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Dew Control on ASA10N


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#1 MarkS

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Posted 03 December 2013 - 07:44 AM

Has anyone fitted secondary mirror heating to an ASA 10N?

 

I've suddenly become interested following the partial ruin of an otherwise excellent photography session by uncontrollable dew formation on the secondary mirror.

 

Are there any reasons why fitting a heater should NOT be attempted? 

 

If there aren't, what suitable units are there on the market?

 

As one of my prime dark sky sites is particularly susceptible to dew formation around this time of year, I eagerly await help on this issue!

 

Mark



#2 mattssporre

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Posted 03 December 2013 - 11:02 AM

Hi Mark,

 

I too have loads of dew this time of the year, but I did not have to go down the heater road.

 

I did some tests and it turned out that I managed using the ASA N10 fans (almost on full) in combination with a dew shield. I bought myself a dew shield for Celestron OTAs and cut a hole for the focuser. It works excellent - both as a dew shield and to block stray light.

 

Maybe you have already tried this?

 

BR
Matts



#3 MarkS

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Posted 03 December 2013 - 11:45 AM

Hi Matts,

 

I have not tried anything yet, as the really bad experience I had happened only two nights ago. Prior to this running the fan on full had been enough.

 

Your reply is most encouraging, and I will try the shield - I would far rather do this than introduce heaters and wires etc!

 

Regards,

Mark



#4 GerhardB

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Posted 03 December 2013 - 03:21 PM

Hi Mark,

 

I agree with Mark. Using a dew shield and running the fan prevents condensation even during the most humid nights.

 

Best regards,

Gerhard



#5 rbrecher

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Posted 02 March 2014 - 04:43 PM

I find my flats don't perfectly correct my light frames.  I get corner artifacts at f/3.6 and am wondering if it could be that my dew shield is too long.  I use a 10" ASA and my dew shield projects about 10" from the front of the scope.  Any suggestions?  Thanks in advance.

 

Clear skies,

Ron



#6 rbrecher

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Posted 02 March 2014 - 04:46 PM

And Matts - did you get the Celestron 11" dew shield?  If you have the part number that would be helpful.  How far does it project from the front of the scope?  Can you please send a photo so I can see how you've cut things around the focuser?  Thank you!



#7 MarkS

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Posted 03 March 2014 - 07:30 AM

Hi Ron,

 

I'm using a Farpoint shield made to fit the 11" Celestron (easier to get than the Celestron). The shield projects about 300mm forward of the ASA10 front.

 

I take my flats with a light box source that the shield faces onto. These flats seem to work fine.

 

Regards,

Mark






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