3 mm eyepiece for skywatcher 200p

[N3ptune]

Hello I would like to get an advice on the eyepieces.

On Christmas night I watched the full moon with my 200p telescope and my celestron 24 ~ 8mm zoom eyepiece, it was quite an experience. I could watch the craters at 125x (8mm) and I had a clear image.  I also have a 2x Barlow Celestron XL but honnestly i can't use it with zoom setting at below 12mm, can't get a sharp contrast and always put back the zoom only set at 8mm, the image quality is much more satisfying to my taste.

So now I am thinking of maybe buying a sronger single eyepiece that will provide more then 125x to watch the craters on the moon and I am really not sure what would be a good pick. The choice would be between 5mm, 4mm and 3 mm

- 3 would give me a strong 333x of power to watch the craters and planets but I fear I will not use it often because of atmospheric limitations. (Will I be able to use such an eyepiece often?)

- 4mm might give me a clear view at 250x compare to 8mm with barlow which is never good (is has never been usable actually)

- 5mm might give me a sharp view at 200x but I might be able to get it with the zoom + barlow. (Never had that chance yet, to get something clear using Barlow + 10mm)

- 6mm might give me a clear view at 166x but i definitly can get an "ok" view with the zoom + barlow. (So 6mm is not a good choice)

- 7mm is too close to 8 mm.

MAX = 400x (200mm x F1000mm)
24mm = 42 Barlow x2 = 84 (I have)
18mm = 55 Barlow x2 = 110 (I have)
12mm = 83 Barlow x2 = 166 (I have)
10mm = 100 Barlow x2 = 200 (I have)
8mm = 125 Barlow x2 = 250 (I have)

7mm = 143 Barlow 2x = 286 (Too close to 8mm)

6mm = 166 Barlow x2 = 332 (I can get a view using the zoom + the barlow to get 166x, not a good choice)

5mm = 200 Barlow x2 = 400

4mm = 250 Barlow x2 = 500
3mm = 333 Barlow x2 = 666

2mm = 500 Barlow x2 = 1000 (Too strong for my telescope)

What would be the best bet for my telescope to watch the craters on the moon and also the planets ? I want to be able to use the new eyepiece tootoo, not just get more power once per year.

Thanks

[N3ptune]

Is it possible to edit my previous message, i just can't find this option anywhere.

[ronin]

Think you need a few more posts to edit, in the past there were problems and editing was made into a feature that required a certain number of posts.

Will ask what is the budget for the high power eyepiece?

There is a Paradigm 3.2mm at $60 (US) and the X-Cel LX 3.5mm at a bit more on your side of the Atlantic.

Also 5mm in both Paradigm and X-Cel LX.

Equally TV do high power eyepieces but at somewhat higher prices.

Just getting a $60-80 item may not deliver as well as a $300 item.

[Putaendo Patrick]

One of the problems of zooms is they tend to perform badly at either end of their range.

A problem of inexpensive higher magnification EPs, Plossls for example, is they offer very little eye relief. Your eyeball has to be pretty well suck on the glass, which some people find uncomfortable.

An alternative is to use your Barlow with a less powerful EP. You could, for example, buy a good-ish 8mm EP which would double with the Barlow to 4mm. Although this might seem like duplicating the supposed 8mm range of the zoom you have, I think that at the limit of the zoom you may be pleasantly surprised.

For the moment, I wouldn't try to push the magnification beyond 200-250 times. There are certainly rare oportunities when this is possible, but as you note, these are few and far between.

[RikM]

I find the most satisfying high power views often come from a magnification of around 1x per mm of aperture. For your 200P that would be 200x and a 5mm eyepiece.

[laudropb]

I think you are right to worry about atmospheric conditions at such a high magnification. I think you would get very little use of a 2mm eyepiece.

[John]

Apart from the other potential issues already mentioned, eyepieces with short focal lengths tend to show up the floaters in your observing eye more obviously and they can get really distracting. I find this starts for me at around 3mm and I found a 2.5mm that I had for a short time was not pleasant to use because of this.

[YKSE]

I agree with RikM, around 1mm exit pupil (5mm eyepiece for your f5 scope) should be about optimum for most seeing conditions.

Your own experience (barlow the zoom in 12mm to equivilent 6mm) more or less confirmed this.

Your barlow is a decent one, it works well with other focal length of the zoom, and your zoom works well in unbarlowed mode, all in your experience, so the degrade view when barlowing to lower than 12mm, is most likely seeing limited, not optically by the zoom or barlow.

Buying a 3mm eyepiece, then trying to barlow to 667x looks like waste of money IMHO.

[N3ptune]

Sub Giant

Ok for the edit message..strange. I guess the moderators have their reasons.  

I was thinking of a budget around 150 Canadian dollars with the taxes to get an eyepiece. But a wider angle would be nice too.

Putaendo Patrick

I don't want any Plossls with my eye on the glass, something comfortable like the zoom. It's also true that the 8mm of the zoom is not phenomenal, but it's certainly not bad. (Without the use of the barlow)

But, now it's a little bit more clear, it's ideal to remain in the range of around 200 maybe 250 max.

The best choices to me right now are a 8mm or a 5mm.

8mm PROS
I would get a even cleaner 125x power image
The image would be clean with the barlow for 250x total power.

8mm CONS
I am not even sure if 250x will be usable often.
I don't really like the effect of the barlow on the image. 

=================

5mm PROS
I would get a clean 200x I can't even get right now with 10mm + barlow.
The power of 200x (I already can't achieve) would certainly be more convenient has a goal then 250x (Because of the atmospheric condition)
I would not need the barlow to get a sharp 200x which is good news.
I could reach up to 400x, theoretical highest power of my telescope with the barlow (If possible or if I go to the desert someday..)

5mm CONS
200x is less then 250x to watch the craters on the moon and planets, what is enough? more or less?
I might never use the 5mm with the Barlow to get 400x power ever.


NOTE:
Overall I never saw anything clearly with higher power then around 166x.. i don't know if getting 250x sometimes is better then getting 200x more often. I tend to think the 5 mm would be a better choice just a slight bit over the 8mm.
 

[Charic]

A 5mm will match your scopes focal ratio f/5 giving you a practical 200x magnification from your 200P Explorer.

Its still possible to 2x Barlow the 5mm , and still achieve a result on the Moon. Barlowing a smaller focal length eyepiece is maybe asking too much from the scope.

My Skyliner is an f/6, so using the same rule, a 6mm provides my 200x power, and I can still Barlow the 6mm ?

Yes I own the 5mm and 3.2, simply because I can?

I can achieve, by having a range of eyepieces better framing of my subject, and if it fits and looks right, then that is the eyepiece I need!

[N3ptune]

At the beginning the idea to get the 3mm was to have 333x, which is close to the maximum capacity of my telescope without the need of the barlow. Because, I thought that I would get a better image quality like that. (Strangely, I still think this right now)

The idea was never to reach 666x, no.

I think the 5mm fits along the zoom because I think it could deliver a better image quality then the zoom at 10mm +  the barlow to get 200x. I can be wrong, maybe zoom at 10mm+barlow is bad because of atmospheric conditions only.

But the following factors, I consider also:

ZOOM at 24mm + Barlow = 84x Compare to Zoom at 10mm 100x

ZOOM at 18mm + Barlow = 110x To Zoom at 8mm = 125x

I prefer the view using the zoom at 10mm and 8mm, much better. That's why I seek to use less the barlow.

[John]

The theoritical maximum power of a scope (eg: 400x for a 200mm scope) is assuming every factor is perfect, ie: scope optics, seeing conditions, scope collimation and cooling, eyepiece quality, suitability of target etc, etc. In reality though we virtually never see all these factors come together. It's mostly the seeing conditions that spoil the fun but the other factors play a part as well.

Richard Suiter in "Star Testing Astronomical Telescopes" came up with 23 factors that work against achieving the optimum performance from a telescope - he called it the "wobbly stack". Seeing conditions were at the top of that list.

Collimation and cooling are worth paying attention to before appliying high magnifications as well. I've used a few Skywatcher 200P F/5 newtonians and they could certainly handle 250x pretty well providing the collimation was good, the scope was fully cooled and the seeing conditions obliged.

Setting aside the above for a moment, I also tend to think that using a lowish cost barlow with a low cost zoom to get high magnifications in an F/5 newtonian is not going to deliver the optimum results. A decent quality barlow with a fixed focal length eyepiece might be a better combination. My preference now is not to use a barlow at all but that does need an expanded eyepiece set.

[N3ptune]

Thanks for these explanations John.

For the last part of you message where it's question of the quality of my zoom and barlow... I understand one should get a good barlow and fixeed focal length eyepiece but obviously I am not there yet..

The truth is right now, I like my zoom and I am having fun with it... (: it's economical and fun.

I get here that the idea is to get a better barlow and better fixed eyepices in order to get the desired magnifications up to at least 250x. But i don't want to do it unfortunately, it will cost too much.

[Mr Spock]

You should concentrate on getting a single, high quality eyepiece which gives you x200 and 20mm eye relief. The large eye relief makes viewing more comfortable and therefore more enjoyable.

[mdstuart]

I have 4.7 and 7 mm eyepieces for my 16 inch scope. The 7mm williams optics is about 250x. I use it far more than the 4.7.

I would buy one 250x 68/82 degree field of view eyepiece second hand...Then if you don't like it you can sell it on and you've only lost the postage.

Mark

[Stu]

The floater issue is exit pupil related. Down to a 1mm exit pupil is generally ok, which is where the x200 for a 200mm scope comes from. I find that with high quality, smaller aperture refractors that down to 0.5 or even 0.4mm is worth using especially on the moon and double stars, but also planets such as Mars.

I do agree though, that a good eyepiece at x200 would get a lot of use, above that, less so.

[Peter Drew]

I agree Mark, that's my ethos (philosophical, not eyepiece!) 

[John]

Let me clarify something, Plossls generally have excellent eye relief.   But it gets shorter as the FL of the eyepiece gets shorter.  I believe most designs work this way. ...

The Plossl design has an eye relief that is around 80% of the focal length of the eyepiece. Likewise the orthoscopic. A few decades ago these were considered "generous" in terms of eye relief because the Huygens eyepiece design offered a misely 30% of focal length and the Kellner 40%-50%.

There are many more complex designs around today that offer consistent eye relief of as much as 20mm across the whole range. To achieve this the designer usually needs to add an optical element towards the bottom (field) end of the optical "stack". In the best designs the additional glass is visually invisible in terms of side effects. In low cost long eyerelief eyepieces the additional glass does have some impact on image quality. With a zoom eyepiece the lower lens set moves which provides the variable amplification as well as providing reasonable eye relief although the latter does tend to vary as the effective focal length of the eyepiece does.

These longer eye relief eyepieces are important developments though for those who need to wear glasses when observing.

An alternative is to use a barlow lens with a plossl or ortho because the barlow lens, as well as providing the image amplification, also pushes out the eye relief to a certain extent. The provisio here is that the barlow lens optics need to be of good quality so that they don't introduce unwanted issues of their own.

Personally I feel, for the undriven dobsonian owner, a wide and well corrected field of view with decent eye relief are excellent eyepiece traits to seek out both for the stunning views they give and their benefits for manually tracking objects at high magnifications. There is some cost involved in acquiring such eyepieces though

[Alan64]

An 8" f/5 Newtonian is an excellent choice, and for observing the gamut.  I have one myself.

I barlow a 9mm and a 12mm regularly, and with 2x and 3x barlows.  I've got a 6mm Plossl arriving tomorrow, and I will be barlowing that as well, at 2x and 3x, and for the "fun" of it if nothing else, and down to a simulated 2mm.

The zoom ocular, whilst enjoyable, serves mainly as a teaching tool in determining which dedicated focal-lengths to be had in future, however it is not intended to replace dedicated oculars in the long term.

Insofar as a better-quality barlow, I'd suggest scouring the internet for an Antares UB2S 2x, and perhaps even a UB3S 3x.  I have both, and they're stellar bargains.  They're assembled in Canada utilising superior optical-glass from Japan.  They would be well worth the effort, and the ideal alternative to the costlier Tele Vues and the Dakin 2.4x...

There's one UB3S 3x left in stock at Agena Astro... http://agenaastro.com/antares-1-25-3x-barlow-lens-ub3s.html

The twist-lock versions are available at present, and only slightly more expensive, if purchased through Agena...

http://agenaastro.com/antares-1-25-2x-barlow-lens-twist-lock-adapter-t-thread-ub2stl.html

Khan carries it, too, perhaps... http://www.khanscope.com/accessDetails.cfm?productID=960

There's even a 5x available, but I think it to be a bit excessive in power... http://agenaastro.com/antares-1-25-5x-barlow-lens-twist-lock-adapter-t-thread-ub5stl.html

It may be intended for use within some sort of imaging/astrophotographic exercise.

This one is interesting, and perhaps still available(?)... http://www.khanscope.com/accessDetails.cfm?productID=580

The apochromatic UB2S, the UB2SD, and of three lenses... http://www.khanscope.com/accessDetails.cfm?productID=579

http://www.lirelanature.com/modules.php?name=ProductList&op=BrowseItem&ItemID=1494

http://www.lirelanature.com/modules.php?name=ProductList&op=BrowseItem&ItemID=1495

Insofar as an ocular of a shorter focal-length, you'll want the larger eye-lens and greater eye-relief that comes with an eyepiece in the 8mm to 12mm range...

http://agenaastro.com/agena-1-25-dual-ed-eyepiece-8mm.html

Interesting... http://www.khanscope.com/accessDetails.cfm?productID=954

http://www.canadiantelescopes.com/accessories/eyepieces/6mm-to-10mm/vixen-optics-8mm-npl-plossl-eyepiece-1-25-39203.html

https://www.astronomics.com/astro-tech-12mm-1-25-inch-paradigm-dual-ed-eyepiece_p16946.aspx

[N3ptune]

I see various options are possible right now, I could do many many things.

Obviously i don't want to spend money right now and start buying a few fixed focal length collection and another barlow (above all, spending on another barlow) in order to get the suited magnifications. 

Even if I rethink this in every angles, I just don't want to do it right now.

This morning, the best bet for my needs seems to be the 5mm (or the 8mm) with comfortable eye relief and around 60 degree angle, maybe 68 if i get a good price for it, maybe use, has suggested.

It's the most economical way to go... to reach my goal.

[N3ptune]

I watched some products on Amazon this time to see about medium quality optic for 5mm. Not a lot of choices on Amazon.

Has I see, for some it's going to be bad, for others it's going to be ok. I post anyway there is no stress to buy anything tonight. I also asked on a local forum to see if I could find used eyepieces.

I was thinking about a budget of 150$ so on Amazon i found these 2 for new.

Celestron X-Cel 5mm with 4.5/5 stars 210 reviews, quite a good score with 210 reviews.  60 degrees and 16mm relief 130$

http://www.amazon.com/Celestron-X-Cel-LX-Eyepiece-1-25-Inch/dp/B0048JJH7Q/ref=sr_1_1?ie=UTF8&qid=1451440403&sr=8-1&keywords=celestron+5+mm+eyepiece

And this one:

Orion: 55 field of view and 20 mm eye relief 180$

http://www.amazon.ca/Orion-8885-Edge-Planetary-Eyepiece/dp/B001DJ99EU/ref=sr_1_12?ie=UTF8&qid=1451326078&sr=8-12&keywords=orion+5+mm+eyepiece

Maybe there is something else too.

Alan64 I am sorry it's not a barlow this time because you already gave me some links for barlows, you worked for me and I thank you for that.

[Alan64]

No need to apologise; not at all.  

In any event, you already have a 2x barlow.

Incidentally, under ideal seeing conditions, your 200mmm f/5 will afford up to 400x, and perhaps more if the primary's parabola was figured by an optician on one of their better days.  The higher magnifications will reveal that level of quality.

1000mm ÷ 2.5mm = 400x.

[N3ptune]

The optician has 10 hours of experience in collimation, his name is N3ptune (Thanks to AstroBaby's tutorial on the subject) On my last observation of the moon, I had a really nice view up to maybe 8mm with my zoom and max 150 with the barlow. Only time will tell if i can reach 200x/400x with that collimation and if the atmospheric is good, which is rare.

Hope to know some day.

The weather is bad, bad, bad we had 30 cm of snow today and it is to be continued tomorrow.

My light bucket is inside its bag for a lot of days I fear. 

What do you think of the 2 pieces from Amazon Alan ?

[ronin]

The XCels-LX are good eyepieces, and if you are intending to view planets they are I think better suited then the Starguiders.

In the US the X-Cels cost very similar to the Starguiders, but here they are about 20% or a bit more higher in cost.

Agena Astro sell the Starguiders ($62).

Reason I say better is not performance but they have a 5, 7, 9, 12mm in the Celestrons

The Starguiders come in 5, 8, 12mm so slightly "worse" selection at the short focal lengths - you might find a 5mm is too much but the 7mm is OK. On planetary viewing people tend to collect loks of eyepieces at small increments.

Not sure if either of the Canadian retailers stock Starguiders under whatever name - they have changed name owing to a conflict in the naming.

[Alan64]

The Orion 5mm has a built-in barlow... http://www.telescope.com/Accessories/Telescope-Eyepieces/Orion-Edge-On-Planetary-125-Eyepieces/pc/-1/c/3/sc/47/e/68.uts

The Zhumell 5mm is the same eyepiece, and at half the price... http://www.telescopes.com/products/zhumell-z-series-planetary-telescope-eyepieces?variant=1962404484

...which is why they're sold out on all but the longest focal-lengths.  I was wanting to try one out, the 6mm, but by the time I got around to ordering one, they had sold out. 

The Orion eyepieces that I have came bundled with my Orion StarBlast 6.

I've no experience with Celestron's oculars, nor those of Meade.  As in the case of the Orion oculars, there may be less-expensive twins of quite a few of those two brands as well, and for less.  I tend to prefer oculars of lesser-known branding, house-brands, or of no branding at all.  Incidentally, all of the aforementioned oculars are made in China.  Some are dressed up per the branding, there at the factory; others are not.

I've seen no mention made of the mounting to which the 200mm f/5 is attached.  Is it an equatorial?  Is it motorised?  Do you have a image of it, taken with a camera perhaps, or could you post an online link to the kit?

The type of mount can play a part in choosing eyepieces.