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Explore Scientific 82 24mm 2" EP won't focus

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#1 citrite_y

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Posted 19 January 2013 - 02:39 AM

Hi all,

Based upon many favorable reviews I decided to purchase one of these for my Birthday and upon testing the device tonight I determined that I was unable to cleanly focus the EP in my Orion XT8 dob. While it was able to get Jupiter reasonably in focus, Jupiter's moons never completely resolved (to fine dots) like they look after I switch over to a Celestron Ultima 30mm.

So now I'm trying to figure out what the cause of the issue might be, collimation? My laser collimator is on order and will take another week before it ships, though if it was collimation (I currently use a collimation cap that came with the scope) I would think that I would see the same problem with the Celestron and my other EPs.

I thought I had read where someone had gotten an EP (it could have been a different brand) and needed to unscrew the lens. With this lens being N2 purged and waterproof I want to avoid messing with it.

Is it possible that this EP is just not going to work with my scope? I had to extend the focuser out as far as it would go but it seemed like it needed to go a little further before the moons would resolve. The EP has a recessed area where the screws make contact and seating the EP beyond that point seems like it's risky. Is there a solution for this that I haven't heard of yet?

Thanks everyone for listening, and yes this is my first time posting.

Thanks,
Bill

#2 Astrojensen

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Posted 19 January 2013 - 02:46 AM

I had to pull my ES eyepieces out of the focuser on my dob A LOT. They were essentially hanging by a thread. The recessed part of the barrel was well clear of the focuser! What is needed is a short extender tube. My ES eyepieces are all extremely sharp, so I can't imagine yours is any different. Try pulling it out a little and see what happens. If it can get to extremely sharp focus, all you then need to do is to get a short 2" extender.


Clear skies!
Thomas, Denmark

#3 x133

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Posted 19 January 2013 - 03:23 AM

I have the same problem with my 9mm and 14mm ES 100 and 30mm ES 82 in my XT8. I have to pull them out about 1/2" out of the focuser with the with the focuser almost all the way out to achieve focus.

Using an extension may not work. I have a 35mm extension, which was the shortest that I could find, that only work on my 9mm since the barrel on the 9mm is shorter than the 14mm and 30mm. When I use the 9mm with the extension, the focuser is almost all of the way in. When I use the 14mm and 30mm with the extension, they stick out to far to achieve focus even with the focuser all the way in.

Eric

#4 Achernar

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Posted 19 January 2013 - 10:11 AM

It ounds like you don't have enough out travel to get it to reach focus. By the way, the Galilean moons are resolved as disks through an 8-inch, and therefore do not appear as stellar points. Even a good 6-inch will show them as disks of varying sizes and hues at high power when the seeing is good. So if you are getting Jupiter sharp, the fact the moons are not starlike points is not due to mis-collimation. Otherwise, the only ways to fix this issue other than a short extension tube is to move the primary mirror cell forward in the tube enough to allow all of your eyepieces to focus, or to swap out the focuser for another one that gives you the extra out travel needed. A short extension tube is the easiest way to fix the problem you are having with this eyepiee, which is a very good eyepiece that will give you panoramic views. Extension tubes are used just like Barlows, and they are inexpensive. I have one of those ES 24mm 82 degree eyepieces myself. It's superb for my 10 and 15-inch Dobs, even though I rack out my focuser quite a bit to get it to focus. Just last night I took in the whole of the Orion Nebula with it through the 15-inch. When I built that telescope, I had to shave off 1/4-inch at a time from the truss-poles to allow all of my eyepieces to focus, and some barely reach focus within the 2-inches of travel the focuser has. Not all eyepieces focus at the same point, some require considerably more in or out travel than others, and a Dob's focuser may or may not be able to accomadate that. Replacing the stock focuser with an aftermarket unit such as a Moonlite is a worthwhile improvement for a Dob because it allows for critcal focusing at high power and they are made with heavy eyepieces and even cameras in mind. However, an extension tube is a way to defer or avoid having to replace the focuser and or eyepiece.

Taras

#5 northernontario

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Posted 19 January 2013 - 10:36 AM

I once made an extension tube out of plumbing pipe to get me going.

I think it's called PVC pipe. It was a very low cost, yet extremely simple and effective solution.

jake

#6 Scanning4Comets

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Posted 19 January 2013 - 10:56 AM

I had the same problem with a 34mm ES 68 degree eyepiece. I had it precariously sitting in my focuser with about 1/2" or less to spare in order to reach focus. I bought a Baader 28mm Fine Tuning Ring and it now easily comes to focus.

I now have it on the 34mm ES with a stiff, rubber parfocal ring.

That's your best bet IMO.

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#7 Scanning4Comets

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Posted 19 January 2013 - 10:57 AM

Here's the eyepiece with the 28mm Baader fine tuning ring screwed to the bottom of the 34mm ES with the stiff rubber ring on the barrel. Best thing about this is that the barrel is now completely "flush" in the focuser without the tapered part getting hung up in the focuser! You can just leave it on there and put the EP back in the case with the FTR attached.

Another good thing about this is that the fine tuning ring is extremely flat black on the inside and also threaded for 2" filters. ;)

Cheers,

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#8 Mike4242

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Posted 19 January 2013 - 11:12 AM

I had the same problem with my XT10i. I absconded with 2 of my wife's elastic hair bands and put them around the barrel. Actually got the idea from another member here with the screen name Craytab.

Here's a pic:

Posted Image

#9 bleep

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Posted 19 January 2013 - 11:14 AM

I had the same problem with my 2" eyepieces on my XT8. i went to Home Depot and bought a couple rubber rings from the plumbing section and now problem solved! Cheap and easy.

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2" eyepiece by ibleep, on Flickr

#10 mfromb

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Posted 19 January 2013 - 12:48 PM

Interesting. I'll have to see how this bears out on my XT8i, if/when my 24mm ES68 ever arrives. Is this something more or less indigenous to the ES82's or should I expect something similar fron the ES68 24?

I have the ES82 11mm and have no focus travel issues, except if I attach the lens module from bottom of my GSO 2.x barlow (approx 1.5x effect), which causes me to have to back the barrel out a bit, to achieve focus. This was a commonly reported condition, so it came as no surprise to me when doing this. Backing it out is not needed when used without barlow or with barlow fully assembled and attached.

Is this limited to the lower powered ES82's, perhaps? Just curious and it would be nice to know what to expect from the ES68. Although, more importantly, I'd like to know WHEN to expect the ES68. I fear I am at the back of a very long line of backorders that encircles the entire planet.

#11 Mr Magoo

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Posted 19 January 2013 - 01:46 PM

I would assume that if this was dropped in a Paracor that would also help would it not?

#12 teelgul

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Posted 19 January 2013 - 02:19 PM

These eye peices seem to be nice in optics and and build.
Why can't they make it with a longer barrel or are they optimized for a certain kind of scope?

#13 csrlice12

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Posted 19 January 2013 - 02:50 PM

I'm wondering to the OPs, did you swap out your focusers, or are you using the stock focuser?

#14 citrite_y

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Posted 19 January 2013 - 03:36 PM

I'm using the stock focuser that came with the XT8.

#15 citrite_y

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Posted 19 January 2013 - 03:40 PM

I still a beginner and have yet to learn exactly what a Paracor is or does. So far from what I gathered it has something do with reducing coma though I don't think that I've seen that yet with any of my EPs.

#16 citrite_y

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Posted 19 January 2013 - 04:16 PM

I like this idea and it makes the most sense. For tonight I'm going to try using a couple of bands temporarily and see how that goes. I actually was expecting to see more expansive views through the EP last night, maybe I've just seen too many photographs and had my expectations set to high. Originally I was going to get a 30 instead of the 24 and still might do that. I just figured that the view from the Celestron Ultima 30 to this EP would have been substantially improved.

#17 keroppilee

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Posted 19 January 2013 - 04:50 PM

my 30mm es 82* focuses just fine in my xt 8 with default focuser

#18 Achernar

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Posted 19 January 2013 - 06:44 PM

Coma correctors greatly reduce or completely eliminate coma, leaving stars pinpoints across the whole field of view assuming the eyepiece itself is up to the job. They will not deal with bad optics or astigmatism that is present in some eyepieces around the outer edge of the field of view. You can snag a used TeleVue original Paracorr with the tunable top for $150.00 to $200.00. They require quite a bit of intravel and do increase the focal length 15 percent. That is no problem for me, since I look mainly at smaller DSO's and planets. There are other coma correctors that do not increase the focal length. If you have an F/5 or less Dob, they are worth trying out to see if the improvement is worth the money to you or not. If you have an F/6 or greater telescope, you don't really need one at all.

Taras

#19 citrite_y

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Posted 20 January 2013 - 01:41 AM

So tonight I retested the EP by not completely inserting it to its recess point and had good results--I was able to cleanly resolve Jupiter and its moons. The EP was sticking out about 1/2" from where it would normally bottom out if it had been inserted all the way into the focuser.

According to my specs the XT8 is an F/6 so that would probably explain why I haven't seen any coma with any of my EPs.

It was nice to get more of the nebula in Orion into the field of view though at this point I have to wonder if I should have gotten a 30mm instead of the 24mm. I'm going to hunt down Andromeda while I still can and see what the view is like with my scope and this EP. So far I've only seen it with my bins.

#20 dan_h

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Posted 20 January 2013 - 10:06 PM

There are a ouple of easy to use solutions that will help.

Check the primary mirror collimation screws. If they have been tighten up it may be possible to move the primary forward 1/2" or so simply by loosening the collimation bolts that much. Of course you will have to recollimate when you do this.

Add a spacer bewtween the focuser and the tube. There are a number of easy to work materials you could use such as cork tile. Get a 1/4" here, and another 1/4" at the primary and you'll be all set.

dan

#21 MingoT

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Posted 21 January 2013 - 03:37 PM

I had the same problem with the ES100 14mm on my Orion XT12i: with the stock Crayford focuser totally extended, the image was still slightly out of focus. I could solve de problem by moving down a little the primary mirror tightening the collimation screws. Of course, you will need to re-collimate. Now it focuses with all my eyepieces.

Best,
Mingo

#22 mdalton

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Posted 21 January 2013 - 06:34 PM

I am having the same issues with my ES 24mm 82* and a Russell 18mm 80* Ultra-wide. My solution was a plastic washer from the plumbing dept. at Lowe's. Surely, there must be a better solution than this. I have an XT10i with stock focuser. I was thinking that the primary may be too far forward or the secondary too far back (or a combination of both) I don't have this problem with any 1.25" eyepiece, only the 2" ones.

#23 csrlice12

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Posted 22 January 2013 - 09:05 AM

Sounds like the newer ES's share a common problem with Naglers....not enough outfocus. On the Naglers, I just line up one of my locking screws with the notch in the eyepiece and let the eyepiece rest on the screw and I tighten the other screw, This gives me enough extra length to bring the eyepiece into focus--Kind of the same idea as Baader focusing rings. Kind of surprized to hear this though as this is a new "problem" with this eyepiece, neither the old nonwaterproof nor the N2 purged version seem to have this problem.

#24 Darenwh

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Posted 22 January 2013 - 12:37 PM

The thing you need to remember is that much of the focus issues have to do with modern scopes. First, focusers have become much lower format than they used to be, this results in only a small amount of travel in the focuser. This is occurring due to the increased use of faster scopes and the desire to minimize the size of the secondary. This has limited the amount of focus travel that newer scopes have. The result is that the range of focus needed may be 2.5" and the focuser travel may only be 2". I also believe that part of the issue is that many primaries are +/- a small amount from the actual stated focal length. Lets look at an 8" F6. That would be a focal length in inches of 48"s. If the variation in mirrors is that they must be within 1" of the stated focal length then you start seeing issues. If your focuser has 2" of travel and the OTA is built without taking into consideration the variation then an eyepiece that would come into focus on one OTA from that manufacturer may need to be out or in another inch for another OTA. Of course, if the manufacturer takes the variation into consideration then they would need to look at the actual focal length of every mirror and then move the mirror and/or the focuser+spider combo up or down in the tube to keep the focus of each scope at the approximate same amount of focus out on the focuser. Older scopes often used focusers with much more range (up to five or six inches) so they rarely ran into the same issues with some eyepieces needing additional in focus or out focus.

#25 Pharquart

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Posted 22 January 2013 - 02:12 PM

I have the same problem with my ES82-24. I can't get enough out focus, but just barely. For kicks, I compared all of my eyepieces. Plossl, RKE, XCel, even another ES82 (though 1.25" format). 7 different focal lengths, at least 4 different optical designs, almost all are different brands. All came within 1/4" of each other at focus. Throw in my 2x Barlow and they all moved almost exactly 1/2" inward. The ES82-24 was the oddball, at about 1/2" more further out than all the rest.

I bought a 2" extender (like a Barlow, but no lens). I had to search to find one that was short enough so that I didn't run into a lack of in focus with it!

There was far more consistency in my other eyepieces than I expected. Almost parfocal, despite their wide differences in design, age, and manufacturer. It was really odd to me that ES would design their eyepiece to be different.

Brian






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