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Sky-Watcher Evostar 100 ED Focus and Polar Align Issue

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#1 Starman00

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Posted 03 June 2023 - 08:55 AM

I usually research the crap out out things before I buy.  This time I didn’t and may be paying the price.
I have:
Sky-Watcher Evostar 100 ED
Asiair Plus
ZWO 183MC
SW SA GTi

I have tried several nights in a row to focus and polar align to no avail. I can’t find anything in the focus and tried PA without focusing and got errors that it could not find enough stars.

I set the gain up going eventually to the max and still no results.

Is the focal length of this scope too long to use with this camera?

I’ll spend more money if I have too and sell what is useless.



#2 AhBok

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Posted 03 June 2023 - 12:19 PM

No, it is not a focal length problem. I image with a SW100ED myself, though I usually use a .75x reducer. You’re best off finding the focus during the day. Just view a distant object and adjust the focuser until you find the correct focus. Then at night focus on a bright star, or better yet, the moon which is currently bright and easy to see.

For deep sky you will eventually want a reducer. For planets a Barlow.

#3 Fabricius

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Posted 03 June 2023 - 02:19 PM

The focuser of the 100ED is very similar to the focuser of my Evostar 120ED.

The focus may shift if heavy gear is connected to the focuser and the scope is aimed upwards.

What helped for me: adjust the focuser tension by tightening the Allen screws (the Equinox has a different focuser, but the principle is the same).


Edited by Fabricius, 03 June 2023 - 02:24 PM.


#4 Mike in Rancho

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Posted 03 June 2023 - 04:37 PM

At the native f/9, the focal plane is about 176mm (just short of 7 inches) behind the end of the focuser body (white part).  I can't measure from the stock visual back anymore as I replaced it with a Clicklock, but from the focuser body should work and that's where the silver drawtube starts extending from anyway.

 

Now with about 5.25 inches of play, the drawtube is pretty long so I imagine most configurations would come to focus.  For sure it will if you have a setup (possibly with extensions) that mimic the standard 55mm DSLR sensor backspacing.  But this may depend on the sensor depth of your particular camera.




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