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Equipment Discussions >> Eyepieces

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M44
sage
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Reged: 03/24/07

Loc: SoCal.
Re: is anyone planning on buying the ES100 30mm? new [Re: Sean Puett]
      #5734459 - 03/15/13 04:33 PM


I am not in the target market for this eyepiece. But I was wondering what would be the weight of 3" diagonal that is supposed to come out this summer? Couple of pounds or more?
A total weight of diagonal + EP is 10 lbs?


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johnnyha
Postmaster
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: is anyone planning on buying the ES100 30mm? new [Re: gatorengineer]
      #5734928 - 03/15/13 08:45 PM

Quote:

Suggest you look at what the baffle tube diameter is which is reported to be 2.1" Now treat that as a 2.1"field stop 14" or so inches in front of the eyepiece. You will find that you edge illumination is exactly 0 for the 3" 30.... Sorry to be the bearer of bad news. The visual back opening on large cats is irrelevant, its the baffle tube that counts.



Yup, that's what I was getting at... Also I imagine with a fork mount you might have a few clearance issues.

It's also quite possible that the extra fl added to the C14 by the length of the 3" diagonal would negate the advantage over a 2" 25mm 100* eyepiece - you may end up with similar magnification.

Edited by johnnyha (03/15/13 11:37 PM)


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gatorengineer
Carpal Tunnel
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Reged: 02/28/05

Loc: Hellertown, PA
Re: is anyone planning on buying the ES100 30mm? new [Re: Sean Puett]
      #5736065 - 03/16/13 11:38 AM

large standard cassegrains will generally have the same baffle tube issues as Schmidt newts, but it would depend on the particular instrument. Sieberts page shows a 24" cass that takes them...

For those wondering 3" EPs are NOT new to the hobby, siebert has been selling them for years and few large amateur refractors I know use them, he also sells 3" diagonals, although I suspect that Explore will see those as well shortly...


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pbsastro
professor emeritus
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Reged: 03/21/07

Re: is anyone planning on buying the ES100 30mm? new [Re: gatorengineer]
      #5736691 - 03/16/13 05:23 PM

Quote:

Suggest you look at what the baffle tube diameter is which is reported to be 2.1" Now treat that as a 2.1"field stop 14" or so inches in front of the eyepiece. You will find that you edge illumination is exactly 0 for the 3" 30.... Sorry to be the bearer of bad news. The visual back opening on large cats is irrelevant, its the baffle tube that counts.




I am happy to be the bearer of good news. That is not right.
If you have a 2.1" (53mm) baffle, obviously you do not get 0 illumination at 52mm. If fact, if placed at 14", I estimate 70% illumination.
Did you really mean a 53mm baffle blocks all the light of a 52mm circumference?

Also my info is that 2.1" (53mm) is the corrector CA, which is placed 7.4" (188mm) from focus (ideal 146mm back focus).
The baffle front ID is 2.25" (57mm), placed at 15" from focus (ideal 146mm back focus).
I estimate that to give about 75% illumination at 52mm circumference. Error margin 5%. So at least 70%.

Official numbers from Celeston (white paper) for C14HD (and C11HD) are 100% at 16mm and 83% at 42mm.
On a side note, 2007 Ken Hutchinson analysis of the standard C14 gives 73% at 52mm circumference.

Finally, the visual back opening is not irrelevant. Both the baffle and the opening must have the proper size. One without the other will not work. What you probbaly meant is that it is irrelevant if larger than a minimum size, but that is true for every baffle regarding vignetting.


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pbsastro
professor emeritus
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Reged: 03/21/07

Re: is anyone planning on buying the ES100 30mm? new [Re: pbsastro]
      #5736778 - 03/16/13 06:03 PM

I think the reason people keep repeating ES30-100 field illumination problems is that it is being regarded as a 3" eyepiece when in fact is is just a 2"+ eyepiece in a 3" body, as the Ethos 21 is a 1.5" eyepiece in a 2" body.
ES 30-100 has a 52mm field stop while the Pan 41 or Plossl 55 have 46mm field stop. Only 6mm difference!
So illumination requirements are not very different.
Now correction is another matter, as the extra magnification of 100 deg will show field edge errors more than 70 deg and 50 deg.
And weight is also much more than the Ethos 21, which has a small 36mm field stop, very far from 46mm, the 2" limit.
But regarding illumination ES 30-100 is just a 2"+.
So most scopes that can handle a Pan41 can deal with the ES30-100 illumination.

Both C11 and C14 have about 70-75% illumination at 53mm and then illumination falls out rapidly, resulting in practice in a 53-55mm field.
So, the ES30-100, with its 52mm field, is exactly tailored to give all C14 and C11 capabilities.

Some people asked for 40-100 or 30-120. Those eyepieces, beside the prohibitive weight (much more than 30-100), would be much difficult to use in available telescopes, and would be ruled out for C14 and C11.

Now a 20-120 would be nice, which I estimate to have the same weight as 30-100. Although a 25-120 would have the same 52mm field stop as the 30-100, it would be much heavier than 30-100, and more demanding on field edge due to extra magnification. The 20-120 would have 42mm field stop, the same as Nag31...
I am so used to the Ethos now, that I am starting to find 100 deg is a little narrow... oh boy...

Edited by pbsastro (03/16/13 07:05 PM)


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gatorengineer
Carpal Tunnel
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Reged: 02/28/05

Loc: Hellertown, PA
Re: is anyone planning on buying the ES100 30mm? new [Re: pbsastro]
      #5739265 - 03/17/13 05:59 PM

This topic has been covered before...

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5673585/page...

Fully illuminated on a c14 is 10mm or 16mm depending upon who you believe in the above thread.......... Test your assumption, by trying to hold a 31 nagler up behind a 1.25" holder see how it looks.....

If it makes you feel better, my TV NP127 cant fully illuminate a 31 nagler, and I can see the difference with an 127IS scope, in a side by side which I have done.


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johnnyha
Postmaster
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: is anyone planning on buying the ES100 30mm? new [Re: pbsastro]
      #5739326 - 03/17/13 06:24 PM

pbsastro - thanks for the detailed explanation, it gives me a much better understanding of how that works. Makes sense to me now that the C14 would work with the 30ES100*.

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Shneor
scholastic sledgehammer
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Reged: 03/01/05

Loc: Northern California
Re: is anyone planning on buying the ES100 30mm? new [Re: hfjacinto]
      #5740003 - 03/18/13 02:29 AM

Not me. Exit pupil too large, focuser diameter too large, trusses too long.
Clears,
Shneor


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Ava
sage


Reged: 11/30/11

Loc: Sweden
Re: is anyone planning on buying the ES100 30mm? new [Re: pbsastro]
      #5742222 - 03/19/13 02:58 AM

According to the EdgeHD white paper the 9.25" has 90% illumination at 42mm, while the 11" & 14" have 83%. If they have a similar falloff curve towards 52mm the 9.25" could potentially be even better suited (brighter at the edges) for the ES30 100.

The 8" on the other hand has 83% at 28mm. I wonder what the edge illumination has fallen to at the edge of the pan 35s 38.7mm field stop...


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Dunkstar
super member


Reged: 03/26/12

Loc: Under the sky
Re: is anyone planning on buying the ES100 30mm? new [Re: Ava]
      #5743714 - 03/19/13 06:48 PM

Celestron lists the baffle tube diameter of the C9.25 as 46mm so you'd risk some vignetting with this eyepiece in that scope, whereas the baffle tube of the C11/C14 is listed at 54mm.

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Peter Glus
sage
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Reged: 05/08/06

Re: is anyone planning on buying the ES100 30mm? new [Re: Dunkstar]
      #5744209 - 03/19/13 10:55 PM

I wonder if this would work well on a Meade 16" SCT?

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pbsastro
professor emeritus
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Reged: 03/21/07

Re: is anyone planning on buying the ES100 30mm? new [Re: Peter Glus]
      #5744816 - 03/20/13 10:26 AM

Quote:

I wonder if this would work well on a Meade 16" SCT?



In terms of illumination I think so. But there wil be field crvature. Although being preportional to FL, it will be smaller than smaller SCTs. But significantly more than EdgeHD. And depending on the model, there may be coma.

Edited by pbsastro (03/20/13 10:27 AM)


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gatorengineer
Carpal Tunnel
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Reged: 02/28/05

Loc: Hellertown, PA
Re: is anyone planning on buying the ES100 30mm? new [Re: pbsastro]
      #5750754 - 03/22/13 09:54 PM

Guys there are simple laws of physics at work here. Your illuminated 16mm on a c14.... Plug it into this program, on the fully illuminated page and see for yourself. As L1 goes to zero field goes up.... What you are missing is that the baffle tube has considerable length.... It is not like a field stop on an ep...

http://www.oldham-optical.co.uk/Design.htm


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