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Canon 6d and field flattener

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#1 vinceproe

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Posted 10 August 2020 - 03:49 PM

does anyone know if the ASTRO-TECH PHOTO-VISUAL COMA CORRECTOR & FIELD FLATTENER FOR FAST FOCAL RATIO NEWTONIAN REFLECTORS will allow me to achieve focus on my 8 inch reflector using a xanon 6d in prime configuration... right now i am using a 2 inch luminous 2.5x barlow which puts my focal length at 2500 mm which is proving impossible to guide ... any other thoughts to get me off the barlow would be appreciated and welcome

#2 nofxrx

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Posted 10 August 2020 - 04:15 PM

I don't think the CC will change the focal length but it will move your camera further away from the focal plane. You need to move your primary mirror up in the tube about an inch in order to reach focus with most visual newts. If you have an imaging newt then something else is wrong.

Which scope do you have?


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#3 TelescopeGreg

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Posted 10 August 2020 - 06:11 PM

I don't know about that particular coma corrector.  I do use the Paracorr-2 with my Celestron 8" f/5 Newtonian scope, and it both fixed the coma problem, and got my DSLR to prime focus.  Its 15% Barlow effect didn't really affect my imaging much.

 

I don't recommend moving the primary mirror in your scope.  I tried effectively doing the same by using a shorter mounting shim in the scope's Moonlite focuser, and while I got the camera to focus, I lost the use of the eyepieces.  They were at the other end of the focus position, and then some.  Also, the secondary mirror isn't sized properly for the closer primary mirror.

 

The Paracorr is expensive, but it worked very well, both optically, and mechanically with the focus problem.



#4 vinceproe

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Posted 10 August 2020 - 06:54 PM

Scope is a Meade R8 on an lx85 eq mount 1000 mm @f5 ... wow the paracorr is expensive which brings up the question of whether i should purchase a scope more favorable to astrophotograpy OR is there some benfit to hetting this 8 inch scope to work for astrophotography any thoughts welcome

#5 vinceproe

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Posted 10 August 2020 - 06:54 PM

Scope is a Meade R8 on an lx85 eq mount 1000 mm @f5 ... wow the paracorr is expensive which brings up the question of whether i should purchase a scope more favorable to astrophotograpy OR a astro camera instead of th 6d ... is there some benfit to hetting this 8 inch scope to work for astrophotography any thoughts welcome

Edited by vinceproe, 10 August 2020 - 06:57 PM.


#6 TelescopeGreg

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Posted 10 August 2020 - 07:16 PM

Yeah, that is a question worth asking.  I tend to flog whatever I'm working on instead of swapping it for something else.  Starting over with new equipment often has new challenges, and I tend to prefer the challenges I know vs inviting a whole new set.  But, in the end, I ended up spending about $860 to "fix" a scope worth maybe a third of that.  But it did end up working, and I learned a lot in the process. 

 

The thing is, any fast Newtonian scope, astrographs included, will need a coma corrector, and a SCT will need a strong reducer / flattener.  Large refractors are way more expensive (I went that route, mostly out of lust, and it was Christmas, after all).  So, there's no getting around needing to spend money if you want long, large, fast optics.  But, not all coma correctors are as expensive as the Paracorr.  Some of the others, I think, will fix the focus problem too, for less.  I just don't know which.  The focus solution wasn't why I picked it up.  I was going for image quality, and it was just a lucky side effect. 

 

Wide(er) field is less expensive, so perhaps the first question to answer is what kind of targets do you want to go after?  I'm into the smaller targets, where the proverbial 80mm APO won't cut it.



#7 vinceproe

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Posted 10 August 2020 - 07:37 PM

Yes i see your point ... reading up on the paracorr i may give it a shot ... i do like both visual and astrophotgraphy .. i enjoy DSO and the power of a larger apeture ... a 20 inch would be find with me ... thank you for the input and congrats on your nice xmas gift

#8 spereira

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Posted 11 August 2020 - 07:10 AM

Moving to DSLR ...

 

smp




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