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8" EdgeHD - Beginning Ep's

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#26 aeajr

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Posted 11 January 2018 - 03:21 PM

 

 

Eye Relief (Designed) 19mm ER at 8mm FL - 16mm ER at 24mm FL

 

 

The website I looked it up on said 11-13mm.  If it is wrong, my apologies, and I take back the above criticism.  FWIW, I tried baader's site first, but could not find the eye relief specified.

 

Baader is on what, its fourth version of the eyepiece.  Maybe the 11-13mm number was  from an older version.  Maybe it was just wrong. 

 

You may sell me on one yet, particularly if that 19mm is actual usable eye relief.  

 

Given the vast number of SCTs out there, you'd think there'd be a market for a 5-12mm "Planetary" zoom maxing out with a 60-degree field and offering 20mm of eye relief.   I'd buy one of those if it could provide "Dual ED" quality views...

 

I was concerned that the Agena Astro specs might be wrong to I checked the Baader site.  Had to hunt down to the instruction manual.

http://www.baader-pl...oom_mark_iv.pdf

 

Brennweite ( focal length?)        8 mm 12 mm 16 mm 20 mm 24 mm

Pupillenabstand ( eye relief?)  19 mm 18,2 mm 17,4 mm 16,7 mm 16 mm


Edited by aeajr, 11 January 2018 - 03:22 PM.

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#27 aeajr

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Posted 11 January 2018 - 03:30 PM

 

In your 8" Edge HD the eyepieces will produce
ES68 40        51x       80arc' TFOV       4.0mm exit pupil
ES82 30        68x       73arc' TFOV       3.0mm exit pupil
And that is a real difference that should have value for your observing.
 
Not a fan of them for my own use, I agree that the Baader zoom fits you need very nicely. I like that development in your thinking.
 
But I'm going to propose you skip the Barlow for now in favor of a GOOD nebular filter set. The Orion Ultrablock Narrowband UHC is a best buy that will take advantage of the larger exit pupil of the 40mm. Add an O-III filter like the Thousand Oaks and you really raise your capacity to see a wide range of objects that would otherwise elude you. A Barlow will not do that and you have the magnification range it will provide covered with the zoom. Nebular filters work by removing light frequencies from the beam transmitted to your eye and the brighter 4mm beam of the 40mm eyepiece will be valuable on dimmer nebulae (and other, unfiltered objects) as the transmitted light will be brighter. Removing those frequencies, BTW, increases the visually apparent contrast of the object you're trying to observe.
 
I think it is because telescope sellers often bundle a marginal quality Barlow in their beginner packages that many beginners think they're necessities. They're not. They're accessories best used for specific purposes that I don't see you needing now.
 
Regardless, very nice telescope and good thinking on your part. I hope you and your family enjoIy it for decades and wear it out observing with it!


I knew someone would come along with actual numbers to back up what I was saying! 

 

Yes, the two EPs have similar field of views, and I am not as well versed in exit pupil yet, but I believe the higher exit pupil will make things brighter (if I am remembering exit pupil characteristics correctly.) If I had to do it over again I would probably choose the 40 over the 30, but I didn't feel like messing with returning a product.  I will probably end up with a 40 someday anyway!

 

I too do not see why a barlow is at all necessary.  I have a great range with what I have and I do not see going below 8mm in my usual seeing conditions.  Now, I have not done much planetary viewing yet, so that may change in the future, but if it does I will add a high quality (probably ES) EP at the below-8 range.

 

And I LOVE the idea of a good filter, that is next on my list.  The DGM NPB is another one that gets great reviews and at $150 is a bargain for a 2" size.  Start with some sort of nebula filter (not a light pollution filter) and add an O-III as the next one.

 

FWIW I have the DGM NBP Nebula, Thousand Oaks OIII.   In my light polluted sky, Bortel 7, or Dark white on the Darksitefinder.com com map,  there is not enough sky to nebula contrast to see most nebula.  I have been able to see a few of the brighter ones, the Orion, the Ring and such but not much else.   The filters helped on these but not much else.  I just don't pursue nebula at my  home site.

 

To make it worse, my ground light pollution is awful too.  My pupils never fully dilate.

 

That is not a knock on the filters, I am happy with them.  It is a recognition that surface brightness in a very light polluted sky is more important than the filters.    And mag numbers for Nebula have no direct relationship to mag numbers for stars when it comes to seeing them against a bright sky.



#28 amzking

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Posted 11 January 2018 - 03:31 PM

Also, I'm confused by your approach to a diagonal and what Baader "quicklock" product you hope to use. 

 

There are lots of SCT users who swear by the 2" Baader clicklock visual back.

https://agenaastro.c...sct-thread.html

 

You need a 2" refractor-style diagonal to go with this visual back.   The Celestron XLT 2" diagonal is an SCT diagonal that does not work with a visual back.   There is a cheaper Celestron 2" mirror diagonal that is sold with the 2" eyepiece kit that includes both a refractor nose and a SCT nose, but it isn't normally sold separately (although you can buy it that way on eBay).

 

I was a bit confused too.  You can buy a 2" diagonal with SCT threads that screws directly on your scope.  I got this one:

https://www.highpoin...2-by-high-point

 

(and crap, now it's on sale for $27 less than I paid.)

 

So unless you feel that you need to quickly release or move your diagonal, I'm not sure why you need that visual back at all.  I do admit, moving the diagonal around is a bit more of a pain in the neck now, but it is doable if you have to.  I just found a good spot for mine and try to leave it alone.  If you are in colder climates you may want the quicklock though.  I'm in Florida, so thermal contracture of metals and needing to constantly wear gloves is not an issue for me.



#29 amzking

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Posted 11 January 2018 - 03:37 PM

 

 

 

Eye Relief (Designed) 19mm ER at 8mm FL - 16mm ER at 24mm FL

 

 

The website I looked it up on said 11-13mm.  If it is wrong, my apologies, and I take back the above criticism.  FWIW, I tried baader's site first, but could not find the eye relief specified.

 

Baader is on what, its fourth version of the eyepiece.  Maybe the 11-13mm number was  from an older version.  Maybe it was just wrong. 

 

You may sell me on one yet, particularly if that 19mm is actual usable eye relief.  

 

Given the vast number of SCTs out there, you'd think there'd be a market for a 5-12mm "Planetary" zoom maxing out with a 60-degree field and offering 20mm of eye relief.   I'd buy one of those if it could provide "Dual ED" quality views...

 

I was concerned that the Agena Astro specs might be wrong to I checked the Baader site.  Had to hunt down to the instruction manual.

http://www.baader-pl...oom_mark_iv.pdf

 

Brennweite ( focal length?)        8 mm 12 mm 16 mm 20 mm 24 mm

Pupillenabstand ( eye relief?)  19 mm 18,2 mm 17,4 mm 16,7 mm 16 mm

 

Here's a link to the full specs for the Mark III zoom.  I couldn't find a similar document for the Mark IV but they appear to be the same for the FL and eye relief you mentioned.

 

http://www.baader-pl...oom-okulare.pdf

 

Also, check out the field of view (FOV) for each focal length, quite interesting.  This is why I prefer my ES 82* at 24mm rather than the Baader.



#30 amzking

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Posted 11 January 2018 - 03:44 PM

 

 

In your 8" Edge HD the eyepieces will produce
ES68 40        51x       80arc' TFOV       4.0mm exit pupil
ES82 30        68x       73arc' TFOV       3.0mm exit pupil
And that is a real difference that should have value for your observing.
 
Not a fan of them for my own use, I agree that the Baader zoom fits you need very nicely. I like that development in your thinking.
 
But I'm going to propose you skip the Barlow for now in favor of a GOOD nebular filter set. The Orion Ultrablock Narrowband UHC is a best buy that will take advantage of the larger exit pupil of the 40mm. Add an O-III filter like the Thousand Oaks and you really raise your capacity to see a wide range of objects that would otherwise elude you. A Barlow will not do that and you have the magnification range it will provide covered with the zoom. Nebular filters work by removing light frequencies from the beam transmitted to your eye and the brighter 4mm beam of the 40mm eyepiece will be valuable on dimmer nebulae (and other, unfiltered objects) as the transmitted light will be brighter. Removing those frequencies, BTW, increases the visually apparent contrast of the object you're trying to observe.
 
I think it is because telescope sellers often bundle a marginal quality Barlow in their beginner packages that many beginners think they're necessities. They're not. They're accessories best used for specific purposes that I don't see you needing now.
 
Regardless, very nice telescope and good thinking on your part. I hope you and your family enjoIy it for decades and wear it out observing with it!


I knew someone would come along with actual numbers to back up what I was saying! 

 

Yes, the two EPs have similar field of views, and I am not as well versed in exit pupil yet, but I believe the higher exit pupil will make things brighter (if I am remembering exit pupil characteristics correctly.) If I had to do it over again I would probably choose the 40 over the 30, but I didn't feel like messing with returning a product.  I will probably end up with a 40 someday anyway!

 

I too do not see why a barlow is at all necessary.  I have a great range with what I have and I do not see going below 8mm in my usual seeing conditions.  Now, I have not done much planetary viewing yet, so that may change in the future, but if it does I will add a high quality (probably ES) EP at the below-8 range.

 

And I LOVE the idea of a good filter, that is next on my list.  The DGM NPB is another one that gets great reviews and at $150 is a bargain for a 2" size.  Start with some sort of nebula filter (not a light pollution filter) and add an O-III as the next one.

 

FWIW I have the DGM NBP Nebula, Thousand Oaks OIII.   In my light polluted sky, Bortel 7, or Dark white on the Darksitefinder.com com map,  there is not enough sky to nebula contrast to see most nebula.  I have been able to see a few of the brighter ones, the Orion, the Ring and such but not much else.   The filters helped on these but not much else.  I just don't pursue nebula at my  home site.

 

To make it worse, my ground light pollution is awful too.  My pupils never fully dilate.

 

That is not a knock on the filters, I am happy with them.  It is a recognition that surface brightness in a very light polluted sky is more important than the filters.    And mag numbers for Nebula have no direct relationship to mag numbers for stars when it comes to seeing them against a bright sky.

 

 

I think I am about a Bortle 5, or burgundy on the darksitefinder map.  Plus the astronomy club plans a darker sky night at the new moon every month (except the summer months.)I'm hoping a filter will be more useful for me.  If I am lucky I will be able to borrow one at our dark sky night this weekend to check.


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#31 jallbery

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Posted 11 January 2018 - 06:25 PM

Thanks, Ed and Alice for confirming the specs on the Baader zoom.

 

Ed,  for reasons known only to Celestron (well, most likely to lower the price and/or raise the profit margin), the EdgeHD comes with a 1.25" visual back and diagonal, despite the fact that it is almost ridiculous to restrict yourself to 1,.25" accessories with an Edge.   Probably 90% of the correction you are paying for occurs outside the 27mm fieldstop of a 1.25" eyepiece  (both coma and deviation from focus due to field curvature are aberrations that increase at an increasing rate with the the distance you move off axis)..   An unlike the non-Edge C8, you don't pay an over-correction in spherical aberration penalty for using a conventional SCT diagonal with an Edge (the Edge is designed for the extra working distance required).

 

Sure, there aren't a ton of objects bigger than 0.76 degrees and for years most SCT users only used 1.25" eyepieces, but its not just about what fits in the field  (although it's sure nice to be able to get as much of Adromeda or the Pleiades, etc. into the field as possible)...  it's about seeing objects in context.   The moon fits easily in a 3/4-degree field, but I'd much rather look at it in a bit wider of a view.   The larger open clusters may fit in a 3/4-degree field but,I appreciate them much more in a wider view that allows you to see how they differ from the surrounding star field.   And in an F/10 scope, it's also about getting the bigger exit pupil to have the brighter view for detecting fainter objects.   Anyway, on my Evo 8, I use the my 38mm SWA a lot.   And before I went to a 2" diagonal, I used the R/C with a 35mm Ultima a lot (and even more in the pre-goto days).

 

Alice-- one point on the need to reposition a diagonal....   The OP is looking at an AVX mount.   On a equatorial mount like the AVX, the diagonal rotates as you move across the sky from east to west or vice versa.  So that means you want to reposition your diagonal more often than you would on an alt-az mount.


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#32 amzking

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Posted 11 January 2018 - 08:30 PM

Thanks, Ed and Alice for confirming the specs on the Baader zoom.

 

Ed,  for reasons known only to Celestron (well, most likely to lower the price and/or raise the profit margin), the EdgeHD comes with a 1.25" visual back and diagonal, despite the fact that it is almost ridiculous to restrict yourself to 1,.25" accessories with an Edge.   Probably 90% of the correction you are paying for occurs outside the 27mm fieldstop of a 1.25" eyepiece  (both coma and deviation from focus due to field curvature are aberrations that increase at an increasing rate with the the distance you move off axis)..   An unlike the non-Edge C8, you don't pay an over-correction in spherical aberration penalty for using a conventional SCT diagonal with an Edge (the Edge is designed for the extra working distance required).

 

Sure, there aren't a ton of objects bigger than 0.76 degrees and for years most SCT users only used 1.25" eyepieces, but its not just about what fits in the field  (although it's sure nice to be able to get as much of Adromeda or the Pleiades, etc. into the field as possible)...  it's about seeing objects in context.   The moon fits easily in a 3/4-degree field, but I'd much rather look at it in a bit wider of a view.   The larger open clusters may fit in a 3/4-degree field but,I appreciate them much more in a wider view that allows you to see how they differ from the surrounding star field.   And in an F/10 scope, it's also about getting the bigger exit pupil to have the brighter view for detecting fainter objects.   Anyway, on my Evo 8, I use the my 38mm SWA a lot.   And before I went to a 2" diagonal, I used the R/C with a 35mm Ultima a lot (and even more in the pre-goto days).

 

Alice-- one point on the need to reposition a diagonal....   The OP is looking at an AVX mount.   On a equatorial mount like the AVX, the diagonal rotates as you move across the sky from east to west or vice versa.  So that means you want to reposition your diagonal more often than you would on an alt-az mount.

Great post, you have validated my 2" diagonal purchase, agreed with me on why larger fields of view are more pleasant, and taught me something I did not know about diagonal movement.

 

Why can't everyone just constantly give me positive affirmations like this?  lol.gif 


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#33 Starman1

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Posted 12 January 2018 - 02:48 PM

My suggestions:

40-41mm 68° 2" eyepiece for low power

20mm 68° for most-used medium power eyepiece

13-14mm for most used high power eyepiece

2x Barlow to convert 20mm to 10mm and 13-14mm to 6.5-7mm for ultra-high power

 

That's pretty much all you'll need: 50x/100x/150x/200x/300x


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#34 acegator25

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Posted 12 January 2018 - 06:07 PM

My suggestions:

40-41mm 68° 2" eyepiece for low power

20mm 68° for most-used medium power eyepiece

13-14mm for most used high power eyepiece

2x Barlow to convert 20mm to 10mm and 13-14mm to 6.5-7mm for ultra-high power

 

That's pretty much all you'll need: 50x/100x/150x/200x/300x

thank you again for all of the help.



#35 acegator25

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Posted 12 January 2018 - 06:11 PM

My suggestions:

40-41mm 68° 2" eyepiece for low power

20mm 68° for most-used medium power eyepiece

13-14mm for most used high power eyepiece

2x Barlow to convert 20mm to 10mm and 13-14mm to 6.5-7mm for ultra-high power

 

That's pretty much all you'll need: 50x/100x/150x/200x/300x

You recommended a combination of 2" and 1.25's in this setup.. what would be the most simplistic way to go about this? I read so many conflicting things about 1.25's not working well in the 2" diags.. I know the 8" edge comes with the 1.25 star diag.. just trying to keep things a little simpler. thanks again.



#36 jallbery

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Posted 12 January 2018 - 06:36 PM

There are generally no problems with using 1.25" eyepieces with a 2" diagonal on an SCT.  

 

I'm not sure where you got this idea.  There are a couple of potential problems:

  1. If you try to use the F/6.3 reducer corrector with a 2" diagonal, 1.25" eyepieces may not come to focus.   But if you have a 2" diagonal and a max field 2" eyepiece, you don't NEED the R/C, so this shouldn't be a problem.
  2. Using a 2" diagonal moves the focal plane back a bit on a standard C8, moving it beyond the design point and introducing a slight bit of negative spherical aberration.  This isn't a big deal, and isn't a deal at all when using an SCT 2" diagonal on a C8 Edge.
  3. Some people worry about the rear baffle of a C8 only being 37-38mm in diameter, and therefore insufficiently illuminating the 46mm fieldstop of a max field 2" eyepiece.   The baffle is not in focus and only causes a soft and mild vignetting (our eyes have a logarithmic sensitivity to to brightness, so we are fairly oblivious to the vignetting)  .   I find a 46mm fielstop perfectly usuable on an 8" SCT, and I'd much rather have a 1.3-degree field with a bit of vignetting than NOT have a 1.3-degree field.

Points 1 and 2 are non-factors with the Edge.  Point three is something worth being aware of, but not worth obsessing over.

 

I don't have an edge, but on my primary scope (a C8) I use a 2" diagonal almost all the time.   I do take it off and use a premium 1.25" prism for planetary viewing when I am trying to squeeze every last ounce out of the scope.   For a non-Edge C8 or smaller, I think there is a lot of good arguments for sticking with 1.25" accessories and using the R/C.   For an 8" Edge, I'd use a 2" diagonal.



#37 BGazing

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Posted 12 January 2018 - 07:17 PM

You can safely skip the 6.7 and go for 8.8 or something in that range, not lower than 8mm.


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#38 Starman1

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Posted 12 January 2018 - 07:49 PM

 

My suggestions:

40-41mm 68° 2" eyepiece for low power

20mm 68° for most-used medium power eyepiece

13-14mm for most used high power eyepiece

2x Barlow to convert 20mm to 10mm and 13-14mm to 6.5-7mm for ultra-high power

 

That's pretty much all you'll need: 50x/100x/150x/200x/300x

You recommended a combination of 2" and 1.25's in this setup.. what would be the most simplistic way to go about this? I read so many conflicting things about 1.25's not working well in the 2" diags.. I know the 8" edge comes with the 1.25 star diag.. just trying to keep things a little simpler. thanks again.

 

Use a 2" refractor-style diagonal and a simple 2" visual back.

The refractor style diagonal:

--can use 2" filters on the front end

--is easier to rotate than the SCT style diagonal

--has a larger through aperture than the SCT style diagonal

--is also usable on refractors

--you can split variable polarizing filters--one part on the eye piece and one on the diagonal--just rotate the eyepiece for perfect dimming

--you can use 2" barlows in front of the diagonal if really high powers are desired.

--they are usually better built.



#39 pete4www

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Posted 20 September 2019 - 04:20 AM

In your 8" Edge HD the eyepieces will produce
ES68 40 51x 80arc' TFOV 4.0mm exit pupil
ES82 30 68x 73arc' TFOV 3.0mm exit pupil
And that is a real difference that should have value for your observing.

Not a fan of them for my own use, I agree that the Baader zoom fits you need very nicely. I like that development in your thinking.

But I'm going to propose you skip the Barlow for now in favor of a GOOD nebular filter set. The Orion Ultrablock Narrowband UHC is a best buy that will take advantage of the larger exit pupil of the 40mm. Add an O-III filter like the Thousand Oaks and you really raise your capacity to see a wide range of objects that would otherwise elude you. A Barlow will not do that and you have the magnification range it will provide covered with the zoom. Nebular filters work by removing light frequencies from the beam transmitted to your eye and the brighter 4mm beam of the 40mm eyepiece will be valuable on dimmer nebulae (and other, unfiltered objects) as the transmitted light will be brighter. Removing those frequencies, BTW, increases the visually apparent contrast of the object you're trying to observe.

I think it is because telescope sellers often bundle a marginal quality Barlow in their beginner packages that many beginners think they're necessities. They're not. They're accessories best used for specific purposes that I don't see you needing now.

Regardless, very nice telescope and good thinking on your part. I hope you and your family enjoy it for decades and wear it out observing with it!


Just wanted to say thanks for this post, even though it's from a while ago. I just upgraded my 8" edge with a 2" visual back, and had no idea where to even start on 2" eyepieces. I chose the ES 68 40mm, ordered brand new. It is my very first "expensive" eyepiece purchase, and I look forward to trying it out in my scope. Many others in this thread made some useful comments as well. One thing I am unsure of, is how this will effect the balance of my scope on my CGEM. I already have to remove the safety stop screw and slide the OTA forward quite a bit to balance it, and since this will add even more weight to the back end, I am guessing I'll need to adjust it even more forward. Is this normal? How far forward can I move the scope forward on my CGEM mount?

#40 havasman

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Posted 20 September 2019 - 09:15 AM

Just wanted to say thanks for this post, even though it's from a while ago. I just upgraded my 8" edge with a 2" visual back, and had no idea where to even start on 2" eyepieces. I chose the ES 68 40mm, ordered brand new. It is my very first "expensive" eyepiece purchase, and I look forward to trying it out in my scope. Many others in this thread made some useful comments as well. One thing I am unsure of, is how this will effect the balance of my scope on my CGEM. I already have to remove the safety stop screw and slide the OTA forward quite a bit to balance it, and since this will add even more weight to the back end, I am guessing I'll need to adjust it even more forward. Is this normal? How far forward can I move the scope forward on my CGEM mount?

Hi Pete,

I hope you enjoy the 40mm. I like mine. I don't know the answer to your balance issue but I can tell you I get a bit anxious with that stop screw being removed. It's a valuable safety feature. I am also unfamiliar with the CGEM. I suggest you might get some good responses if you start a new forum topic regarding balancing your scope on that mount as there's a good population of both among the forum participants.




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