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Not sure which eyepiece to buy for Explorer 150p

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Hi Everyone,

I just bought a SW Explorer 150p after recently becoming fascinated with astronomy. I'm a complete noob apart from reading everyone's informative posts on this forum over the last 2 weeks.

I have looked at Jupiter for a few nights early last week when we had some clear skies. They were fantastic views especially compared to the tesco telescope I initially bought! I could see Jupiter's moons which was also a first. I was a little disapointed though as I could barely make out the cloud belts as Jupiter appeared quite small. I was using the 10mm eyepiece wiith the 2x barlow that come standard with this scope. This brings the magnification up to 150x.

I understand that this scope should be able to go up to 300x. This would mean a 5mm with 2x barlow would achieve this.

Would this be the right eyepiece to get? Or should I get a 3mm instead? Or am I completely off track?

Thanks for your advice in advance!

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The maximum mags quoted are usually theoretical. With our usually turbulent

atmosphere limiting what can be clearly seen, 150x is much more realistic.

Jupiter is way past it's best just now, and will be lost in the sunset glow as

we get into spring. However, Saturn is coming into view at a more convenient

hour before long. Low in the SE late evening at the mo.

Loads of other objects to view with a nice 6" scope like yours.

Best regards, Ed.

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I'd stick to 150x - 200x as Ed recommends - I rarely get to use 300x with my 10" scope. One of the 4mm TMB Planetary II eyepieces would do a good job for you - they cost around £40 each.

Edited by John
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Thanks for your advice John.

I've had a search for places selling them and then came across threads comparing Paradigm's to TMB Planetary II. This hobby ties you up in knots with what to do and buy!

That matches my budget at least.

Any suggestions on whether to go for the former or latter eyepieces?

Also, I know you recommend the 4mm John but I as most others on this forum want to try and stretch the capabilities of their scopes.

So would a 5mm TMB which could go to 2.5mm (pushing to the max!) with 2x barlow

or 3.2mm TMB be suitable? This would bring my scope to 234.3x

In Stellarium a 3.2mm brings Jupiter to a decent size where I feel a 4mm is still quite small. I don't know how realistic Stellarium is but it is quite close on

its virtual view of Jupiter with a 5mm eyepiece compared to what I saw.

Best regards,


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....Also, I know you recommend the 4mm John but I as most others on this forum want to try and stretch the capabilities of their scopes....

No problem - I quite understand :)

I just didn't want you to waste money on an eyepiece that would hardly ever get used.

If you do start using a barlow lens - make it a good one - it's a shame to spoil an otherwise good quality optical train with an average barlow lens.

Edited by John
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Both 3.2mm and 2.5mm (a barlowed 5) are too much; your views will be blurry.

However, since Sky's The Limit (the main sellers of the TMB Designed Planetaries) offer a scheme where you can take a selection and return the ones you don't want, the advice is a bit academic - just get three of them and see what works for you.

(then you'll discover that the 4mm gives you the best views after all, but we won't say "we told you so..." even though I've just purchased a 4mm last week for exactly the same reason :) )

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Thanks very much for your knowledge and also the pointing out Sky's the Limit. That's a great way to do business.

Unlike others who don't have a clue about customer service! My only knowledge I can share is "Don't ever buy from Seben on ebay". It may be obvious to experienced astronomers but Noobs like me should be aware.

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I've just ordered a 4mm from Sky's the Limit. Can't wait!

I just saw your deep sky album Rik. Those are fantastic photos! Can I ask what size ep's you used? And were they the standard ep's that came with your 150p?

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I am glad you like them :(, but I am really just starting out with imaging and there are far more experienced and accomplished members over on the imaging forum. :)

All my images are taken with a DSLR camera body attached to the focuser via a 2" adaptor. That is at 'prime focus', so without a camera lens or eyepiece in place.

This is completely different from what you will see at the eyepiece. If you take a look at my sketching album, that will give you more of an idea what to expect visually. At least for DSO's from an average suburban UK observing site.

Edited by RikM
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  • 2 weeks later...

I just wanted to thank everyone on this thread who advised me on getting the 4mm TMB Planetary II.

I used it tonight on jupiter and the views were great! Also I can see that going with more magnification would of made the views worse. Jupiter was significantly darker in the TMB eyepiece compared to my standard 10mm and 25mm ep's. And although the image is smaller with my standard ep's the view was more crisp and bright. The 4mm ep's was definately on the border of the limits for viewing tonight.

Tonight was by far the best I have seen jupiter. I could clearly see it's cloud belt and Io move from the side of jupiter to the front of jupiter. Then the clouds came in :glasses1:

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