More Focus on Jupiter & Saturn

[mystery21c]

Dear All

I'm new to astronomy and ready to get into it, I have recently bought the Dob Skywatcher 200p F6 Telescope 8" so I would imagine getting some realistic views of the planets. I've used stellarium to locate the planets and seems to be very accurate.

I've looked at the moon and seems to be very clear with the eypieces I've got, 5mm, 10mm and 25mm with 3x Barlow, however, I managed to look at Juipiter last night with clear skys and also Saturn early this morning with clear skys, both planets appear no bigger than a bright "O" in my eyepiece no matter what eyepiece I use, but my problem is, and I need some help with this one, I can't see any detail of these planets.

It looks like I'm just looking at stars although I know that's not the case, I would love to see some detail of Jupiters gases or the rings of Saturn and would love some advice on how to achieve this?

Any responses welcome, Happy Christmas and New Year.

[perrin6]

1. The main issue is probably that the mirror hasnt cooled to the air temperature causing the image to be degraded. It takes at least an hour to equalize.

2. There might be what's called 'bad seeing' when the atmosphere is turbulent high up.

3. Dont use the barlow next time - just the 10mm or 5mm alone, these should give adequate magnification (10mm - 120X; 5mm 240X), the barlow will make the image far too big & indistinct. (or barlow the 25mm as I think it is a good eyepiece, from what I hear- this combination would be about X150)

4 Try to focus the image as accurately as you can. Focus on a nearby star first perhaps, as this will be easier to focus precisely on.

5 Have patience! It takes time to get used to the subtle details on the planets.

[nightfisher]

ditto the above!

[dweller25]

You have bought a very good planetary telescope.

The advice above is excellent - particularly about cool down times.

You do need to check collimation.

Jupiter is very low and well past it's closest approach so it's not at it's best now, however at x120 so will see the main bands.

Saturn will be next - closest approach will be in the spring.

HTH

[geordieskies]

hi Mystery, Merry Christmas. I've recently bought the same 'scope and so far have only used it indoors (No way am I going outside until we have some better weather).

Even through double glazed windows in an area with light pollution I can clearly see Saturn with a distinct ring, a noticeable band on Jupiter and also some of its moons and Venus is a definite disc (or part of). With the 10mm EP both Jupiter and Saturn are still very small but easily recogniseable. I'm really looking forward to getting the big Dob outside in a darker area and I've even sourced some adaptors from Ebay to connect my cameras to attempt a few planetary pics. I also bought a digital inclinometer from Ebay which is identical to the "Wixey" type but a few pounds cheaper. What a clever little gadget, all Dob owners should have one. My next gadget will be a digital compass if I can find a reliable/accurate one. Can anybody out there recommend one?

Like you, I've noticed that the planets are very bright but if you persevere and keep looking (try looking slightly to one side of the planet) the detail should begin to appear.

Good Luck and Season's Greetings......Geordieskies

[Chris H]

When looking at Jupiter can you see it's four moons?

When looking at Saturn using your 10mm eyepiece can you see it's ring system?

If the answer to both these questions is no I would hazard a guess that your not looking at the planets and are looking at stars by mistake.

[brantuk]

With a focal length of 1200mm and a 5mm ep your magnification is 240x. This is at or very close to the maximum you can expect from this scope/ep combination under the best "seeing" conditions available in the UK.

Generally most scopes will have a limit of around 200x in the UK assuming adequate cool down time, good collimation, good tracking, and near perfect seeing - which doesn't happen often - few can push it much further.

150x-200x is much more common and even then the "seeing" comes in and out in fleeting seconds throughout a session.

To get better clarity you'd need to take a series of short exposure webcam frames (typically several hundred), and stack and process the best ones together to form a composite image which can be enlarged.

Hope that helps

[mystery21c]

Dear All

Thanks for so many responses, this seems to help a bit.

To answer Kris77, I can't see Jupiters 4 moons and I can't see Saturns rings, it does look like I'm looking at stars, but after referring to Stellarium I'm looking in the right place, for example; Jupiter the other night was the brightest light in the sky and all the stars were visible to the naked eye, and Jupiter was where it should be according to Stellarium.

Regarding temperature, I've tried using it inside through double glazing like GeordieSkies but with similar results, not good.

I don't know a lot about collimation and after all my scope is new and I can see good views of the moon, but is it possible that allignment could be way out, and therefore just not be able to focus on these large planets, because....maybe... the delivery guy just threw the scope on the truck??, but then, if that was the case and allignment was bad, would it be obvious when looking at the moon, as I'm getting good views?

Thanks again to all.

[John]

Until you view i) not through windows and ii) having allowed the scope to properly cool, it's not possible to tell if it needs collimation or not. If the scope has been thrown around then it will need collimating.

The moon looks pretty good throught practically anything to be honest so it's not a discriminating test.

You need to get the scope outside, let it cool and then find Jupiter and some other objects and study them for a while at varying magnifications to see how the scope is really performing.

[Capricorn]

If you cannot see the moons of Jupiter then I suspect that you are pointing at the right area but not at Jupiter. The field of view of just about any scope is not exactly "wide". The right direction is simply not enough.

If you have a disk but not Jupiter then the scope may not be focussed right.

If you have a finder then get it well aligned.

If no finder then get one.

Then point the scope at Jupiter using the finder and centre it.

Have the longest eyepiece in the scope and then it should appear in the scope.

The swapping between the finder and the eyepiece has to be done without any movement of the scope, as in don't touch it!!!

As you increase the magnification Jupiter (or anything else) will move rapidly out of view.

Collimation will be necessary, so get in practise.

Forget the barlow and until you get used to it all forget the 5mm, anything you see with that will go out of view quickly and need refinding.

Remember that Saturn is both small then Jupiter and is further away, So basically it is small and so more difficult to locate and see, and with the magnification required will wander out of the field of view pretty quick.

The learning curve is not gentle for a dob. I have read of people taking three or more months to get the hang of one and see anything. And that is not the longest.

[Staffy]

Could be that your finder scope is not aligned properly and although you are looking at Jupiter and Saturn through the finder scope you are actually looking at another star nearby through the main scope. I opened up my new scope last night and initially had a similar problem. When I did work out where I was going wrong and lined up properly on Jupiter - what a difference, all the Galilean moons and a nice big stripe across the planet itself.

[pop]

i have same prob jupiter not clear can see the moons

[mystery21c]

Dear All

Thanks so much for all your responses, I'm getting an idea of what's going on.

I think it might be Collimation.

I'm new to Collimation and have never done it before, I've been following Astro Baby's Guide which seems very simple to use, but have only completed stages 1-3, nothing on the primary mirror yet: Astro Babys Guide to Collimation

I checked the scope this moring and it was 1cm out of allignment, would this be enough for Jupiter to appear as just a white disc and not get any detail? or would it need to be furthur out than this?

Thanks

[dweller25]

How did you know the scope is 1cm out of alignment ???

[John]

Personally I think it's premature to jump to the conclusion that your collimation is miles out until you have tried observing without a window in the way and with the scope properly cooled.

If you start fiddling with the collimation now you could make things worse and have no way to check that.

I'd be amazed if the secondary mirror (you say that you have not checked the primary mirror yet) was "1cm out" to be honest.

[mystery21c]

When I looked through the collimation cap which was put over the focusing tube and looked through it, I could see the centre spot on the primary mirror was not in line with the secondary mirror, it was not centred. It looked to be out by roughly 1cm.

I've read these types of scopes need to be collimated regularly, but I was just curious to know if 1cm would be classed as "a lot out of allignment", and if it was, would this be the main cause of me not seeing any detail of Jupiter?

Have a good New Year:-)

[brantuk]

1cm is massively out if you are correct. To check collimation - focus on a bright star. Then defocus slowly one way for a short distance, then in the other direction for a similar distance. In both directions you should see perfectly concentric circles of light. If you don't see concentric circles, then it needs collimating. This is called a "star test" and should be done after every collimation to confirm it's set correctly.

Hope that helps

[pvaz]

1cm is pretty much off. A couple of mm is ok but ideally you want it centered.

Astro Babys Guide to Collimation

[MattTee]

Hi Mystery,

I agree with jahmanson regarding collimation,

I would try to look at Jupiter once more (you really should be able to see the moons even if they don't look like clear bright pin holes).

Not being able to see the moons would suggest that in the first instance you need to check the star finder scope.

As Jahmanson said fiddling with the collimation could make things worse so you need to be sure first.

Matt.

[Moonshane]

I agree with all the comments. in a scope like yours you need to ensure the black dot is right inside the centre circle and as evenly centred as possible. if you have the sort of collimation eyepiece that comes with these scopes that I think you have then it's an excellent tool and perfectly adequate to get good visual collimation. like the one in the pic? 1cm is miles out but easily corrected.

to line up your finder do it during the day but watch out for the sun. get eg a distant pylon in your 25mm eyepiece (the target does not matter but get one as far away as possible). then put in your 10mm eyepiece and centre the target in the main scope. with the pylon centred in the scope, adjust your finder until the target is also centred in the finder. check it's centred in both and you are done. move to another target in the finder and with the target on the cross hair centre you should then have it in the scope eyepiece too.

this will help a lot.

[Glider]

As you focus in and out do you go through a point where you actually do have a distinct 'disc', or is it a point? You have said several times you see a disc.

Could it be that you are focused on the right thing but the disc is just so bright to your eyes it is saturated and totally washed out?

Does the telescope have a large end cap with a smaller hole that you can uncover?

If so, put the cap on and just uncover the smaller hole. It'll cut down the light reaching your eye and might show more detail on the planets (if they are there!)

[mystery21c]

I've managed to collimate the telescopy so everything is centered, hopefully this will give me some detail of Jupiter and Saturn, I can't believe it was delivered so much out of allignment. I'll try and do a star test asap, was hoping tonight but there's a lot of cloud cover.

Thanks Glider for the tip about removing the small cap off the end of the telescope to let in less light. I didn't think I'd need to remove this for looking at planets and galaxies, I thought it might Only be used for looking at the Sun, with a solar filter of course, but I'll give it a try and see it removing it gives me more detail.

Thanks

[John]

...Thanks Glider for the tip about removing the small cap off the end of the telescope to let in less light. I didn't think I'd need to remove this for looking at planets and galaxies, I thought it might Only be used for looking at the Sun, with a solar filter of course, but I'll give it a try and see it removing it gives me more detail.

Thanks

You won't see more detail looking through a smaller hole.

Be aware that using the scope using the cap on but the small cap off, while reducing the light, also reduces the effective aperture of your scope to the size of the hole in the cap - and reduces your light grasp, resolution, detail and contrast to the equivalent of a scope with a mirror the size of that hole - I can't see the point in investing in a decent aperture scope only to reduce it's performance to that of something much smaller myself

You eye will soon adjust to the brightness and then you will start to see the detail that is there.

[Glider]

It has worked for me in the past in the context that the image is so bright to start with that you see nothing but a white disc, otherwise everything you say is true.

[mystery21c]

Yes, it worked!!!! I saw Jupiter for the first time in my life through a telescope last night through my Skywatcher 8" 200p, it was crystal clear and I could see the 5 moons aswel, which appreared as pinpricks of light, but although small through my 5mm lens, I could see the 5 orange bands of gases.

The moon last night with the moon filter looked spectacular, the contrast was amazing, the moon was only a quarter full.

Thanks for all your help guys, the collimation made a big difference, but also taking it outside to adjust to the temperature made a big difference.

Now just waiting for Saturn to get a bit closer so I can take some pictures with the new Philips webcam I've just bourght with the IR/UV Filter

Bournemouth UK