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C14,versus a 10" apo... What will you do?

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#1 azure1961p

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Posted 19 March 2013 - 02:20 PM

Hypothetically: you are an observer of deepsky galaxies and such as much as mars and the moon. Even more amazingly you are given a choice (oh hell it s free) of a ten inch apo or c14 - which would you pick?

Because the planetary is at least good in a c14 and its got the extra aperture for galaxies, I'd opt for a 14.

Am I wrong or can the apo wver match the 14 on galaxies. Contrast only goes so far.

Pete

#2 Whichwayisnorth

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Posted 19 March 2013 - 02:26 PM


A ten inch APO would be so expensive that I would get that one and sell it.

#3 GlennLeDrew

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Posted 19 March 2013 - 02:33 PM

If someone were offering for free either a C14 (Edge, I'm assuming) or a 10" apo, I'd choose the former. A lot easier to make an observatory for! And the extra aperture is a boon.

#4 saemark30

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Posted 19 March 2013 - 02:54 PM

If someone was offering a C14 or a 10" apo for free, I would take the 10" APO until I needed the money and then sell it.
I could then buy 10 to 100 C14's or go with a 18" dob and have change for a 180mm APO.
Heck it depends if you just want to see Messiers or NGC stuff.

#5 Darren Drake

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Posted 19 March 2013 - 02:58 PM

Deep sky obviously goes to the C14 with almost twice the light. Lunar/planetary is close but the seeing issues favor the apo. Resolution would be better in the C14 but the contrast on small features in the apo about makes up for it. This makes lunar planetary about a draw (Assuming the C14 has very good optics.) Overall winner is the C14.

#6 WadeH237

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Posted 19 March 2013 - 03:06 PM

I already have a C14, so I would go for the APO. Mounting could be an issue, but i suspect that my AP1600 could probably even carry a 10" APO.

#7 bilgebay

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Posted 19 March 2013 - 03:08 PM

I would get the 10" APO and sell it. Then I would invest the money on a remote observatory and all the equipment needed for that.

#8 Paul G

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Posted 19 March 2013 - 03:09 PM

I would get the 10" APO and sell it. Then I would invest the money on a remote observatory and all the equipment needed for that.


:)

#9 MikeBOKC

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Posted 19 March 2013 - 05:35 PM

Well a ten inch APO is sort of a fantasy isn't it? I am sure some exist and are permanently mounted in professional or university observatories, but I doubt if there are more than a few dozen worldwide something like a 60 inch Newt. The cost would be stratospheric likely $20k or more, and the mounting requirement would be equally prohibitive as to space and cost. A c-14 however actually exists and is achievable. However, given the option of either at no cost, I'd probably take the 10 inch APO, set it up and charge five bucks a head for the hundreds of CN members who would make weekly pilgrimages to view and caress it and buy myself a couple of C-14s to play with in the adjoining field. Then I'd list it in the classifieds and watch 10,000 heads explode . . .

#10 Jared

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Posted 19 March 2013 - 05:42 PM

Hypothetically: you are an observer of deepsky galaxies and such as much as mars and the moon. Even more amazingly you are given a choice (oh hell it s free) of a ten inch apo or c14 - which would you pick?

Because the planetary is at least good in a c14 and its got the extra aperture for galaxies, I'd opt for a 14.

Am I wrong or can the apo wver match the 14 on galaxies. Contrast only goes so far.

Pete


You're asking this question on the Cats and Casses forum... I hope you're not surprised by the answers!

By my calculations, the C14 would have an advantage of roughly 25% in actual image brightness (throughput) , once you account for light loss from central obstruction, typical reflectivity for modern mirrors (with enhanced over coatings), etc.. That's a real advantage, but not anything like the 2x you'd expect from just comparing straight apertures.

If I assume a 90% Strehl for the Edge and a 95% for the refractor, then the MTF curves at critical frequencies would be almost identical for the two with a slight edge to the C14.

I wouldn't want to have to figure out a mount for the refractor, and I believe it can be difficult to get a triplet above 8" or so to cool fully if you don't live in Florida. The same can be said for a C14, of course... Obviously, the C14 is the more practical scope in terms of ease of mounting and ease of use. But there is still something special about big refractors. If I didn't have to worry about an observatory or about mounting it, I'd go with the 10" apochromat.

#11 highfnum

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Posted 19 March 2013 - 06:02 PM

any specific examples of 10 inch apo

#12 BKBrown

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Posted 19 March 2013 - 06:22 PM

If I'm not picking up the tab, the 10" Apo...the APM/LZOS 254mm f/9 is my "dream" scope". But at 42,773 euros ($55,177 US) it is unattainable by mere mortals. Not only the cost of the scope, but you'll spend a hefty percentage of that price getting a first rate mount and accessories; and of course it cries out for an observatory. So even if you got the scope free, you'll be dropping 50k for other stuff. At least I could use my TEC 140 as a wide field finder :grin:

Clear Skies,
Brian

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#13 PatHolland

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Posted 19 March 2013 - 09:11 PM

If I bought a 10" APO, I would need to take out a loan for my divorce attorney. My APO and I would most likely have to get an apartment somewhere - but at least we'd be together. :grin:

#14 Scott Beith

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Posted 19 March 2013 - 09:35 PM

10" apo all the way!

#15 David Pavlich

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Posted 19 March 2013 - 09:53 PM

10" apo all the way!


Well, duh!! :lol:

David

#16 Scott Beith

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Posted 19 March 2013 - 09:59 PM

:lol: :grin:

#17 David Pavlich

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Posted 19 March 2013 - 10:06 PM

First, you're comparing an off-the-shelf SC to a hand built refractor. This is a common comparison, one I could never understand.

Now, let's get Mike Lockwood to make us a hand figured primary and secondary mirror to the very best of his ability...maybe Mike's best mirrors ever! And we'll also get Mike to figure the corrector as closely matched to these mirrors as his prolific skills will allow.

Now, let's make sure that the OTA has active cooling. And let's make sure that the tolerances of the mirror riding on the baffle tube is incredibly tight, to the point that the lube is specially formulated so that it can be very slippery but the amount of lube is only a few microns. And the focusing mechanism is extremely rigid to limit image shift to virtually nothing.

Ok...now we would have a fair comparison in optics, mechanics and price. :grin:

David

#18 Cotts

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Posted 19 March 2013 - 10:29 PM

Not to gloat or anything but my 16" f/5 Teeter/Zambuto at a 'mere' $7K would be a better than either of those scopes for resolution, contrast and light gathering (taken together). The 10" would have better contrast but with noticeably less resolution and light gathering. The 14" SCT would be closer but still not quite the equal of the 16".

Now, if they were giving them away, I'd still take the 10" APO - there is still that refractor 'mystique'..

Dave

#19 Stelios

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Posted 20 March 2013 - 01:01 AM

The question should have precluded the possibility of resale, as obviously the much more expensive APO makes more sense then. But if the scope was non-transferable, even if it came gifted with an appropriate mount, I think the C14 would win unless one had or could build an observatory in a dark site. Transporting a 10" APO and appropriate mount seems a daunting undertaking, even for non-girly men.

#20 Erik Bakker

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Posted 20 March 2013 - 03:11 AM

Hi Pete,

I have observed for hundreds of nights with a 10.5 " Alvan Clark for over a decade. A mere doublet operating at f/15 and like a big dob it requires a ladder :grin:

Include is a picture of this scope, so you get an idea of the size, mount and housing such a scope needs.

The images were very nice, but no match for my MW 16" f/5. In sizes larger than around 7", refractors loose some of the advantages we all know from smaller sizes. They can take a very long time to cool for example, especially in (airspaced) triplets. If one wants superb images from a large scope, a high-end dob with a small CO and proper thermal management is a great choice. Or a ditto Newt, Mak-Newt. And even well designed and manufactured MCT's or SCT's from a high-end maker deliver great images.

But money, housing etc. no object, a 10" f/15 apo will do better than any 14" SCT including a C14. The aperture difference is just too small.

You can do a scaled-down experiment with some more easily obtainable instruments: a 90mm f/9 Vixen fluorite or 92 mm f/7 A-P Stowaway vs a Celestron C5.

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#21 WadeH237

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Posted 20 March 2013 - 07:30 AM

The view in the eyepiece is the combination of many factors.

APO refractors between 4" and 6" seem to be a sweet spot in that they don't really have anything that the user needs to do to make them perform. They cool quickly and are permanently collimated. Plus, they present phenomenal wide field views and have amazing contrast. There is truly something special about looking through them.

But over 6", they quickly start to get big and heavy. A couple of weeks ago, Roland Christen posted an interesting discussion on the largest practical size for APO refractors using current design technology. In particular, he said that for a 10" APO triplet, it was impossible to get visual colors to come to the same focus, while also correcting for spherical aberration. This discussion was in the context of why a 10" Mak-Cass was putting up better views side-by-side than a 10" APO at a particular star party.

In larger sizes, reflecting telescopes are really the way to go. Even a mass produced SCT can put up stunning views when it's at temperature equilibrium and properly collimated. At a star party last year, I was observing through my C14 early in the night. When I was ready to walk the telescope field, I left it pointed at M13 with a 31mm Nagler. The next day, a camper near me said that while I was gone, a short line formed at my C14. Some of the people looking through it made comments that it put up the best view of that object at the event - even better than the large dobs on the field.

But back to the question at hand, if I were looking for a telescope to use every day, I'd take the C14. If I were looking for a seriously cool scope to bring out to a star party, I would take the 10" APO. The question would be a lot harder if I were forced to choose between a C14 and something like an AP-130 or AP-175.

#22 mgwhittle

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Posted 21 March 2013 - 07:15 PM

Having a 175mm triplet with no prior experience with APOs this size I was surprised at the length of time required for it to cool down for best performance. Going from 70 indoors to 50-55 outdoors with falling temperatures this winter has required cool down times exceeding an hour, closer to two hours some nights. My unvented C11 easily beats it on cool down times by a factor of 2. In addition, anything larger and I would need help getting it up on the mount.

Having said that, once up in the rings and cooled down......WHOA! The purity of the image is outstanding. Yeah, I'll take a 10 inch APO.

#23 jrbarnett

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Posted 21 March 2013 - 09:08 PM

10" unobstructed FTW!

But I'd want both. I'd center punch the C-14. Well, six or seven of them, and use them for counterweights for the 10-incher.

:grin:

- Jim

#24 stevew

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Posted 21 March 2013 - 09:17 PM

Hypothetically: you are an observer of deepsky galaxies and such as much as mars and the moon. Even more amazingly you are given a choice (oh hell it s free) of a ten inch apo or c14 - which would you pick?


Pete

"Hypothetically" If I could have a scope butler to set up, tear down, mop my brow, and hand me eyepieces whenever I call out "Jeeves,..9mm Nagler!!"
then I'd take the 10 inch apochromat.
If I had to hump it around and set it up myself, the C14.

Steve

#25 DJCalma

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Posted 21 March 2013 - 09:21 PM

I'd take a 7" apo over a C14, does that count? Never been a fan of those short, stubby looking things aside from small Maks. Although, to be fair I've never seen the views through an Edge HD.






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