Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Eyepieces

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | (show all)
stevenp_86
professor emeritus
*****

Reged: 11/30/11

Loc: Ontario Canada
25mm ES 100* confirmed? sale date? preorder?
      #5046181 - 01/30/12 03:42 PM

im gona pick up one of these bad boys on the day of release, when will that be? how much?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Dr Morbius
Post Laureate
*****

Reged: 02/06/07

Loc: ManorvilleNY-but not for long
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: stevenp_86]
      #5046202 - 01/30/12 03:53 PM

Your guess is as good as mine, although it can't be much more than the 20mm.

Post Extras: Print Post   Remind Me!   Notify Moderator  
csa/montana
Den Mama
*****

Reged: 05/14/05

Loc: montana
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: stevenp_86]
      #5046225 - 01/30/12 04:01 PM

Astronomics pre-order

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Black
member


Reged: 01/29/12

Loc: Colorado, USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: csa/montana]
      #5046264 - 01/30/12 04:23 PM

This morning, I cancelled the ES 24mm 82* I had ordered Saturday.... now I'm chompin at the bit for the 100* 25mm to get here!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Smithfr2000
member


Reged: 09/12/09

Loc: Nantes - France
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Jeff Black]
      #5046287 - 01/30/12 04:32 PM

I thought 21mm focal length was the maximum physically possible in a 2" barrel ?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Black
member


Reged: 01/29/12

Loc: Colorado, USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Smithfr2000]
      #5046305 - 01/30/12 04:44 PM

There are quite a few 2" EPs over 21mm. I have a TeleVue 35mm Panoptic. I have 42mm and 50mm 2" EPs ordered and on the way now.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Robert70
professor emeritus


Reged: 02/11/11

Loc: The Garden State: NJ
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Jeff Black]
      #5046463 - 01/30/12 06:08 PM

how much? Very expensive if you ask me.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Lane
Post Laureate


Reged: 11/19/07

Loc: Frisco, Texas
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Robert70]
      #5046521 - 01/30/12 06:37 PM

Now if it had 25mm of eye relief I could get excited too. But I suspect this will be yet another wonderful eyepiece that I cannot use being an eyeglass wearer

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jim Romanski
Carpal Tunnel
*****

Reged: 01/02/05

Loc: Guilford, Connecticut
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Smithfr2000]
      #5046561 - 01/30/12 06:56 PM

Quote:

I thought 21mm focal length was the maximum physically possible in a 2" barrel ?




It's not that you can't have an eyepiece with a focal length longer than 21mm. Televue stated that for their 100 degree Ethos eyepiece that 21mm was the practical limit. They said they didn't want to make one longer or they would have to compromise in key areas such as eye relief, weight and most importantly vignetting.

No picture, no specs except for the obvious ones and no anticipated release date???

I'll wait on this one and see how ES decided to make their compromises.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scott in NCAdministrator
80mm Refractor Fanatic
*****

Reged: 03/05/05

Loc: NC
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Jim Romanski]
      #5046582 - 01/30/12 07:03 PM

From the Astronomics link that Carol kindly provided, I see that ES is also coming out with a 100 degree 5.5mm EP. That's exciting to me as well!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Scott in NC]
      #5046599 - 01/30/12 07:11 PM

An ES 100 degree 5.5mm might be worth reserving for the big "It's Christmas!" or "It's my birthday!" excuse.


Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Sarkikos]
      #5046729 - 01/30/12 08:19 PM

Quote:

An ES 100 degree 5.5mm might be worth reserving for the big "It's Christmas!" or "It's my birthday!" excuse.


Mike




You could always celebrate your "Un-Birthday" , but you may have to do the celebrating in the dog house.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Joe Ogiba
Postmaster
*****

Reged: 02/14/02

Loc: NJ USA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Jeff Black]
      #5046764 - 01/30/12 08:39 PM

Quote:

There are quite a few 2" EPs over 21mm. I have a TeleVue 35mm Panoptic. I have 42mm and 50mm 2" EPs ordered and on the way now.



I have an 80mm 2" eyepiece but I am sure he was talking about 21mm 100° AFOV 2" eyepieces. I guess the 25mm 100° will be using close to the maximum fieldstop in 2" barrel. BTW the 21mm Ethos has a 36.2mm fieldstop with a weight of 2.25 lb compared to my 40mm Pentax XW with a 46.5mm fieldstop.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Darenwh
Carpal Tunnel


Reged: 05/11/06

Loc: Covington, GA
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Joe Ogiba]
      #5046770 - 01/30/12 08:41 PM

Actually the 5.5mm will be out close enough to my wife's birthday that I could buy it for her!!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Scott in NCAdministrator
80mm Refractor Fanatic
*****

Reged: 03/05/05

Loc: NC
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Darenwh]
      #5046802 - 01/30/12 09:06 PM

Quote:

Actually the 5.5mm will be out close enough to my wife's birthday that I could buy it for her!!




Hope she's an astronomer, too. Otherwise you'll really be in the doghouse!


Post Extras: Print Post   Remind Me!   Notify Moderator  
stevenp_86
professor emeritus
*****

Reged: 11/30/11

Loc: Ontario Canada
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: Scott in NC]
      #5046806 - 01/30/12 09:09 PM

just like the time when homer gave marge that bowling ball

Post Extras: Print Post   Remind Me!   Notify Moderator  
Sean Puett
Carpal Tunnel
*****

Reged: 09/06/10

Loc: always cloudy, washington
Re: 25mm ES 100* confirmed? sale date? preorder? new [Re: stevenp_86]
      #5046900 - 01/30/12 10:20 PM

That's a great idea. I'll get my wife the 5.5mm for mother's day. Do any of you have a room i can rent?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: 25mm ES 100* confirmed? sale date? preorder? [Re: Sean Puett]
      #5046954 - 01/30/12 10:47 PM

The only thing worse than buying your wife something for her hobby, is buying her something for your hobby.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
tmbuser6
sage
*****

Reged: 07/01/11

Re: 25mm ES 100* confirmed? sale date? preorder? [Re: Jeff Black]
      #5047012 - 01/30/12 11:15 PM

Quote:

There are quite a few 2" EPs over 21mm. I have a TeleVue 35mm Panoptic. I have 42mm and 50mm 2" EPs ordered and on the way now.




Mr. Black, et al., I think the matter is a bit more complicated than you may realize. You see, it is already well established that the ES-100 design is at least /very/ similar to that of the Ethos, at least according to x-ray analysis. Basically, these eyepieces work with a negative-power Smyth lens group /ahead/ of the field stop, which is internal, about half way to the next lens, which is a positive meniscus. These 4 lenses operate together as a powermate-like group with the field stop placed within the group after the third lens.

Look at the bottom of any of these eyepieces and you will see that there is no external field stop present like in a normal eyepiece, and if you bring your finger up to the field lens while looking through, you will not find any point where you can bring your finger into focus looking thorough the eyepiece! That is because the focal plane is well inside.

It is this group which is both essential to and really the basis for the performance of the eyepiece. Due to the negative power of the Smyth lens group and the placement of the focal plane and field stop inside where they must be, the aperture of the Smyth group must be /larger/ than the field stop aperture. If you look hard into the bottom of one of these eyepieces, you may be able to tell that.

The net result of all of this is that this places an upper limit to the maximum focal length of such an eyepiece to be around 22mm if you wish to not have any vignetting. So, unless Explore has reinvented optics (I don't expect that to be the case), the only other option I can see is to allow for some vignetting to take place.

There were a great many people hoping for a 100 degree Ethos from TeleVue that was long enough to take the place of the 31mm Nagler so that they could retire that eyepiece in favor of an all-Ethos line of eyepieces, and they were hoping for something like a 24-25mm for that purpose, but the practical limit of the design without making compromises was 21mm due to the confines of a 2" barrel, that is why they didn't make it any longer. In order to make a longer focal length, you would need to go to a larger barrel.

And I suspect that was a similar constraint in ES choosing 20mm for their very similar eyepiece. SO, either Explore has chosen to allow a considerable amount of vignetting to occur in the periphery, or they have departed greatly from the original design, which I do not see happening while also maintaining equal performance. Therefore, we do not really know what we are buying here and I myself would be a bit hesitant to invest in one blindly before others have had a chance to sample the eyepiece and evaluate it.

The one maxim that holds true for all of optics is that there are no free lunches: You do not gain in one area without giving something up somewhere else. For ES to have crossed the 22mm threshold still within the limits of a 2-inch barrel, they must have made some compromises elsewhere. ;^)

I would expect the eyepiece to likely have both visible vignetting (limb-darkening around the edges), not be a true 100-degree AFOV, and/or probably have a loss of eye relief (smaller eye lens) as a consequence, which is already at a minimum in the present ES design.

Regards,

Wayne


Post Extras: Print Post   Remind Me!   Notify Moderator  
stevenp_86
professor emeritus
*****

Reged: 11/30/11

Loc: Ontario Canada
Re: 25mm ES 100* confirmed? sale date? preorder? [Re: tmbuser6]
      #5047053 - 01/30/12 11:40 PM

hmm...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | (show all)


Extra information
23 registered and 30 anonymous users are browsing this forum.

Moderator:  ausastronomer, droid, cbwerner, kkokkolis 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 20275

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics