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Equipment Discussions >> Eyepieces

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: your favorite EP for planetary observation (f/10)? new [Re: Rick M.]
      #5740239 - 03/18/13 08:41 AM

I've never looked through a Delos, but judging from the reports I've read, it seems a toss up, at least for planet observation. So that would make me gravitate toward the XW's, which are less expensive whether bought new or used.

For deep sky, there may be an advantage to the Delos. Some observers say the Delos have a bit better light transmission than the XW. But if the Delos do not actually have better light transmission - or somehow allow dimmer objects to be perceived than through the XW's - I see no advantage for the Delos over the XW's.

Mike


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andydj5xp
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Reged: 05/27/04

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Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5740292 - 03/18/13 09:16 AM

Quote:

For deep sky, there may be an advantage to the Delos. Some observers say the Delos have a bit better light transmission than the XW.




The intensity perception of the human eye is a logarithmical one. Light throughput differences of say 3% (98% to 95%) would correspond to just 0.26dB in logarithmical measures. I have a hard time to imagine that anybody would be even close to discriminating such minute intensity differences.

I'm aware that some fellow CNers report to be able to do so. But the noticed differences will almost certainly not been caused by intensity differences but something else. There are lots of possible sources for perceived differences between eyepieces.

Andreas


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Sarkikos
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Re: your favorite EP for planetary observation (f/10)? new [Re: andydj5xp]
      #5740415 - 03/18/13 10:30 AM

Andreas,

I am skeptical but have an open mind to reports from first-hand experience in the field. On the other hand, I allow theory and studies to inform my experience, not determine it.

The received data from perception studies might be based on conditions, objects and subjects that are not strictly transferable to amateur astronomy. When attempting to discern faint, LSB objects near the LM of an instrument, I think it might be possible for small differences in light transmission to have a more crucial effect.

Quote:

I'm aware that some fellow CNers report to be able to do so. But the noticed differences will almost certainly not been caused by intensity differences but something else. There are lots of possible sources for perceived differences between eyepieces.




The variation in perception of faint objects through different eyepieces might not be due to an appreciable difference in light transmission that is measureable through instrumentation. The effect might be due to other attributes of the eyepieces. But still, a perceived variation is there and will make a difference in the discernment of faint objects through the eyepiece.

Maybe we should be using a different term than "light transmission" to make the Optics Police happy. Maybe something like "Perceived Limiting Magnitude" would be better?


Mike


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Sorny
professor emeritus


Reged: 03/15/12

Loc: Southern MN
Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5740788 - 03/18/13 02:03 PM

15mm or 20mm in my binoviewer, with the power switch either disengaged, or using barlow or reducer depending on seeing. I do most of my viewing with the 20mm pair, not just planetary.

If I'm going mono, then it is either my 8mm or 13mm or 17mm depending on seeing conditions. I've got a C11, so what works for me won't be quite the same as a C9.25...


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Rich V.
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Re: your favorite EP for planetary observation (f/10)? new [Re: Rick M.]
      #5740837 - 03/18/13 02:34 PM

With my C9.25 I find my XW 10 is most useful for planetary. On rare nights of great seeing the XW 7 comes into play.

Seeing would have to be crazy good to be able to use an eyepiece that's less than 7mm in a C9.25 so barlowing a 10mm probably wouldn't be very useful for you on most nights...

I used Plossls before I got into Pentax EPs and they were fine for planetary viewing with a driven scope so you don't have to break the bank if you don't want to.

Rich


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Lane
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Reged: 11/19/07

Loc: Frisco, Texas
Re: your favorite EP for planetary observation (f/10)? new [Re: Sorny]
      #5740854 - 03/18/13 02:46 PM

The view in the 6mm Delos does look more curved to me than the view in the 5mm or the 7mm Pentax XW. However the stars are still sharp all the way across. So I suppose it is not really a problem but it does look different for some reason. The same thing might apply to the 10mm eyepieces.

For light transmission, I have compared my 6mm Ortho to my 6mm Delos and compared my 7mm Ortho to my 7mm Pentax XW just to see if I could find a faint star in one that I could not find in the other, but I was not able to find one. I was also comparing other eyepieces at the same time, two of them being the TMB Planetary 6mm and 7mm, and I was able to see a very faint star in my Delos/Pentax eyepieces that I could find in the TMB eyepieces. So it is definitely possible to have light transmission differences that can be detected.


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Sarkikos
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Re: your favorite EP for planetary observation (f/10)? new [Re: Lane]
      #5741166 - 03/18/13 05:05 PM

This agrees with my experience. When I had TMB Planetaries, the image always seemed darker compared to other eyepieces of the same focal length.

Mike


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Phil Cowell
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Reged: 05/24/07

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Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5741425 - 03/18/13 06:55 PM

12mm and with good seeing 8mm Brandon's. Good color rendition razor sharp on planets. Give them a try in your scope the view speaks for itself. Better than descriptions can.

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johnnyha
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Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5741428 - 03/18/13 06:56 PM

I had a TMB Planetary and the view actually WAS coffee-colored.

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Sarkikos
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Re: your favorite EP for planetary observation (f/10)? new [Re: johnnyha]
      #5741438 - 03/18/13 07:00 PM

They make TV Plossls look like cafe au lait!

Mike


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Rick M.
super member


Reged: 03/16/13

Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5741682 - 03/18/13 08:37 PM

I must say I'm amazed by the wealth of knowledge/experience displayed in this thread!

Rick


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azure1961p
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Re: your favorite EP for planetary observation (f/10)? new [Re: Rick M.]
      #5741710 - 03/18/13 08:48 PM

Just keep in mind a lot of experience and opinion is from many with focal ratios shorter than 10 and thats significant.

Pete


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Rick M.
super member


Reged: 03/16/13

Re: your favorite EP for planetary observation (f/10)? new [Re: azure1961p]
      #5741795 - 03/18/13 09:25 PM

Quote:

Just keep in mind a lot of experience and opinion is from many with focal ratios shorter than 10 and thats significant.

Pete




Good point, Pete.

Rick


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Sarkikos
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Re: your favorite EP for planetary observation (f/10)? new [Re: Rick M.]
      #5741814 - 03/18/13 09:37 PM

The original question was for a favorite high power eyepiece for planet observation in an f/10 scope. My favorite eyepiece for high-power planet viewing in my C6 f/10 SCT is a Pentax XO 5.1 - amazing as that may sound to some observers.

The C6 is my only f/10 scope, but I do have scopes from f/4 to f/13.

Mike


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azure1961p
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Re: your favorite EP for planetary observation (f/10)? new [Re: Sarkikos]
      #5741858 - 03/18/13 09:52 PM

Quote:

The original question was for a favorite high power eyepiece for planet observation in an f/10 scope. My favorite eyepiece for high-power planet viewing in my C6 f/10 SCT is a Pentax XO 5.1 - amazing as that may sound to some observers.

The C6 is my only f/10 scope, but I do have scopes from f/4 to f/13.

Mike




I wasnt referring to you Mike. I trust your results as a rule actually. It is a n issue I've seen rear its head elsewhere enough to think it worthy of mentioning.

Cheers,

Pete


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Scott BeithAdministrator
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Reged: 11/26/03

Loc: Frederick, MD
Re: your favorite EP for planetary observation (f/10)? new [Re: azure1961p]
      #5741972 - 03/18/13 10:38 PM

8mm and 11mm TV Plossls get my vote depending on seeing conditions.

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nevy
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Loc: UK
Re: your favorite EP for planetary observation (f/10)? new [Re: Scott Beith]
      #5742055 - 03/18/13 11:39 PM

In my C11 (F10) , with the usuall yukky seeing on most nights a17 mm tv plossl or 17 ethos is about all it can take but ocassionally when seeing permits , a 13 or 10 can be used , the 10 would give 280x.

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nevy
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Re: your favorite EP for planetary observation (f/10)? new [Re: nevy]
      #5742056 - 03/18/13 11:42 PM

Although things could change since I got a cat cooler , I haven't had the chance to use it yet.

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Sarkikos
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Loc: Suburban Maryland, USA
Re: your favorite EP for planetary observation (f/10)? [Re: azure1961p]
      #5742342 - 03/19/13 06:51 AM

Quote:

Quote:

The original question was for a favorite high power eyepiece for planet observation in an f/10 scope. My favorite eyepiece for high-power planet viewing in my C6 f/10 SCT is a Pentax XO 5.1 - amazing as that may sound to some observers.

The C6 is my only f/10 scope, but I do have scopes from f/4 to f/13.

Mike




I wasnt referring to you Mike. I trust your results as a rule actually. It is a n issue I've seen rear its head elsewhere enough to think it worthy of mentioning.

Cheers,

Pete




Understood. I just wanted to underline the point that it wasn't me you were talking about.


Mike


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