Pick me a planetery eyepiece on a $150 budget...

[Ravenit]

Hi guys
Looking to get a nice quality planet eyepiece for my skywatcher 6inch dob.
The cheaply 10mm that came with it barlowed x2 is OK but need better.
I don't want a 5mm plossl with a pin hole so from the list bellow what is recommended or feed free to add to it. $150 max budget including postage.
Price listed is online price

Explore scientific 4.7mm 82d water proof $140
Baader Hyperion 5mm $140
Vixen Lanthanum 4 or 6mm $139
William optics SPL 3or 6mm $108
Baader orthoscopic 6mm $74
Maede series 5000 HD60 4.5 or 6.5mm $80
Maede series 5000 ultra wide water proof 5.5mm $129
Celestron Xcel lx 5mm $70

Thanks

[Profiler]

The answer depends on what degree of eye-relief (ER) you want in the eyepiece and what balance you place on fov versus optimal optical performance.

If you want a good amount of eye-relief with maximum optical performance although smaller fov then the pick of the bunch IMHO would be the Vixen LV

Thereafter I would pick the Baader Hyperion which still gives good ER but not as sharp but larger fov

The opposite end of the spectrum would probably be the Explore Scientific which has modest ER but a big fov and still pretty sharp

[MortonH]

Assuming your Dob's focal length is 1200mm many of those options may give too much magnification unless you have a steady sky.

I'd consider the Explore Scientific 6.7mm.

[Ravenit]

Yes 1200mm. Eye relief is important as its a family / friends scope so ease of viewing is a must as well as a large for would be good.
I have viewed Saturn at 10mm 2x Barlow so 5mm and it looked good.
5mm is 240x magnification on my scope

[MortonH]

I used to have an 8" f/6, so also 1200mm focal length, and found that a 6mm Radian was excellent for planetary at 200x. Later I swapped it for a 5mm Radian to get more power but found the atmosphere wouldn't support 240x on a lot of nights.

Better to get a good eyepiece you can use all the time. Of course, Radians are now discontinued but you can get them used for a good price.

[omegacrux]

Another option
Celestron Ultima LX
They come up every now and then , for about $120
Or order a new one from the US way cheaper than here

David

[MortonH]

TMB planetary 6mm for $83.99...


http://www.vtioptics.com.au/tmb-6mm-planetary-ii-best-value-planetary-eyepiece-just-89-99-delivered-within-australia-why-buy-poor-quality-clones-get-the-real-tmb-grab-a-piece-of-history-as-this-ep-is-eol-and-only-very-few-left/

[brian nordstrom]

:thumbsup::thumbsup::thumbsup: That's probably the best deal in astronomy today !.

I would jump on this fast as they state they only have a few ,, grab one now with both hands and be impressed as there is not a better 6mm eyepiece on the planet for this price available anywhere :D .

Thanks for the link Morton .

Brian.

[David Niven]

Agreed and they are good, considering the price.

[Ravenit]

Thanks guys grabbed the TMB with both hands and both feet.
Really hope these are real as there is so much talk around about the TMB clones on ebay.
What I can see is the clones have 6MM but real has 6mm in small letters, someone else said they came out of the same factory.????

Anyway thanks for the link, VTI need to get credit card payments happening on their site as the direct deposit option can take a few days to process.
Thanks again guys for the recommendations...

[MortonH]

Pretty sure these are the real ones at VTI. Hope you enjoy it.

[Ravenit]

Bit of feedback guys. I really like the tmb. So much clearer and made out the gap in Saturn rings.
Kids like the larger eye relief and bigger field of view.
Cheers

[MortonH]

:thumbsup:

[ThunderStorm]

I don't want to hijack this post but a quick one:
looks most of the eyepieces are 1.25inch? Becasue 2inch are much more expensive?

[Camelopardalis]

There's no physical need for a 2" barrel with such short focal lengths. Look at 20+ mm eyepieces and it becomes a more mixed story.

[brian nordstrom]

:thumbsup::thumbsup:
Brian.

[brunono2]

FYI- Agena astro has an explore scientific 4.7 82 for 99.99 USD at the moment normal 140 USD- they have low postage costs

Cheers

Bruno

[ThunderStorm]

Ah...most of 2" eyepiece are 20+mm eyepiece?

[MortonH]

Sort of. It depends on the "apparent field of view" or AFOV. The larger the AFOV, the wider the actual field you'll see through the eyepiece.

You'll see a variety of different values for AFOV. They can range from 45° to over 100°.

For example, you can get one 9mm eyepiece with AFOV of 50° and another 9mm eyepiece with 100° AFOV. They give the same magnification because their focal length is 9mm, but the overall view will be much wider in the 100° eyepiece.

Now, the greater the AFOV the larger the physical size of the eyepiece. So once you get to around 20mm in focal length, if you want your AFOV to be greater than 70° or so you physically need a 2" eyepiece.

It's only a rough rule as there are so many different AFOVs, e.g. 45°, 50°, 60°, 65°, 68°, 70°, 72°, 82°, 100°, and even some over 100°.

When the manufacturer designs an eyepiece of a given focal length, the AFOV he wants will determine whether it needs to be 1.25" or 2".

Hope that's not too confusing!

Cheers.

[dannat]

the makig of either a 2" (say 50mm) or 1.25"(30mm) ep depends on the field stop (basically the edge of fov of the eyepiece)

a 9mm eyepiece will have a field stop close to 9mm, therefore there is no reason to fit it into a 2" housing -the 1.25" size is more than enough

a 40mm will benefit as if you put it into a 30mm housing you are clipping the fov, so it will benefit from the larger 2" housing -you can effectively use a arger fov in the longer f/l eyepieces

[Camelopardalis]

Many, but not all :D take a look at the diagram on this page from Televue (http://www.televue.com/engine/TV3b_page.asp?id=212&plain=TRUE#def)

Basically, the field stop is a limiting factor in the cylindrical "beam" of light that flows from the telescope objective to your eye, which limits the maximum field of view of the optical system (note: there can be other factors too), and is determined by considering the focal length of the eyepiece and its AFOV.

For a 1.25" setup (diagonal + eyepiece), the maximum beam size is 27mm across since the physical barrel eats up some space...this is sufficient for most of the shorter focal length eyepieces, and popular designs up to 24mm@68*AFOV (Panoptic and others) and 32mm@50*AFOV (plossls). To cram in more sky than that, it needs a larger barrel...

So we have a 2" setup (diagonal + eyepiece), with the maximum beam size of about 46mm across...this increase in the maximum beam size of about 70% is more significant than it sounds, as it increases the field area, the circle of sky you see in the eyepiece, by almost 3x (actually, 2.9x). There are a lot of eyepieces out there that take advantage of the extra sky "real estate" available. From the 20mm 82 degree designs upwards, all the way through to the 40/41mm 68-70 degree AFOV (Panoptic/Paragon/Pentax/etc) and the 55mm plossls.

To confuse the issue further, some eyepieces have a 2" barrel for physical reasons, generally when they're big and heavy and the maker feels they'd be precarious in a 1.25" focusser/diagonal ... ES 100 degree range is an example here where the whole range have a 2" barrel, even down to the 5.5mm model!

[MattT]

To 'replace' a 5mm XW I have just bought an ES 4.7 82º not the first one of these I have had. This time I did the cheap postage…just for interest in how long it takes to get here. Cost…all of $127 AUS dollars, including post!
The 4.7 from memory was as good as the 6.7 with a little less ER.
My computer has gone back to it's old ways with loading VTI…in other words it doesn't :screwy:
Matt

[MattT]

Package from Agena Astro ordered on the 1st arrives on the 10th with first class international post…pretty good :thumbsup::thumbsup: 7 days is the norm with the more expensive post.

In the meantime still waiting on a filter sent from Sydney on the 5th to get to Melbourne…:whistle:

[Camelopardalis]

Ah, it's stuck in the domestic post vortex...it'll get chucked out when it's good and ready :lol:

[MattT]

:lol: In time for the new Moon I hope