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Maksutov-Cassegrain vs. Dobsonian


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#1 jerryromano

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Posted 27 August 2008 - 04:00 PM

I am looking to upgrade from my ETX-70, but I don't know how a Maksutov-Cassegrain compares with a Dobsonian. For example, which has more light collecting capability: an ETX-125 or an 8" LightBridge? Which one will allow for greater magnification? Any information would be appreciated.

#2 provencial

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Posted 27 August 2008 - 10:44 PM

The longer the focal length (f-ratio) the greater the magnification. The larger the apriture, the greater the scopes light collecting ability.
An ETX 125 is awesome for planetary viewing because of it's long focal length, not so great for deep space objects and it's a very lightweight and portable scope.
The Dob on the other hand, would be really good for deep space objects, but it can be a pain having to collaminate the optics perfectly for good planetary viewing, I found a cheshire collamination eyepiece is mandatory. And the extra weight of a big Dob can be a beast to carry around and set-up.
All in all, both are good choices.

#3 jerryromano

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Posted 28 August 2008 - 05:35 AM

So, the fundamental principles are the same no matter what type of telescope I choose, and like everything else in life, each type makes compromises depending on its use. Thank you for the advice.

#4 Philip Pugh

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Posted 03 September 2008 - 07:27 PM

You might find this of interest:

http://philippugh.fo....com/Owner.html

I've heard some discouraging news about the ETX range. The optics are great and I suspect the ETX 125 will perform pretty much as my Mak but the tracking isn't so good.

I'd like to hear from anyone who has had a better experience.

#5 provencial

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Posted 03 September 2008 - 09:33 PM

I've also had poor results tracking with the ETX125 IN ALT/AZ mode, improved a bit by polar aligning the scope but still tracking is less than anything to be desired for astrophography.
But for visual observing I can live with it.

#6 Tony

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Posted 04 September 2008 - 04:43 PM

I got this of Jupiter with my ETX 125, using a 3x telextender and LPI camera, about 400 frames one night of nearly perfect seeing. Optics are pretty amazing for this scope. AltAz seems to work ok for short exposures, polar is better if you can aligh it well.. I use a Celstron 7x50 illuminated reticle polar alingment finder scope and the ring camera adapter with a counter weight to support the whole mess. I had to take my scope down to Meade in Irving about 3 times before I got proper tracking with the motors... I'm keeping my fingers corssed that I don;t have to send it to Mexico! its a wonderful scope when it works!!

#7 Tony

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Posted 04 September 2008 - 04:44 PM

forgot to add photo sorry

#8 skywise

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Posted 04 September 2008 - 05:46 PM

What a nice shot. Excellent contrast. Which moon is it?
Brad Snowder
Planetarium Manager
Western Washington University

#9 provencial

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Posted 04 September 2008 - 09:24 PM

Tony, thats a really great image of Jupiter.
I guess the ETX can do astrophotography well in the right hands!
Well done  :(!

#10 kanders2

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Posted 17 December 2008 - 07:12 PM

Light gatering is purely a function of aperture.  Dobsonians are the cheapest way to get aperture, since about 75% of the cost is the mirror.  I started out with a 10" Dob that could fit in my Mustang.  Now I have a 17.5" Split tube dob that required an Expedition/Navigator to transport it inside (and I rarely use the 10" dob now).

Magnification is changed by swapping out eyepieces, and you rarely go above 300x anyway (except in calm steady cold clear winter nights)

KA :D




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