Magnification of Skywatcher 200P

[Ayrton]

I'd been waiting for my first scope for about 6 weeks (the boat from China was very slow it seems!), so I rigged it up over the weekend in eager anticipation. However having found Jupiter, whilst I was very pleased to see a coloured band on it and 4 moons, it was a little smaller in the eyepiece than I expected.

This scope is 200mm across and 1200mm long. With a 10mm eyepiece my understanding is that the magnification is 120x. At that rate, how big would you expect Jupiter to appear in my field of view? I thought my expectations were realistic but I did think it would be bigger than a small pea...

Similarly with the moon, at about 60% full last night, I could see more than half of what was lit with the 10mm. The detail I could see was very exciting but again I thought I'd be closer in.

Have I set this up wrong somehow? Or were my expectations unrealistic?

Yours,

<man desperately in need of Barlow?>

[Ben Ritchie]

You're right, but your 'maximum power' of 120x is fairly low for typical lunar/planetary viewing - something close to 200x is a good rule of thumb for maximum power under typical UK skies, and you can go higher when conditions are good.

You could get a 2x barlow, but that pushes the magnification to 240x which is a touch higher than ideal, or a 6mm eyepiece.

edit: to put it another way, Jupiter is around 50 arcseconds across at closest approach, your 10mm eyepiece will have a field of view of about 24 arcminutes, roughly 30 times larger - hence Jupiter looking small.

[John]

Even with quite high magnfication, eg 250x, Jupiter does not appear much bigger than a pea. 200x - 250x is about the most you can usefully use under our seeing conditions in the UK (even though a 200 aperture scope is "theoretically" capable of 400x).

The good thing is that your scope will show some nice details on that "pea".

You could try a 2x barlow lens with your 10mm eyepiece or (better) get soemthing like a 6mm eyepiece to give you a bit more power (200x).

The planets do appear quite small through a scope to be honest - we probably get used to seeing enlarged images and expect thats how the will look visually.

[NGC 1502]

Yes, maybe your expectations were for a much larger view of Jupiter.

But I much prefer a smaller but sharper view, than larger and fuzzier.

Under good conditions however, your scope should easily go to a greater

magnification than 120x.

Best regards, Ed.

[darkly]

Hello there.

I have a 200P and love it to bits, it'll show DSO's as well as planets, best of both worlds really.

You probably got a 2 x Barlow with it, shove that on the scope and then your 10mm onto the Barlow. That'll up the magnification but also any atmospheric distortion.

I treated myself to a Revelation Photo-Visual Eyepiece kit, Eyepiece Sets - Revelation Photo-Visual Eyepiece kit

which covers pretty much the full range of magnifications for the 200P and also has a selection of filters to get started with, this'll keep you going throughout winter.

First thing I noticed was how much better the eye pieces were than the supplied ones! You'll especially notice this using the Barlow at first.

Your scope can also handle a 2" 38mm Panaview Skywatcher - Skywatcher PanaView 2" eyepieces eyepiece really well, see Astro Baby's site, Astro-Baby Astronomy Website loads of 200P info there.

Once you get a handle on it you're going to love the 200P, a year on and it still makes my day every time I use it.

[Ayrton]

Thanks for the responses people. I'm not quite sure what I did expect, from Jupiter I suppose I thought I'd get at least 5 pence and may be 10 I will reset my expectations accordingly!

In the short term I think I will try this and maybe have a word with Santa about a high quality 6mm or something...

[darkly]

This scope is 200mm across and 1200mm long. With a 10mm eyepiece my understanding is that the magnification is 120x.

Correct me if I'm wrong peeps but;

With a 200P, a 10mm eyepiece gives a magnification of 100x

Add a 2 x barlow and it becomes equivalent to a 5mm eyepiece and gives a mag of 200 x

The spec for a 200P is quoted as;

Magnifications with supplied eyepieces (and barlow) x40 (x80) x100 (x200)

Highest Practical Power (Potential): x400

Diameter of Primary Mirror: 200mm

Telescope Focal Length: 1000mm (f/5)

Eyepiece Supplied (1.25"): 10mm & 25mm

2x Deluxe barlow

Taken from FLO site

I use an Eye piece calculator that I found somewhere on this site (NOT MY OWN WORK).

I hope this helps some what.

Also, using this calculator i made a small spread sheet of EP's and their mags which I keep to one side with my gear (It saves thinking, although I use it less and less now)

Hope this helps.

EP_Calc_v2.xls

Eyepiece and Barlow mags 1 04-01-10.xls

[lukebl]

It's all down to practice and training your eye to tease out the details.

Even the biggest scopes can't manage much greater magnification in the UK due to air turbulence and quality. For one brief moment a few weeks ago, the air was so still I managed to view Jupiter crisply with my 3x barlow and 9mm eypiece (which gave 400x magnification). It was a fabulous moment, but lost within a few minutes!

[Ben Ritchie]

With a 200P, a 10mm eyepiece gives a magnification of 100x

Confusingly there are two 200Ps, a f/5 OTA and a f/6 Dob. The OP has the f/6 one with focal length 1200mm, hence 120x with a 10mm eyepiece

[darkly]

That's what I found last year, we had one really crisp night, very cold and absolutely still, perfect viewing!

When I thought about it afterwards, I remembered that I'd seen similar nights before I had the scope when I'd been out for fire wood / coal and ended up just staring at the sky for ages.

It took me by surprise that time, this year I'm all geared up for it when it happens.

And it will happen - posative vibes everyone.

[darkly]

Confusingly there are two 200Ps, a f/5 OTA and a f/6 Dob. The OP has the f/6 one with focal length 1200mm, hence 120x with a 10mm eyepiece

Right, I just saw 200P and jumped right in there

I'll know next time

[Ben Ritchie]

That's what I found last year, we had one really crisp night, very cold and absolutely still, perfect viewing!

They're rare, but worth the wait - I had one with Saturn a few years ago which was unforgettable. More common are nights that aren't spectacular in themselves but have intermittent moments where the seeing stabilizes, so it pays to spend time at the eyepiece watching and waiting.

[Ben Ritchie]

Right, I just saw 200P and jumped right in there

I'll know next time

I've done exactly the same thing before now

[John]

.... More common are nights that aren't spectacular in themselves but have intermittent moments where the seeing stabilizes, so it pays to spend time at the eyepiece watching and waiting.

So true. During an hour or so observing an object you might just get a few seconds here and there when you can really see what your scope can deliver. These moments are what it's all about IMHO

[darkly]

Cheers, looking back up the thread the clues were there;"This scope is 200mm across and 1200mm long." all along !!!

DOH!

[spaceboy]

It's easy to think your going to see large images of planets given some telescopes advertise 400x magnification. But in reality your looking through miles of turbulence, dust, carbon monoxide or is it dioxide? and light pollution so the truth of the fact is even if you could use 400x magnification you have to bare in mind Jupiter although is huge it's 365 million miles from earth. I think the fact that Joe public can get pea size images of distant planets is amazing in it's self. Given good seeing and a well adapted eye more detail can be appreciated from even this small image.

Give it time and you will start to get used to all the tricks of getting your eyes dark adapted and keeping them that way as it make such a difference.

SPACEBOY

[perrin6]

'Patience and time...patience and time...' Planets are 'small', skies are often obscured and even when clear they can be turbulent, . I don't think Astronomy has got easier over the centuries (although it has got a lot cheaper recently-due to hard working, underpaid chinese people mainly, I think) - it's got harder due to light-pollution, in fact.

Astronomy can be 95% boredom and frustration - 5% joy and wonder. Take last night for example; My nose was running like a train due to a cold but it was clear so I 'had' to get the scope out - lights were blazing into my eyes from the building site at the end of my garden making it hard to see anything clearly. It took an hour for the mirror to cool so had to wait for the blobby stars to become less blobby (they never got sharp), then the scondary got dewed up so out came the handheld fan. Then the stars still didnt look as good as they should (was a mist developing or was there dirt on the eyepiece or had I breathed on it, perhaps the temperature had dropped sharply so that the mirror was too warm again and the cooling fan had to be switched on again?). After 3 hours I had seen two planetary nebulae that I'd never looked at before - and they both looked similar. Am I going to be out there again tonight if it's clear - you bet !

Just keep watching 'Jupe' and wait for those magic moments when the 'cloud of obstacles' disperses and allows you to glimpse things you've never seen before and will remember for the rest of your life .

[lukebl]

I mentioned a few posts earlier the need to be patient, and that I recalled one moment of perfect seeing a few weeks ago. Well, I have just experienced the most perfect seeing I've ever experienced this evening. It is getting foggy, and I turned the scope on to Jupiter with a 4mm eyepiece (300x) and the view was absolutely breathtaking. There was no turbulence at all, and I could see more detail that I've ever seen before - a whole range of subtle markings. The combination of the lack of any turbulence in the atmosphere at all, and the reduction in the planetary glare caused by the fog, resulted in perfect conditions. That was through a 250mm, and your 200 would undoubtedly have a similar view.

So the message is, be patient, learn to use the scope, and enjoy those rare moments of perfection!

[darkly]

Nice one !!! You must be well chuffed tonight !!!

Probably won't sleep now.

It's a shame how random nights of good seeing are though, too many factors have to be just right I guess.

Yes, I'm stuck out here feeling a teeny bit envious (for all the right reasons though).

[John]

..It's a shame how random nights of good seeing are though, too many factors have to be just right I guess...

While nights of consistent great seeing are pretty rare, short moments of really good seeing can crop up even on mediocre nights. If you spend time on an object like Jupiter these short glimpses can still make for a rewarding session - as well as confirming that your scope / eyepieces / eyes can cut the mustard when they get the chance

[darkly]

Yes, I'm with you.

Although, what I should have said was "shame how random moments of good seeing are"

but yes, I fully agree with you.

[spaceboy]

Hi Ayrton

I think when I was a beginner you find you are drawn to the planets as they seem the obvious choice and often the easiest thing to find. I still get great pleasure from viewing the planets and more so when Saturn is up high but there is so much more out there. I know it can be a pain in the neck and I mean that literally when trying to find DSO's but most can be viewed with only moderate seeing conditions at low power and give just as much wow factor. Granted to really explore deep space in all it's glory you need dark skies but open clusters, brighter nebula and galaxies can be made out using filters in LP areas. You have a scope that is suited to either DSO or planets, so on them nights when you find it a strain on the eye to look at planets drop in a low power EP and have an explore of the Messier catalog. You will need advice on what part of the catalog you will get to see under your given sky but there are plenty of people with the know how on this forum to help.

SPACEBOY