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ES 25mm 100 AFOV Shipped

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#126 JMW

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Posted 26 January 2013 - 04:38 PM

I am not trying to decide on which one to keep. For me, the ES 25mm 100 AFOV is a keeper along with the 21 Ethos and 31T5 Naglar. I think it is finally time to put my T4 Naglars on the market. I really like the 22T4 and 17T4, less so the 12T4. These were my first 3 Televue eyepieces. I just can't fit them all in my case. It is also getting to be a bit heavy. I may buy a Paracorr type II with the proceeds from selling the T4s. Do you think there is any advantage in trying to sell 3 T4s as a set?

#127 Astrojensen

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Posted 26 January 2013 - 05:12 PM

Do you think there is any advantage in trying to sell 3 T4s as a set?


Very likely not. You almost have to sell the set at a somewhat lower price than if you sell them individually, since nearly all people aren't interested in all three focal lengths, but only one of them, maybe two. If there's someone out there looking for them all, he will contact you anyway and you might be able to make him a better deal, since you will only have to send one package, instead of three, thereby cutting your expenses and trouble.

But I think you'll be able to sell them much faster, if you sell them individually.


Clear skies!
Thomas, Denmark

#128 plav1959

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Posted 26 January 2013 - 05:46 PM

You may have an issue selling as a set, but the good news is they should sell very quickly. I put a 22T4 and a 12T4 on AM and they were both sold within a couple of hours. I'll be very interested to hear how the 25 does in your dob, both with and without a type II paracorr.

#129 MRNUTTY

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Posted 26 January 2013 - 07:49 PM

I got that 24T4 ;-)

#130 Shneor

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Posted 30 January 2013 - 05:55 PM

What do you mean when you say field curvature offset coma?
Field curvature slowly defocuses the star images, but they stay round. Coma stretches the star images radially into fan shapes.
Field curvature can defocus coma, too, making the comatic image slightly larger and out of focus, but it doesn't reduce coma. It can only make the appearance of it worse.
So what you say cannot be reconciled.
I notice a slight amount of astigmatism near the edge, and depending on which side of focus you sit, this could appear to reduce the radial width of the comatic star (while stretching it circumferentially). On the other side of focus, it would make it worse.
I got a quick glance at the Perseus Double Cluster with the eyepiece in a Paracorr II, and the star images displayed a trace of astigmatism, but no obvious coma or field curvature. Since the Paracorr corrects the last two, it's not surprising what I saw. Without the Paracorr, it displayed the normal amount of coma for an f/5 scope and a 100 degree field, i.e. a lot.
However, if the eyepiece actually corrected coma, it would display coma in the Paracorr, and it did not.
Once again, current eyepieces do not correct for coma. If they did, they'd only be useful in short f/ratio newtonians.

Edit:
It just dawned on me that what you are calling field curvature is actually rectilinear distortion (wherein straight lines appear curved near the edge of the field, so ||| becomes )|( in the eyepiece.
Yes, the eyepiece has a lot of that, as do other 100 degree eyepieces.
The correction of RD is impossible in a widefield eyepiece without leaving in tons of Angular Magnification Distortion (AMD), which is considered to be the more deleterious form of distortion in astronomical viewing.
RD is more noticeable when panning quickly, but usually doesn't bother most observers.
AMD, on the other hand, distorts images terribly, so most modern designers opt for RD over AMD.

Field curvature is when the focal plane is curved toward or away from the eye at the edge and it results in out of focus stars. I don't think that was what you were talking about.

Hi Don,
Sorry to take so long to respond, the flu laid me low for almost a couple of weeks, and I lost interest in almost everything.

I think you are correct in describing the distortion. I don't claim it was planned, but in an area roughly 60-90% of the radius, coma seemed to be less than it ought to be.
If the weather cooperates, I'll check it out again this weekend. Last time, I neglected to change to my observing contact lenses, and that may also have affected the view. The distortion was obvious when panning, however.

Clears,

#131 Scanning4Comets

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Posted 30 January 2013 - 06:11 PM

I am not trying to decide on which one to keep. For me, the ES 25mm 100 AFOV is a keeper along with the 21 Ethos and 31T5 Naglar. I think it is finally time to put my T4 Naglars on the market. I really like the 22T4 and 17T4, less so the 12T4. These were my first 3 Televue eyepieces. I just can't fit them all in my case. It is also getting to be a bit heavy. I may buy a Paracorr type II with the proceeds from selling the T4s. Do you think there is any advantage in trying to sell 3 T4s as a set?

--------------------
Jeff


Jeff,

Why would you keep all three considering they are all so close in focal length?

#132 JMW

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Posted 30 January 2013 - 09:18 PM

I almost always take two scopes to view at dark sites. Sometimes I will also set up a C11 EdgeHD along with the dob and refractor. Most of my viewing is with my 17mm or longer eyepieces. I only go shorter to look at planets or planetary nebula. There is a big difference from the 21 Ethos and Nagler 31T5 so I don't think they are redundant. It will take a summer of viewing before I would make any decision regarding pruning any eyepieces other than my T4 Naglers. I have a Pelican 1550 case and store my eyepieces standing up so I do have a lot of room.

#133 Jobryant

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Posted 06 March 2013 - 12:18 PM

Well I couldn't resist and I had to order me one of these ES25100s. I placed my order from Atronomics on March 1st and received it in the mail yesterday March 5th.

First thing is I really like the cool box the EP came in it's awesome. Unfortunately while I was admiring mine I noticed it was damaged a bit. Normally I wouldn't care too much about the condition of the box but with such a nice looking box like this one I must admit I was pretty bummed when I found the flaw.

The main reason for acquiring this EP is to see if I could use it for my daytime viewings. The allure of viewing with a 25mm 100 degree EP during the day was too much for me to resist even after reading all the early reports suggesting it will probably not work very well for terrestrial viewing. I'll be comparing it against my current daytime champ the 30mm Leitz. I really like the Leitz so in order for me to keep the 25mm ES it will need to perform very well. Side note all the testing was done during the day.

So far I've only been able to use the new EP for about an hour and my initial gut feeling is that I won't be using the ES25100 as a daytime EP. Reason being is that during this short time I already think that the distortion will more than likely be too great for me to overcome. Normally I can handle distortion very well but the amount in the ES25100 is pushing it for me. I felt that I got a bit light headed after viewing with it so no matter how good the EP is if it makes me sick I won't be using it. Hopefully I will get use to looking through a fishbowl without loosing my lunch.

These first impressions are just that and I'll need more time viewing with the EP before making my final decision. With that being said here are a few other things I noticed so far.

In my 50mm F5.6 and 114mm F5.3 refractors curvature was noticeably present. When focusing on axis I'd say about 80% looked in really sharp and in focus at one time. When focusing more towards the outer 1/3rd of the FOV my eyes of 36 years were able to barely overcome the majority of the curvature and I was able to get sharp focus across the entire FOV. The Leitz was the better EP when it came to curvature. More testing is needed to see if coma is present or not.

I felt the on axis sharpness was great on par with the Leitz which is excellent on axis. Color and contrast looked great but I definitely need more time testing this because I was more concentrating on checking the sharpness of the EP then anything else.

I must say I was pleasantly surprised how comfortable the EP was in regards to eye relief, eye placement and lack of blackouts. All these features came together really well for me. I was able to see the entire 100 degrees without nearly as many blackouts as I initially thought I would experience. Yes I did need to tilt my head a bit to see the edges but it was very naturally feeling and not awkward at all for me to do. Even though eye placement to prevent blackouts was fairly easy for me to obtain and hold I found that there seems to be an eye placement sweet spot that was very hard for my to achieve but once found I noticed a reduction in the color fringing seen around the edges.

So far I prefer to remove the rubber eye guard while viewing. The rubber eye guard does in fact feel soft and comfortable against your skin so that's not a issue. I've never like using the eye guards no matter what EP is the reason for me not using the eye guard.

Well that's about it for now. Overall I feel it's a great EP but like others mentioned before me probably not going to be a favorite for terrestrial viewers.

#134 Rinaldo

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Posted 06 March 2013 - 07:54 PM

That box is GREAT!

#135 star drop

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Posted 07 March 2013 - 10:19 AM

The heck with the eyepiece. Let's play with the box?

#136 DRodrigues

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Posted 31 March 2013 - 05:13 PM

So far I've only been able to use the new EP for about an hour and my initial gut feeling is that I won't be using the ES25100 as a daytime EP. Reason being is that during this short time I already think that the distortion will more than likely be too great for me to overcome. Normally I can handle distortion very well but the amount in the ES25100 is pushing it for me. I felt that I got a bit light headed after viewing with it so no matter how good the EP is if it makes me sick I won't be using it. Hopefully I will get use to looking through a fishbowl without loosing my lunch.

Jobryant, did you got used to this ep for daylight use?
Did you ever used an Ethos 21 or 17, for daylight use? If so, how do you compare those to the ES100 25?
I use an Ethos 17 for my cr-birding http://www.pt-ducks....htm#Test of 82º,%20100%C2%BA%20and%20102%C2%BA%20AFOV%20zooms and love it... ;)

#137 davidpitre

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Posted 31 March 2013 - 06:45 PM

I will defer that opinion until I have a chance to try them both out in the Obsession 20F5.

I don't know if you know your fully dilated pupil size, but for me the 31 Nagler would not be my choice for a 20" f/5 , as it gives about a 6.5mm exit pupil. This is larger than many older eyes can accommodate. At 5.1mm the ES 25mm seems more useable.

#138 Fred1

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Posted 01 April 2013 - 10:00 AM

Has anyone determined the Paracorr setting for the ES 25mm 100°? I fiddled with it some in a friend's 16" f/4.2 as I haven't had a chance to try it in my own scope, yet. Seemed the C or D setting was getting it close. I think B was best for my ES 9mm 100°. Comments?

#139 Starman1

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Posted 01 April 2013 - 10:14 AM

Has anyone determined the Paracorr setting for the ES 25mm 100°? I fiddled with it some in a friend's 16" f/4.2 as I haven't had a chance to try it in my own scope, yet. Seemed the C or D setting was getting it close. I think B was best for my ES 9mm 100°. Comments?

You can figure it out easily.
Put in an eyepiece for which you know the correct setting of the Paracorr.
Focus the telescope with the Paracorr set to the correct setting for that eyepiece.
Remove the eyepiece and insert the 25mm.
Focus using the tunable top of the Paracorr, not the focuser knobs.
When the eyepiece is in focus, that is the correct setting of the Paracorr for that eyepiece.
Make a note of it and that will be the setting you select before inserting the 25mm the next time.
You may have to make a tiny focuser adjustment to get perfect focus, but this principle works for all eyepiece that have a proper setting within the range of the Paracorr's tunable top (and 99%+ do).
The only thing required is 1 eyepiece for which you know the correct setting of the Paracorr, and you can determine that by trial and error by using every setting of the Paracorr and focusing then looking at the edge of the field and picking the setting that is best corrected (and it can even be done with the stars slightly out of focus).

#140 Fred1

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Posted 01 April 2013 - 03:45 PM

Thanks, Don. That's what I did, but perhaps it's the rectilinear distortion of the EP (plus my own slight astigmatism) that's having me waffle between C and D. I used a 24mm Pan set to D and focused before inserting the ES 25mm. I should be able to spend more time on it Wednesday night when I'm out with my 18".

#141 Jobryant

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Posted 01 April 2013 - 10:21 PM

Yes I only tested it out during the day. I probably would have kept it if it had been a bit more digiscoping friendly. I've have used a 17mm Ethos for my daytime viewing but that was a few years ago with a different scope. I really liked the Ethos during the day and the only reason why I got rid of it was the magnification was too much for my liking. I prefer mags no higher then 20x.

#142 Fred1

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Posted 03 April 2013 - 08:08 AM

Thanks, Don. That's what I did, but perhaps it's the rectilinear distortion of the EP (plus my own slight astigmatism) that's having me waffle between C and D. I used a 24mm Pan set to D and focused before inserting the ES 25mm. I should be able to spend more time on it Wednesday night when I'm out with my 18".


It's setting B same with the 9mm and 20mm ES 100° eps. The 20mm and 25mm are roughly parfocal, the 9mm is not. BTW, I REALLY like the 25mm. I believe it will be my most used wide field ep. Same TFOV a my TV 31mmNT5 but with a more comfortable exit pupil, slightly better contrast with darker background. My first night with it was superb with not nearly as much outer field distortion as I expected. it's really a non-issue for me. Although the Orion Nebula was setting and it was still twilight the E and F stars were readily visible with plenty of detail in the nebula. NO filter in play. It's a keeper. Best SQM reading last night where I was was 5.56 NELM. Should be able to get to a darker site tonight with at least 6.0 skies.

#143 JimMo

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Posted 03 April 2013 - 03:13 PM

BTW, I REALLY like the 25mm. I believe it will be my most used wide field ep. Same TFOV a my TV 31mmNT5 but with a more comfortable exit pupil, slightly better contrast with darker background.


I appreciate this statement as I just reluctantly traded my venerable 31T5 for an ES 25/100 for the same reasons. I can't afford to have both at once so I hope my experience mimics yours when used in my dob. I hope to have it by Friday in order to take it to our messier marathon this weekend.






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