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Equipment Discussions >> Refractors

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bratislav
sage


Reged: 09/07/06

Re: New Ed Ting review of the AP 175 new [Re: vahe]
      #5874578 - 05/20/13 08:20 PM

Quote:

Not much substance in that review, Ed has written more in depth reviews in the past.





Star testing a refractor (even APO) using extrafocal images in polychromatic light is a monumental waste of time.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: New Ed Ting review of the AP 175 new [Re: Sgt]
      #5874981 - 05/20/13 11:45 PM

That may well be, but I don't think there are any amateur triplets in existence large enough to put that proposition to the test.

- Jim


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clintwhitman
Caveman
*****

Reged: 01/01/07

Loc: CALI SoEasyACavemanCanSlewIt
Re: New Ed Ting review of the AP 175 new [Re: jrbarnett]
      #5875213 - 05/21/13 06:46 AM

Jim I agree with your "refractor being the best"!
Even though it happens only once in awhile. With the right seeing and the 228mm AP triplet refractor. Once you can break 600 power it is a game changer for viewing any of the planets!
I did like Ed's commentary of the way everything gets quiet and you start to breath deeply.
The 4 views I remember most have all been through refractors. Knee buckling views at 5/5 seeing
Jupiter in Robert Provins 7" AP at 500x
Jupiter in John Pons 10" Zeiss, Ganymede Transit at 650 Xs
Mars in The Pearl 9" AP at 720 Xs The Best, held for 1 hour.
Saturn in the Pearl at 750 Xs

(aveman


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t.r.
Post Laureate
*****

Reged: 02/14/08

Loc: Upstate NY
Re: New Ed Ting review of the AP 175 new [Re: clintwhitman]
      #5875273 - 05/21/13 07:57 AM

Ya know, the seeing really can't be overstated as the limiting factor for planetary performance regardless of unobstructed aperture used. I have seen for myself, in average seeing a couple of times, where a 5" apo did as well as a 7" apo in side-by-side comparisons, where only the brightness of the planet differentiated the view. Having viewed through 3-7" apos, my most memorable view came from a 4" Genesis refractor while in Seoul, S. Korea. Known for its smog, this too means very stable seeing in the summers there and I had two fantastic sessions, one while viewing intricate micro detail on Jupiter at 260x in the Genesis (it wanted more magnification) and the other while viewing Saturn at opposition in an 8" SCT no less, at 325x...the rings looked grooved like a vinyl record!

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JimP
Pooh-Bah


Reged: 04/22/03

Loc: South Carolina
Re: New Ed Ting review of the AP 175 new [Re: Darren Drake]
      #5875355 - 05/21/13 09:12 AM

Excellent report. Gorgeous telescope. I'd love to have one but, for the time being, I'll settle for my AP 130 GT.

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Astrojensen
Post Laureate
*****

Reged: 10/05/08

Loc: Bornholm, Denmark
Re: New Ed Ting review of the AP 175 new [Re: t.r.]
      #5875368 - 05/21/13 09:25 AM

Totally true about the seeing. Even in a very small telescope, such as a 2", seeing is the limiting factor from most locations. The images may look relatively sharp on most nights in such a small aperture, but when you look closely, most of the time the micro detail suffers once you get above 50x (not 50x per inch, but just 50x!) and I've had evenings where the image looked GREAT at 50x in my 63mm Zeiss, but once I went to 84x, enough magnification to reveal the smallest lunar/planetary detail the scope can resolve, it has been clear that the seeing was clearly insuficcient to reveal the finest detail.

But once in a while, you get a superb night and the small scope reveal things you never dreamed it could show, suddenly making it crystal clear that even with a 2" scope, seeing is extremely important. And it only gets more important as the aperture increases.

In my country, that super-crisp view of the planets at high magnification is an extremely rare occurrence, but I've had a few moments over the years, sights that remain etched into my brain. Sights that makes you want to crawl into your telescope and live there forever.


Clear skies!
Thomas, Denmark


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: New Ed Ting review of the AP 175 new [Re: jrbarnett]
      #5875814 - 05/21/13 12:50 PM

Quote:

Ring detail is highly seeing dependent.
- Jim




And seeing is highly altitude dependent. With Saturn this low for northern latitude observers, we can't expect the views we had in the past. I can't today get the views with my 7" apo that I got easily a few years ago with my C9.25 when Saturn was high in the sky. I struggle to go much above 300x on Saturn with the apo when I routinely used 450x with the C9.25.

Tanveer.


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: New Ed Ting review of the AP 175 new [Re: Kent10]
      #5875846 - 05/21/13 01:02 PM

Quote:

Speaking of planetary performance, I have viewed Saturn each night and it is very nice. I can easily see the Cassini Division and various shades of yellow on the planet. I have only viewed from my neighborhood back yard and so the seeing may not always be the best with all the homes. I also think I see the moons quite easily. I keep wondering how much more there is to see through my Tec 160Fl if I do get better seeing, perhaps I should take the scope out of the city. What more can I expect to see with a 6.3" refractor? I realize I might have to be patient and wait for seeing to clear and I have only viewed for a few minutes at a time both mono and in a bino. Thanks.




I've found that the best seeing often occurs right after sunset or in the early morning hours. My best planetary views have been had during these periods. It pays off to rise early and take a peek. As an added bonus, the scope is thoroughly cooled by then (left covered under a tarp to protect from the dew). The early morning, of course, works better before the planet is at opposition.

One hard target to spot is the polar hexagon. I haven't heard anybody report seeing it so far. I've seen the bluish/gray polar cap but couldn't perceive any hexagonal shape. I suspect it will take something like 10/10 seeing with a fairly large aperture to make out unambiguously.

Planetary observation is a game of patience. Try sketching over an hour and so and see how much more you'll notice.


Tanveer.


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: New Ed Ting review of the AP 175 new [Re: Kent10]
      #5875851 - 05/21/13 01:05 PM

Quote:

It was easy then but later I could not see them at all. Same with the Plato craterlets. Nearer full moon I could easily see 4 but the last couple of nights I can only barely make out something and that is because I know where to look. It should get easier in the coming days I think.




The Plato craterlets are hard to spot at any time except full lunar noon and morning/sunset. But even a 4" scope will show you four in good seeing. The Plato area is one of my favorites - try observing Mons Teneriffe near Plato as well. It's rewarding in a variety of illumination angles.

Tanveer.


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Kent10
Pooh-Bah
*****

Reged: 05/08/12

Re: New Ed Ting review of the AP 175 new [Re: TG]
      #5875863 - 05/21/13 01:10 PM

Quote:

Quote:

It was easy then but later I could not see them at all. Same with the Plato craterlets. Nearer full moon I could easily see 4 but the last couple of nights I can only barely make out something and that is because I know where to look. It should get easier in the coming days I think.




The Plato craterlets are hard to spot at any time except full lunar noon and morning/sunset. But even a 4" scope will show you four in good seeing. The Plato area is one of my favorites - try observing Mons Teneriffe near Plato as well. It's rewarding in a variety of illumination angles.

Tanveer.




Yes last night I could just barely see the 4. It was tough. It should be easier tonight and the coming days. Thanks for your recommendation of Mons Teneriffe! Will take a look.

Edited by Kent10 (05/21/13 01:31 PM)


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Kent10
Pooh-Bah
*****

Reged: 05/08/12

Re: New Ed Ting review of the AP 175 new [Re: TG]
      #5875966 - 05/21/13 01:44 PM

Quote:



I've found that the best seeing often occurs right after sunset or in the early morning hours. My best planetary views have been had during these periods. It pays off to rise early and take a peek. As an added bonus, the scope is thoroughly cooled by then (left covered under a tarp to protect from the dew). The early morning, of course, works better before the planet is at opposition.

One hard target to spot is the polar hexagon. I haven't heard anybody report seeing it so far. I've seen the bluish/gray polar cap but couldn't perceive any hexagonal shape. I suspect it will take something like 10/10 seeing with a fairly large aperture to make out unambiguously.

Planetary observation is a game of patience. Try sketching over an hour and so and see how much more you'll notice.


Tanveer.




Thanks for the suggestions Tanveer. Once I did leave my scope out overnight, covered, and in the morning my objective had frost on the inside. I didn't know at the time if it was frost or an oil leak in my Tec. So I sent it to Yuri and I guess it eventually melted and was frost because he saw nothing wrong. I must have been very unlucky because others have left their scopes out without frost but I am still a little scared to try it again.

Edited by Kent10 (05/21/13 02:06 PM)


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Darren Drake
Carpal Tunnel
*****

Reged: 10/09/02

Loc: Chicagoland
Re: New Ed Ting review of the AP 175 new [Re: TG]
      #5875972 - 05/21/13 01:45 PM

Quote:

Quote:

Ring detail is highly seeing dependent.
- Jim




And seeing is highly altitude dependent. With Saturn this low for northern latitude observers, we can't expect the views we had in the past. I can't today get the views with my 7" apo that I got easily a few years ago with my C9.25 when Saturn was high in the sky. I struggle to go much above 300x on Saturn with the apo when I routinely used 450x with the C9.25.

Tanveer.




Yes this is generally true but not always. Damian Peach took this when Saturn was only 38 degrees up.

http://www.damianpeach.com/sat1213/2013_04_20rgb_dp.jpg


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JimP
Pooh-Bah


Reged: 04/22/03

Loc: South Carolina
Re: New Ed Ting review of the AP 175 new [Re: Sgt]
      #5876211 - 05/21/13 03:37 PM

Quote:

I have read that beyond a certain size, the thermal inertia of a big slab of glass in a triplet become difficult to manage and become a limiter of performance. What is the experience of the big apo people?




I have TMB 8" F/9 LZOS and TMB 10" F/9 LZOS triplet apos. I have had no significant problems with cool-down with either scope. In the summer the scopes are in observatories with air conditioning. That keeps the scopes from overheating on hot summer days. I open the observatories at sunset. When the seeing is good here the temperature falls one degree or less per hour. I have had many nights of good seeing where the temperature did not change over 2-3 hours. Neither scope has any problems keeping up with that kind of change in temperature.


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StarDust1
super member


Reged: 08/21/12

Re: New Ed Ting review of the AP 175 new [Re: Astrojensen]
      #5876683 - 05/21/13 06:49 PM

Quote:

that super-crisp view of the planets at high magnification is an extremely rare occurrence, but I've had a few moments over the years, sights that remain etched into my brain. Sights that makes you want to crawl into your telescope and live there forever.


Clear skies!
Thomas, Denmark





Thomas, I have had the same experience as you. I still remember the views that I had one night on Saturn, it was rock solid, in the Mewlon 210 at more than 500x. I just wish for one of those moments on Jupiter, then I'm a happy camper


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ValeryD
Vendor (Aries)
*****

Reged: 11/26/05

Loc: Kherson, Ukraine.
Re: New Ed Ting review of the AP 175 new [Re: t.r.]
      #5877273 - 05/22/13 01:10 AM

Quote:

Well, even according to TEC (Yuri) and at least one CN'er, the difference on planetary between the TEC140 and TEC160 came down to slightly sharper clarity of Cassini's...and not much else.




I think such observations were done at moderate seeing at best. When I compared the views of Saturn between 150mm APO and 180mm APO during very good seeing, the difference was PRINCIPAL.
In a bigger APO I saw all details much better defined, sharper, larger with better color rendition and I saw more details.
High quality aperture rules. Always.


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johnnyha
Postmaster
*****

Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: New Ed Ting review of the AP 175 new [Re: Kent10]
      #5877281 - 05/22/13 01:18 AM

Quote:

True. I am just not sure yet what really good seeing is I think.


Sorry Kent I meant the Ed Ting review, its difficult to judge a scope with so-so seeing (not that there's any doubt about the quality of the new AP175s). Sounds like there was a good image of Saturn nonetheless.

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mgwhittle
Pooh-Bah
*****

Reged: 08/24/11

Loc: Chattanooga, TN
Re: New Ed Ting review of the AP 175 new [Re: johnnyha]
      #5878229 - 05/22/13 02:42 PM

From what I can see with my 175EDF, is that it is less affected by seeing than other scopes I have owned. I suspect that it's because it's concentrating so much energy into the airy disk and not throwing much out to the diffraction rings. Instead of a blob that dances around when the seeing is bad, you can see the airy disk dancing around, allowing me to split doubles that would only be a mess in other telescopes I own or have owned.

As far as the comments that the magic of this scope is related to imaging more than visual, I disagree. Visually, the contrast is so strong in the 175EDF, I have been able to detect more faint galaxies this spring with it than my C11 set up right next to it under my light polluted skies.


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Paul G
Post Laureate
*****

Reged: 05/08/03

Loc: Freedonia
Re: New Ed Ting review of the AP 175 new [Re: mgwhittle]
      #5879047 - 05/22/13 08:48 PM

Quote:

From what I can see with my 175EDF, is that it is less affected by seeing than other scopes I have owned. I suspect that it's because it's concentrating so much energy into the airy disk and not throwing much out to the diffraction rings. Instead of a blob that dances around when the seeing is bad, you can see the airy disk dancing around, allowing me to split doubles that would only be a mess in other telescopes I own or have owned.

As far as the comments that the magic of this scope is related to imaging more than visual, I disagree. Visually, the contrast is so strong in the 175EDF, I have been able to detect more faint galaxies this spring with it than my C11 set up right next to it under my light polluted skies.




The superb contrast is more important for visual use than it is for imaging since one can boost contrast during image processing. Add to that the fact that the objective is nulled at peak visual wavelength and you have a great visual scope.


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