Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

C8 Edge vs Non-Edge: How noticeable in 68 degree eyepieces?

  • Please log in to reply
43 replies to this topic

#1 starcruiser

starcruiser

    Explorer 1

  • -----
  • topic starter
  • Posts: 55
  • Joined: 04 Jun 2018

Posted 14 August 2019 - 12:05 PM

For example: Through a ES 24mm 68, how noticeable is the difference (the supposed improvement of the edge version in visual)?

 

Choose category below:

 

1. Immediately noticeable and obvious. Upgrade recommended if you own non-edge.

2. Somewhat noticeable, but only if you happen to compare side by side. May not be worth the upgrade cost if visual only.

3. Barely noticeable, if at all even when comparing side by side.



#2 mboothe

mboothe

    Sputnik

  • -----
  • Posts: 35
  • Joined: 25 Jan 2015

Posted 14 August 2019 - 12:21 PM

2. If you haven’t bought yet definitely get the edge. If you have already then don’t worry about it. My  Celestron 8edgeHD has much better views than my old 8” LX 200 emc.



#3 Richard O'Neill

Richard O'Neill

    Vanguard

  • *****
  • Posts: 2129
  • Joined: 19 Aug 2014

Posted 14 August 2019 - 01:52 PM

 In what way are the views much better? 



#4 dustyc

dustyc

    Mariner 2

  • *****
  • Posts: 243
  • Joined: 10 Oct 2014
  • Loc: Phoenix,AZ

Posted 14 August 2019 - 02:10 PM

68 degree eyepieces? Category 2.

However, if you ever plan on using 82, 92, or higher degree oculars then Category 1.

Really obvious at a dark sky site when cruising the Milky Way. Stars stay sharp right out to the field stop.  


  • Sarkikos and Mike Mc like this

#5 Traveler

Traveler

    Gemini

  • *****
  • Posts: 3049
  • Joined: 19 Aug 2007
  • Loc: The Netherlands

Posted 15 August 2019 - 12:28 AM

I can live with my standard C8 and my Pentax (70 dgerees) EP's and Baader zoom ...For me there is no need to upgrade to a C8 Edge…

 

Maybe it would be a different story when astrophotography is my primairy goal with a C8...but at that focal lenghts (2000mm or 1300 with reducer and on top of that the crop factor of my Nikon DSLR), astrophotography is not my cup of tea...



#6 aa6ww

aa6ww

    Surveyor 1

  • *****
  • Posts: 1965
  • Joined: 23 Oct 2011
  • Loc: Sacramento, Calif.

Posted 15 August 2019 - 11:01 AM

I never saw a difference in visual performance when I had my Edge HD vs standard SCT. When looking at planets or double stars or most objects where you center the object in the field of view, you wont notice any difference.
Even in big open clusters I saw no difference.
For a while, I tried to convince myself there was a world of difference in the Edge vs non Edge visually. There wasn't.

If there's a difference visually, I never saw it and the people I observe with never saw it either.
Visually, the visual Edge difference is extremely visible in the forums. When you get out and actually use your gear, you wont notice any difference. Then again, I tend to keep objects I look at in the center of the field of view.

I did know a guy online that use to say he had an alt az mount without tracking and he would let objects drift to the edges of the field of view before repositioning his object. This may be where the Edge visually is advantageous.

I use good eyepieces from TeleVue and Explorer Scientific. Even my Standard XLT SCT's are extremely sharp at the edges.

I don't do astrophotography however and I think the eye of the camera can see many things we don't notice visually.

Some people see much more then I do, so I cant dispute what others say they can or cant see. Some swear by the performance advantage of the Edge. Some people notice field curvature but I never see it also. I'm glad I don't have that type of vision.

..Ralph

Edited by aa6ww, 15 August 2019 - 11:05 AM.

  • Bean614 likes this

#7 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 15 August 2019 - 12:12 PM

I have an EdgeHD 8".  I don't have a standard 8" SCT.  But I do have standard 5" and 6" SCTs. 

 

I am a visual only amateur astronomer.  I have never done AP, don't do AP and never intend to do AP.  Imaging is good observing ruined.  grin.gif

 

I notice that the field is flatter and the stars are sharper in the outer field when I'm observing through the EdgeHD 8".  Of course, the wider the apparent field of the eyepiece, the more obvious the improvement.    The closest comparison I can give from the other instruments I own, is the NP101-is Petzval and the Canon 10x42 L IS binoculars.  

 

If you like a wide flat field, get the EdgeHD.

 

Mike


Edited by Sarkikos, 15 August 2019 - 12:15 PM.

  • Jon Isaacs likes this

#8 Eddgie

Eddgie

    ISS

  • *****
  • Posts: 24292
  • Joined: 01 Feb 2006

Posted 15 August 2019 - 03:05 PM

First, opinions may vary according to the visual accommodation of various users.  Older observers will more than likely have less visual accommodation than younger observers and are therefore more likely to see that the edge of the field is out of focus.

 

In my late 50s and early 60s, the field curvature of the standard SCT was not really bothersome to me when using Panoptics (35mm, 27mm) but as I got older and lost even more accommodation, I started to see that while the outer field was still decently sharp in the 41mm Panoptic, it was not as sharp as when using the same eyepiece in the EdgeHD 8".

 

The 31mm Nalger was "unusable" to me in the C14 due to the very out of focus and aberrated stars, but the 41mm and 27mm Panoptics still presented decent images at the edge of the field.  Again, not as good as the EdgeHD 8", but not enough to bother me that much. 

 

So, my advice has been that older observers with poor accommodation are better off using the 41mm Pan in place of the 31mm Nagler, and 27mm Panoptic in place of the 20mm Nagler or 21mm Nagler T4. 

 

Again, the field will not be perfect with the Panoptics, but it will still be reasonably sharp if the observer has even a small mount of accommodation.  

 

(If the observer has any visual accommodation at all, I recommend focusing the Panoptics a bit away from the center of the field to try to get a balance between center and edge of field sharpness) 


Edited by Eddgie, 15 August 2019 - 03:06 PM.

  • Sarkikos likes this

#9 Astrojedi

Astrojedi

    Soyuz

  • *****
  • Posts: 3901
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 16 August 2019 - 01:09 AM

Do you have a SCT right now? If so, does the coma and field curvature bother you? If not, then don’t worry about it. If it does then get the EdgeHD.

If you don’t have a SCT and are looking to decide which one to get, then get the EdgeHD.

I have been observing with SCTs for decades. I was very late to get an EdgeHD. For the longest time I thought this was all Celestron hype till I looked through one. You really notice not just the pinpoint stars but the flatter field especially when panning star fields (no more bubble effect assuming you use a decent EP). The difference in star clusters with my 82deg 30mm is night and day between the Edge and non Edge versions. They look sublime in the EdgeHD.

Folks here will spend $500 on a single EP to obtain optical perfection but then somehow claim it does not matter if you use an EdgeHD scope. If I had to choose between an expensive EP or the EdgeHD, I would pick the EdgeHD hands down as the best way to improve the views. No competition imo. No other optical design delivers such a flat field and pinpoint stars across the fov as the EdgeHD in this price range. Seriously, comparable scopes are 3-4x the price or you have to fiddle with coma correctors and EP spacers etc. 


Edited by Astrojedi, 16 August 2019 - 01:15 AM.

  • Sarkikos likes this

#10 bobhen

bobhen

    Gemini

  • *****
  • Posts: 3108
  • Joined: 25 Jun 2005

Posted 16 August 2019 - 06:41 AM

“Visually” people have used standard SCTs for 50 years with little complaint about edge sharpness. When observing objects, most of the action is not at the edge of the field. And, for example, if some lunar feature you want to observe is at the edge, just move it to the center of the field.

 

The Celestron Edge SCTs have more to offer imagers than visual observers.

 

HOWEVER, having said the above, the Edge SCTs have one HUGE advantage that standard SCTs do not. The have vent ports where aftermarket (Tempest) fans can be installed. The fans will help with initial acclimation and even more important they can also be run when observing to eliminate reforming tube currents as nighttime temperatures drop.

 

The ability to add fans IS the reason for a visual observer to buy the Edge version. If you live in a very mild climate and just do visual then the standard version is just fine.

 

Bob



#11 Traveler

Traveler

    Gemini

  • *****
  • Posts: 3049
  • Joined: 19 Aug 2007
  • Loc: The Netherlands

Posted 16 August 2019 - 06:55 AM

...But dear Bob, these vent holes are not a pre (anymore) if you read what people write about the use of Reflectix...but that is another topic. ;-)



#12 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 16 August 2019 - 07:05 AM

“Visually” people have used standard SCTs for 50 years with little complaint about edge sharpness. When observing objects, most of the action is not at the edge of the field. And, for example, if some lunar feature you want to observe is at the edge, just move it to the center of the field.

 

The Celestron Edge SCTs have more to offer imagers than visual observers.

 

HOWEVER, having said the above, the Edge SCTs have one HUGE advantage that standard SCTs do not. The have vent ports where aftermarket (Tempest) fans can be installed. The fans will help with initial acclimation and even more important they can also be run when observing to eliminate reforming tube currents as nighttime temperatures drop.

 

The ability to add fans IS the reason for a visual observer to buy the Edge version. If you live in a very mild climate and just do visual then the standard version is just fine.

 

Bob

 

It really depends on the observer.  As has been mentioned above,  people tend to lose much of their ability to accommodate for focus as their grow older.  I am 63, and field curvature is much more obvious to me than 10 years ago.   If a telescope or eyepiece has field curvature, I will see it. 

 

Also, not everyone uses their EdgeHD 8" primarily for planet/lunar.  In fact, I use mine for deep sky at dark sites.  I hardly ever observe planets or the Moon through the EdgeHD 8".   For deep sky, a wide flat field has a clear advantage.  100 degree eyepieces are the ones I usually have in the EdgeHD.  Observers haven't had 100 degree eyepieces until relatively recently, so maybe that is why many have not complained about edge sharpness in the standard SCTs.

 

For me THE main reason why I prefer the EdgeHD 8" is the flat field.  Sure I added the TEMP-est fans to the vents and they aid in acclimation of the OTA.  But I would not have bought the EdgeHD if it weren't for the flat field.  For me, the vent holes would NOT have been sufficient reason to buy the EdgeHD.

 

Mike


Edited by Sarkikos, 16 August 2019 - 08:10 AM.

  • Eddgie likes this

#13 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 16 August 2019 - 07:07 AM

...But dear Bob, these vent holes are not a pre (anymore) if you read what people write about the use of Reflectix...but that is another topic. ;-)

Only some people.  Other people still use the vent holes even though they wrap the OTA with Reflectix.

 

Mike



#14 MrRoberts

MrRoberts

    Ranger 4

  • *****
  • Posts: 334
  • Joined: 20 Jun 2016
  • Loc: Barrington, Illinois

Posted 16 August 2019 - 07:25 AM

All I can say is the C-8/E I keep near Tucson is great. For visual use I do use mostly TV ep's (Ethos 13/17, Nagler 31) sometimes with the focal reducer and sometimes without. When visual I hook it up to my Ioptron AZM Pro and intend to put my newly purchased Esprit 80mm on the counterweight side this October.

Attached Thumbnails

  • IMG_0204-2.jpg
  • IMG_0396-2.jpg

  • Sarkikos likes this

#15 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 77793
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 16 August 2019 - 07:28 AM

Seriously, comparable scopes are 3-4x the price or you have to fiddle with coma correctors and EP spacers etc.

 

The beauty of the coma corrector for a Newtonian, you pay your $500 and coma is no longer an issue, with any Newtonian, forever. It's as if you could buy a coma corrector/field flattener for an SCT that turned every SCT you own and will ever own into an EDGE...  

 

Jon


  • Sarkikos likes this

#16 bobhen

bobhen

    Gemini

  • *****
  • Posts: 3108
  • Joined: 25 Jun 2005

Posted 16 August 2019 - 07:55 AM

It really depends on the observer.  As has been mentioned above,  people tend to lose much of their ability to accommodate for focus as their grow older.  I am 64, and field curvature is much more obvious to me than when 10 years ago.   If a telescope or eyepiece has field curvature, I will see it. 

 

Also, not everyone uses their EdgeHD 8" primarily for planet/lunar.  In fact, I use mine for deep sky at dark sites.  I hardly ever observe planets or the Moon through the EdgeHD 8".   For deep sky, a wide flat field has a clear advantage.  100 degree eyepieces are the ones I usually have in the EdgeHD.  Observers haven't had 100 degree eyepieces until relatively recently, so maybe that is why many have not complained about edge sharpness in the standard SCTs.

 

For me THE main reason why I prefer the EdgeHD 8" is the flat field.  Sure I added the TEMP-est fans to the vents and they aid in acclimation of the OTA.  But I would not have bought the EdgeHD if it weren't for the flat field.  For me, the vent holes would NOT have been sufficient reason to buy the EdgeHD.

 

Mike

SCTs (Edge or standard) by design are not wide field telescopes.

 

Even if used for just deep sky viewing, the “vast” majority of deep sky objects will easily fit in the field of view of a standard SCT without edge distortion distorting the object of interest.

 

Those deep sky objects that are so large as to not fit would be better viewed in a refractor that is made for wide field viewing, like a TV 101 or 127mm refractor anyway. A lot of people mount 80mm refractors on their SCTs for just such a reason.

 

I owned standard 8, 10 and 11” SCT for 22 years and never remember once saying to myself, gee I really wish the edge of the field were sharper.

 

Of course, there are always exceptions and your viewing habits might be that exception but the vast majority of visual observers use their SCTs as “general observing” telescopes to observer the moon, sun and planets along with deep sky objects.

 

Bob



#17 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 77793
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 16 August 2019 - 08:21 AM

SCTs (Edge or standard) by design are not wide field telescopes.

 

Even if used for just deep sky viewing, the “vast” majority of deep sky objects will easily fit in the field of view of a standard SCT without edge distortion distorting the object of interest.

 

Those deep sky objects that are so large as to not fit would be better viewed in a refractor that is made for wide field viewing, like a TV 101 or 127mm refractor anyway. A lot of people mount 80mm refractors on their SCTs for just such a reason.

 

I owned standard 8, 10 and 11” SCT for 22 years and never remember once saying to myself, gee I really wish the edge of the field were sharper.

 

Of course, there are always exceptions and your viewing habits might be that exception but the vast majority of visual observers use their SCTs as “general observing” telescopes to observer the moon, sun and planets along with deep sky objects.

 

Bob

 

Coma and to some extent field curvature, are not just issues at low powers, they also are seen at higher magnifications.  Look at something like M7 in a 10 inch scope, there's a lot to see there that isn't visible in a 4 inch.  But it will overflow the field of view of most any SCT.  Or a bright globular like M13, these can be NP-101 perfect in an SCT if one wants.  

 

Jon


  • Sarkikos likes this

#18 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 16 August 2019 - 08:51 AM

SCTs (Edge or standard) by design are not wide field telescopes.

 

Even if used for just deep sky viewing, the “vast” majority of deep sky objects will easily fit in the field of view of a standard SCT without edge distortion distorting the object of interest.

 

Those deep sky objects that are so large as to not fit would be better viewed in a refractor that is made for wide field viewing, like a TV 101 or 127mm refractor anyway. A lot of people mount 80mm refractors on their SCTs for just such a reason.

 

I owned standard 8, 10 and 11” SCT for 22 years and never remember once saying to myself, gee I really wish the edge of the field were sharper.

 

Of course, there are always exceptions and your viewing habits might be that exception but the vast majority of visual observers use their SCTs as “general observing” telescopes to observer the moon, sun and planets along with deep sky objects.

 

Bob

Even without the Celestron reducer, the EdgeHD 8" will show a 1.2 degree field in a 31 T5 and a 1.28 degree field in a 41 Pan.  That's wide enough to contain M44.  Nearly all of the Pleiades.  The Trifid and M21 nicely framed.  All of IC 4665.  The Leo Triple.  The Double Cluster with some nice framing.

 

If you screw on the Celestron reducer, you have a 1.71 degree field in the 31 T5 and a 1.87 degree field in the 41 Pan.  This will show M42, M43, NGC 1975 and NGC 1981 in the same field of view.   The M24 star cloud.  All of the Pleiades. 

 

In any case, at whatever magnification and image scale, if you like 100 degree or 110 degree eyepieces, if you notice field curvature, you will notice the improvement in the EdgeHD 8".

 

If you have never noticed field curvature in standard SCTs, it could be due to your ability to accommodate for field curvature.  Or you aren't using the wider field eyepieces.  Or maybe you just never looked very closely at the outer field.

 

Mike


Edited by Sarkikos, 16 August 2019 - 08:52 AM.

  • fred1871 and Rustler46 like this

#19 bobhen

bobhen

    Gemini

  • *****
  • Posts: 3108
  • Joined: 25 Jun 2005

Posted 16 August 2019 - 10:43 AM

Even without the Celestron reducer, the EdgeHD 8" will show a 1.2 degree field in a 31 T5 and a 1.28 degree field in a 41 Pan.  That's wide enough to contain M44.  Nearly all of the Pleiades.  The Trifid and M21 nicely framed.  All of IC 4665.  The Leo Triple.  The Double Cluster with some nice framing.

 

If you screw on the Celestron reducer, you have a 1.71 degree field in the 31 T5 and a 1.87 degree field in the 41 Pan.  This will show M42, M43, NGC 1975 and NGC 1981 in the same field of view.   The M24 star cloud.  All of the Pleiades. 

 

In any case, at whatever magnification and image scale, if you like 100 degree or 110 degree eyepieces, if you notice field curvature, you will notice the improvement in the EdgeHD 8".

 

If you have never noticed field curvature in standard SCTs, it could be due to your ability to accommodate for field curvature.  Or you aren't using the wider field eyepieces.  Or maybe you just never looked very closely at the outer field.

 

Mike

I’m not saying that there is not an improvement with the Edge design, of course there is. 

 

I’m saying that for vast majority of targets the view in a standard SCT is NOT detrimental to the “enjoyment” of viewing those objects. Or in other words, for the visual observer, the expense of the Edge SCT over the standard is out of proportion when compared to the improvement in “enjoying” the visual experience, as evidenced by the decades of very happy standard SCT users.

 

I now have a Mewlon 210. The Mewlon 210 is a narrow field instrument and has coma at the edges of the field. But again, when used for observing the vast majority of deep sky objects like: globular clusters, planetary nebula, galaxies, small and medium size open clusters, etc., that fit in the field, the edge distortion does not impact nor distract from the “enjoyment” of the view, and goes mostly unnoticed unless you go looking for it.

 

After an imaging session, you have a permanent record of edge distortion, so the Edge SCT would be the better choice. But after a visual session with my Mewlon 210, I always remember the great views and “never” remember any edge distortion “ruining” that experience.

 

Bob


  • Rustler46 likes this

#20 WadeH237

WadeH237

    Aurora

  • *****
  • Posts: 4564
  • Joined: 24 Feb 2007
  • Loc: Snohomish, WA

Posted 16 August 2019 - 10:56 AM

I’m saying that for vast majority of targets the view in a standard SCT is NOT detrimental to the “enjoyment” of viewing those objects. 

Enjoyment is a very subjective thing.

 

To you, it seems that the object of interest is the only thing that matters.  To some of us, the field around the object of interest is also important.  In particular for me, if the stars at the edge of the field are comatic, then it distracts me from the object of interest.  I am not planning on ever buying another SCT that doesn't have coma correction.  I don't find the field curvature as objectionable as coma, and I find that I enjoy both the Meade ACF scopes and the EdgeHD scopes much more than standard SCTs for visual.

 

In my opinion, the only place where the EdgeHD doesn't have a significant advantage over a standard SCT is in planetary imaging - and in that case, they should be pretty equal (although the standard SCT has two less optical surfaces than the EdgeHD, so there might be a slight advantage to the standard SCT).  Since I don't do planetary imaging, though, this is not a factor for me.


  • Sarkikos and fred1871 like this

#21 Astrojedi

Astrojedi

    Soyuz

  • *****
  • Posts: 3901
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 16 August 2019 - 11:26 AM

Almost every object I have looked at looks better in the EdgeHD due to the flatter field and no coma, surprisingly even Jupiter. In the EdgeHD Jupiter's moons show us as small disks - I don't have to center them to observe them. Just makes it so much more immersive. In my regular C8 the moons used to be comatic and it diluted the experience. Did not realize this till I got the EdgeHD.

 

Another example: NGC6960 - the wispy filaments looks sharp and contrasty in the EdgeHD from edge to edge. In the C8 they used to soften towards the edge. Again I actually never realized this was happening till I looked through the EdgeHD.

 

Star clusters just look stunning. I actually prefer the EdgeHD to my smaller refractors as the clusters looks more 3D - have more depth, resolution and I can just see more stars.

 

To me there is just no debate.

 

To really evaluate a scope you have to use it for some time - at least a couple of months. Then if you cannot bear to part with it, it is a keeper. The decision becomes very obvious and clear. This is how I felt about the EdgeHD 8.


  • Sarkikos and fred1871 like this

#22 Astrojedi

Astrojedi

    Soyuz

  • *****
  • Posts: 3901
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 16 August 2019 - 11:57 AM

The beauty of the coma corrector for a Newtonian, you pay your $500 and coma is no longer an issue, with any Newtonian, forever. It's as if you could buy a coma corrector/field flattener for an SCT that turned every SCT you own and will ever own into an EDGE...  

 

Jon

 

True... but coma correctors are fiddly. Each EP requires a different spacing. Further it imposes focus travel requirements. For example in my 14” truss dob certain EPs don’t come to focus with the coma corrector. It also adds weight and throws off the balance. Sure all of this is solvable with some effort but nothing beats a integrated, seamless and transparent solution. When a scope is designed bottoms up with a feature it always works better.


  • Rustler46 likes this

#23 Astrojedi

Astrojedi

    Soyuz

  • *****
  • Posts: 3901
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 16 August 2019 - 12:48 PM

And just to be clear I am not dinging coma correctors. In fact I think they are really useful especially with wide field EPs in fast scopes (both my dobs are ~f4.5 so not too fast and I can get away most of the time without using a coma corrector).

 

I am just highlighting that relatively speaking they are not as straightforward as an integrated solution. They take some getting used to and you need to make sure your scope has sufficient focus travel.



#24 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 16 August 2019 - 01:38 PM

I’m not saying that there is not an improvement with the Edge design, of course there is. 

 

I’m saying that for vast majority of targets the view in a standard SCT is NOT detrimental to the “enjoyment” of viewing those objects. Or in other words, for the visual observer, the expense of the Edge SCT over the standard is out of proportion when compared to the improvement in “enjoying” the visual experience, as evidenced by the decades of very happy standard SCT users.

 

I now have a Mewlon 210. The Mewlon 210 is a narrow field instrument and has coma at the edges of the field. But again, when used for observing the vast majority of deep sky objects like: globular clusters, planetary nebula, galaxies, small and medium size open clusters, etc., that fit in the field, the edge distortion does not impact nor distract from the “enjoyment” of the view, and goes mostly unnoticed unless you go looking for it.

 

After an imaging session, you have a permanent record of edge distortion, so the Edge SCT would be the better choice. But after a visual session with my Mewlon 210, I always remember the great views and “never” remember any edge distortion “ruining” that experience.

 

Bob

You can say for any instrument, for the vast majority of objects, the view of the object in the instrument is NOT detrimental to the enjoyment of viewing the object.  That's simply because there are many, many more objects of smaller apparent diameter compared to those of larger apparent diameter.  This will always be the case.  So what?

 

The important and pertinent points are that an EdgeHD 8" will show any field which has a wider apparent field of view - no matter the magnification or image scale - as a flat field with sharp stars from edge to edge.  A standard SCT will not.  Each observer needs to decide for themselves whether or not that is worth the higher price.  For me - and many other VISUAL observers - it is worth it.

 

Again, I don't give a fig about imaging or having a permanent record.  I never got that and never will.  But if I have a choice - and I do - I'd rather see a nice flat field.  I do get that.

 

Mike


Edited by Sarkikos, 16 August 2019 - 01:52 PM.


#25 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30204
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 16 August 2019 - 01:45 PM

True... but coma correctors are fiddly. Each EP requires a different spacing. Further it imposes focus travel requirements. For example in my 14” truss dob certain EPs don’t come to focus with the coma corrector. It also adds weight and throws off the balance. Sure all of this is solvable with some effort but nothing beats a integrated, seamless and transparent solution. When a scope is designed bottoms up with a feature it always works better.

 

I have a Paracorr 2.  It is not fiddly.  You set the position of the focuser once at the beginning of the session.  Once.  Then for each eyepiece, you use the adjustable top of the P-2 to focus the eyepiece.  The eyepiece will be set automatically to optimal coma correction.  No fiddling necessary.

 

Well, this is true for nearly every eyepiece.  Among all the eyepieces you see in my sig, there is only one that doesn't come to optimal coma correction.  But it's close enough not to worry about it.

 

Mike


Edited by Sarkikos, 16 August 2019 - 01:46 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics