Moon clear , Jupiter fuzzy

[Rufus357]

Hi Everyone,

very new to this and hoping for some advice. I have a Celestron 130eq and using the kit 10mm eyepiece I am getting amazingly clear views of the moon. However when I view Jupiter with and without a 2x Barlow I am only getting fuzzy, smudged views. I have collumated the scope.

What do I need to do to get better views of Jupiter? Better eyepiece?

On the moon is normal that the depth of field is limited so I cannot get all of the surface in focus?

 

thanks in advance!

 

 

[JOC]

Jupiter is very low on the horizon at the moment and you are looking through a lot of atmosphere before you get there.  I would continue without the Barlow - more magnification isn't always good for Jupiter, many people find 'smaller' is often clearer and often better.  Also it is not a solid rock like the moon (it is a fuzzy gaseous mass) and so will never have crisp edges as the moon does.  If you get a cool, clear evening after the rain has washed out the dust from the atmosphere and the earth is bunging up loads of thermals you might find the image becomes much clearer.  With the depth of field remember how much closer (in miles!) the centre of the moon is to you than the outside - it then seems reasonable that it isn't all possible to be in focus at the same time.  Some EP's have less good properties at their edges than in their centres too which might not help.

[michael.h.f.wilkinson]

1 hour ago, JOC said:

Jupiter is very low on the horizon at the moment and you are looking through a lot of atmosphere before you get there.  I would continue without the Barlow - more magnification isn't always good for Jupiter, many people find 'smaller' is often clearer and often better.  Also it is not a solid rock like the moon (it is a fuzzy gaseous mass) and so will never have crisp edges as the moon does.  If you get a cool, clear evening after the rain has washed out the dust from the atmosphere and the earth is bunging up loads of thermals you might find the image becomes much clearer.  With the depth of field remember how much closer (in miles!) the centre of the moon is to you than the outside - it then seems reasonable that it isn't all possible to be in focus at the same time.  Some EP's have less good properties at their edges than in their centres too which might not help.

Any shift in focus between centre and edge of the moon is probably due to field curvature in the optics. The focus shift needed from the centre to the edge of the moon for a telescope with a 1 m focal length is 15.6 fm (0.0156 nm). Shifting from infinity to the mere 384,000 km distance to the moon (give-or-take) requires 2.6 nm. I doubt your focuser can be that precise . It is less than a wavelength of light, so negligible.

[cjdawson]

Hi @Rufus357, Welcome to SGL

 

Looks to me by the questions that you are asking that you are new to the trials and tribulations of telescope ownership.   Firstly, let me say welcome to the family.  I'm sure that we'll all help you up that steep learning curve, and in a few months you'll be having a fantastic time.  Please remember that on SGL that there is only one stupid question - the one that is not asked!   So ask away, the more questions, the more you'll learn.

 

On to replying to your post.

As JOC said, juptier is low in the sky, this means that there's more astmosphere, which makes the image a bit more fuzzy.

I've got the spec of your scope up on FLO's website, and done some envelope maths of the eyepiece magnifications to help you get started....

 

20mm eyepiece - 32.5x

10mm eyepiece - 65x

20mm with barlow - 65x     (32.5x doubled)

10mm eyepiece - 130x    (65x doubled)

 

Strictly speaking, there will be some people that will take huge offence to what I just did there.  We tend not to talk about magnification, so much as power, eyepiece size, f/ration and focal length.  Which can be very confusing to those just starting out.

 

Using a rule of thumb, your scope has a 130mm apeture.  so divide that by 2 and you end up with 65.   This is the maximum magnification that you should get on a fantastic night.   So your 10mm eyepiece, will top out of your scopes capabilities.

However, it's not quite true!   It's a rule of thumb.   There are other things that come into play that effect the result.    The weather, has the biggest effect.   There are two things that people talk about, the seeing and the transparency.   Then the transparency is good, this means that there's not alot of "stuff" in the air.   (Dust, vapour, gasses, etc)   the more transparent it is the easier it is to see through.    I'm sure you've seen the good days when you can see that radio/tv mast that's 30 miles away, but the next day you can't.       Then we have "seeing", this is when the light is bouncing around dew to turbulance in the air.  The more steady the air, the better the seeing conditions are and the more stable and image that you'll have.

Those fantastic nights that I mentioned are the rare ones when the seeing is good (nice stable image with no movement) and good transparency (no stuff in the air blocking the light)

 

The next thing I'm going to assume is that your telescope is brand new.  It's a newtonian type telescope, and that means it will need to be columnated.  Yes, it should have been done at the factory, and I'm pretty sure it was.  However, telescopes are delicate instruments and it's highly likely that the columniation has been knocked.  The way to tell is find a bright star, and defocus the telescope, you'll end up with a ring of light when the start is out of focus.  What you need to look for is the placement of the hole in the middle of the ring.   If it's perfectly in the middle, great you are good.  If it's off to one side, then your telescope will need a tweak.

 

Long post isn't it?

Here's why I've gone to all this trouble.   To get the best views from your telescope, you need firstly to make sure it's columnated correctly, then don't over power it, and remember that some nights are better than others.

 

So, why was the moon good and Jupiter not so good?

Firstly, the 2*Mag per MM of aperture rule goes out of the window when it comes to the moon.  You can run higher and still have good views.  Jupiter is at mag -2.1 and the moon (full) is -12.6  The sun is -26.7.    So what this means is that the moon is about 5 times brighter than Juptier.  That means 5 times the light, so it's easier to see.

Give yourself time and patience, you'll get better at looking at Jupiter (observing it) spend time just looking around it, let your eye adjust, pick out the cloud bands, the fuzzy astmosphere edge of the planet.  The moons of Juptier and just remember that the view you have is much much better than Galileo had when he made the discoveries. ?

 

[Red Dwarfer]

Focus on the four Galilean Moons first . When they are tack sharp , Jupiter will be too - low elevation spoils the view as well , so Jupiter is best towards the South East and South ?

[Rufus357]

Thanks guys. Some really useful background info and tips there. Thanks for taking the time to explain the basics , will really help get me off the ground.

[Rufus357]

2 hours ago, Red Dwarfer said:

, so Jupiter is best towards the South East and South ?

Probably going to say something stupid here ....?  do you mean when it’s south from me? I am in the southeast UK and Jupiter has been SSW at around 10:30 pm when I have been viewing 

[laudropb]

Hello and a warm welcome to the SGL.

Just to clear up a point made earlier. To get a rough idea of the maximum magnification your scope is capable of you do not divide the aperture by 2, in fact you multiply it by 2. Thus in theory your scope is capable of 260 x. In practice you will seldom achieve this because of atmospheric conditions. Your image at 65x should be fairly clear if not very detailed. As has been suggested try focusing on one of the moons. Take your time and get the image as sharp as possible. Then move on to Jupiter. The disc should be fairly well defined and the 2 equatorial belts should be showing. Unfortunately the supplied 10 mm eyepiece that comes with the scope is not of the best quality and at 130x it probably will not give a very sharp image.

[Red Dwarfer]

1 hour ago, Rufus357 said:

Probably going to say something stupid here ....?  do you mean when it’s south from me? I am in the southeast UK and Jupiter has been SSW at around 10:30 pm when I have been viewing 

Jupiter rises in the East - like the Sun - and if it is viewed when it's just above the horizon it will look like a fuzz ball as you are looking through layers of Earth's atmosphere - as the night goes on it gets higher and it is best viewed then ...

Try the Moons first then Jupiter should be clear - it takes the eye a little while to adjust to the brightness , so just stare directly at it and after a minute or two detail ( the two main weather bands ) will start to be seen ?

[Rufus357]

Thanks for clarifying. I will definitely try taking the focus from the moons and see where that gets me

[Sunshine]

I've always stuck to 25x per inch of aperture as most useful magnification considering average atmospheric conditions.

[Stu]

13 hours ago, Rufus357 said:

Probably going to say something stupid here ....?  do you mean when it’s south from me? I am in the southeast UK and Jupiter has been SSW at around 10:30 pm when I have been viewing 

The planets are at their highest when they cross the meridian ie they are directly to the South.

Right now this is happening at 9.50pm for Jupiter, when it is at around 23 degrees altitude from London. 

Regarding magnification,  Jupiter generally is a low contrast target and doesn't benefit from too much magnification. I think for your scope somewhere around x130 to x150 will possibly be optimum for it when it is well positioned. 

Generally speaking x130 gives you a 1mm exit pupil (aperture/magnification) which will be a comfortable high mag. In theory,  0.5mm would be a top end ie x260 but I think that is pushing too far, x180 is probably more like it. 

Getting a better quality eyepiece such as a BST Starguider should give you sharper views though. 

[ronl]

At this time of year it doesn't really go properly dark, so you need to block out stray light,

I use an observing hood, but a dark towel will do the job, putting it over the focuser and your head

will make a difference, but as others have said, the seeing conditions are not that good at the moment.

[Stu]

9 minutes ago, ronl said:

At this time of year it doesn't really go properly dark, so you need to block out stray light,

I use an observing hood, but a dark towel will do the job, putting it over the focuser and your head

will make a difference, but as others have said, the seeing conditions are not that good at the moment.

Jupiter is bright enough to be observed even in daylight,  in fact twilight is in some ways better than complete darkness as it reduces the glare. I've also found that observing at this time allows you to see more colour on the planet because your cones remain stimulated by the ambient light. Worth trying without your hood

 

[ronl]

I have tried with and without the hood, and personally I find it better with the hood,

great colour and view.

[cjdawson]

14 hours ago, laudropb said:

Hello and a warm welcome to the SGL.

Just to clear up a point made earlier. To get a rough idea of the maximum magnification your scope is capable of you do not divide the aperture by 2, in fact you multiply it by 2. Thus in theory your scope is capable of 260 x. In practice you will seldom achieve this because of atmospheric conditions. Your image at 65x should be fairly clear if not very detailed. As has been suggested try focusing on one of the moons. Take your time and get the image as sharp as possible. Then move on to Jupiter. The disc should be fairly well defined and the 2 equatorial belts should be showing. Unfortunately the supplied 10 mm eyepiece that comes with the scope is not of the best quality and at 130x it probably will not give a very sharp image.

 

OOPS!   I got it backward.    d'oh, so yeah the 130, should be capable of 260x under perfect conditions.  (Planet near Zenith, good seeing and transparency on a still night in the middle of nowhere)  I should have realised that I'd got it backwards as my 200mm scope is capable of 400x, but I've never run it visually at anything over 250x visually so far.  (never felt the need to do so, saturn simply blew me away at that power)

 

6 hours ago, Sunshine said:

I've always stuck to 25x per inch of aperture as most useful magnification considering average atmospheric conditions.

The rule of thumb is normally 50x per inch, which (d'oh, see earlier) is 2x per mm.   But yeah, in reality, you don't get 50x per inch, so running somewhere between 25x and 40x is probably more useful.  I like the ability to get up to 40-50x for that rare perfect night.

 

[rockystar]

On 20/06/2018 at 13:17, cjdawson said:

Jupiter is at mag -2.1 and the moon (full) is -12.6  The sun is -26.7.    So what this means is that the moon is about 5 times brighter than Juptier.

I think this means it is 100x brighter.  -1mag is twice as bright as 0 mag, -2 twice as bright as -1, -3 twice as bright as -2, etc; the Moon is 10 orders of magnitude brighter than Jupiter, which makes it 10^2=100x brighter. 

Welcome to SGL

 

 

[Stu]

1 hour ago, rockystar said:

I think this means it is 100x brighter.  -1mag is twice as bright as 0 mag, -2 twice as bright as -1, -3 twice as bright as -2, etc; the Moon is 10 orders of magnitude brighter than Jupiter, which makes it 10^2=100x brighter. 

Welcome to SGL

 

 

That's not quite right, each change in mag is approx x2.5, so 5 magnitudes difference equates to x100 ie a mag 1 star is 100 times brighter than a mag 6 star.

[rockystar]

31 minutes ago, Stu said:

That's not quite right, each change in mag is approx x2.5, so 5 magnitudes difference equates to x100 ie a mag 1 star is 100 times brighter than a mag 6 star.

Cheers.  My original calc was wrong too, it should have been 2^10, which is 1024, and not 10^2. This correction makes it an even crazier difference.  2.512^10.5 = 15856 difference in brightness!

I'm sure this isn't quite reflective though, as Jupiter is much smaller (relatively speaking) on the sky, so that brightness of the Moon is spread over a larger area.