Looking at planets

[Blakout]

Hi everyone ,Ive got an 8 " DOB (skywatcher) and im looking for some help on eyepieces for looking at planets , would these 2 eyepieces be a good selection ? 82 fov explore scientific 14 and 4.7 mm , and 2x barlow .

Thanks in advance :)

[MattT]

I'd get the 11mm and 6.7 instead. I don't have the 14mm but read that it suffers from field curvature noticeably. I do have the 6.7 and its great. With 2X barlow the 11 becomes a 5.5 and 6.7 a 3.5 (sort of). ES 82's :thumbsup:
Matt

[erick]

Neil, you don't need a wide apparent field of view to study the Planets. Plossl AFOVs of around 50 deg are sufficient. But you do want to get down to around 7-10mm focal lengths and have a 2x barlow to hand for those nights of good seeing.

[casstony]

Using a driven mount 30 degrees afov is enough, but the 82 degree eyepieces would be handy in an undriven dob.

[erick]

Yes, Tony is right. At high magnification with a small AFOV and with an undriven dob, you need nice smooth bearings, and a good ability to "nudge", to keep the planet, or area of the Moon, in the field of view.

[Blakout]

Thx for the replys so far guys , is there any disavantage in going wide FOV ?

[erick]

No, except it probably costs more for quality glass and it may well be a heavier and larger eyepiece, if that matters to you (and your scope - balance).

[mental4astro]

I'd beg to differ, Eric ;) !

You cannot see the whole field in anything over 70degrees without moving your head around. This may be ok for some people, but not everyone.

My own opinion, & that is what is being asked, I think ultra wide fields are over rated - our human eyes can't see the whole field at once.

I've tried a variety of these, from cheapies to Naglers, Ethos & ES 100's (thanks Eric :thumbsup:). The image quality of these ranged from ok to bloody amazing (Eric's ES 14mm 100), but that I had to move my head around, & that they all have problems with critical eye positioning, takes away for me my consideration of them to be in my kit.

To say that an object stays in the FOV for longer is miss leading, as you need to constantly chase down the object every time you pull your head away. In EPs with upto 70degrees, the object just is or isn't in the FOV so there is no double guessing.

Consider the Vixen LVW's or the TV Delos range if you want to spend the big ones. The ES 68's are great too, but shorter eye relief & only go down to 16mm in focal length. The Hyperions are good too, but maybe not all models are in the same league as the LVW's or Delos.

[casstony]

Even if the eye can't see more than 70 degrees, the peripheral field of view helps to frame a DSO or show it's full extent, or helps to track a planet with a dob. I don't see much point going larger than 82 degrees but I find the 65 degrees of the Vixen LVW's a little restrictive.

[Blakout]

Thx for the advice guys , at this stage I think the ES are more in my price range .

[Blakout]

well ive ditched the idea of getting the ES 6.7 and 11 mm in favor of the 10 mm delos , now i need some advice on a 2x barlow for the delos .

thx for the advice so far guys that and other threads on this forum have been a huge help in making my mind up , looks like bintel are as good a place as any to buy the TV gear from .

[erick]

You won't go wrong with a TV barlow, 2x or 3x.

[bratislav]

I think you should speak only for yourself. Human eyes can certainly see more than 70 degrees. Why do you think NASA spent all that money and research time to develop well over 100 degree eyepieces for Lunar landing simulators ?

I have no problems seeing full 82 degrees in my Naglers. Without moving my head. In fact they are starting to look a bit narrow these days as I have no issue seeing full 100 degrees in Ethos ;)

I do accept though that some people have issues with wide fields.
I'd suggest that any prospective buyer spends some time at star parties and TRY the eyepiece in question before plonking the money down. Eyepieces are very individual items. What works for some (even MOST), might not work for you.

[Blakout]

Thx Eric , Ive gone for a TV 2x barlow and Pentax XW 10mm ,Ive gone with Suzys idea of buying a quality eye piece to save money by limiting upgrades in the future , it was a toss up between the 10mm Delos and the Pentax , the Pentax wins out for being posted to your door $90 cheaper than the delos , thx again for the advice once again guys :)

[Profiler]

As we are all price shoppers would you mind telling us where you found the better deal on the Pentax vs the Delos?

[Blakout]

http://www.bhphotovideo.com/ the postage was $40 for Pentax 10mm ,TV x2 barlow and some sports binoculars for my mum :) So was pretty happy with the postage ,

[mental4astro]

Peripheral vision! Yes!




Our peripheral vision I believe is a little over 180degrees. I have never said that ultra wides don't work. Man, I will never forget the view of Eta Carina using Eric's ES 14mm 100deg with an NPB filter in my 17.5" dob!!! If we talk about the effective visual range of our eyes, that's a different matter I'll argue.

Our effective averted vision is limited to a narrow band around our central vision. If you think about the productive viewing that you actually do, it really limited to that area around our central vision, and therefore the 68-72 degree range. Peripheral vision is not what I'm talking about, purely effective productive visual range.

There is also the critical "sweet spot" that your eye needs to be placed in to use ALL of these ultra wide EPs. To far out or in of this spot and aberrations such as kidney beaning comes into play. If you are happy to deal with this, that is absolutely fine. Of course it is a very subjective matter. I find this sweet spot too limiting, for me. I just can't tolerate the constant relocation of my head to avoid these aberrations. With my passion for sketching I can do hundreds of head movements from EP to paper and back over a three hour period. The much more forgiving situation that sub 72 degree EPs offer me make them as wide as I go with EPs in my collection.

Explore Scientic 68's, Delos, Panoptics, LVW's, Hyperions. These are what you'll find suit me, :D.

[Tom Hancock]

I will go for the ES 6mm or 4.7mm 82Deg fov ep as they are really excellent and so affordable.
And these ep are sealed and moisture proof.