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Mars a tiny white dot
Posted: Sun Feb 07, 2010 2:50 pm
I am new to this but I thought I would be able to see more detail with my 130mm Skywatcher, it didn't appear red at all I could see no detail, it was just like looking at a star without a telecscope, in fact it appeared more orange to the unaided eye.
I must be doing something wrong - I used stellarium to find it and it seemed pretty obviously in the same location so I'm sure I had it in me sights.
Maybe the scope's broken?
thanks for any help
Posted: Sun Feb 07, 2010 6:40 pm
I'm new to this too!
I don't think your scope has broke because Mars looks exactly the same through my scope.
I have a skywatcher capricorn 70 EQ1.
Posted: Sun Feb 07, 2010 7:10 pm
How disappointing, I thought there might be something wrong as the Jodrell Bank Centre for Astrophysics site says
To see significant detail on the surface requires a telescope of 4 inches or more. As the north pole is tilted towards us, we should be able to easily spot the, brilliant white, north polar cap.
... isn't 130mm more than that? Or is it referring to some other measurement?
Posted: Sun Feb 07, 2010 9:03 pm
Mars disc is small and very bright at present. I think you will need to use as much magnification as is practical to expand the disc and reduce the glare in your eyepiece. In good seeing, your 130mm should be able to stand magnification of x200 or so, and I think for Mars you need to get close to that if you can. I don't know the focal length of your 'scope (is it f6?) but I guess you will need an eyepiece of 5mmFL or less, or a 10mm (or less) plus a x2 barlow lens.
HTH a bit,
Posted: Sun Feb 07, 2010 9:11 pm
What magnification were you using? Mars is quite bright at the moment so it is quite blinding through a scope, but it should look like a disc (albeit quite small) and not a star. It's pretty obvious with the unaided eye right now, so it would be hard to confuse it with anything else.
I had my first proper look at it last week (last time Mars was visible 2 years ago it was much smaller and I too was disappointed - it's larger this time round). Admittedly my scope is 200mm, but I had to whack the magnification up a bit to see the detail - at low power I found it too bright and the details get lost. At 270x I could make out the polar cap and markings like Syrtis Major. I saw the polar cap at half that power, and a hint of surface features.
It will also depend on the seeing conditions. It can be hard as a beginner to see details - you need to persevere and you will find things start to pop into focus the longer you look.
Posted: Sun Feb 07, 2010 9:19 pm
Can I refer you to Martin J. Powell who correctly states:
With an apparent magnitude of -1.3 and a maximum apparent disk diameter of 14".1 (14.1 arcseconds, where 1 arcsecond = 1/3600th of a degree), Mars at this opposition is not as bright nor as large (when seen through a telescope) as it was at its previous opposition in December 2007, when the planet reached magnitude -1.6 and had an apparent diameter of 15".8. This is because, at the 2010 opposition, the planet is further away from the Earth than it was at the 2007 opposition.
Posted: Sun Feb 07, 2010 9:49 pm
I was using a 25mm eyepiece which came with the scope. I have only had it a few weeks so only have the two eyepieces that came with it.
What eyepiece would you recommend using?
Posted: Sun Feb 07, 2010 11:19 pm
I think Brian hit the nail on the head.
A 25mm eyepiece may be only providing x30 magnification if your 130mm scope if f 6 (ie 130 x 6 = 780mm focal length).
All being well given good seeing conditions you might better use X200, (even possibly x250 on a night of good seeing).
A 6mm eyepiece would provide 780 divided by 6 = X130. Using a x2 barlow lens as well producing x260.
A 8 mm eyepice with x2 barlow giving almost x200.
Observing planetary detail needs quite a bit of practice. If seeing conditions are very poor the planet is likely to look a somewhat fuzzy blob in the telescope possibly jumping about as well. In very good seeing usiing suitable magnification to me Mars usually appears a sort of pinkish-creamy-orange colour , the polar caps appearing sparkling white, I hesitate to describe the colour of Mars's darker features.
In poor seeing Mars often lacks much colour but careful observing can reveal the polar cap and other dusky features at varying levels of apparent brightness.
Best of luck from Cliff
Posted: Mon Feb 08, 2010 8:46 pm
Thanks for the advice I think I need to invest in some new eyepieces.
Posted: Thu Feb 11, 2010 2:32 pm
Thanks very much for the help.
My smallest lens is 10mm, on the side of the scope it says F=650, does this produce a x65 magnification or x130 with a Barlow (which I have) ?
Anyway I tried that combo, its true Mars appeared more 'disc-like' than other objects, not red though.
There was a lot of glare and also a slight spectrum of red on one side and white on the other and it never really appeared sharply in focus - could this be a lens cleaning issue - or should I just buy a 6mm eyepiece. (Any good online outlets?).
I live in an unlit street in Cornwall - conditions are good for viewing, I'm just not very good at it!
Posted: Thu Feb 11, 2010 8:45 pm
Yes, your mag estimates are correct. To get close to x200 you will need to use an eyepiece of 3mm FL. This could be a 6mm plus x2 barlow lens, this combination will give you more comfortable viewing (longer eye relief). Remember, to use x200 you will need the seeing to be excellent, something that doesn't occur every day in the UK.
You'll often see coloured fringes (red, blue) either side of the bright planets if you are observing them when they aren't high in the sky. This is the effect known as atmospheric dispersion, where the atmosphere acts like a prism. The effect is greater when the planet is lower in the sky and you are looking through a thicker layer of air. So it helps to observe when the planet is highest in the sky, due south, and after the air turbulence of the day has subsided.
For eyepieces have a look at suppliers in the SPA members discounts tab at the top of the page,
Posted: Thu Feb 11, 2010 9:00 pm
I never used your sort of scope but I think the 130 Sktwatcher is a good one. I think your F650 refers to a focal length of 650mm so you are right assuming your 10mm eyepiece will produce X65 magnification.
Mars is currently just more than 13 arc seconds apparent diam dwindling to 12ish by the month. Say then it will be roughly 0.2 arcminutes apparent diameter the Moon is about 30 arcminutes diameter so in effect using your X65 power provides an image of Mars roughly comparable with 0.5 the size of our full Moon as seen by unaided eye.
That means using a X2 barlow would very roughly provide you with a Mars immage like a unaided eye Full Moon.
Now that might seem pretty big but I must say that in practice planetary images through a telescope tend to seem smaller in some respects than might be expected. (I think various factors come into play creating this apparent optical illusion).
However, apart from such things as needing to get experience in observing to get the best out of your telescopic views of planets. Good steady atmospheric seeing conditions are needed to get the best telescopic views of Make sure your telescope is steadily mounted and also that is is adjusted in collimation as best you can.
Best of luck from Cliff
PS I hope I got the above calculations about right, but apologise in advance if I made any bad mistakes. In good seeing I think your 130mm scope should allow say up to X250 magnification making Mars appear roughly twice the our Moon's unaided eye apparent size until March after which Mars will be getting apparently smaller.
Posted: Thu Feb 11, 2010 9:28 pm
Thanks for that - well it might be an illusion but I wouldn't say I got that size from my 130mm magnification (10mm eye + Barlow) last night, , but I care more about the detail and colour of which there was none - shouldn't it be pinkish?
I think I may get a 6mm lens before the end of the month.
Posted: Mon Feb 15, 2010 10:14 am
You could always try some medium transmission colour filters, yellow/green/blue to enhance surface features
Posted: Wed Feb 17, 2010 5:50 pm
thanks for the suggestion - by "enhance" I hope you mean make them visible? As i mentioned before all I can see is a not very clear small white disc.
Bought a 6.5mm eyepiece will try again when the clouds clear.