New eyepiece??

[Jimb01985]

Hi guys I have a celestron nexstar 130SLT with a 9mm & 25mm 1.25 eyepieces. I also bought a celestron excel Barlow. I was looking at Saturn for the first time the other day. It was amazing!! ? But I would like to be able to see more detail my best view was with the 9mm and the Barlow. Any suggestions as to what eyepiece(s) I should get?

[John]

Hello and welcome to the forum !

How often have you viewed Saturn ?

The reason I asked is that what we call the "seeing conditions" have a big impact on how much detail you can actually see and these vary night to night, sometimes quite considerably. Also experience of observing an object and time spent on it, also increases the detail that you can pull out.

Also did you allow your scope some time to cool down before observing ? - again this can make quite a difference to the clarity of the image.

An additional eyepiece might make some difference but the factors I've mentioned above are far more influential I think.

 

 

[Carbon Brush]

Hello and welcome to SGL. I remember my first view of Saturn through a 'proper' scope. Amazing doesn't begin to describe it.

Thumbs up for everything John said.

I would add checking collimation if you haven't done this yet. Then again if you are happy with the view from 9mm barlowed, collimation can't be far out.

To be fair, eyepieces supplied with scopes are OK-ish. You have to remember the manufacturer is trying to put a full package together for a low price.
At this stage see how you get on and consider another eyepiece at leisure.

Your profile pic shows you wearing specs. Do you keep these on for the scope?
This will have a big impact on any eyepieces you purchase.

Enjoy Saturn and much more, David.

 

[Ricochet]

You may find that a 2x barlow and 9mm eyepiece is the optimum planetary magnification for your scope. I would probably be inclined to look for something at about 7mm and try that with your barlow on the planets. If it isn't an improvement it would still be useful on other targets. 

[heliumstar]

You were wowed by the image so why not straight to 4.5mm that will give you the same magnification as the view you were wowed but with higher quality eyepiece you should in theory be able to see more details. Baader Morpheus 4.5mm comes to mind, Vixen SLV 4mm as well. Or like Ricochet said 7mm can be useful and barlow it down to 3.5. Don't be afraid of high magnification. It can surprise you at times what can be done in these low cost scopes. I went to 260x with achromatic refractor and Saturn was beautiful. Yours is a Newtonian so not sure how it compares but if I were you I would try and go to 200x and above. Just to see what happens.

[japacheze]

There are many factors that influence the level of detail you can experience. Let me concentrate on just the numbers.

Think of your scope / eyepiece combination in terms of exit pupil (which directly translates to magnification per mm of aperture). It's all about aperture, and you can only ask your scope to perform within its aperture constraint. 

You already noticed that your 9mm ep with a 2x barlow was great, and Ricochet mentioned that this is the optimum for your scope. I wholeheartedly agree. This combination gave you 144x at an exit pupil of 0.90mm.

A great exit pupil for planetary detail is 1.0mm . You can push this to .75-.8mm, but I do not recommend anything beyond that. An exit pupil of .5mm is often used for double stars, but I don't recommend it for planets.

So how does this relate to your eyepiece/barlow selection? Exit pupil is easily calculated by taking the focal length of your eyepiece (divide by 2 if using a 2x barlow), and dividing that by the focal ratio of your telescope. Yours happens to be f/5.

If you want more magnification than a .8mm exit pupil can provide on your scope, then you need a bigger scope. 

Here are some figures you can use:

 

[Louis D]

Take the money for another eyepiece and save up for a larger aperture telescope.  I liked the views through my 8" Dob, but I wanted greater planetary detail, so I bought a 15" Dob a couple of years later.  The difference is dramatic.  However, I'm not sure UK skies are agreeable with large apertures like Texas skies.  That, and the planets are 20+ degrees lower in the sky making it more difficult to see them through so much more atmosphere.

[baggywrinkle]

As a Norfolk (UK) inhabitant the skies here currently are pretty bad and Saturn suffers like Mars and earlier in the year, Jupiter, from being at very low altitudes so the seeing is bad anyway.

The good thing about investing in eyepieces is that as you grow with the hobby they can be used on new equipment. You usually only sell on those supplied with the original equipment.  Generally those supplied ep's are not of the greatest quality either.

The 130SLT , an F5,  is pretty fast, the theoretical max magnification would be around 260 x on a very good evening.

A 2x barlow with your current 9mm would give around 140x BUT the eye relief on that ep would  not be good and the image further dimmed as the light is going through another lens (the Barlow).

For general observation the Baader 8-24mm zoom give pretty good eye relief through its range and IMO decent views for the price. It is not 100% at all points but few ep's are unless you are paying Televu type prices for individual lenses.

I would not invest in the Celestron chocolate box of ep's. The ones lower than 9mm have very bad eye relief and are generally unusable with many entry level telescopes.