Best EP

[Stargazer 2013]

Hi guys..Fantastic forum by the way.I just bought a

Skywatcher Explorer 130P  and have the normal 10mm and 25mm eye pieces,I wanted to know what is the best EP to view Saturn/Jupiter? I have a x2 Barlow coming soon and would it be too much of a magnification with  x260 ?  I just need to find these planets

[Andy_E]

Hi Stargazer, the 130p has a focal length of 650, which will give 130x with your 10mm+2xbarlow. This should be fine to view both planets and shouldn't be pushing your telescope too far.

[AlexB67]

It may a bit high, really does depend on the night and conditions too. As such it is pushing the max magnification for such a scope, but wait and see, what you see is what matters. I am sure if the skies are up to it on the night the views will be good on Jupiter. Saturn is out of reach right now in the sky in the UK     

Depending which barlow you bought, it may have the 1.5x adapter option by removing  the lower part of the barlow and attaching that directly to the eyepiece, that would  give you  a lower magnification too.

Good luck with it.

[Stargazer 2013]

Hi Stargazer, the 130p has a focal length of 650, which will give 130x with your 10mm+2xbarlow. This should be fine to view both planets and shouldn't be pushing your telescope too far.

Hi

It said where the place I  bought the scope from if I used x2 barlow I could get x260..I am still learning lol

[triton1]

I would suggest a bst star guider 8 mm.I,ve had great views of Jupiter and Saturn with mine and at £49 it won,t break the bank.260x magnification though might be pushing it abit unless seeing conditions are excellent.Hope this helps Jonn

[bingevader]

Yep, 260x is too much. Manufacturers like to post theoretical maximums. The practical maximum in this country is around 200x. So a safer bet would be to go for something around x150. Then you'd have an eyepiece you could use the majority of the time rather than when conditions are ideal. In your 'scope that would be about a 5mm eyepiece.

Cheers

[Stargazer 2013]

Thanks for your replies. So I would be better just using my scope with just the 10mm without the barlow?

[Andy_E]

The above posts are correct that 260x will be too much. However, your current EP set will give you; 25mm = 26x, 10mm = 65x, 25mm+2x barlow = 52x and 10mm+2x barlow = 130x.

to achieve 260x you would need a 2.5mm EP... looks like something has got lost in translation about your telescope. To work out the magnification, divide the focal length of the telescope (in your case 650mm) by the focal length of the EP.

Hope this helps, Andy.

[RikM]

The 10mm with the barlow will be fine for now. You work out the magnification by dividing the focal length of your telescope (650mm) by the focal length of the eyepiece (10mm) 650/10 = 65x then adding the 2x Barlow 65 x 2 = 130x magnification. The same as you would get with a 5mm eyepiece.

A lot depends on where you observe from and how stable the atmosphere is, also how well aligned (collimated) the mirrors, focuser and eyepiece are. it may be possible to use a little more than 130x magnification on some nights but not on others.

Something to remember is that with some simple eyepiece designs like Plossls, as the focal length of the eyepiece gets smaller, you need to get your eye closer to the lens to see through it. If you wear glasses this may be a problem.

[Stargazer 2013]

wow..so much to learn..Again thanks for advice

[ronin]

For the time stick to a 5mm eyepiece (130x). As long as the image is good you will see Jupiter very well, it is big enough that lesser magnification is OK. 130x is good for Saturn.

Never sure how good the 10mm and a barlow will come out.

I would not expect the scope to get anything like 260x, it should get 150x and maybe 180x after that the image quality will drop off. A 4mm would give 162x, which I would say is as far as sensible. There are not many 4mm around so if the barlow is good suggest an 8mm eyepiece and then you can use it as an 8mm or barlow it to try 4mm. The 8mm on Jupiter should be pretty good.

[Stargazer 2013]

ok..I better start saving for the smaller eye pieces

[AlexB67]

wow..so much to learn..Again thanks for advice

As long as it is enjoyable and enjoy the views nothing to worry about , If there is one tip I would give early, as advertisers love to do this in some cases, and it is an easy trap to believe in,  that is the hype surrounding maximum magnification possible with telescopes, especially more so for toy scopes bought from non specialist stores I should add, not your scope which should be a well capable instrument.

You'll find  in time most things are actually viewed at much lower magnification and some things at higher mag, like planets, double stars, but ultimately it is not about how big as possible you want to see something, but it is a compromise of factors that gives the best views in terms of clarity, contrast and size, there are competing factors. Some of it a bit subjective as well, some like higher mag more than others and will feel their optimum is not the same as that of the next person. 

[ronl]

To help you understand the different types of eyepieces try this link

http://www.swindonstargazers.com/beginners/eyepieces.htm it's a 

beginners guide to eyepieces, and there are other links to further

articles all about eyepieces, it's a great site, you will learn a lot from

it, I certainly have. 

[Stargazer 2013]

To help you understand the different types of eyepieces try this link

http://www.swindonstargazers.com/beginners/eyepieces.htm it's a 

beginners guide to eyepieces, and there are other links to further

articles all about eyepieces, it's a great site, you will learn a lot from

it, I certainly have. 

yes very interesting that ..Thanks

[brantuk]

The highest practical power of 260x magnification assumes absolutely perfect observing conditions and a perfectly set up scope. In the UK you can rarely achieve that with our weather - if at all. I usually work to around 80% of the quoted maximum for any of my scopes. So in your case I'd suggest around 200x would be a more realistic figure on a good transparent night. You'll get a great  amount of planetary detail with that.

[Stargazer 2013]

what size lens would I need to achieve this brantuk? At the moment I can only avhieve 130x with a 10mm and x2 barlow

 

[Stargazer 2013]

I am more of a planetary person..Stars keep moving when I try to focus and just look like dots in the sky

[brantuk]

Well a 4mm eyepiece gives you 162x magnification, a 3mm ep = 216x mag, so somewhere between the two would be the closest. The big issue is going to be that you'll need pretty good quality eyepieces because you have a focal ratio of f-5. The faster the scope the better the eyepieces usually need to be.

I suggested 200x as a more realistic practical maximum - you'll still see a good deal of detail at 162x. For planets I generally observe around 150x to 180x - and I only attempt to push it up a bit on really good nights. But then I do have some longer focal length scopes - my shorter fl scopes like your's get used more for low mag wide field observing - and a very limited amount of imaging.

So you "might" get reasonable results with a 4mm (or a barlowed 8mm) on a really good transparent night - but it's not really the scope for high magnifications. A Maksutov or Sct would be better at that.

[Stargazer 2013]

Thanks for your input

[wookie1965]

A 5mm BST would be good in your scope great for fast scopes £49 so wont break the bank plenty of eye relief if you wear glasses, i have it and Jupiter 2 nights ago was fantastic in it by the way my scope is a fast scope f5 and i wear glasses.

[Stargazer 2013]

I heard about the f5 being a fast scope but what does fast scope actually mean? Is it moving from one star to another quickly? 

[brantuk]

It refers to the focal ratio of the scope calculated as the focal length divided by the diameter. Eg a 200P with a focal length of 1200mm would be 1200/200=f6. F7 is regarded as medium speed with f10 being slow and f5 being fast.

Now I'll get blown out of the water probably - but it mostly has little relevance to observing. It's more of an "imaging critical" measurement. At f5 your scope will gather light quicker than an f10 scope - which means the time taken for long exposures of deep space objects will be shorter (or quicker). It's highly relevant to taking pics of distant, faint objects like clusters and nebulae.

As far as observing goes - slow scopes are more tollerant of lesser quality eyepieces. But the BST eyepieces mentioned above by Wookie are highly regarded for use in faster scopes by a lot of the folks who own them (I must try one sometime). For the price they certainly seem to offer good vfm.

That's my laymans understanding of it cos I have little experience imaging. But I'm sure someone will offer "corrective comments" lol.

[Stargazer 2013]

Ok.Thanks..I have been reading up and heard that Jupiter is more or less the best time to see it.

By the end of November, Jupiter is up by early-to-mid evening (approximately 8 p.m.). Jupiter in mid-evening means we are getting closer to the giant planet’s yearly opposition, which will happen in early January 2014.As I look at the moon is Jupiter more or less NW of the moon?

Would love to see it as I have just got my x2 Barlow lens

[brantuk]

The moon moves quicker across the sky than Jupiter so it all depends on what time you are looking to determine where they are in relation to each other. Last night I was outside and Jupiter was quite high in the East at 10:30pm - certainly very observable if the weather was clear. By midnight it was even higher still in the South East and the moon was well out of the way in the South West. Orion was reasonably placed too just a little lower than Jupiter and nearer the South - well worth a look at if the horizons not too murky.

So pop your head out between 10pm and midnight tonight and you'll see them dead easy if it's clear. Did you download Stellarium yet? If not then do so - it's a cracking bit of software for finding where stuff is at your observing location any time of day or night.