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CPC11HD Edge/Meade ACF12" LX90 VS 10" Newton /DSO

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#1 ivan86

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Posted 09 April 2013 - 02:22 AM

Hello guys ,

i would like to buy a CPC 1100 HD Edge for my visual observing of deepsky objects and planets.
I will use the CPC most of the time from my light polluted sky (limit magnitude 4 / 4.5) and about once a month from dark sky (l. m. 6 / 6.5).

I have a lot of experiece with a 10" dobson GSO under that sky so i know what to expect from this kind of aperture.

My question is: the CPC 11" how will perform when compared to the 10" dobson on deep sky observing ?

I did alredy some math, if i include the greater obstruction of the Celestron C11 and the light loss from the extra glass in the optical path i can conclude this:

1. both have the same light trasmission
2. both have the same theoretical contrast (D-d)
3. the C11 have a bit more of resolution

So both should perform more or less equal.

Now, these are theoretical assumptions, im looking for some real life experience under sky, maybe someone of you have compared these telescopes.

Thanks
and best regards
Ivan

#2 GlennLeDrew

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Posted 09 April 2013 - 03:29 AM

I'd seriously consider the Cat, if indeed it's the HD version with field correcting optics. It loses appeal if of the 'standard' SCT design, and very much so if the mount is a GEM (ugh!).

The Newt's main strength is the ability to deliver a wider field (which I very much prize), but from a more light polluted location, and with imaging off the table anyway, the Cat's smaller field is no great impediment in the main.

#3 ivan86

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Posted 09 April 2013 - 04:17 AM

Sorry but i could not understand. What you mean with CAT?

#4 GlennLeDrew

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Posted 09 April 2013 - 05:13 AM

Cat = Catadioptric, a common abbreviation, which also appears in the name for another Forum here, "Cats and Casses".

#5 MikeBOKC

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Posted 09 April 2013 - 07:46 AM

Visually they shuold be abuot the same, with the narrower field of view in the SCT the primary difference. However, since you are using the scope mostly in fairly dense light pollution, the go to capability of the 11 inch CPC would be a real plus in easily locating targets.

#6 ivan86

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Posted 09 April 2013 - 08:38 AM

Ok thanks GlennLeDrew.

MikeBOKC @ one of the reason is in the easily locating targets under light polluted sky ;)

I see that you own a C11" and a 14" dob, is there a big difference on DSO?

I saw also the Meade ACF LX90 12", this telescope with the extra inch could be more brighter on deepsky. But people say that the mount is not enought stable for this telescope and quality control in Meade is not as good as in Celestron.

#7 MikeBOKC

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Posted 09 April 2013 - 11:02 AM

There is a difference on DSOs between the CPC11 and the Orion 14g, but it is not dramatic. Brighter. more detail visible in the 14 by I would say a factor of one third, which is nto show-stopping but readily apparent nonetheless.

#8 MitchAlsup

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Posted 09 April 2013 - 11:20 AM

i would like to buy a CPC 1100 HD Edge for my visual observing of deepsky objects and planets.
I will use the CPC most of the time from my light polluted sky (limit magnitude 4 / 4.5) and about once a month from dark sky (l. m. 6 / 6.5).

I have a lot of experiece with a 10" dobson GSO under that sky so i know what to expect from this kind of aperture.

My question is: the CPC 11" how will perform when compared to the 10" dobson on deep sky observing ?

I did alredy some math, if i include the greater obstruction of the Celestron C11 and the light loss from the extra glass in the optical path i can conclude this:

1. both have the same light trasmission
2. both have the same theoretical contrast (D-d)
3. the C11 have a bit more of resolution

So both should perform more or less equal.

Now, these are theoretical assumptions, im looking for some real life experience under sky, maybe someone of you have compared these telescopes.


My guess is that your analysis is about right. There are advantages to the Newt/DOB and advantages to the SCT.

My particular C11 blew away my friends M10 DOB.

But to get wide fields of view, one must resort to wide FoV EPs (40mm WF, 41 PanOptic, 31 NT5, 30mm Lietz, 30mm Ziess) So the maximum exit pupil is a bit on the small side (4mm) rather than the desired 6-7mm (5mm for those of us over 60).

#9 KerryR

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Posted 09 April 2013 - 11:23 AM

I have a 10" f4.5 newt, a CPC11 standard.

The CPC11 does a better job of eliminating stray light from local lights when observing from urban locations. This makes the CPC11 show better contrast under urban observing conditions. The same could be achieved by adding a long extension to the front of the 10" newtonian, but the extension would need to be quite long if there are local lights that can shine far down the tube. A taller focuser can also make stray light control easier.

Goto is of great help under urban skies where star hopping can be very difficult.

#10 SeattleScott

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Posted 09 April 2013 - 07:52 PM

I agree, the baffling and dew shield of the SCT will help with local lights. Adding a dew shield and flocking to the reflector could help offset this, but certainly out of the box, the advantage is to the SCT. Plus, with light polluted skies, you don't necessarily want to max the exit pupil and field of view with a reflector anyway, compromising the reflector's advantage in terms of FOV. If you plan to use GoTo with the CAT than FOV isn't an issue for locating objects anyway. Just an issue with being able to frame the largest targets.

Otherwise I think the optical quality is going to be the biggest difference in the views through the eyepiece. Given the SCT is made in China it is always a bit of a gamble, but Chinese optics are much better these days, and the Celestron's have been getting great reviews, esp the Edge series. And I would like to think that you are getting a little more quality control with the SCT considering the staggering price difference compared to the dob.

Keep in mind though that the CPC 1100 is a bit of a beast in terms of weight. My back would much rather haul out a 10" dob than a fork mounted 11" SCT.

#11 David Pavlich

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Posted 09 April 2013 - 09:49 PM

Under typical conditions, it'll be difficult to see a difference considering that both scopes are collimated, cooled and using the same magnification. The exception that has been mentioned is FOV. Objects like M45 look good in the Newt, but the SC won't get the whole thing into the eyepiece.

The CPC series of scopes are among the best for visual work with the 11" the king. Easy to align, great gotos and the eyepiece is always in a good location. And it tracks very well. If you've noticed that I'm an SC fan, you're right. I have an 11" Edge in my observatory and a 10" Meade R on a CG5-GT for my outreach scope. :grin:

David

#12 ivan86

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Posted 10 April 2013 - 01:35 AM

Thanks, i read exactly what i was hoping to read :)

Last question, between the CPC 1100 HD Edge and the Meade LX90 ACF 12" i prefer the Meade for bigger aperture but im a bit scared because seems that:
1. Meade quality control is not as good as in Celestron
2. LX90 mount is not enought stable with a 12" even for visual observing (sound strange to me, hope is not true)
3. If i broke something Meade do not send single piece to replace a part so if i have a damage after warranty i cannot repair a part but i must replace all
4. goto system on Meade is not so good as for Celestron

Someone with some experience can confirm this rumors?

Many thanks
Ivan






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