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OTA choice for video

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#1 Neal_MLC

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Posted 20 August 2014 - 04:03 PM

I am buying an 8” Newtonian astrograph this fall for use with my Mallincam Micro EX and I have narrowed it down to either an Astro Tech

https://www.astronom...ube_p17402.aspx

 

or an Orion

 

http://www.telescope...19/p/101450.uts

 

 

I am looking at these because I think they will give me the versatility of video or visual, depending on my mood and provide room for future growth as my interests (budget) evolve.

 

I would really appreciate your opinions or experiences with either scope.

 

Thanks for your help!!



#2 Dwight J

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Posted 20 August 2014 - 07:01 PM

Should be no problem with infocus travel with the Micro.  



#3 GlennLeDrew

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Posted 21 August 2014 - 05:08 AM

How about inward focuser travel when a reducer is installed?



#4 mclewis1

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Posted 21 August 2014 - 10:24 AM

I've heard that a few folks are using video camera/reducer combinations with these "imaging" style Newtonians. At f4 they are already "fast", but some might like to push that speed a bit.

 

On paper it should very likely work for most popular combinations ... both scopes either come with or are suggested to use with a 2" extension tube to get most eyepieces to focus (the focal point is quite a bit above the existing focuser). These scopes are designed for imaging setups with cameras like a DSLR which requires more than 55mm of outward spacing above the focuser body. The focusers on these scopes usually have about 35mm of travel and the suggested extension tube for the AT model is an additional 35mm. So there is likely at least 60mm of inward travel available from the original stock focal point.

 

The Mallincam Micro like most similar cameras requires only an additional 12.5mm of outward spacing  ... and then as Glenn mentioned you have to take into account the additional inward travel required because of the focal reducer.

 

Some examples ...

 

Antares .5x 1.25" model on a 1.25" nosepiece (actual spacing of about 37.5mm with a video camera) - additional inward travel required is 24mm (will provide about f2.4)

Antares .5x 2" model (actual spacing of 79mm) - inward travel required is 79mm (so not likely to work). If the spacing was reduced to 65mm you likely will be able to run at f2.4. Same speed as the 1.25" model but with less vignetting (edge darkening).


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#5 Neal_MLC

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Posted 21 August 2014 - 11:52 AM

When I used the Micro on my friends SE80mm refractor I wasn't able to get it to focus when I pushed it below F3 as I just couldn't move it "in" enough. This is "In" travel?  I am hoping to use a .5 focal reducer to get down to F2 but that is not a deal breaker if it doesn't work as I am content with F4.

 

I didn't know about needing an extender for visual use but that's not a deal breaker either.  I guess that's why I am here, to learn.

 

Neal



#6 mclewis1

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Posted 21 August 2014 - 01:10 PM

When I used the Micro on my friends SE80mm refractor I wasn't able to get it to focus when I pushed it below F3 as I just couldn't move it "in" enough. This is "In" travel?  I am hoping to use a .5 focal reducer to get down to F2 but that is not a deal breaker if it doesn't work as I am content with F4. Neal

Neal,

 

Yes, you've got it.

 

Many focal reducers can be used with a little less spacing which delivers less focal reduction and requires a bit less in travel. There are some specialty reducers designed to give the very best optical performance with larger sensors that are very particular about the spacing ... but most of the common models are flexible enough to use with a variety of spacings. Generally less spacing is possible but when you go to more spacing the optical quality falls off rather quickly.


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