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Lenses?


Kaznkev
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I have a skywatcher telescope that came with 10mm & 25mm lenses.

I'm thinking of buying a x2 Barlow but what would be the best option if I want to look at, and get a good view, of Saturn and other planets?

After doing the Orion course I would also like to get a good look at the Orion Nebula.

Would the lenses I have along with a Barlow give me a good chance of viewing these or should I be looking at somthing else like a plossl or the skywatcher UWA planetary eyepieces?

I just don't know enough about different eyepieces and attachments to make up my own mind yet so any advice would be greatly aprieciated.

*sorry if this question is asked all the time by the newbies.

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Hi mate,

I think the general consensus, which I agree with having been through a similar scenario, is upgrading eye pieces (EP's) from the supplied is a good idea. The stock EP's aren't usually the best. I've just written a review between the Celestron X-Cel (an affordable mid range EP) and the Celestron Luminos (a premium EP). Without re-writing the thread, I would recommend both, but I have bought the luminos.

The ep's you have with your 650mm focal length scope, will give you a magnification of 65x (10mm EP) and 26x (25mm ep). You divide the focal length of the scope by the focal length of the EP. The shorter the focal length of the EP, the more magnification you get, so a 5mm EP will give you 130x mag.

A 2x Barlow essentially halves the focal length, so a 10mm EP used with a Barlow gives you a magnification of 130. Essentially it means if you choose your EP carefuuly, you can fill the gaps using the Barlow.

The longer focal length, less magnification EP, will allow you to see objects such as the Pleidas. Using higher mags would be like looking at a few stars rather than seeing the cluster as a whole. The higher mags, such as the 10mm should allow you to see the details of Jupiter for example. The 25mm wouldn't give you enough magnification to see the bands. The 10mm should allow you to,see the Orion nebular and the trapezium stars. If you read my review of both EP, I could see the nebular with both of those, one being a 23mm and one being a 25. The magnification on my skywatcher explorer150p is is a bit more as the focal length is 750.

Also, seeing conditions, light pollution would have a major effect on your viewing. Even viewing over the top of a roof radiating its heat will have an effect.

To sum up, have a think about your budget and decide what EP you want. If you want a Barlow so you buy less ep's don't buy, for example a 10 and a 5 because the 10 plus a Barlow essentially gives you the 5.

I hope that makes sense! This is the first time I have offered advice on the forum, so I hope what I have written is correct. I am sure I will be corrected if not!!

Cheers.

Alistair

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Astroboot have a bargain Revelation 2x Barlow currently, got one last week for Skywatcher 100P and very happy with it

for what its worth the SW 25mm seems quite good but didnt get got on with 10mm, mostly due to eye relief (cos we all wear glasses in our house) and got a SW LER 9mm. Telescope House had some good deals on Revelation plossls last time I looked

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130P is 650mm FL.

As Orion Nebula is about a degree across you want about 50x so that means a 15mm eyepiece (OK 13 to be exact but more chance of a 15mm eyepiece, and M42 is a little bigger).

That will put all of M42 in view.

The see the central bit, where the Trapesium is, then you will need more, lets say double so about 100x to 120x, which is 6mm to 8mm area.

Which eyepieces, you have the choice of plossls - GSO/Revelation/Vixen or BST Starguiders or Celestron X-Cel's. They are the ones most often referred to, and are therefore probably the safest bet. Must look at alternatives one day. Be aware that 2 eyepiece will from the previous cost a minimum of £70 and up to £120.

Check the used side ABSUK, someone may have some for same that could suit.

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If you just want to improve the current situation without bust the bank, a suggestion would be the 2xbarlow as given above and the 9mm planetary ep you mentioned.

Keep the 25mm and the 9mm and you have the following with a barlow.

25mm = x25

25mm+B = x52

9mm = x72

9mm+B = x144

That gives you 1 low power, 2 in the medium range and 1 high power.

Most members on here would agree that this is a good point to start your observing until you find your feet and to get there would cost you around an extra £50. I don't think thats to bad a spend and should keep you going for at least another 6 months. (or until you get aperture fever)  :grin:

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Hi mate,

I think the general consensus, which I agree with having been through a similar scenario, is upgrading eye pieces (EP's) from the supplied is a good idea. The stock EP's aren't usually the best. I've just written a review between the Celestron X-Cel (an affordable mid range EP) and the Celestron Luminos (a premium EP). Without re-writing the thread, I would recommend both, but I have bought the luminos.

The ep's you have with your 650mm focal length scope, will give you a magnification of 65x (10mm EP) and 26x (25mm ep). You divide the focal length of the scope by the focal length of the EP. The shorter the focal length of the EP, the more magnification you get, so a 5mm EP will give you 130x mag.

A 2x Barlow essentially halves the focal length, so a 10mm EP used with a Barlow gives you a magnification of 130. Essentially it means if you choose your EP carefuuly, you can fill the gaps using the Barlow.

The longer focal length, less magnification EP, will allow you to see objects such as the Pleidas. Using higher mags would be like looking at a few stars rather than seeing the cluster as a whole. The higher mags, such as the 10mm should allow you to see the details of Jupiter for example. The 25mm wouldn't give you enough magnification to see the bands. The 10mm should allow you to,see the Orion nebular and the trapezium stars. If you read my review of both EP, I could see the nebular with both of those, one being a 23mm and one being a 25. The magnification on my skywatcher explorer150p is is a bit more as the focal length is 750.

Also, seeing conditions, light pollution would have a major effect on your viewing. Even viewing over the top of a roof radiating its heat will have an effect.

To sum up, have a think about your budget and decide what EP you want. If you want a Barlow so you buy less ep's don't buy, for example a 10 and a 5 because the 10 plus a Barlow essentially gives you the 5.

I hope that makes sense! This is the first time I have offered advice on the forum, so I hope what I have written is correct. I am sure I will be corrected if not!!

Cheers.

Alistair

For magnification, you divide the telescopes focal length by the focal length of the eyepiece, This is correct as stated (yellow).

The fitting of a Barlow will effectively DOUBLE the telescopes focal length! It doesn't half anything?

The eyepiece you fit will have  a new magnification due to the higher focal length of the telescope, NOT that the Barlow has halved the eyepiece in anyway!

Put in an 8mm Eyepiece , you'll have 65x power. Now Barlow that eyepiece. Its still an 8mm, only now producing 130x power, due to the doubling of the telescopes focal length( optically doubled by the Barlow ) 

Hard to fathom  maybe, but that's how it works.

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Thanks for all the advice.

I think I'll get the 2x Barlow and try it with the 10mm and 25mm I have a see how I go from there.

Then possibly replace my EP's for better quality ones.

I'm just using it in my back garden (closed in and quite dark) just now but I'm going to the highland Perthshire lodges in May and that is in the middle of nowhere so I should get dark skies while I'm there. I have a book that says Saturn takes center stage while I'm there so I want to have what I need (and a good knowlage of it) by the time I go.

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The Skywatcher 2x deluxe Barlow (£20) was my choice, no regrets. As for eyepieces, its the 10mm that you see the greater difference from using another eyepiece. I chose an 8mm BSTStarguider, again, no regrets.

Edited by Charic
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For magnification, you divide the telescopes focal length by the focal length of the eyepiece, This is correct as stated (yellow).

The fitting of a Barlow will effectively DOUBLE the telescopes focal length! It doesn't half anything?

The eyepiece you fit will have  a new magnification due to the higher focal length of the telescope, NOT that the Barlow has halved the eyepiece in anyway!

Put in an 8mm Eyepiece , you'll have 65x power. Now Barlow that eyepiece. Its still an 8mm, only now producing 130x power, due to the doubling of the telescopes focal length( optically doubled by the Barlow ) 

Hard to fathom  maybe, but that's how it works.

That's basically what I meant to say, I have obviously just said things in the wrong way. I'm a newbie too!!

I knew I would be corrected!! Sorry to confuse.

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Not a problem. Until the Barlow is fully understood, there are many ways to try and  describe what it does to the eyepiece, and how it doubles you eyepiece collection?

I,  myself, would say something similar, which, was pointed out to me, as being slightly misleading, so now I understand the theory a little better, I'll chip in now and then, just to highlight the point.

The end result is almost the same , its how we arrive at that result that matters!

Like you, I'm still learning, and I know for sure, I'll never know it all  :confused:

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I'm not sure we need to get too hung up on it though.

I think for the mathematically challenged amongst us, the thought of dealing with smaller numbers is probably more appealing. :D

Hence the halving of the EP focal length rather than the doubling of the 'scope FL (I know it makes no odds with the Skyliner, because the numbers are so easy! :rolleyes: ).

I suppose we could be more careful about how we phrase things: A 2x barlow appears to halve the FL of the EP.

There's nothing wrong with that, in the same way that there's nothing wrong with saying the sun appears to travel across the sky, and that's probably enough for some people.

I suppose a more precise phrase might be: A 2x barlow has the effect of doubling the 'scopes FL, but the numbers are easier if you just halve the EP FL, or double the original magnification. :)

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Thanks for all the advice.
I think I'll get the 2x Barlow and try it with the 10mm and 25mm I have a see how I go from there. 
Then possibly replace my EP's for better quality ones.

I wouldnt. i'd keep what you have and invest in an 8mm and a 15mm eyepiece. Honestly, most new telescope owners thing a 2x barlow is the first port of call. Its not.

I'd forget the barlow and just upgrade your EPs. 

Edited by LukeSkywatcher
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Depends on the pack....

8vn4b4.jpg

The sale is for a set of four eyepieces for Eyepiece for Telescopes. They will fit a 1.25" telescope. The focal length of the four are 4mm, 8mm, 12.5mm and 20mm, respectively.

It is necessary to point out that these eyepiece are threaded at the rear end to take any standard 1.25" filters.

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Thanks for the pic, Kaznkev.... Please don't take this for an expert opinion ( I am most certainly not an expert), but I do recall reading somewhere awhile ago that ep's marked with an H (as those appear to be) are to be avoided...

Edited by ghostdance
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Just did a quick google to clarify my inexpert post. The H marking means Huygens. These are said to be of poorer quality than some (most?) Plossl designs. I think, like the Ramsden designs, Huygens are an earlier design than Plossls....that's not to say they'd be necessarily worse than your stock ep's - as I said, I'm no expert. But...

Not meaning at all to wreck your buying, but better to buy better even if that means only one or two eyepieces than a whole set. Obviously tho, I guess the price for that set is quite tempting (ie low)?

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Just did a quick google to clarify my inexpert post. The H marking means Huygens. These are said to be of poorer quality than some (most?) Plossl designs. I think, like the Ramsden designs, Huygens are an earlier design than Plossls....that's not to say they'd be necessarily worse than your stock ep's - as I said, I'm no expert. But...

Not meaning at all to wreck your buying, but better to buy better even if that means only one or two eyepieces than a whole set. Obviously tho, I guess the price for that set is quite tempting (ie low)?

They are only £10.60 + £3.90 postage.

As I'm just starting out I think these ones will do the job. Once (if) I get more experience and start to require better quality I will spend more.

I just don't want to overspend and then find out that I'm buying more than I need.

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With respect as has been said, these really are about the poorest quality eyepieces made being of the non-achromatic Huygens design. Even the stock ones supplied with scopes are quite a bit better than these.

They simply won't allow your scope to perform well at all.

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