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Equipment Discussions >> Refractors

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doctordub
Pooh-Bah


Reged: 01/11/06

Loc: New Rochelle, New York
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Jan Owen]
      #5480784 - 10/20/12 06:19 PM

Jan,
my eyes accomidate well so I don't notice field curvature in this scope with a 21mm Ethos.
CS
Jonathan


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Jan Owen
Pooh-Bah
*****

Reged: 02/12/06

Loc: Sun City West, Arizona
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: doctordub]
      #5480868 - 10/20/12 07:26 PM

I don't doubt that; but I'm an old fart. My eyes aren't able to deal with accomodation as well as they did back in the last century... So, I'm always looking to see how new scopes do in this regard... We humans, even old ones, manage it better than a camera does. But the older we get, the worse it becomes... Heheheh!!!

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Joe Bergeron]
      #5480895 - 10/20/12 07:48 PM

Joe, I'm sorry if I wasn't clear, but I meant that the Savior intervened and sent bugle-blowing cherubim to intercede on my behalf with a minus violet filter in tow. In fact, given that divine provenance of this particular filter, I fully anticipate that it will be come the object of epic quests for ages to come.

- Jim


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galaxyman
Vendor - Have a Stellar Birthday
*****

Reged: 04/04/05

Loc: Limerick, Pa
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: stevew]
      #5481257 - 10/21/12 12:38 AM

Quote:

Quote:

Here's a dirty little secret - the C6's images are actually a little brighter and on clusters and at like magnification (~88x in each) it goes a little deeper to boot.

Regards,

Jim



Very curious.....




That is interesting, though side by side DSO observing between my ES 6" f/6.5 and a high quality 6" APO showed DSO's (planetary nebula, galaxies, and globs) in image brightness fairly close with the APO presenting (as it should) the better overall view per the review. The owner of the APO (very green observer) thought much of the time the views were nearly identical.

The CAS seasoned observers that were there saw what I was seeing. The APO as the superior scope, though at nearly 10 times the cost it better be.

I guess my point would be that a C6 would not be the equal of a high end 6" APO in image brightness. The other possibility is my particular ES 6" is a bit better than Jim's AT 6" example?

From very good dark sites my current 6" refractor has caught galaxies near 13.5 mag., so a good 6" achro can go deep when pushed.

Would like to hear from other owners of the AT 6" f/5.9 on pushing the scope on DSO's as in planetary nebula and galaxies.



Clear Dark Skies


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: galaxyman]
      #5481647 - 10/21/12 09:53 AM

Got a chance to view Jupiter last night with the AR152 and a Baader Semi-Apo filter. I was at our club's dark site and the guy that set up next to me had an EON. All I can say is that with a good CA filter these scopes can indeed be used as planetary scopes. The owner of the EON actually said he thought he was seeing more detail on Jupiter in the AR152. I disagreed though. While it did look much much better than I had ever hoped for in the AR152, the EON was putting up a more contrasty image with richer colors. There was one smaller thin belt south of the main SEB that I could see a little bit easier in the EON. I could see the same belt in the AR152, but it was a little more washed out looking. However, there were a few festoons in the NEB and SEB that were easier to see in the AR152. The color in the AR152 was more of a cooler whitish color while the EON showed nice rich warm color tones. The purple fringe was there in the AR152, even with the semi-apo filter, but it did not intrude onto the planet's disk to my eye.

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: galaxyman]
      #5481715 - 10/21/12 10:47 AM

Yeah. Or it could be that I didn't roll out the C6 until after I got home, and the targets compared were higher and therefore embedded in less atmospheric glow, as I suggested earlier when asked about the apparent brightness difference mentioned originally.

I will put them side-by-side at some point, and throw in a C8 ($799 new as an OTA) for giggles, too. The optics on the AT152 aren't its problem. They are quite good, also as I reported in the original post. It's the physics that limit its potential, I suspect, as it is with any scope design really.

Regards,

Jim

Edited by jrbarnett (10/21/12 10:48 AM)


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galaxyman
Vendor - Have a Stellar Birthday
*****

Reged: 04/04/05

Loc: Limerick, Pa
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: jrbarnett]
      #5481868 - 10/21/12 12:21 PM

Quote:

Yeah. Or it could be that I didn't roll out the C6 until after I got home, and the targets compared were higher and therefore embedded in less atmospheric glow, as I suggested earlier when asked about the apparent brightness difference mentioned originally.

I will put them side-by-side at some point, and throw in a C8 ($799 new as an OTA) for giggles, too. The optics on the AT152 aren't its problem. They are quite good, also as I reported in the original post. It's the physics that limit its potential, I suspect, as it is with any scope design really.

Regards,

Jim




Hi Jim

Understand.

I'm guessing an estimate of overall light loss in the C6 is around 25% with coatings (though good), CO, and slight loss of aperture (150mm to 152mm).

I do think for the money it's a crapshoot, and though for some they like the AT over the ES with the shorter 6" achros. I personally wouldn't trade my particular ES 6" for the AT 6", for cost it wouldn't make sense, and my ES just may be a particular good one. Hard to say without seeing through say five or more for comparison. We do have another in the CAS, but we haven't had them side by side.

I will admit that down the road I will upgrade to a 6" ED (like the new APM). The other two achros ( APM 8" and the Celestron 4") are staying in my collection, with the 8" for certain


Clear Dark Skies


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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nicknacknock
professor emeritus
*****

Reged: 02/20/12

Loc: In a galaxy far far away...
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: galaxyman]
      #5484670 - 10/23/12 01:17 AM Attachment (64 downloads)

This has been a very interesting thread, given that I am receiving day after tomorrow my Teleskop Service 152mm (another variant of the Kumming Optics unit).

I am on a strict diet of DSO hence not worried about chromatic aberrations.

Jim, I read many reviews of the 152mm scope on this forum and yours appears to be the least biased of all, highlighting both the positive and negative attributes of this scope.

To claim (as done on other posts) that a Fraunhofer Achromat is color free on planets and moon is pushing into the realm of SF.

An extract from “Choosing and using a Refracting Telescope” by Dr Neil English (Part of Sir Patrick Moore’s Practical Astronomy Series)sums it up pretty nicely in 3 short paragraphs why color will always be evident in an achro:

"Modern achromatic doublet objectives are designed to bring two precise wavelengths (colors) of light to a common focus – red (656 nm corresponding to the Fraunhofer C spectral line) and blue green (486 nm corresponding to the Fraunhofer F spectral line).

In a contemporary C-F corrected achromat, colors lying outside this range of wavelengths (called the C-F focus) remain unfocused. These include deep red at one end of the spectrum and violet at the other. But that’s not a big problem. Fortunately, the human eye is not terribly sensitive to either of these radiations, and for the most part the position of C-F focus imparts a very natural color to the image.

In an ideal objective, all wavelengths between the C (red) and F (blue-green) Fraunhofer lines ought to be brought to a single focus, but in practice there is some color spread in the final image. This is what opticians call secondary spectrum and is the origin of the false color (chromatic aberration) seen in almost all achromatic refractors".

But, for my meatetarian diet of DSO, I say bring it on!

For those interested, I attach the bench test of the scope (Ronchi & diffraction rings).


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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Mike4242]
      #5484927 - 10/23/12 09:22 AM

Quote:

Got a chance to view Jupiter last night with the AR152 and a Baader Semi-Apo filter. I was at our club's dark site and the guy that set up next to me had an EON. All I can say is that with a good CA filter these scopes can indeed be used as planetary scopes. The owner of the EON actually said he thought he was seeing more detail on Jupiter in the AR152. I disagreed though. While it did look much much better than I had ever hoped for in the AR152, the EON was putting up a more contrasty image with richer colors. There was one smaller thin belt south of the main SEB that I could see a little bit easier in the EON. I could see the same belt in the AR152, but it was a little more washed out looking. However, there were a few festoons in the NEB and SEB that were easier to see in the AR152. The color in the AR152 was more of a cooler whitish color while the EON showed nice rich warm color tones. The purple fringe was there in the AR152, even with the semi-apo filter, but it did not intrude onto the planet's disk to my eye.




About the purple fringe 'not intruding onto the planet's disk': The purple fringe does intrude and that is whole problem. Every part of the disk is producing its own little diffraction pattern, complete with purple fringe. The diffraction patterns collectively form the image you see and the purple is right there with them. The purple is only bright enough to see against a black background so the planet seems to be 'surrounded' by a purple ring when, in fact, it is completely covered with it, reducing contrast.

Dave


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dlapoint
scholastic sledgehammer


Reged: 08/18/03

Loc: Moncton NB Canada
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Cotts]
      #5485009 - 10/23/12 10:26 AM

excellent review. I was wondering how the ca compared to a 5" f6.5 ar?

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: dlapoint]
      #5485068 - 10/23/12 11:09 AM

I have me a good buddy, CNer cuzimthedad, who has an Antares 6" f/6.5. Mayhaps he and I will get the Astrotelescopes f/5.9 and Antares f/6.5 out at the same time, and see for ourselves how the two compare.

I wanted an excuse to go bug Dan and borrow his field on December 21st, anyway, weather permitting. It's only fitting that I use a big, fast crown & flint achro to observe the approaching cosmic doom on Mayan Apocalypse night. An odd scope on an odd night. But then again, we are the "Off Fisher Lane IRREGULARS" after all.

Regards,

Jim


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Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: dlapoint]
      #5485244 - 10/23/12 01:02 PM

Quote:

About the purple fringe 'not intruding onto the planet's disk': The purple fringe does intrude and that is whole problem.




Good point. I'm sure it's reducing the contrast, but to the eye the planet itself doesn't look purple, which would be really annoying. I've seen photos of Jupiter through achros and the planet itself looks purple in the photos.

However, even though the CA does reduce contrast, and you may be missing some planetary detail in the achro, that doesn't mean you can't enjoy what is visible. If you're primary interest is seeing the maximum amount of low contrast planetary detail, then an ED or apo is definitely the way to go. But I don't think it makes sense to say flat out that these scopes can't produce nice views of planets. Not apo nice, but not that bad either.

After reading all of the forum posts about how these scopes are terrible at planets, I expected a horrible view when I looked through the EP, but was greeted instead by a pretty darn nice view of Jupiter.


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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Cotts]
      #5485387 - 10/23/12 02:23 PM

Quote:

About the purple fringe 'not intruding onto the planet's disk': The purple fringe does intrude and that is whole problem. Every part of the disk is producing its own little diffraction pattern, complete with purple fringe. The diffraction patterns collectively form the image you see and the purple is right there with them. The purple is only bright enough to see against a black background so the planet seems to be 'surrounded' by a purple ring when, in fact, it is completely covered with it, reducing contrast.




a little context is perhaps needed here. neil is correct that in normal situations the eye is relatively insensitive to spectral wavelengths below ~460nm. however light in that region is very potent. the filtering is mostly due to the atmosphere and yellow pigmentation in the lens and retina, yet violet light has over 30 times the impact on color perception as an an equal quantity (irradiance) of red or green light. and violet or purple mixtures are among the most chromatic (saturated, intense) colors we experience -- they "jump out" far more than a yellow or green hue. it is deceptive to downplay the importance of violet light in color vision.

in addition, both lightness contrast and edge detail are perceived through the R and G cones exclusively. to the extent that planetary detail is perceptible at all, the B cones have no part in it. since violet light is not focused on the retina when a yellow light image is in focus, it seems to detach from and hover around the in focus image. this effect is just as distracting when seen against a bright background, for example by looking at the sidewalk through a prism. and note that the eye adds its own violet defocus to the defocus native to an achromat.

light wavelengths outside the sensitivity range of a receptor cannot "obscure" the receptor response, no more than xrays or microwaves can obscure your perception of sunlight. however the R and G cones respond to wavelengths across almost the entire visible spectrum, so defocus in extreme wavelengths would have some (very small) effect on image clarity, separate from a perceptible "violet" tint. this is different from the question whether a defocused violet tint is perceptible at all and whether it is distracting.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: drollere]
      #5485700 - 10/23/12 05:20 PM

Great points, Bruce.

There's no coincidence that the Emperors of Rome chose purple for their state raiment (the "trabea"). Needless to say, they wanted to be noticed, no "shrinking violets" that lot (yeah, sorry, bad pun).

- Jim


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doctordub
Pooh-Bah


Reged: 01/11/06

Loc: New Rochelle, New York
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: nicknacknock]
      #5491629 - 10/27/12 12:22 PM

Quote:

This has been a very interesting thread, given that I am receiving day after tomorrow my Teleskop Service 152mm (another variant of the Kumming Optics unit).

I am on a strict diet of DSO hence not worried about chromatic aberrations.

Jim, I read many reviews of the 152mm scope on this forum and yours appears to be the least biased of all, highlighting both the positive and negative attributes of this scope.

To claim (as done on other posts) that a Fraunhofer Achromat is color free on planets and moon is pushing into the realm of SF.

An extract from “Choosing and using a Refracting Telescope” by Dr Neil English (Part of Sir Patrick Moore’s Practical Astronomy Series)sums it up pretty nicely in 3 short paragraphs why color will always be evident in an achro:

"Modern achromatic doublet objectives are designed to bring two precise wavelengths (colors) of light to a common focus – red (656 nm corresponding to the Fraunhofer C spectral line) and blue green (486 nm corresponding to the Fraunhofer F spectral line).

In a contemporary C-F corrected achromat, colors lying outside this range of wavelengths (called the C-F focus) remain unfocused. These include deep red at one end of the spectrum and violet at the other. But that’s not a big problem. Fortunately, the human eye is not terribly sensitive to either of these radiations, and for the most part the position of C-F focus imparts a very natural color to the image.

In an ideal objective, all wavelengths between the C (red) and F (blue-green) Fraunhofer lines ought to be brought to a single focus, but in practice there is some color spread in the final image. This is what opticians call secondary spectrum and is the origin of the false color (chromatic aberration) seen in almost all achromatic refractors".

But, for my meatetarian diet of DSO, I say bring it on!

For those interested, I attach the bench test of the scope (Ronchi & diffraction rings).




I would love to see that done with a green filter or OIII
CS
Jonathan


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stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: nicknacknock]
      #5491806 - 10/27/12 02:53 PM

Nicos, thanks for showing the test for your scope.
I'm not sure why anyone would think a large fast achromat would not have any chromatic aberration.
However your test does show the real strength of this scope, a smooth and well polished figure that helps it produce the sharp images that most owners rave about.

Steve


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doctordub
Pooh-Bah


Reged: 01/11/06

Loc: New Rochelle, New York
Re: Overdue First Light: Astrotelescopes 152 f/5.9 new [Re: Cotts]
      #5492804 - 10/28/12 09:38 AM

Quote:

Quote:

Got a chance to view Jupiter last night with the AR152 and a Baader Semi-Apo filter. I was at our club's dark site and the guy that set up next to me had an EON. All I can say is that with a good CA filter these scopes can indeed be used as planetary scopes. The owner of the EON actually said he thought he was seeing more detail on Jupiter in the AR152. I disagreed though. While it did look much much better than I had ever hoped for in the AR152, the EON was putting up a more contrasty image with richer colors. There was one smaller thin belt south of the main SEB that I could see a little bit easier in the EON. I could see the same belt in the AR152, but it was a little more washed out looking. However, there were a few festoons in the NEB and SEB that were easier to see in the AR152. The color in the AR152 was more of a cooler whitish color while the EON showed nice rich warm color tones. The purple fringe was there in the AR152, even with the semi-apo filter, but it did not intrude onto the planet's disk to my eye.




About the purple fringe 'not intruding onto the planet's disk': The purple fringe does intrude and that is whole problem. Every part of the disk is producing its own little diffraction pattern, complete with purple fringe. The diffraction patterns collectively form the image you see and the purple is right there with them. The purple is only bright enough to see against a black background so the planet seems to be 'surrounded' by a purple ring when, in fact, it is completely covered with it, reducing contrast.

Dave




I agree Dave, which is why I believe the scope snaps to focun with my Chromacor.
CS
Jonathan


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thesubwaypusher
scholastic sledgehammer
*****

Reged: 07/08/04

Loc: New York City
Re: Overdue First Light: Astrotelescopes 152 f/5.9 [Re: dakota]
      #5494835 - 10/29/12 03:28 PM

I still maintain that this is a fantastic telescope for the money.

Enjoy Hans!


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Jan Owen
Pooh-Bah
*****

Reged: 02/12/06

Loc: Sun City West, Arizona
Re: Overdue First Light: Astrotelescopes 152 f/5.9 [Re: thesubwaypusher]
      #5494847 - 10/29/12 03:34 PM

Hope you're riding out the storm (Sandy) safely... Take care!!!

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Jan Owen
Pooh-Bah
*****

Reged: 02/12/06

Loc: Sun City West, Arizona
Re: Overdue First Light: Astrotelescopes 152 f/5.9 [Re: doctordub]
      #5494852 - 10/29/12 03:36 PM

Hope you're safe & on relatively high ground out of harm's way, while you ride out Sandy!!! Take care!!!

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