetesimal]

Thanks Northern Soul man - you've given me encouragement there, maybe that's worth more than filters and EPs!

[Northern Soul man]

Hi Ya if the stars are "flaring" could be 2 things - either the scope needs collimating (Cheshire at the ready!!!!) or could be the ep your using - when you get a clear night (I know don't think we've got 1 here for a few nights) try a little test on a star - say Polaris - move the focuser so that you move Polaris into and out of focus and have a look to see if the star is round or that when moving the focuser, the star tends to grow in size 1 side more than the other - if it does - your gonna have to get friendly with your Cheshire - as when the scopes are out of collimation the contrasty detail is lost. I have tried a variable polarising filter on Jupiter and the brighter planets, also on the Moon. The filter consists of 2 filters which rotate against each other and these dim the brightness by as much as 1 - 40%, this dims each object as much as you want to, you can experiment with it, but wait and see if you get anymore replies regarding filters - remember when using a filter your putting another layer of glass in the optical plane - so, in effect, your degrading the image even more - I know - this Astronomy is mind blowing!!!

Don't rush into buying any filters just yet, see if you can hook up with a member or two on here - if they have any, you can try before you buy [ pity your not closer to me as I have a load of filters you could try mate - Paul.

[Planetesimal]

Well Paul, I took your advice and did a star test - definitely not symmetrical flaring. So I got the cheshire out this afternoon for the first time.. Turns out the primary's centre spot was well off cenre, so a little tweak with the adjusting thumb screws on the primary and that was sorted. I didn't do a full secondary alignment but looking through the cheshire I can see the full circle of the primary and all three clips, so I'm going to assume it's close enough!

Another star test tonight will confirm whether the blobby flares have gone away (or are at least symmetrical).

A side effect of my first collimation experience was spotting a few dust motes on the primary mirror . Luckily turning the OTA upside down and giving the back of the mirror a gentle tap dislodged them, phew!

[Northern Soul man]

Nice 1 Planetesimal, glad you've got it sorted, a lot of gazers get a little hung up on perfect collimation - don't worry too much if its not exact - remember the bubbling and boiling atmosphere will degrade your views a lot more than a slightly out of collimation scope if your like me I just get out there and observe - the more you check your collimation and adjust the easier it becomes, but , by the sounds of it, its near enough mate - just enjoy. Paul.

[Luke]

i find a variable polarising filter a huge help on planets as the planet is usually too bright for me in our 10 inch dob, drowning out the detail. My missus though is fine without the polariser and finds the setting I use too dark. I also use the polariser on the moon as that tends to blow my eyeball out!

[Planetesimal]

At the moment I use my rock star shades to view the moon...

[Northern Soul man]

Hi Ya Luke, I've just been out looking at Jupiter and yes, I use the polarising filter a lot, the view is just so bright - with the filter in line - lets the belts through a lot better - even the North temperate belts visible, but the turmoil in the North EQ belt really visible tonight - looking at the planet - you can fit 1000 Earths inside Jupiter you know - amazing. Paul