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

Eyepiece Discontinuations

  • Please log in to reply
110 replies to this topic

#51 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 78977
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 February 2018 - 12:07 PM

Additionally, I find that close jumps at low power usually aren't necessary.  If I start out with a really good low power that frames objects well,

if I feel I need a higher power to improve resolution or view smaller details, anywhere from a 60% to 100% jump is just fine for the next step up.

Having a bunch of low powers usually results in my just using one eyepiece to the exclusion of all the others.

 

 

There's a number of factors to consider when choosing an eyepiece for a particular object.  There's the field of view, there's the resolution, there's the image brightness, the exit pupil characterizes these nicely.

 

It seems very often the image brightness is a forgotten factor.  Framing a large dim object is may not be the only issue, getting the brightest possible image can also be important.  The 41mm Panoptic is 1.75x the brightness of the 31mm Nagler, this can be a significant advantage for my old eyes when viewing something like Barnard's loop with an H-Beta filter or enjoying the nebulosity of the region known as the Heart and Soul Nebulae in a large aperture scope.  

 

I consider myself an omnivorous observer so want my eyepiece set to optimize the views across the range of useful magnifications, from the large and dim to the tiny and bright.

 

Jon


  • turtle86, StarCurious and Redbetter like this

#52 BarrySimon615

BarrySimon615

    Pa Bear

  • *****
  • topic starter
  • Posts: 4339
  • Joined: 01 Mar 2004
  • Loc: New Orleans, LA

Posted 14 February 2018 - 12:30 PM

To each his own, dependent upon his or her telescope or telescopes and his or her observing interests, likes and dislikes.  Like many here I have multiple "sets" of eyepieces, so while I may be missing a particular focal length eyepiece in one set, I can virtually always find that size in another set.

 

Since the discussion has diverged somewhat from the original discussion line of the thread I will attempt to get it more in line with that purpose with two questions -

 

1) What ONE eyepiece that has been discontinued in the past would you like to see brought back (and why)?

 

2) If you could substitute one new focal length eyepiece in one of your sets (homogeneous sets - one Manufacturer and one type such as the TV Nagler Type 6 or the Pentax XW, Explore Scientific 82 degree series, etc.) for one in your set now that you consider an "odd ball" what would be the old one and what would you replace it with?

 

Barry Simon



#53 Redbetter

Redbetter

    Cosmos

  • *****
  • Posts: 7984
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 14 February 2018 - 12:32 PM

When it comes to matching seeing/scope/exit pupil for high power planetary detail I am finding I can match it to an estimated arc second rating across apertures.  I have roughed out some equivalent arc second values for my scopes using a Pickering rating for each, from 60mm to 20".  It is rather approximate of course, but I am finding some value in it.  These Pickering values run from -1 to 10/10 to capture the useful range for the 20".   The smallest scopes top out at their max optimum planetary contrast magnification levels rather easily, while the medium and larger scopes are progressively throttled back by the seeing. 

 

No doubt that the useful levels will vary substantially for others (and depend also on locale rather than just a given eye).  However, I can lump the seeing levels into max useful magnification levels for the big scope:

  • ~150x awful to very poor seeing (-1/10 to 0/10 in the 20"), not really worth pointing a scope at planets since the detail is minimal with multiple images and constant motion on awful nights,  smallest scopes might still use this much power, but show far less than they do on better nights, making less power more pleasing/comfortable in them.
  • ~175-200x poor seeing (1/10 in 20"), small scopes coming into their own.  60ED and 80ED should be almost topped out (at somewhat lower powers, 120-144x in 60ED, 150-170x in 80ED)
  • ~225-250x "meh" mediocre seeing (2/10 in 20"), 80ED topped out, 110ED nearing top out (around 200x)
  • ~275-300x decent seeing (3/10 in the 20"), 80ED is showing all the detail it can, 110ED topped out in power (~200x) near the max detail it can show, 8" SCT nearing top out in power but still has another gear with respect to detail
  • ~350-400x good to great seeing (4/10 to 5/10 in the 20"), 110ED showing all the detail it can provide, 8" SCT topped out at ~300x, 10" Dob nearing top out at 350-400x?
  • ~500x, excellent seeing (6/10 in the 20"), 20" still has headroom for more, 8" SCT at max detail at ~300x, 10" Dob should be topped out and near max detail somewhere in the 400x range.  I have had the 20" and 8" together in these conditions and better on multiple nights, but it has been many years.  The 10" has never been under such skies so far. 

For the big scope, some of the same values apply to tiny galaxies and other DSO's as well.  For the same seeing level I tend to be limited to the above powers for classifying/identifying galaxies.  The exceptions are that I can bump a notch higher in magnification at a given Pickering value for detection/confirmation even though no more structural detail can be gleaned because of the seeing.   And in the two poorest levels of seeing I still will use around 200x to get some image scale. 


Edited by Redbetter, 14 February 2018 - 01:15 PM.

  • Jon Isaacs likes this

#54 Alan French

Alan French

    Night Owl

  • *****
  • Posts: 5671
  • Joined: 28 Jan 2005
  • Loc: Upstate NY

Posted 14 February 2018 - 12:45 PM

I'd love some nice zoom eyepieces with modest ranges, maybe a 6 to 9mm and a 9 to 12mm, with at least 15mm of eye relief. I doubt I'll see either.

 

Clear skies, Alan


Edited by Alan French, 14 February 2018 - 12:45 PM.

  • Phillip Creed likes this

#55 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 78977
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 February 2018 - 01:06 PM

I'd love some nice zoom eyepieces with modest ranges, maybe a 6 to 9mm and a 9 to 12mm, with at least 15mm of eye relief. I doubt I'll see either.

 

Clear skies, Alan

 

Alan:

 

Last fall I bought one of the Baader Mark IV 8-24 zooms after reading a lot of good things in this forum about them and then trying a friends older model for an hour.  The eye lens is about 24mm in diameter which is sufficient to provide about 18mm of eye relief.

 

The data sheet specs out 16mm or greater at all focal lengths.

 

http://www.astro-opt...zoom-manual.pdf

 

I think it's a pretty darn good eyepiece.  The field of view is narrow for my tastes at the 20mm and 24mm focal lengths, I measured it with a projection technique at 44 deg and 49 degrees respectively, at 16mm, 54 degrees, at 12mm, 59 degrees and at 8mm, 68 degrees.  

 

I use it primarily for teasing out faint galaxies in my 16 and 22 inchers and it's quite sharp across the field at F/5.. It's competing against the 21mm, 13mm and 8 mm Ethos eyepieces so it's got to be pretty decent to hang with that crowd.  And to my old eyes, it does a good job on the planets.

 

If you get a chance to look through one, I'd give it try.  

 

Jon


  • Alan French, Sarkikos, eros312 and 1 other like this

#56 Redbetter

Redbetter

    Cosmos

  • *****
  • Posts: 7984
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 14 February 2018 - 01:08 PM

 

Additionally, I find that close jumps at low power usually aren't necessary.  If I start out with a really good low power that frames objects well,

if I feel I need a higher power to improve resolution or view smaller details, anywhere from a 60% to 100% jump is just fine for the next step up.

Having a bunch of low powers usually results in my just using one eyepiece to the exclusion of all the others.

 

 

There's a number of factors to consider when choosing an eyepiece for a particular object.  There's the field of view, there's the resolution, there's the image brightness, the exit pupil characterizes these nicely.

 

It seems very often the image brightness is a forgotten factor.  Framing a large dim object is may not be the only issue, getting the brightest possible image can also be important.  The 41mm Panoptic is 1.75x the brightness of the 31mm Nagler, this can be a significant advantage for my old eyes when viewing something like Barnard's loop with an H-Beta filter or enjoying the nebulosity of the region known as the Heart and Soul Nebulae in a large aperture scope.  

 

I consider myself an omnivorous observer so want my eyepiece set to optimize the views across the range of useful magnifications, from the large and dim to the tiny and bright.

 

Jon

 

 

Yes, while one can get away with fewer options on the low power end, there is still a real need for the anchor max exit pupil eyepiece:  e.g. the 55 Plossl that Don sees no need for with an 8" SCT is more important to me than a 40mm Plossl or 41Pan.  And using it with an H-Beta and the 110ED f/7 in many ways gave the best look at Barnard's loop I have yet had.  I have had wider in the 60ED, and detailed up close in the 20", but this combo in the 110 was more balanced. 

 

It is hard to tell what exit pupil/image scale is going to work best on a given object or given night even.  Last week on planetary nebula Abell 31 I found the 26mm T5 to be a great match with the DGM NPB in the 20".  This gave me the right mix of brightness and image scale to begin resolving enough of the outer area to consider it generally round while including brighter inner structure, rather than just lumpy (the brighter inner portions) around a center as I saw at higher magnification and smaller exit pupil.  The combo also worked well on Abell 33, making the soap bubble more opaque than at higher magnification--actually surprisingly close to the impression in images now that I look at them.

 

Galaxies and clusters without nebulosity are less sensitive to this since they don't require consideration for filters, and it mostly comes down to framing and searching for detail.  However, the larger dwarf galaxies with exceedingly low surface brightness and large reflection nebulae as found in the Pleiades benefit from maximizing apparent image brightness.  


  • Jon Isaacs likes this

#57 BGazing

BGazing

    Apollo

  • -----
  • Posts: 1176
  • Joined: 25 Feb 2016
  • Loc: Belgrade, Serbia

Posted 14 February 2018 - 01:51 PM

When it comes to matching seeing/scope/exit pupil for high power planetary detail I am finding I can match it to an estimated arc second rating across apertures.  I have roughed out some equivalent arc second values for my scopes using a Pickering rating for each, from 60mm to 20".  It is rather approximate of course, but I am finding some value in it.  These Pickering values run from -1 to 10/10 to capture the useful range for the 20".   The smallest scopes top out at their max optimum planetary contrast magnification levels rather easily, while the medium and larger scopes are progressively throttled back by the seeing. 

 

No doubt that the useful levels will vary substantially for others (and depend also on locale rather than just a given eye).  However, I can lump the seeing levels into max useful magnification levels for the big scope:

  • ~150x awful to very poor seeing (-1/10 to 0/10 in the 20"), not really worth pointing a scope at planets since the detail is minimal with multiple images and constant motion on awful nights,  smallest scopes might still use this much power, but show far less than they do on better nights, making less power more pleasing/comfortable in them.
  • ~175-200x poor seeing (1/10 in 20"), small scopes coming into their own.  60ED and 80ED should be almost topped out (at somewhat lower powers, 120-144x in 60ED, 150-170x in 80ED)
  • ~225-250x "meh" mediocre seeing (2/10 in 20"), 80ED topped out, 110ED nearing top out (around 200x)
  • ~275-300x decent seeing (3/10 in the 20"), 80ED is showing all the detail it can, 110ED topped out in power (~200x) near the max detail it can show, 8" SCT nearing top out in power but still has another gear with respect to detail
  • ~350-400x good to great seeing (4/10 to 5/10 in the 20"), 110ED showing all the detail it can provide, 8" SCT topped out at ~300x, 10" Dob nearing top out at 350-400x?
  • ~500x, excellent seeing (6/10 in the 20"), 20" still has headroom for more, 8" SCT at max detail at ~300x, 10" Dob should be topped out and near max detail somewhere in the 400x range.  I have had the 20" and 8" together in these conditions and better on multiple nights, but it has been many years.  The 10" has never been under such skies so far. 

For the big scope, some of the same values apply to tiny galaxies and other DSO's as well.  For the same seeing level I tend to be limited to the above powers for classifying/identifying galaxies.  The exceptions are that I can bump a notch higher in magnification at a given Pickering value for detection/confirmation even though no more structural detail can be gleaned because of the seeing.   And in the two poorest levels of seeing I still will use around 200x to get some image scale. 

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.



#58 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 42734
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 14 February 2018 - 03:39 PM

 

 

Additionally, I find that close jumps at low power usually aren't necessary.  If I start out with a really good low power that frames objects well,

if I feel I need a higher power to improve resolution or view smaller details, anywhere from a 60% to 100% jump is just fine for the next step up.

Having a bunch of low powers usually results in my just using one eyepiece to the exclusion of all the others.

 

 

There's a number of factors to consider when choosing an eyepiece for a particular object.  There's the field of view, there's the resolution, there's the image brightness, the exit pupil characterizes these nicely.

 

It seems very often the image brightness is a forgotten factor.  Framing a large dim object is may not be the only issue, getting the brightest possible image can also be important.  The 41mm Panoptic is 1.75x the brightness of the 31mm Nagler, this can be a significant advantage for my old eyes when viewing something like Barnard's loop with an H-Beta filter or enjoying the nebulosity of the region known as the Heart and Soul Nebulae in a large aperture scope.  

 

I consider myself an omnivorous observer so want my eyepiece set to optimize the views across the range of useful magnifications, from the large and dim to the tiny and bright.

 

Jon

 

 

Yes, while one can get away with fewer options on the low power end, there is still a real need for the anchor max exit pupil eyepiece:  e.g. the 55 Plossl that Don sees no need for with an 8" SCT is more important to me than a 40mm Plossl or 41Pan.  And using it with an H-Beta and the 110ED f/7 in many ways gave the best look at Barnard's loop I have yet had.  I have had wider in the 60ED, and detailed up close in the 20", but this combo in the 110 was more balanced. 

 

It is hard to tell what exit pupil/image scale is going to work best on a given object or given night even.  Last week on planetary nebula Abell 31 I found the 26mm T5 to be a great match with the DGM NPB in the 20".  This gave me the right mix of brightness and image scale to begin resolving enough of the outer area to consider it generally round while including brighter inner structure, rather than just lumpy (the brighter inner portions) around a center as I saw at higher magnification and smaller exit pupil.  The combo also worked well on Abell 33, making the soap bubble more opaque than at higher magnification--actually surprisingly close to the impression in images now that I look at them.

 

Galaxies and clusters without nebulosity are less sensitive to this since they don't require consideration for filters, and it mostly comes down to framing and searching for detail.  However, the larger dwarf galaxies with exceedingly low surface brightness and large reflection nebulae as found in the Pleiades benefit from maximizing apparent image brightness.  

 

Well, I regard 50x as the lowest useful power in an 8" SCT, which is a 40mm eyepiece.  I don't like lower powers than that because the image is simply too small.  I don't care for what I call "binocular views" in a telescope because I have binoculars for that.  Even in my f/7 refractor, I rarely use an eyepiece longer than 18.2mm (2.6mm exit pupil, 39x, 1.53°).

And, as I have stated before, my dark-adapted pupil diameter is 4.5mm and an exit pupil of that size has a lot of astigmatism that I don't see when the exit pupil is 4mm or smaller.

Last, I find the image at 50X in the 8" to be plenty bright enough at a dark site.  I never felt the need to go lower, ever, over the 11 years I owned an 8" SCT.  And I used a magnification around 100x (2mm exit pupil) easily 20x as much for DSO viewing. 

Today, I tend to view large objects like M42 at 107x (56' field, 3mm exit pupil) or more, in the 12.5".  That nebula damages my night vision--brighter is unnecessary.  And I see more stars and detail in the nebula at that magnification than at lower mags.

 

As for discontinued eyepieces, I just looked at my Buyer's Guide from 2004.  There are hundreds of eyepieces that have been discontinued, and that doesn't even include all the eyepieces discontinued before then.  It looks like a lot of eyepieces get discontinued for one reason or another.  What's available today is merely a snapshot in time.


  • RAKing likes this

#59 ACG

ACG

    Explorer 1

  • *****
  • Posts: 85
  • Joined: 10 Sep 2011

Posted 14 February 2018 - 06:05 PM

Both nagler (2.5 and 11) will never be mythical eyepieces and very highly valued despite their withdrawal. Throughout the history of Televue that ocular of the disappeared is mythical and people pay real fortunes for them? There are none. No Televue eyepiece is paid more expensive than a new one. There is a lot to choose from within the brand itself. If Televue disappears then, but I repeat the market is flooded. Do not run to buy one and another because you're not going to make money. Only if you need it

#60 Alan French

Alan French

    Night Owl

  • *****
  • Posts: 5671
  • Joined: 28 Jan 2005
  • Loc: Upstate NY

Posted 14 February 2018 - 06:10 PM

Both nagler (2.5 and 11) will never be mythical eyepieces and very highly valued despite their withdrawal. Throughout the history of Televue that ocular of the disappeared is mythical and people pay real fortunes for them? There are none. No Televue eyepiece is paid more expensive than a new one. There is a lot to choose from within the brand itself. If Televue disappears then, but I repeat the market is flooded. Do not run to buy one and another because you're not going to make money. Only if you need it

I think you are taking my comment far too seriously. ;)

 

Clear skies, Alan


  • Peter Besenbruch likes this

#61 Redbetter

Redbetter

    Cosmos

  • *****
  • Posts: 7984
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 14 February 2018 - 06:39 PM

 

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.

 

Huh?  As I said the maximums I am using are not that high in the refractors and exit pupil/eye limitations are an issue...as is the beginning of diffraction blurring.  They are already topping out around 150 - 170x in the 80ED (with 150x being the common preferred level for my eye), around 200x in the in the 110ED--typically I stop at 192x but will go into the low 200's trying to get that last bit while dealing with floaters and such.  The 60ED has been pushed a bit more at 120 to 144x, mainly for image scale, but detail-wise it is topping at about 120x and floaters/etc. are already an issue at 120x (0.5mm exit pupil).

 

If you want high, there are refractor people who claim 100x/inch for planets...0.25mm exit pupils.  That works for me for very close double stars where floaters are not an issue and the goal is to study the diffraction patterns, but not for planets.

 

The SCT is around 300x for an 8".  Nominally it tops out with a 7mm at 290x, but with a 2" diagonal the magnification is a bit higher than that, around 300+.  That is nominally 0.7mm exit pupil, still within the comfort zone for my eye.  It is below that (e.g. with the refractors in the 0.5 to 0.6mm range) that floaters become more of a pest.



#62 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 78977
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 February 2018 - 07:46 PM

Well, I regard 50x as the lowest useful power in an 8" SCT, which is a 40mm eyepiece.  I don't like lower powers than that because the image is simply too small.  I don't care for what I call "binocular views" in a telescope because I have binoculars for that.  Even in my f/7 refractor, I rarely use an eyepiece longer than 18.2mm (2.6mm exit pupil, 39x, 1.53°).

 

And, as I have stated before, my dark-adapted pupil diameter is 4.5mm and an exit pupil of that size has a lot of astigmatism that I don't see when the exit pupil is 4mm or smaller.

 

Last, I find the image at 50X in the 8" to be plenty bright enough at a dark site.  I never felt the

need to go lower, ever, over the 11 years I owned an 8" SCT.  And I used a magnification around 100x (2mm exit pupil) easily 20x as much for DSO viewing.

Today, I tend to view large objects like M42 at 107x (56' field, 3mm exit pupil) or more, in the 12.5".  That nebula damages my night vision--brighter is unnecessary.  And I see more stars and detail in the nebula at that magnification than at lower mags.

 

 

Don:

 

I am wondering how much time you spend observing large objects and regions of nebulosity in their entirety.  I spend a quite a bit of time.  Binocular summation provides about a 20% aperture advantage so 10x50s are the equivalent of a 60mm telescope at the same magnification. And using filters with binoculars is problematic.

 

For me, the range the interesting range in my 4 inch is between 13x with a 4.9 degree field with a 7.6mm exit pupil and about 26x with a 3.85 degree field and a 3.9mm exit pupil I find there's just a whole lot of interesting views.  This is the entirety of the Veil, the North American/Pelican Complex, the Heart and Soul nebular complex, the California, the Pleiades, Barnard's loop and many other interesting fields.  The Milky Way show many interesting fields of nebulosity gradients. 

 

The 1.79 degrees at 39x with a 2.3mm exit pupil is not much different in size and magnification than the 1.62 degrees at 48x I get with my 12.5 inch, but that 6.6mm exit pupil is about 8 times brighter to my eye.

 

Of course part of this is about your eyes and about my eyes.  My eyes open wide and even at the largest exit pupils shows very little astigmatism.  

 

But still, I have to think it has mostly to do with object choice.  I am not viewing Orion with a large exit pupil, it's very bright and not particularly large, like you I find I see the most using smaller exit pupils and greater magnifications.  It's those big objects and wider fields like those previously mentioned, those objects are where a small refractor shines.  

 

Jon


  • droid likes this

#63 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 42734
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 14 February 2018 - 07:53 PM

Seeing the entire Veil in one view holds no interest for me.

Seeing the filigree in the broom handle section with a single line O-III filter at 140x does.

I had a scope in the '80s that could see the entire North America nebula or the entire California nebula, and I looked at them then, with filters.

The large nebula are really, in my opinion, more photographic objects than visual.

Even when I take the 4" to a dark site, I spend most of my time on objects of 10' to 45' in size. 



#64 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18416
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 14 February 2018 - 07:59 PM

 

When it comes to matching seeing/scope/exit pupil for high power planetary detail I am finding I can match it to an estimated arc second rating across apertures.  I have roughed out some equivalent arc second values for my scopes using a Pickering rating for each, from 60mm to 20".  It is rather approximate of course, but I am finding some value in it.  These Pickering values run from -1 to 10/10 to capture the useful range for the 20".   The smallest scopes top out at their max optimum planetary contrast magnification levels rather easily, while the medium and larger scopes are progressively throttled back by the seeing. 

 

No doubt that the useful levels will vary substantially for others (and depend also on locale rather than just a given eye).  However, I can lump the seeing levels into max useful magnification levels for the big scope:

  • ~150x awful to very poor seeing (-1/10 to 0/10 in the 20"), not really worth pointing a scope at planets since the detail is minimal with multiple images and constant motion on awful nights,  smallest scopes might still use this much power, but show far less than they do on better nights, making less power more pleasing/comfortable in them.
  • ~175-200x poor seeing (1/10 in 20"), small scopes coming into their own.  60ED and 80ED should be almost topped out (at somewhat lower powers, 120-144x in 60ED, 150-170x in 80ED)
  • ~225-250x "meh" mediocre seeing (2/10 in 20"), 80ED topped out, 110ED nearing top out (around 200x)
  • ~275-300x decent seeing (3/10 in the 20"), 80ED is showing all the detail it can, 110ED topped out in power (~200x) near the max detail it can show, 8" SCT nearing top out in power but still has another gear with respect to detail
  • ~350-400x good to great seeing (4/10 to 5/10 in the 20"), 110ED showing all the detail it can provide, 8" SCT topped out at ~300x, 10" Dob nearing top out at 350-400x?
  • ~500x, excellent seeing (6/10 in the 20"), 20" still has headroom for more, 8" SCT at max detail at ~300x, 10" Dob should be topped out and near max detail somewhere in the 400x range.  I have had the 20" and 8" together in these conditions and better on multiple nights, but it has been many years.  The 10" has never been under such skies so far. 

For the big scope, some of the same values apply to tiny galaxies and other DSO's as well.  For the same seeing level I tend to be limited to the above powers for classifying/identifying galaxies.  The exceptions are that I can bump a notch higher in magnification at a given Pickering value for detection/confirmation even though no more structural detail can be gleaned because of the seeing.   And in the two poorest levels of seeing I still will use around 200x to get some image scale. 

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.

 

I use powers much higher than that.  I don't get warmed up below 400x on scopes bigger than 8".  Used 400x last nite with a C5.  I am lucky to have some of the best seeing you could hope for.  And Feb has the best seeing in my area when we have a blocked upper level pattern with warm temps and sea fog. 



#65 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 78977
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 February 2018 - 11:30 PM

Seeing the entire Veil in one view holds no interest for me.

Seeing the filigree in the broom handle section with a single line O-III filter at 140x does.

I had a scope in the '80s that could see the entire North America nebula or the entire California nebula, and I looked at them then, with filters.

The large nebula are really, in my opinion, more photographic objects than visual.

Even when I take the 4" to a dark site, I spend most of my time on objects of 10' to 45' in size. 

 

It's all in what we enjoy. 

 

I enjoy both the entirety of the Veil in the 4 inch as well as the remote little patches visible is the 22 inch.  When that scope is capable of 51' view, I don't see much purpose using the 4 inch viewing smaller objects other than to see if I can see them.  The 4 inch excels at the big, bright wide fields of view, it provides a nice break, a change of pace...

 

I consider such objects lifelong projects.  Every time I look, it's new and fresh and I see something new, even if it's just a little bit.  

 

YMMV

 

Jon 


  • turtle86 and Sarkikos like this

#66 Redbetter

Redbetter

    Cosmos

  • *****
  • Posts: 7984
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 15 February 2018 - 01:42 AM

 

Well, I regard 50x as the lowest useful power in an 8" SCT, which is a 40mm eyepiece.  I don't like lower powers than that because the image is simply too small.  I don't care for what I call "binocular views" in a telescope because I have binoculars for that.  Even in my f/7 refractor, I rarely use an eyepiece longer than 18.2mm (2.6mm exit pupil, 39x, 1.53°).

 

And, as I have stated before, my dark-adapted pupil diameter is 4.5mm and an exit pupil of that size has a lot of astigmatism that I don't see when the exit pupil is 4mm or smaller.

Last, I find the image at 50X in the 8" to be plenty bright enough at a dark site.  I never felt the need to go lower, ever, over the 11 years I owned an 8" SCT.  And I used a magnification around 100x (2mm exit pupil) easily 20x as much for DSO viewing. 

Today, I tend to view large objects like M42 at 107x (56' field, 3mm exit pupil) or more, in the 12.5".  That nebula damages my night vision--brighter is unnecessary.  And I see more stars and detail in the nebula at that magnification than at lower mags.

 

It is unnecessarily limiting to me to eschew the possibility of the brightest possible image, particularly for nebula at a dark site.  In your case it makes more sense as result of pupil limitation, but yours is on the lower end of the pupil range, so not what I would recommend to others.  And 2.6mm exit pupil is just far too dim for the best view of a number of the telescopic objects I observe, as in the Abell's I mentioned above--particularly with a filter.  I was comparing the views at 3.2mm exit pupil and 5.2mm exit pupil to conclude the larger exit pupil was showing the objects much better.  But I typically don't use short focal length refractors to observe mid size DSO''s that I see better with larger aperture.  Instead I use them for objects that are harder to frame properly or take in context with large scopes.  These are showpiece objects that are problematic in long focal length scopes.   Astigmatism doesn't impact the view of large nebulae from what I have seen.

 

M42 is a rather poor comparison because it is so bright.  When folks ask what filter should be used for M42 I reply:  sunglasses.  It is completely the opposite of the sort of things that respond well to large exit pupils. 

 

I don't care for binoculars that much although I have a few pair, which is why I use a telescope.  After a few minutes with binoculars I am ready for the comfort and increased capabilities, steady view, and flexibility of a telescope.  Binocular eyepieces don't compare favorably, they tend to be fixed magnification, filtering isn't easy to accomplish, and they are far more of a pain to use.  I am not keen on telling beginners to start with binoculars either for the same reasons.  There are binocular people and there are telescope people and some that are happy either way.  I use binoculars more for scouting objects, particularly in twilight conditions for hunting comets or even planets when they would otherwise be difficulty to find because of the lack of star references. I also use them for fast moving objects that I can't track well with a scope.  But I don't use them for seasons at a time.

 

I felt limited by the 40mm in the first few months I had the 8" SCT.  I gave it some time, but a few months later I moved to 2" using the 55 Plossl, with the 40 staying in its box except when I needed its 1.25" filter capability.  I did start using 35 Pan about 6 months after that because it was sent to me in error (Pocono sent a mislabeled 2" eyepiece box with the wrong eyepiece) and I found it a good intermediate, particularly in town.   The 41 Pan didn't even exist at the time from what I recall. 

 

Operating at mid power and high power all of the time and completely skipping low power is a personal choice, but it is not something I want to do, nor is it something I recommend.  I do like to view some things at both low and mid (and/or high) power.   The Veil, Barnard's Loop, NAN, California, Heart & Soul, Pleiades, Rosette, Andromeda, etc. fall into those categories.  These are some of the showpiece objects, and for me they are some of the best reasons to have a refractor with low power capability.

 

I use the refractors least in the mode you employ.  In the case of an 8" SCT I wouldn't be inclined to use a 4" refractor for 39x when I could use the 8" SCT for 37x.   Oh, I will look at some relatively large open clusters and such at mid powers where they are well framed, but I prefer the refractors for wide field viewing at low power, as well as for planets and double stars near their maximum power. 



#67 Peter Besenbruch

Peter Besenbruch

    Fly Me to the Moon

  • *****
  • Posts: 7011
  • Joined: 21 Aug 2014
  • Loc: Oahu

Posted 15 February 2018 - 02:02 AM

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.

Here in Hawaii, the seeing ranges from 50x tops to basically as high as I can push it, and "'gosh-darn' the floaters; full speed ahead." That means 385 to 540x on a 7". Fortunately, one of my eyes has fewer floaters than the other. I am so looking forward to planetary season.



#68 Deep13

Deep13

    Skylab

  • *****
  • Posts: 4427
  • Joined: 25 Jan 2005
  • Loc: NE Ohio

Posted 15 February 2018 - 02:05 AM

The only mythical EP I have is the 14mm Unicorn, 180 deg. AFOV, 30mm ER with no field curvature at f/2.



#69 BGazing

BGazing

    Apollo

  • -----
  • Posts: 1176
  • Joined: 25 Feb 2016
  • Loc: Belgrade, Serbia

Posted 15 February 2018 - 04:28 AM

 

 

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.

 

Huh?  As I said the maximums I am using are not that high in the refractors and exit pupil/eye limitations are an issue...as is the beginning of diffraction blurring.  They are already topping out around 150 - 170x in the 80ED (with 150x being the common preferred level for my eye), around 200x in the in the 110ED--typically I stop at 192x but will go into the low 200's trying to get that last bit while dealing with floaters and such.  The 60ED has been pushed a bit more at 120 to 144x, mainly for image scale, but detail-wise it is topping at about 120x and floaters/etc. are already an issue at 120x (0.5mm exit pupil).

 

If you want high, there are refractor people who claim 100x/inch for planets...0.25mm exit pupils.  That works for me for very close double stars where floaters are not an issue and the goal is to study the diffraction patterns, but not for planets.

 

The SCT is around 300x for an 8".  Nominally it tops out with a 7mm at 290x, but with a 2" diagonal the magnification is a bit higher than that, around 300+.  That is nominally 0.7mm exit pupil, still within the comfort zone for my eye.  It is below that (e.g. with the refractors in the 0.5 to 0.6mm range) that floaters become more of a pest.

 

I was thinking about 60ED in particular. At 360mm focal length 120x is 0.33 exit pupil. Hence 'whoa'. 



#70 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18416
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 15 February 2018 - 06:30 AM

I guess the only eyepieces i would like to see come back are the Tele Vue Circle NJ Plossl's and Wide fields from the mid 80's and at mid 80's prices.



#71 Sarkikos

Sarkikos

    ISS

  • *****
  • Posts: 30680
  • Joined: 18 Dec 2007
  • Loc: Per sylvam ad astra

Posted 15 February 2018 - 07:25 AM

 

Whoa. You are using some wicked high magnifications for those small fracs and SCT. You must be completely floater-free.

Here in Hawaii, the seeing ranges from 50x tops to basically as high as I can push it, and "'gosh-darn' the floaters; full speed ahead." That means 385 to 540x on a 7". Fortunately, one of my eyes has fewer floaters than the other. I am so looking forward to planetary season.

 

I have floaters also, and they're getting worse.  I no longer observe the Moon at exit pupils less than about 0.8mm.  And I feel much more comfortable at a 1mm exit pupil.  The Moon is bright enough that you can see all that there is to see at relatively wide exit pupils.   You just have to try.

 

Planets are not so bad.  Their apparent size is small enough that eye floaters are not so obvious as when observing the Moon.

 

Double stars are no problem at all for me at very high magnifications and very narrow exit pupils, despite the floaters.  With stars, you're dealing with the diffraction pattern of a pointicular object, not an extended object.

 

Mike


Edited by Sarkikos, 15 February 2018 - 07:30 AM.

  • Peter Besenbruch likes this

#72 turtle86

turtle86

    Mr. Coffee

  • *****
  • Posts: 5163
  • Joined: 09 Oct 2006

Posted 15 February 2018 - 07:47 AM

Seeing the entire Veil in one view holds no interest for me.
Seeing the filigree in the broom handle section with a single line O-III filter at 140x does.
I had a scope in the '80s that could see the entire North America nebula or the entire California nebula, and I looked at them then, with filters.
The large nebula are really, in my opinion, more photographic objects than visual.
Even when I take the 4" to a dark site, I spend most of my time on objects of 10' to 45' in size.

 
It's all in what we enjoy. 
 
I enjoy both the entirety of the Veil in the 4 inch as well as the remote little patches visible is the 22 inch.  When that scope is capable of 51' view, I don't see much purpose using the 4 inch viewing smaller objects other than to see if I can see them.  The 4 inch excels at the big, bright wide fields of view, it provides a nice break, a change of pace...
 
I consider such objects lifelong projects.  Every time I look, it's new and fresh and I see something new, even if it's just a little bit.  
 
YMMV
 
Jon



I agree. My best view of the Veil was in Tom Clark's 42", in which it is a huge, bright careening object. The delicate filamentary detail was astounding, though it was obviously only possible to view small segments at a time. At the same time, the Veil is a delightful object to view in my humble 120mm achro. At that aperture, I can appreciate it in its context among the stars and see its overall structure as celestial puffs of smoke emanating from the supernova explosion long ago. It's all good. grin.gif

#73 Redbetter

Redbetter

    Cosmos

  • *****
  • Posts: 7984
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 15 February 2018 - 03:23 PM

 

I was thinking about 60ED in particular. At 360mm focal length 120x is 0.33 exit pupil. Hence 'whoa'. 

 

 

Incorrect.  Exit pupil = eyepiece focal length/focal ratio or to match the information you are using above = aperture / magnification

 

Either way it is being done with a 3mm eyepiece focal length = 3/6   or  60/120 = 0.5mm

 

If one wanted to back derive it without knowing the eyepiece ahead of time knowing only aperture, scope focal length, and magnification then the focal ratio and eyepiece focal length can be calculated.  Eyepiece focal length = 360/120 and focal ratio = 360/60.  Plugging these into the exit pupil formula = (360/120) / (360/60) where the 360's in numerator and denominator reduce to 1 and subsequent rearrangement yields 60/120 = 0.5mm



#74 BGazing

BGazing

    Apollo

  • -----
  • Posts: 1176
  • Joined: 25 Feb 2016
  • Loc: Belgrade, Serbia

Posted 15 February 2018 - 05:20 PM

My bad again, miscalculated, thanks for pointing out. I am sloppy these days, at least that makes me extra cautious...and slow... when writing on work.



#75 Lt 26

Lt 26

    Vanguard

  • *****
  • Posts: 2384
  • Joined: 19 Feb 2009
  • Loc: Northwest Illinois

Posted 15 February 2018 - 08:10 PM

The 11mm was only T6 I held onto. This the 32 Plossl and a barlow are my grab and go set.

Dereck


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