Sure, but you wouldn't use that in an f/4.9 dob. The exit pupil would be way too large and the secondary shadow might be obtrusive.
True field in the 30mm ES will be 1.64 degrees. That's large enough for most large targets--not quite large enough to see ALL of the Pleiades or North America Nebula or California nebula or Veil nebula, etc., but certainly large enough for just about everything else. And large enough to see major portions of the really big things.
A note to consider, however, is that just about every object in the sky is a degree in diameter or smaller. Purchasing an eyepiece just for the 10-20 objects that are a bit larger seems like it would be a "supplemental" purchase for later, when filling in the "in-between" sizes and magnifications.
The 24mm x 82 ES would yield a true field of 1.28 degrees, which is still very large, and the magnification would be better for a much larger number of objects.
A 40mm 70 AFOV (or 41mm 68 AFOV Panoptic) would provided the widest TFOV for a 2"(48mm) barrell. I had this before I got a 30mm 82 AFOV and used it as my finder eyepiece, I may still be using it slightly more than the 30mm 82 AFOV for the large or multiple objects.
Time to ask the experts
Posted 22 December 2013 - 12:27 AM
Posted 22 December 2013 - 03:23 PM
More resolution is definitely needed, I have not looked at the Jr. I didn't realize that had gotten that cheap! I just spent $900 on a Leica ASPH this week.
Not to hijack the thread any further with this electronic eyepiece future stuff, but this time of year the idea of having the scope outside with me and display inside by the fireplace has some real appeal. Brrrrr.
The Mallincam Universe delivers a total size of 3032 X 2016. At that resolution one would be splitting hairs comparing the electronic view with visual. There are images made by the Universe on file at the Yahoo Mallincam site.
-35 C and clear is the forecast for tonight. Not quite that cold in my armchair. A click on my observatory site will explain all.
Posted 18 January 2014 - 01:31 AM
This is a long post but I want to give an update to this thread with a few observations from last night (Jan 16, 2014) using my (new to me) ES 24mm 82deg eyepiece for the first time. Before purchased this eyepiece I spoke with an ES rep on the phone and was impressed with their helpfulness and goal of customer satisfaction. They stand behind their products and – even when they are bought used. As you know I don't have much experience with higher quality, wideview eyepieces, so these thoughts are from a limited perspective and should be “taken with a grain of salt”.
I was using my 12” Orion dob (1500mm FL) which according to the spreedsheet from Starman1's “2013 Eyepiece Buyer's Guide” give a magnification of 63x and a true field of view of 1.31 deg.
I'm not sure how sky steadiness and transparency is defined but here's some thoughts. I've seen worse “twinkle” in stars during the winter at my location but then again I've seen steadier skies too, so lets call it low average of what I'd want to observe in. Late afternoon and early the next morning showed, scatterer high, thin clouds, possibly cirrostratus or leftovers from contrails but during the early part of the night when I observed the clouds where only at the far horizon. As you probably already guessed there was a lot of “light pollution” from the full moon, but this was the best night I've had in awhile and with a new eyepeice I used the opportunity I had. Comparisons where made with the Meade 25mm and no-name 1.125” eyepeieces mentioned in my first post. Telescope was collimate with my newly acquired Astronomics Cheshire/sight tube rather then the sight cap that came with the scope which I've used in the past and while I'm still learning the collimation thing, I believe I was close, if not, on. Temperature was in the low twenties and scope was precooled with box fan for about 30 minutes. Not sure if scope ever reached ambient temp because I could not see any hint of diffraction rings without fan blowing on back of scope and only glimpses of them in between what I assume was atmospheric turbulence. (telescope dons not have built in fans and I have not added any – yet).
Because of the less then ideal conditions I didn't spend a lot of time observing. The objects that got the time were, Sirius, Pleiades, Orion neb and the Moon. Sirius was used with a 9mm Meade eyepiece to check collimation, seeing (or lack thereof) and align the telrad. While the ES 24mm is large and my only experience with 2” eyepieces I did not have any trouble balancing it in my scope, in fact it was easier to balance then some of the lighter eyepieces. A side note is that this scope, even compared to a typical Orion, has less then ideal balance and movement (in both axis). I don't use glasses so eye positioning was easy to find and maintain with no noticed kidney bean. The field stop is seen easily enough when looking for it and I believe I could get close enough to see it all at once. While the field of view is wide and impressive I did not have the feeling that I was going to 'fall into' the view. Stars at the edge of the field show aberrations which I guess is coma since I don't use a coma corrector. While not to bothersome and almost ignorable (my perspective) it was noticed and will take father evaluation to decide if its expectable or if I'll need to start looking for a coma corrector.
The Orion nebula was beautiful and impressive. The trapezoid, with stars A through D, was clearly seen and possibly a glimpse of E through the less then idea seeing conditions. With the excess moon light, it seemed that I could see as much nebulosity in the Meade 25mm as the ES 24mm, although I would guess under darker skies the nebulosity would extend beyond the field of view shown in the Meade. The ES did a wonderful job framing the view and giving the perfect perspective and perspective is everything when it comes to enjoying the view. The view alone of the Orion neb made the price of admission worth it.
With the ES eyepiece the Pleiades cluster had a lot of stars in the field of view compared to either of the 1.25” format eyepiece. It began to have the open star cluster feel although it was missing the perspective seen in the Orion neb. And while good I'm still looking for that perfect, in between view of my previous eyepieces and my 10x50 binoculars. That said, I think there is enough there to see some nebulosity under darker skies. I look forward to revisiting this star cluster with ES 24mm and will not miss the 'soda straw view of two or three stars' seen with previous eyepieces. I'm guessing it will take a different telescope, like a 6” f5 refracter, to really make this eyepiece shine with the Pleiades. Oh well, I guess I need an excuse to dream about the iStar 6” f5
It took me but a couple of seconds viewing the moon to realize that while the wide field is nice for viewing the moon this not a lunar eyepiece and is best left to deepsky objects. On axis and close to the center the view was great but let the moon wonder close to the edge and it turned into a rainbow of color. Has anyone else notice this problem? I'll try again with a not so full moon and see what I think, but this eyepiece has not removed my long term goal of a quality set of lunar/planetary eyepieces.
Objects that I want to cover in the future include, Beehive, Andromeda galx, and a few other larger star clusters and galaxies. I would also like to check the color problem with Jupiter and revisit the few objects I viewed, especially the Orion neb. Overall I'm happy with my initial experience with the ES 24mm 82 deg. At this time I'm not planning to sell this eyepiece but look forward to many future nights of wonderful viewing. Now I can't wait to get my hands on a used copy of the ES 14mm 100 deg (or 82 deg) to enjoy a closer view of planetary neb's & globular clusters.
Thanks for all the advice and help Get out there and enjoy your astronomical observation
Posted 18 January 2014 - 12:59 PM
I think everyone has!