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4 or 5mm plossl much improvement than a 6mm?


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Hello All.

Well its been a few months since I had my scope out. Hard to find the time just recently.

I did manage to get it out of the shed last night to have my first ever look at Mars an Venus. Ended up though viewing more of Jupiter (My favourite)

My question is I have a 6mm Meade Plossl which is very good but I just want to see if I can get just a little more magnification out of my scope. I have a Skywatcher 130P Newt.

With my 6mm I can see faint banding of Jupiter, However if I use my barlow x2 or x3 I just can not get it in focus enough to make out any decent detail.

If I bought a 5mm or 4mm plossl would this make much of a difference to my magnification and perhaps bring me that little bit closer to Jupiters detail I so long to see.

I kind of know the the best way forward is for a bigger scope but family commitments prevent me from upgrading.

Thanks in advance for your help.

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I agree with Peter, you used too much magnification. Air turbulence will degrade the view at higher magnification.

The 6mm gave you a magnification of 108x, while a 5 and 4 will give you 130 and 162x. Both are OK if you can live with the extremely short eye relief of short focal length plossl. Alternatively, I'd suggest a good 10mm plossl and a good barlow (such as a TAL 2x) which should be more comfortable to use.

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The 5mm will let you see well on saturn and jupiter will look great (if you can keep them in the eyepiece long enough!) tRY THE 5MM AND IF ALL GOES WELL, TREAT YOURSELF to the 4mm in the future. also 5mm should bring out the core of m42 brilliantly.

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More magnification rarely leads to more detail being seen. Often the opposite as Peter (Cornelius Varley) says, especially with Jupiter. What you will get is an enlarged version of what you have now, probably with less contrast and therefore less detail visible.

Also, Jupiter is getting lower down now and you are viewing through more of the atmosphere which gets in the way of detail too. In early December this year Jupiter will be at opposition again and high in the sky in Taurus. You should get better views of it then.

The main reasons for not seeing as much detail as you would like are probably the seeing conditions and perhaps collimation needs a tune. It also takes a lot of time at the eyepiece to pick out the subtle details beyond the main 2 cloud belts as they flicker in and out of visibility as the seeing comes and goes.

Edited by John
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Thanks for your replies. I figured I was using too much magnification when I used the barlow. I think I should have asked my question better. Basically with my 6mm the detail is great and image is sharp. Just a tad on the small size (Jupiter) so I was thinking whether a 5 or 4mm plossl on its own would make much of a difference to the image I currently see using just the 6mm with no barlow.

To spend another £30 -40 on a 5 or 4mm and then see no real improvement / enlarging of the object I would be a little disappointed. I really like my Meade 6mm plossl so much so that I bought a 26mm one too. I dont use the skywatcher ones that came with the scope any more.

I guess I am looking for options on improving Jupiter, to barlow or not to barlow that is the question using bigger plossl's or to just go for small plossl wiht short eye relief.

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Thanks John.

Nice reply. I did view Jupiter late last year when it was at its peak. My first sight of it since starting this hobby 12 months ago. It was a great sight. Last nights viewing to my eyes I was still seeing the same amount of detail. I can only just see faint banding of Jupiter. Maybe I have reached the maximum potential that my scope can give me. I guess in this hobby that is always the problem. We always want to see much more than we can.

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personally, I prefer individual eyepieces than barlow plus eyepiece but in this case as you have a barlow and the 10mm, you may find this better initially and it will certainly confirm the image size even if not perfectly clean.

then you can go ahead with a bit more confidence to buy a good quality 10mm plossl to use with the barlow.

buying eyepieces is a massive area and prices range from maybe £10 used to maybe £700 new so it's really about assessing the sort of observing you do, the capability of your scope and yur budget and buying the best for all of those.

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Once again thanks for your replies. I think I might stick with just using plossl's rather than barlowing to get more magnification.

I find that my Barlows are only really good on the moon and Saturn.

I would love to see Jupiter in more detail but looks like the only way I will be able to achieve this is through upgrading the scope to a bigger aperture.

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Using a correct eyepiece instead of the barlow will give much better, clearer results.

ie 10mm+barlowx2 vs 5mm = 5mm always looks better.

I don't agree, a 5mm eyepiece is harder to make well than a larger 10mm, and the eye relief in the 5mm will be much shorter. If you have a good barlow, a barlowed 10mm can give you better and more enjoyable results than a 5mm.

The Skywatcher kit barlow is poor, but I always found barlowing a 25 mm Keller gives more pleasant result than using a shorter unbarlow Kellner.

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I don't agree, a 5mm eyepiece is harder to make well than a larger 10mm, and the eye relief in the 5mm will be much shorter. If you have a good barlow, a barlowed 10mm can give you better and more enjoyable results than a 5mm.

The Skywatcher kit barlow is poor, but I always found barlowing a 25 mm Keller gives more pleasant result than using a shorter unbarlow Kellner.

Each to their own I guess.

I have a 25mm Kelner and it is very good but I go with my 12.5mm over barlowing the 25mm any night as you get much crisper, clearer views.. Same with all my eyepieces.

The only one I do barlow is the 20mm and that is only because I do not own a 10mm.

Barlowing is good when you can't afford/cant find the eyepiece but you are using a lot more glass this way and the picture will never be as good as a well made eyepiece of the correct focal length.

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Very true.

A zoom eyepiece is even better at that, one eyepiece to do it all.

I have been wondering about zoom eyepieces for a long time now. Are they worth it? and do they work well?

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A Baader Hyperion Clickstop zoom cost around £125 used. It's the cheapest of the prime killer.

Cheaper zoom eyepieces don't perform anywhere as well as primes. Zoom eyepieces are more complicated to make, so in order to achieve similar quality to primes they will be more expensive.

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Check your scope for good collimation, if you are not seeing pretty decent banding on Jupiter at 100x there is something amiss. The scope should be easily capable of it and 100x should show banding up well.

Wouldn't recommend a 4mm plossl eyepiece for anything, bought one once and learnt that it is close to useless.

There was a thread on CN once that asked What can you use a 4mm plossl for? Using one to view through a scope was not one of the options. Think the most common recommendation was take the lens out and use it to collimate the scope.

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Not many people would get any use out of a 4-5mm EP. I have a 6mm Celestron Omni and that only gets used very rarely and only ever when observing the moon. Anything below 6mm would be too much magnification for the 130P and the exit pupil on the EP would be way too small to be of any use.

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I use my 4mm to see a nice large M42 and trapezium. Lots of detail but not sharp, bit blurry, but still super.

The 6mm is great too.

I use the 6mm to enjoy large views of jupiter and enjoy it a lot.

With the 4mm I can see a hint of the cassini division on saturns rings and with the 6mm I get a sharper image but no cassini division.

My scope is an f/8 so this possibly helps.

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