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Question about alignment stars alt ?


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#1 fjhdavid

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Posted 27 June 2016 - 01:06 AM

hello,

 

Do you know if there is a maximum Alt for alignment stars (my DLSR limits alt to 60°)

 

thanks

François



#2 Bob Arnold

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Posted 27 June 2016 - 04:08 AM

Hello Francois,

 

There in no Alt alignment star limit. I too was concerned about my camera striking the telescope base while aligning. My solution was to use a diagonal.  

 

Regards, Bob 


Meade LS-8 ACF, ZWO ASI120, Mallincam Skyraider DSc, Ipad Air-SkySafari Pro, SkyFi, and an assortment of had to have items that don't get used.


#3 fjhdavid

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Posted 28 June 2016 - 05:03 AM

it is not a good idea, especially if you use a focal reducer and you have to keep a distance between focal reducer and focal plan (it is 85mm with a 0.63 celestron).

 

in addition, the pointing is somehow less precise (problematic with a barlow)

 

star diag is for visual only



#4 Mark Sibole

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Posted 30 June 2016 - 08:52 AM

Using a diagonal isnt a perfered method for imaging as it adds more glass to the imaging train ,

BUT it can be done.I have shot many images with a diagonal with no problems at all.I have used a diagonal with and without a .63 focal reducer and also have had no problems at all...


Mark Sibole
MTSO Observatory
Fife Lake, Mi.

http://astronomy.qteaser.com

#5 fjhdavid

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Posted 30 June 2016 - 02:44 PM

but the 0.63 focal reducer becomes a 0.4 with distorsions...

 

http://www.weasner.c...l_reducers.html

 

in addition, you will exceed the "best focus range" which is about 5 to 6 inch for SCT, and damage image quality



#6 Bob Arnold

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Posted 17 July 2016 - 11:00 AM

Using a star diagonal with my Mallincam DSc camera allows pointing to zenith without crashing into the mount base. The focal reducer I use screws directly into the camera so there is no issue with focus range. 

 

The diagonal supplied with the LS is not the best quality and I've read that as much as 10% of light is lost. Also the single thumbscrew that holds the camera (or eyepiece) in place causes a slight misalignment in the light path and can affect image quality and object centering. In addition, it marred the finish of things plugged into it.

 

I replaced the stock diagonal with a Teleview dielectric diagonal. 99% light efficiency and the camera is held in place by a brass ring that the thumbscrew tightens. Pricey solution but I got mine on sale.  I'm very happy with the results.

Bob


Meade LS-8 ACF, ZWO ASI120, Mallincam Skyraider DSc, Ipad Air-SkySafari Pro, SkyFi, and an assortment of had to have items that don't get used.





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