Moving on from supplied EPs

[SmokeyJoe]

Birthday coming up so I have decided to ask for some new EPs.  I have read the informative post by The Warthog on Eyepieces.  I have a Skywatcher 200p Newtonian, (focal length 1000mm, dia 200mm) which I make f5. So The Warthog recommends 25mm, 18mm and 8mm and a 2xBarlow.  I am thinking of the Celestron X-CEL LX partially because of price but also because of the eye relief, I wear glasses and have an astigmatism. I have three questions.

1. There is not an 8mm in this range would I be better off with the 7mm or 9mm.

2. I already have a 2xBarlow that came with the scope. Is there any advantage in buying the celestron Barlow from the X-CEL range they make a 2x and a 3x.

3. Are there any better options around the same price which give long eye relief.

Thanks once again.

[alanjgreen]

Hi Dom,

you will be fine with the xcel lx, they are good value.

as far as what sizes to buy, you need to think about the magnifications that they give in your scope.

your scope is 1200mm focal length.

a good spread of magnifications is something like 50,100,150,200, 250 or 25,75,125,175,225

if you divide focal length by magnification then the answer is the eyepiece size.

so 1200/50 = 24 ( a 24mm EP will give x50 magnification in your scope)

1200/100 = 12 ( a 12mm will give x100)

50,100,150,200,250 = 24,12,8,6 and 4.5

25,75,125,175,225 = 48, 16, 10, 7, 5

the main thing is to try to keep the gaps to x50, any less and you won't see much difference at the eyepiece.

i don't think you need both 25 AND 18 looking at the numbers above. After 25 you can jump to 12.

if you can't get the number you want then 1mm either way makes no difference so don't worry about that  

just be sure to make sure you work out the actual magnification that you are getting, and then make sure it's not too close to what you already have.

Alan

[alanjgreen]

Barlow.

dom, be aware that a bad Barlow will ruin the view from all eyepieces.

if you are going to buy the actual eyepieces you need then forget buying a Barlow and use the money on eyepieces instead.

if you want to make a Barlow a key part of your magnification range then buy a good one. A televue 2x Barlow would be a lifetime purchase. They are £100 but they will compliment your eyepieces rather than ruin them.

personally, I would not use the free Celestron Barlow unless I had no other choice.

so, decide if long term you want to barlow or not. Then if you are buy a good one as a once only purchase knowing that you have the best.

Alan

[billyharris72]

I'd second that the Ex-Cel LXs are decent eyepieces, and would be a good choice. You might also look at the BST Starguiders (slightly cheaper, very similar).

I'd say get the 25mm and 18mm, then go down to 7mm, for the following reasons.

1) The 18mm to me is a much better eyepiece for faint objects like galaxies than the 25mm. I don't know why (slightly darker sky, slightly better image scale) but I find the 18mm Ex-Cel to be a real keeper.

2) Barlowing these will get you 12.5mm and 9mm, so you could skip the 12mm and 9mm eyepieces.

3) The 7mm is a whole new set of focal lengths (x 142 and x285 barlowed).

As to whether it is worth investing in a new Barlow, it depends on the quality of the one you have. The Ex-Cel barlow itself is nothing special, so if you have a doublet Barlow, metal construction, well blacked etc then I would not bother. Maybe wait and see how you get on and then make the purchase if you decide you need it?

Billy.

[Louis D]

Since you don't have any 2" wide fields, I'd recommend looking into getting a 32mm to 40mm 65 to 72 degree AFOV eyepiece to allow you to view larger objects like the Pleiades, Collinder 70, the Hyades, etc., and to be able to use it as a finder eyepiece when locating smaller objects.  I love scanning the skies at low power to relax and explore.  It's sort of like getting in your car and cruising to no particular destination.

[laudropb]

I have used the Celestron X-cel LX eyepieces for a couple of years now and I have to say I am very happy with them. I would purchase the 7 mm to give you that extra magnification for planetary observing. The only problem I had was that the screw up rubber eyecups tended to screw off. A careful application of a small drop of superglue soon solved that problem.