181 replies to this topic

[Scanning4Comets]

Now, back to our daily posting and relevance. 

Edited by Cygnus2112, 06 June 2016 - 09:00 AM.

[russell23]

I'm terribly sorry if you can't understand my reply. Too much to fathom I guess.

 

I have trouble following where people are actually disagreeing on this eyepiece/coma issue since it seems to jump around.  I think two things seem to be straightforward:

 

1.  The mirror creates the coma.

 

2.  Depending upon the eyepiece optical design and FL the degree to which the coma produced by the mirror can be detected will vary from eyepiece to eyepiece.

 

Taking these together it seems that we can conclude that some eyepieces are better than others if you are not going to use a coma corrector.  If I've been reading Markus correctly over the years this seems to be what his main point is on this topic.

 

But we can also say that you should not blame the eyepiece for coma when the mirror creates the coma.  I think from reading the disagreements with Markus on this that perhaps at times that seems to be the point of contention. 

 

It seems to be that both sides of this long running disagreement have fair points if expressed correctly.  And perhaps that is the real disagreement - how to properly express the observation that some eyepieces do not reveal the coma as much as others. 

[Scanning4Comets]

 

I'm terribly sorry if you can't understand my reply. Too much to fathom I guess.

 

I have trouble following where people are actually disagreeing on this eyepiece/coma issue since it seems to jump around.  I think two things seem to be straightforward:

 

1.  The mirror creates the coma.

 

2.  Depending upon the eyepiece optical design and FL the degree to which the coma produced by the mirror can be detected will vary from eyepiece to eyepiece.

 

Taking these together it seems that we can conclude that some eyepieces are better than others if you are not going to use a coma corrector.  If I've been reading Markus correctly over the years this seems to be what his main point is on this topic.

 

But we can also say that you should not blame the eyepiece for coma when the mirror creates the coma.  I think from reading the disagreements with Markus on this that perhaps at times that seems to be the point of contention. 

 

It seems to be that both sides of this long running disagreement have fair points if expressed correctly.  And perhaps that is the real disagreement - how to properly express the observation that some eyepieces do not reveal the coma as much as others. 

 

 

Another BINGO! ! !

 

Darn it , I am rich from two Bingos now LOL

Edited by Cygnus2112, 06 June 2016 - 07:59 AM.

[Phil Cowell]

Thanks for clarifying Ill remember you don't understand the scientific method from now on. 

 

 

 

I sleep fine thanks, obviously you didn't by the length of the reply. You must enjoy making lists but it doesn't change the fact your basing tests on an aberrant platform. GIGO testing. Simple answer and it didn't take a novel to try to justify it. Sorry if you don't like Physics or honesty.

 

Your "as you have said a million times" statement also indicates your ability to quantify needs maybe remedial mathematics?

 

 

 

 

 

Ok so you reject reality again. Or is your answer you have a defective baseline so it should be good to anyone else who doesn't want valid comparisons? Alrighty then.

 

 

 

Starman is 100% correct, if you want to apply any form of rational metrics you have to start without aberrant optics for the testing rig. You do not meet this baseline testing criteria with your current setup.

Sorry that just reality, reject it all you want but it's still reality. 

 

 

I hate to say it, but it needs to be said: someone who does not use a coma corrector in a fast dob is not qualified to talk about the edge of field aberrations in an eyepiece.

 

 

 

 

Try the same experiment in a coma-corrected dob and your results might be reversed.

 

 

I hate to say it, but you are incorrect. Not everybody uses one, and all eyepieces don't act the same as each other in a fast scope. You might use one, and others might, but that doesn't say that people who do not use one cannot make judgements in telescopes. That comment is way off base. 

 

I've had administrators PM me asking why every eyepiece discussion I talk about ends up in a paracorr debate saying it is ridiculous. I'm not here to go back and forth again beating an already dead horse Don. 

 

 

http://www.cloudynig...ptic/?p=7255216

 

 

 

Starman is 100% correct, if you want to apply any form of rational metrics you have to start without aberrant optics for the testing rig. You do not meet this baseline testing criteria with your current setup.
Sorry that just reality, reject it all you want but it's still reality.

 

Reality:

 

Tested a 24mm Panoptic in my 10" f/4.7. Tested many eyepieces in the same rig along with other scopes.

 

Correction was excellent in the 24mm Pan. Eye relief was not to my liking, so I tried fixing it. What I did helped a lot. Checked the eyepiece for transmission on The Veil against a 25mm Sterling. The Veil was a lot brighter in the Sterling.....Sterling has better transmission, 24mm Pan now sold, and a replacement is on the way.

 

Tested many other eyepieces in the same rig. No coma corrector. Why? As I have already stated a million times, I don't want an extra piece of glass to fiddle with in between observing. I try to choose my eyepieces that have good correction in a fast scope without a CC. Out of the ones I will be getting, only ONE will have something that needs correcting, but I am willing to live with that because comfort, transmission, etc is excellent. Out of the 6 eyepieces in my last collection, 5 of them had excellent correction: 24mm Pan, 14mm Delos, 10mm XW, 7mm XW, 5.5mm Meade. Only the 34mm Es 68 shows such a small amount of coma that It does not bother me, plus I don't use it a whole lot...so I see no point in buying a $300 piece of gear for one or two eyepieces. Already stated why the 24mm Pan was sold, (do I need to repeat it again?) 

 

Lots of other people do not use a coma corrector because they choose not to, and as I have said another million times on here, not all eyepieces show the same amount of coma as each other.

 

Take the 22mm LVW and put it up against other 22mm eyepieces and the difference is obvious. The 22mm LVW is corrected better than a 22mm Nagler, 22mm Ultima LX, 20mm XW, etc. Sure some of those others have a diff AFOV, BUT THE BOTTOM LINE IS THAT THE 22MM LVW IS BETTER CORRECTED, but throughput is less than other offerings. The 24mm Pan is better corrected as well, but as I saw, transmission is lacking as well.

 

Let's plug in a few more shall we?

 

10mm XW vs 10mm Hyperion. Same AFOV almost. The 10mm XW smacks the Hyperion upside the head correction wise, transmission wise, everything....all without a coma corrector. Add a couple more shall we? Hmmmmmm.....Let's see here...10mm XW vs 10mm Luminos. The Luminos will get it's @ss handed to it by the XW....Oh...and that's without a coma corrector.

 

8mm Delos Vs 8mm Hyperion, outcome is obvious....no coma corrector. Yes the Delos and XW is more money...but that is not the point now is it? The point is, without a coma corrector, the Delos & XW's are fine on their own. Namely these FL's below, and others:

 

XW's: 10mm, 7mm, 5mm, 3.5mm

Delos: 14mm, 12mm, 10mm, 8mm, 6mm, 4.5mm, 3.5mm

LVW's: All of them (except a tiny bit of FC in the 17mm)

Some Naglers: 20mm T2, 31mm T5

 

I could list dozens of more that are good w/o a CC. Some people are just far too picky and want perfection. I choose not to have absolute "perfection" and enjoy the night sky without a CC. I have explained it dozens & dozens of times why....but I keep getting the same old same old from some of you. If you want absolute perfection, you should be in a different hobby. LOL.

 

BOTTOM LINE: Eyepieces can and will be tested without coma correctors because VISUALLY NOT ALL EYEPIECES ARE CORRECTED THE SAME. I've explained it and if any of you can't fathom it, then you need to take your blinders and your preconceived notions off. A CC does help, but it is ridiculous to make claims that without CC, validating certain eyepieces in short FL scopes in all in vain.

 

Funny how every thread I create always ends up in a "coma corrector" discussion. Eyepiece transmission: "You have no valid points, you're not using coma correction". Eyepiece comfort: "You have no valid points, you're not using a CC" Eyepiece correction: "You have no valid points, you don't have a driven mount". Get serious. So, I guess without a driven mount, I can't pan stars around the field to check for correction?

 

There's your reality.  Maybe you and other certain parties can sleep well tonight....or not.

 

 

 

I'm terribly sorry if you can't understand my reply. Too much to fathom I guess.

 

Your "as you have said a million times" statement also indicates your ability to quantify needs maybe remedial mathematics?

 

 

Repeated so many times, yet you choose to go on & on & on about it still? LOL

 

[Phil Cowell]

Thanks for clarifying Ill remember you don't understand the scientific method from now on. 

Add you to the not heliocentric yet list.

 

 

 

I sleep fine thanks, obviously you didn't by the length of the reply. You must enjoy making lists but it doesn't change the fact your basing tests on an aberrant platform. GIGO testing. Simple answer and it didn't take a novel to try to justify it. Sorry if you don't like Physics or honesty.

 

Your "as you have said a million times" statement also indicates your ability to quantify needs maybe remedial mathematics?

 

 

 

 

 

Ok so you reject reality again. Or is your answer you have a defective baseline so it should be good to anyone else who doesn't want valid comparisons? Alrighty then.

 

 

 

Starman is 100% correct, if you want to apply any form of rational metrics you have to start without aberrant optics for the testing rig. You do not meet this baseline testing criteria with your current setup.

Sorry that just reality, reject it all you want but it's still reality. 

 

 

I hate to say it, but it needs to be said: someone who does not use a coma corrector in a fast dob is not qualified to talk about the edge of field aberrations in an eyepiece.

 

 

 

 

Try the same experiment in a coma-corrected dob and your results might be reversed.

 

 

I hate to say it, but you are incorrect. Not everybody uses one, and all eyepieces don't act the same as each other in a fast scope. You might use one, and others might, but that doesn't say that people who do not use one cannot make judgements in telescopes. That comment is way off base. 

 

I've had administrators PM me asking why every eyepiece discussion I talk about ends up in a paracorr debate saying it is ridiculous. I'm not here to go back and forth again beating an already dead horse Don. 

 

 

http://www.cloudynig...ptic/?p=7255216

 

 

 

Starman is 100% correct, if you want to apply any form of rational metrics you have to start without aberrant optics for the testing rig. You do not meet this baseline testing criteria with your current setup.
Sorry that just reality, reject it all you want but it's still reality.

 

Reality:

 

Tested a 24mm Panoptic in my 10" f/4.7. Tested many eyepieces in the same rig along with other scopes.

 

Correction was excellent in the 24mm Pan. Eye relief was not to my liking, so I tried fixing it. What I did helped a lot. Checked the eyepiece for transmission on The Veil against a 25mm Sterling. The Veil was a lot brighter in the Sterling.....Sterling has better transmission, 24mm Pan now sold, and a replacement is on the way.

 

Tested many other eyepieces in the same rig. No coma corrector. Why? As I have already stated a million times, I don't want an extra piece of glass to fiddle with in between observing. I try to choose my eyepieces that have good correction in a fast scope without a CC. Out of the ones I will be getting, only ONE will have something that needs correcting, but I am willing to live with that because comfort, transmission, etc is excellent. Out of the 6 eyepieces in my last collection, 5 of them had excellent correction: 24mm Pan, 14mm Delos, 10mm XW, 7mm XW, 5.5mm Meade. Only the 34mm Es 68 shows such a small amount of coma that It does not bother me, plus I don't use it a whole lot...so I see no point in buying a $300 piece of gear for one or two eyepieces. Already stated why the 24mm Pan was sold, (do I need to repeat it again?) 

 

Lots of other people do not use a coma corrector because they choose not to, and as I have said another million times on here, not all eyepieces show the same amount of coma as each other.

 

Take the 22mm LVW and put it up against other 22mm eyepieces and the difference is obvious. The 22mm LVW is corrected better than a 22mm Nagler, 22mm Ultima LX, 20mm XW, etc. Sure some of those others have a diff AFOV, BUT THE BOTTOM LINE IS THAT THE 22MM LVW IS BETTER CORRECTED, but throughput is less than other offerings. The 24mm Pan is better corrected as well, but as I saw, transmission is lacking as well.

 

Let's plug in a few more shall we?

 

10mm XW vs 10mm Hyperion. Same AFOV almost. The 10mm XW smacks the Hyperion upside the head correction wise, transmission wise, everything....all without a coma corrector. Add a couple more shall we? Hmmmmmm.....Let's see here...10mm XW vs 10mm Luminos. The Luminos will get it's @ss handed to it by the XW....Oh...and that's without a coma corrector.

 

8mm Delos Vs 8mm Hyperion, outcome is obvious....no coma corrector. Yes the Delos and XW is more money...but that is not the point now is it? The point is, without a coma corrector, the Delos & XW's are fine on their own. Namely these FL's below, and others:

 

XW's: 10mm, 7mm, 5mm, 3.5mm

Delos: 14mm, 12mm, 10mm, 8mm, 6mm, 4.5mm, 3.5mm

LVW's: All of them (except a tiny bit of FC in the 17mm)

Some Naglers: 20mm T2, 31mm T5

 

I could list dozens of more that are good w/o a CC. Some people are just far too picky and want perfection. I choose not to have absolute "perfection" and enjoy the night sky without a CC. I have explained it dozens & dozens of times why....but I keep getting the same old same old from some of you. If you want absolute perfection, you should be in a different hobby. LOL.

 

BOTTOM LINE: Eyepieces can and will be tested without coma correctors because VISUALLY NOT ALL EYEPIECES ARE CORRECTED THE SAME. I've explained it and if any of you can't fathom it, then you need to take your blinders and your preconceived notions off. A CC does help, but it is ridiculous to make claims that without CC, validating certain eyepieces in short FL scopes in all in vain.

 

Funny how every thread I create always ends up in a "coma corrector" discussion. Eyepiece transmission: "You have no valid points, you're not using coma correction". Eyepiece comfort: "You have no valid points, you're not using a CC" Eyepiece correction: "You have no valid points, you don't have a driven mount". Get serious. So, I guess without a driven mount, I can't pan stars around the field to check for correction?

 

There's your reality.  Maybe you and other certain parties can sleep well tonight....or not.

 

 

 

I'm terribly sorry if you can't understand my reply. Too much to fathom I guess.

 

Your "as you have said a million times" statement also indicates your ability to quantify needs maybe remedial mathematics?

 

 

Repeated so many times, yet you choose to go on & on & on about it still? LOL

 

[Starman1]

 

All I want to know is, "What do you mean when you say an eyepiece has 'less transmission' than another"?

A simple addition of what you saw is almost required, because that statement is interpretation, not observation.

 

What I mean when I say that eyepiece A shows less transmission than eyepiece B, is that eyepiece A allows dimmer stars, galaxies and/or nebulae to been seen than eyepiece B, OR that eyepiece A allows dimmer stars, galaxies and/or nebulae to be seen more easily than eyepiece B.

 

As a prerequisite, I accept that ideally the eyepieces should be of equal or near-equal focal length.  But I also accept that it is useful to know which eyepiece appears to have greater transmission, even when the focal lengths are not exactly the same.  

 

A corollary is that I do not consider the apparent darkness of the background a good indication of what I am calling "transmission."  The crucial point is the ability of the eyepiece to show me dim objects.  I have had experience with eyepieces that I would not say have the best transmission based on my working definiton, and yet they presented a background that was darker than other eyepieces which showed dim objects more easily.  Examples of eyepieces that have less than optimal transmission but present dark backgrounds are Brandons and Sirius Plossls.

 

I don't make any assumption about what is the cause or causes of the apparent difference in transmission.  It could be caused by a difference in the glass used.  But not necessarily.  It could be caused by a difference in scatter control.  But not necessarily.  It could be caused by a difference in the coatings.  But not necessarily.  It could be the result of other variables of which I am unaware.  IMO, I am not required to give the cause or causes of the difference in perceived transmission.  I only report that I see a difference.

 

I could give a similar account of what I mean when I say eyepiece A appears to be sharper than eyepiece B.  Eyepiece A appears to be sharper than eyepiece B, if eyepiece A allows finer planet/lunar surface detail to be seen than eyepiece B, OR if eyepiece A allows finer planet/lunar surface detail to be seen more easily than eyepiece B.  And etc., as above.  

 

For example, given the above working definition of "sharpness," my experience is that XO's are sharper than the Leica ASPH Barlow, which is about as sharp as the XW's and Delos, which in turn are a bit sharper than the Nagler Zooms and the Baader Zoom.  This is when observing bright planets, and at the center of field of view.

 

Mike

 

A couple notes on your statements:

1) you cannot say which eyepiece has more transmission if the focal lengths are different.  Differences in exit pupil will trump transmission differences most of the time.

2) No one is arguing you should not say that one eyepiece allows fainter stars to be seen or that faint galaxies are brighter in one than another.  What I'm arguing is that without some lab measurements to back it up, you simply cannot assert the difference is due to transmission.

It might be, it might not be.  You have no way of knowing without measurements.  That you saw what you saw is not in question.  Attributing it to a cause is.  As you point out, it could be other things in play.

By the way, I too see the differences in the visibility of faint targets from eyepiece to eyepiece.  I just don't assert the cause is a difference in transmission.  It might be a variety of factors all working together that results in what I see.  I just don't know.

[Cotts]

OK. Everyone.  Time Out.

 

Locked for mod review....

 

Dave