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Using Tele Vue Powermate with WO FLT132

Tele Vue Refractor Planet Imaging Astrophotography
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#1 Mike1485

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Posted 25 November 2022 - 06:42 AM

I am after some help using a 2" Tele Vue 4x Powermate with my William Optics FLT132 refractor and a ZWO ASI533MC . I have so far been unable to achieve focus with the Powermate. Does anyone else have similar equipment which they have set up successfully and could give me some pointers please?



#2 Boeglewatcher

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Posted 25 November 2022 - 07:09 AM

Ok, I am not using the Powermate but the Baader FFC on my FLT. So, televue says that the magnification is always around 4x and fairly independent of the distance of the camera focal plane to the power mate. So, just go w 30mm or 40mm or so for this distance.
 

now, point the scope to a known object 1km away or so. Make sure the object is inside the camera FOV.
if you use a star or Jupiter, once you are getting closure to the focus a small position outside of the FOV is still ok. You’ll see a bright light which you can then slew to and continue to focus on that one.
The focus is very sensitive to the position of the focuser, so you have to go in 5mm (better 3mm) steps.
start out at 6cm and work your way inwards. Take a pic (I’ll say gain 400, 10sec needed when imaging stars/Jupiter).
For my FFC the focus is at 6cm and it is really sensitive. At 5,8cm the stars are already very defocused and dim.

 

if you have found focus position on a 1km object, the focus for the stars will be shorter. 

good success, hope I could make myself clear.

cs Joachim


Edited by Boeglewatcher, 25 November 2022 - 08:15 AM.


#3 Mike1485

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Posted 25 November 2022 - 09:44 AM

Thanks Joachim - that is really helpful - I was creeping with the focuser but perhaps boosting gain and exposure time would be a good thing to try.  I presume the Tele Vue pushes straight into the ROTO Lock - then I am thinking to use a 21mm spacer + 11mm spacer + 6.5mm to the sensor = 38.5mm. I hope that makes sense.  Thanks again for the help - I will post back how I get on after the next clear night (maybe a while frown.gif ).



#4 Boeglewatcher

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Posted 25 November 2022 - 10:06 AM

Yes, you need high gain when searching the focus. Once the stars are focused you can image Jupiter at 1/100sec (w matching gain setting).

cs joachim 



#5 dcaponeii

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Posted 25 November 2022 - 10:38 AM

Sometimes you'll need an extension between the camera and the scope to reach focus beyond what you think the back focus should be. With my 80mm refractor I needed about 4" if I recall to keep enough focus tube engaged with the focuser so it would not sag.



#6 Mike1485

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Posted 25 November 2022 - 06:42 PM

Thanks for this input - all I need now is for the clouds to clear so I can have a crack at implementing your suggestions smile.gif .



#7 Mike1485

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Posted 29 November 2022 - 10:03 AM

I am happy to say that everything is now up and working - at least all the bits that are in my control, the clouds are still ever-present! Thanks for all help.
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