Another Eyepeice advise question

[Mez7000]

Hi Guys

Firstly, apologies as its another eyepeice related question...

Was out the other night mainly looking at the moon and then onto Jupiter.

Started on the moon with a 25mm and then took it down to 10mm (basically standard lenses supplied with scope) which gave excellent detailed views of the surface - infact quite breath taking really, so much so I got the kids and wife to take a look and think I may have given them the astonomy bug - in the words of my daughter "its bleddy big" and my youngest was disappointed, as the man in the moon was not there!

So onto Jupiter, at 25mm got basic points of light for the planet and moons but when I increase to 10mm got basically a 3-5mm view of Jupiter, a white disc with no detail, although the evening viewing had had a lot of cloud cover so I wondered if this was to reduce my viewing?

Basically, what I'd like to know is what I expect to see at this magnification (90x based on 900mm scope with 10mm lens) and what lens I should get to get better views, max on the scope is 260x so would buying a 5mm lens give better views? Should I use a barlow on the 10mm?

Again apologies, really first time out since I had it and just want to get a gut feeling as to what I should be seeing, understand I'm not going to get a full eye view of jupiter but since I've still getting to grips with the scope, I still unsure if I'm doing things right or not so some guidance would be ace.

What eyepeices would any one recommend, I like to probably purchase a 32mm, 12.5 or 15mm (or would using the barlow cover this with the 25mm) and probably 5mm ?

Thanks

Mark

[nightfisher]

The seeing really affects viewing jupiter and since its low in the night sky you are viewing it through more pollution, if you want to get another ep, go for a 32mm and then you can barlow it to 16, so very versatile, and 32 is great for looking at deep sky like nebula, when we get some really good seeing, then drop down to 10mm ep on jupiter, but no lower

[Watcher]

There is a calculation to establish your maximum useful magnification for your scope, but I can't remember it. I did find this page though, which suggests that more than 60x per inch of apeture in smaller scopes is achieveable, but only in exceptionally good seeing conditions: Highest useful magnification

[Capricorn]

The 10mm eyepiece tends to always be poor, the barlow usually isn't great so barlowing the 10mm will probably give something very poor.

Suggest that you go no lower in an eyepiece then the f number of the scope. So whatever your scope is that would give 130x magnification. I find my f/5 scope works best with a 6mm eyepiece, a 5mm just doesn't perform.

If you have an f/5 scope then to get 60x the dia you would need an eyepiece of 2.5 or 2mm, sorry but that is joke territory.

Was a nice thread on CN asking what use is a 4mm eyepiece, as a guide most uses are not as an eyepiece.

If the scope is f/5 then you will need a decent 5mm eyepiece.

[valleyman]

Jupitor will appear as a disc as you discribed, but once you have the focus correct and the 10mm is about as small as you want to with EP's the eye will adjust to the light from Jupitor and within a few minutes you will start to see the band round it, Try averting your vision (looking from the side of the eye and not the center). Remember there is only one band round it at the moment and not the two as seen in pictures.

[Moonshane]

In the UK and for most targets I tend to work on a maximum magnification of about 1.5x aperture in MM so for a 130mm scope it would be about 195x. This is in ideal conditions though. I have been using a 12" scope (450x based on the above) but for eg Jupiter have been getting best results around 120-150x. Some targets take more magnification well like the moon where I can regularly use 300x+.

The above calculation would mean that a 10mm eyepiece with a barlow (effectively 5mm) would give just under your max magnification but you'd be hard pressed to use that a lot of the time and perhaps buying 12mm (75x) or 12.5mm eyepiece would be a good bet as this would barlow to 6mm (150x) and give a more useable magnification more of the time. One good thing with regard to your scope is that it's f7 (assuming as you say it's 900mm focal length and 130mm aperture) so you will be able to use cheaper eyepieces to good effect.

good luck

Shane