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Whats The Best Eyepiece For Viewing Mars


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Hello I live in Hampshire, UK and have a Dobsonian style telescope.

I am brand new to this. go easy.

I was wondering what would be the best mm lens for viewing planets (particularly Mars and Jupiter) - I have a 10mm,  a wide angle 20mm and a Barlow Lens.

These came with the telescope and from what ive read these arnt too good for veiwing planets, ive had some amazing veiws of the moon but when i look at stars altough sometimes i can see stars through the scope that i cant see in the sky with my own eyes it is still like looking at a star, like the same size as you would expect it to be if you just looked up! so what would be the best mm eyepeice for this problem.

thanks everyone 

joel

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Astrospy, do you know the model number, we can tell from this.

You won't ever see stars as anything other than points of light, they are too far away so this is not something you can fix. Planets on the other hand can be seen with nice detail, but to recommend an eyepiece, we do need to know the scope.

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The telescope looks like a Skywatcher 130/900. The aperture is 130mm and the focal length 900mm and the mount is an EQ2. There should be a black label somewhere near the focuser with this information on, In fact the label is visible in the photo. On the label will be this information F=nnn D=nnn where nnn is a number.

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OK - you have an equatorially mounted Newtonian.

51cm in diameter = 20 inches, that is a big scope and not what's in your profile, more likely is it's a 5.1 inch diameter ???

Just below the focuser there is a sticker that tells you what the scope is.

Assuming it's a 5.1 inch (130mm) diameter mirror with a 900mm focal length, then ideal eyepieces are :-

Jupiter : x180 which is a 5mm eyepiece

Mars : x250 which is a 3.5mm eyepiece

Hope that helps.

** EDIT - I was typing while the other guys posted **

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For Jupiter I suggest you aim at 80x to 100x in magnification terms.

Mars really depends on what you means by viewing Mars ?

Mars is small, a lot smaller then Jupiter. Although Mars is closer to the earth Mars will appear smaller then Juipter when Mars is at it closest to us and Jupiter is at it's furthest. Basically do not expect to see markings or polar caps. A small red disk is generally all it ever makes, and every 2 years it swungs into view there are wails of general dispair when people observe Mars.

If the scope you have is the 130/900 then you are needing a decent 10mm for Jupiter. The BST's do not come in 10mm so I suspect it would mean the 8mm, above 100x but might deliver. Alternatives are something like the Vixen plossls - they do a 10mm, or the Altair 9mm Lightwave - giving 100x.

Saturn is likely to be the main planet after Jupiter, and for that consider 120x to 150x, which is 7.5mm to 6mm eyepiece. So the 8mm BST would give 112x, the 6mm Altair 150x, there is a 7mm X-Cel for 128x. Problem with planet viewing is that a 6mm may not work but the 7mm might, or the 6mm and the 7mm do not work and the 8mm does.

Not sure what the 130/900 will actually deliver (assuming that is the scope) I think the mirror is spherical, which might reduce the possibilities, but the focal length is fairly long.

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I don't agree that Mars only ever shows a small red disk, with no polar caps or markings. At anything from 100x or more it is possible with patience and a well cooled, collimated scope to see polar caps and hints at least of dark markings. At around 200x you start to see real detail. The sketch below was done with my 6" f11 dob at 160x. The real eyepiece size was the little blob shown in the sketch. The image checked afterwards on http://www.calsky.com/ is shown below and confirms I was 'really' seeing what I thought I was seeing.

post-5119-0-00304200-1397949236.jpg

post-5119-0-05245200-1397949252.jpg

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I have had similar positive experiences with Mars and small scopes. Here is my sketch during the same opposition that Shane captures with an image taken at the same time. I was observing with my Vixen 102mm refractor:

post-118-0-58501700-1452470872.jpg

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post-38669-0-63012800-1452476346.png

I think you may have a 6" F/8 (1200 mm focal length) Newtonian on an EQ2 mount. If it is a 1200mm focal length telescope, a 6 mm eyepiece would give you 200x.

(If the 1200 is right, an  n  mm focal length eyepiece would give you  1200 / n  times magnification)

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I'm pretty sure the OP stated that they had a Dob. As for all planetary targets, I'd go for a wide angle eyepiece that can give at least 150x magnification at the least.

He says it's the scope on his profile pic.

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He says it's the scope on his profile pic.

Oh sorry. Yes, he does. I blame my ADHD lol. It looks like an old blue coloured SW Explorer 130 to me. I'm guessing f/7, 900 mm f/l.

I have the same scope except mine is black. I'd use a 10mm Delos with a Powermate to give 225x then in that case. The 72° FOV should make it easier to keep Mars in frame with a manual mount.

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While figuring out your telescope's focal-length and what eyepieces to use - a little about viewing stars:

Stars will not get bigger. They will get brighter. This is what a telescope excels at - capturing light and amplifying it. So you can see stars that would otherwise be invisible to you. And those you can see with just your eyes will appear brighter.

Planets, on the other hand, will appear larger. Though they won't look like pictures in magazines and books, you will be able to see some good detail. Try Jupiter - that's always a favorite. And your scope will show you the famed rings around Saturn.

Now back to our regular programme..... :p

Dave

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Oh sorry. Yes, he does. I blame my ADHD lol. It looks like an old blue coloured SW Explorer 130 to me. I'm guessing f/7, 900 mm f/l.

I have the same scope except mine is black. I'd use a 10mm Delos with a Powermate to give 225x then in that case. The 72° FOV should make it easier to keep Mars in frame with a manual mount.

Thats a good suggestion :icon_biggrin:

It's just a shame that the eyepiece and Powermate will cost around 4x as much as the scope is worth :undecided:

I agree with your diagnosis of the scope - it certainly looks like an Explorer 130 to me as well.

Welcome to the forum Joel - feel free to ask further questions on how to get the best from your scope :smiley:

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