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Quality eyepieces/barlow/coma corrector for fast f4 dob?


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Hi all, this is probably old ground, but my head is absolutely spinning from all the information out there, so any first-hand information/experience etc is appreciated.

I'm starting an eyepiece collection from scratch for my recently acquired 20" f4 skywatcher dob, which will eventually be used to hunt some of the more obscure DSOs under Bortle 2&3 skies, and hopefully Bortle 1 when I can get over to West-coast Scotland once or twice a year.

I wear eyeglasses, though may try the screw-on Televue astigmatism corrector and lose the glasses for viewing, so eyepiece relief is not a primary issue, contrast and image quality is. 

I have the bog standard SW 10mm 1.25" and 2" 28mm eyepieces. To my novice mind, the 28mm actually isn't too bad considering it's a £30 eyepiece! I wasn't too impressed with the 10mm, but have only spent a very brief time with the scope and the collimation/overall image quality will no doubt improve once I gain experience with this procedure.

I'm looking to build up a small set of quality eyepieces (2-3 for now), a 1.6 or 2x barlow and a nice coma corrector over the summer, budget willing.

- Due to the fast nature of this scope, I have narrowed down my choices to either the Pentax XW line or the Televue lines between the Delites, Delos and possibly an Ethos or two if a real bargain comes along.

As a long-time Pentax camera/lens fan, I noted with interest the excellent reviews on the 'affordable' XW line, tested down to f4. Sadly the 2" XWs are apparently no longer produced by Pentax and rarely come up for sale.

Of course the Tele-Vue lines mentioned above all seem to get high marks.

I have heard mixed reviews regarding super wide-field 100 eyepieces - for faint DSOs I have heard they can let in too many other stars, reducing contrast or even eliminating very faint objects such as the Horsehead nebula, even with appropriate H-beta filter which seems mandatory for this type of DSO.

Are there any other excellent eyepieces besides the Pentax/Tele-Vue line that shine at f4? Any of the Meade, WO, Siebert, ES models, Vixen LVW, etc? 

I am assuming a Paracorr 2 coma corrector is probably going to be a requirement as well for a crisp image out to the edges. Would a Paracorr 1 or 2 allow a f4.5-tested Pentax zoom or Baader Hyperion Mk IV zoom to perform highly at f4?

I am also looking at either a Televue 2" Big Barlow or a 2" Powermate for my barlow.

Sorry for all the questions, life at f4 ain't cheap as I'm finding out!

 

Clear skies all.

 

 

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Hi Again

I feel that a coma corrector will require to be a Paracorr. I use (although not every time with a F4.6 Dob) a Paracorr type 2 and mostly Tele Vue eyepieces, the Paracorr chart available to print on-line, is a clear reference for settings, which are straight forward. Unless one comes available at a good price used, first priority will be for, as you mention three used quality eyepieces. As others in another thread had indicted, highly recommend the Delos line, for comfortable eye placement, 20mm eye relief, ethos like contrast. Ethos if as you say, if listed used at reasonable cost, a little less in eye relief 15mm. 21mm ethos, with a focal length of 2000mm will be x95  - without a paracorr - which will increase magnification by 15%. Low power could become a 30mm - 31mm e.p, approx. x64. Mid power could for example become a 17.3mm Delos x116 or 14mm Delos x143 or for that matter, a 17mm ethos (perhaps not quite applicable enough - 15mm ER though for wearing glasses?). 13mm is a popularly used focal length with a broad range of telescopes, perhaps 10mm for higher power x200.  

The journey begins with just getting the scope, fortunately there is a thriving used market. You clearly have access to some of the UK's potentially best dark skies and significant aperture, perhaps you could consider enquiring to link up with the dob mob upon their forays north, among many things will be an opportunity to share and trial eyepieces.

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Don’t worry about the missing Pentaxs, I believe that they weren’t quite up to the standard of the rest of the range.

The Parracor 2 is a small fortune and, in my opinion, not required unless you go hyper wide eg. Ethos. These eyepieces need more intravel than the original Parracor can manage. I can’t tell the difference between 1 and 2 in performance terms on Delos eyepieces at f4. Don’t get the earliest mk1’s as they were a lot less solid than the later versions. The SIPS system by Feathertouch is probably as good as it gets and makes a new Parracor II seem cheap.

If you have to wear glasses, you will struggle to get the benefit of the wide, wide views as you can’t get close enough to the lense. I found that the narrower 70° quality eyepieces such as Delos and, I’m told, Pentax, very comfortable and the Coma not too intrusive. My low mag eyepiece in the f4 Dob is an ES 82° 24mm in a Parracor 1. The field of view is about the same as the Ethos 21mm but with pin point stars. I do class the Ethos 21mm as the best eyepiece I’ve ever used, bar none. But ££?££?££.

I would be wary of going the zoom route. It would be employing an 18 stone [removed word] to ride your thoroughbred racehorse. Generally, zoom eyepieces fall into the ‘jack of all trades - master of none’ category. Although, the Leica offering is supposed to buck that trend (see Ethos price comment re price).

As mentioned already, 30mm eyepieces at f4 would lead to a washed out view bus to its 7.5mm exit pupil. 22 mm without a Parracor or 24mm with is my maximum. 

Good luck.

Paul

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I expect that a consideration will be balance. I am not familiar with this particular scope, how effectively it is set up for operating with heavy eyepieces and a paracorr. I quite agree with Paul, just perhaps a 17.3mm and 10mm Delos combination, will be applicable for wearing glasses, not so heavy, in comparison with alternatives and comfortably engaging allowing you to see the field stop in the 72 degree AFOV. What would be the eye relief for the APM / Lunt 20mm? Also agree not to necessarily go down the zoom route.

Edited by scarp15
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Thanks very much all! I will probably start out with something around 20mm, then perhaps a 13/14mm and go from there. Admittedly, I'm a bit of a Pentax nut, so those are very appealing at 70*view and £249 new. The reviews on the XWs are solid as well, no real complaints (for the 1.25" series - I won't lie awake now wondering about the rare 2" range!). Tele-vue or the APM/Lunt 20mm - that's one that escaped the radar, thank you.

I will see how those look first and then think about which/any coma corrector. My novice eyes may not be too discerning and hopefully I'm too much of an amateur to notice what I might be missing, and save a few quid in the process, haha. 

I shall hold off on the zoom idea unless I find a used pair for BVs down the road a year or two - that's same generally speaking with camera zoom lenses vs fixed focal length primes, the primes almost always win on ultimate sharpness and image quality.

Already there have been a few interesting used eyepieces come up within just the past week, so I'm sure over the summer my ship will arrive.

I really appreciate your input - I'd be delighted if someone wanted to use the 20" dob and bring their eyepieces for a shootout when it gets darker again. We can drive out to some excellent Bortle 2 about an hour from me. The more the merrier!

Perhaps I should organise my first NE Scotland Cairngorms 'star party' BYOEPs (bring your own eyepieces), haha - or *groan* ?. Cheers all!

 

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16 minutes ago, Ships and Stars said:

Perhaps I should organise my first NE Scotland Cairngorms 'star party' BYOEPs (bring your own eyepieces), haha - or *groan* ?. Cheers all!

 

Well that sounds like a good idea.

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2 minutes ago, scarp15 said:

Well that sounds like a good idea.

I have some excellent spots here I'm familiar with from camping, open views, close to the road but far enough off to set up gear and walk around, and rarely any cars pass by after dark. Incredible skies. With a bit of luck, I could even persuade a kind estate owner to let us drive up a particular track I know to a hilltop spot for the best field of view.  Might get them on-board as well!

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Paul & Scarp - missed part of that - thank you for the 17.5/10mm Delos idea - that sounds right in my novice mind, I'd prefer to keep my glasses on, especially at night wandering around the scope because I will drop them and flatten them in short order! I don't think I'm going to be able to reliable squeeze more magnification than those EPs at 2m focal length unless conditions are superb, and if so, then will barlow if possible. I feel like I'm headed in the right direction now, a couple of EPs, then barlow/coma corrector. Much appreciated!

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Great, get the eyepieces first and allow time to consider further decisions based upon this. 

The camping could be interesting, it has been a while, I have backpacked at this time of year, across almost all the Munroe's through the Cairngorms except for Carn a' Mhaim. My strongest imposing memories are of Cairn Toul and the corries below Braeriach.

Edited by scarp15
spelling (groan)
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The XW's are really excellent in the focal lengths 10mm down to 3.5mm. I've not gone for the 14mm and 20mm because of reports of field curvature so I've gone for the 14mm and 17.3mm Delos instead. A 24mm Tele Vue Panoptic and the 2-4mm Televue Nagler zoom completes my 1.25 inch eyepiece set.

For my 12" dob though I tend to use the Nagler / Ethos set spanning 31mm, 21mm, 13mm, 8mm and 6mm. They cover the vast majority of observing with that scope.

In your opening post you mentioned 100 degree eyepieces letting in too many stars. This situation refers usually to observing the Horsehead Nebula where ideally keeping the nearby star Alnitak out of the field of view helps to see this very, very hard to see nebula. Otherwise I feel that 100 degree eyepieces are superb deep sky observing tools. I've owned and used a number of different brands of 100 degree eyepieces and found them to be really high quality eyepieces - the manufacturers seem to regard them as flagship products and put their best efforts into their production.

If you are a glasses wearer when observing you may well find that 100 degree eyepieces are not for you however because of their eye relief which tends to max out at 15mm and in terms of what is useable, make it challenging for the glasses wearer to see the full field of view.

 

 

 

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7 hours ago, scarp15 said:

Great, get the eyepieces first and allow time to consider further decisions based upon this. 

The camping could be interesting, it has been a while, I have backpacked at this time of year, across almost all the Munroe's through the Cairngorms except for Carn a' Mhaim. My strongest imposing memories are of Cairn Toul and the corries below Braeriach.

Let me see what I can finagle with the estate owners. Miles of empty tracks, one or two discerning astronomers. No harm eh?

 

7 hours ago, John said:

The XW's are really excellent in the focal lengths 10mm down to 3.5mm. I've not gone for the 14mm and 20mm because of reports of field curvature so I've gone for the 14mm and 17.3mm Delos instead. A 24mm Tele Vue Panoptic and the 2-4mm Televue Nagler zoom completes my 1.25 inch eyepiece set.

For my 12" dob though I tend to use the Nagler / Ethos set spanning 31mm, 21mm, 13mm, 8mm and 6mm. They cover the vast majority of observing with that scope.

In your opening post you mentioned 100 degree eyepieces letting in too many stars. This situation refers usually to observing the Horsehead Nebula where ideally keeping the nearby star Alnitak out of the field of view helps to see this very, very hard to see nebula. Otherwise I feel that 100 degree eyepieces are superb deep sky observing tools. I've owned and used a number of different brands of 100 degree eyepieces and found them to be really high quality eyepieces - the manufacturers seem to regard them as flagship products and put their best efforts into their production.

If you are a glasses wearer when observing you may well find that 100 degree eyepieces are not for you however because of their eye relief which tends to max out at 15mm and in terms of what is useable, make it challenging for the glasses wearer to see the full field of view.

 

 

 

 

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Hey John, what are you up to say, mid-October? Ever flown into the lovely grey and damp city called Aberdeen? I might be able to suss a ticket.  one hour west are some of the clearest skies in western Europe, Bortle one, if you can stand my conversation that long! Need to ok this with the wife, she still doesn't understand star charts, thinks I've dabbled with colour by numbers. Over and Out!

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