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poppasmurf

Dew Control

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I have ordered some dew control at last. When the gear gets here and I have had a chance to use it I'll do a quick review. The gear ordered is Thousand Oaks 4 channel dew controller (http://www.myastroshop.com.au/products/details.asp?id=MAS-078B, a power supply (http://www.myastroshop.com.au/products/details.asp?id=MAS-096F) and a dew strap from a new range out from Prostar (http://www.myastroshop.com.au/products/details.asp?id=MAS-078A3). The dew straps have a nice little feature, they can be used straight from a 12V power supply and have their own independant power adjustment, or from a controller like the Thousand Oaks one or similar. I will still need to get a secondary heater for the RC at some point.

 

Shane

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19 hours ago, poppasmurf said:

The dew straps have a nice little feature, they can be used straight from a 12V power supply and have their own independant power adjustment,

That's handy. 

Ray

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The new gear arrived today, along with the bloody rain. I had hoped that I would be able to get it all hooked up during this full moon phase to test it out but not to be, maybe before the moon buggers off for some DSO imaging I hope.

First impressions, all appear well made, the dew strap has a stretchable velcro strap for attachment with about 40mm stretch which is more than I need for the guide scope but should fit and hold well.

The controller is supplied with plugs for unused ports that fit very solid and take some effort to remove which I like as that should keep any moisture out, also has a quite long cord for power is another thing I like.

As for the power supply, reasonable length on the input and output leads and also has a fan for cooling that I wasn't expecting to see on a budget unit.

With luck the rain and cloud won't hang around too long so I can try it all out, I should be able to at least get things attached and leads routed in the next day or so.

 

Shane

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First night out and trying the strap out using only the power supply lead with adjuster. Luckily I have the original mount power lead with the 3.5mm jack and cigarette plug to go into the power supply I purchased as I will need to get a longer RCA lead made to reach the controller. It is a rather heavy dew here at the moment and the dew strap is keeping the guide scope wonderfully clear or I would already be done after about 90 minutes imaging. I am rather impressed and quite happy with the budget Prostar strap, without the included lead with independant power control I would definately be buggered. I reccommend them as an alternative to more expensive brands without hesitation. I would say the only down side is the lack of length of the RCA lead, as it is too short to reach the controller which is to be mounted on the pier. I emailed Steve about this as a bit of feedback.

 

Shane

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Received the secondary heater for the RC today. Installed as per instruction and gave it a rip tonight to see what its like. It certainly keeps the dew off but the fit isnt so good and now my star shapes are horrendous. Examples are a 10 min shot from a while ago and varying length shots tonight. The original shot has nice round stars but tonights all have weird flaring, I believe it is because the outer edge of the secondary heater slightly protrudes into the light path. Not sure if I can trim it so there is no protrusion or not. These pics have only had a stretch.

 

Shane

600s L test shot pre sec heater.jpg

120sec post sec heater.jpg

600sec post sec heater.jpg

900sec post sec heater.jpg

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2 hours ago, poppasmurf said:

I believe it is because the outer edge of the secondary heater slightly protrudes into the light path

That's a strange problem. Those star shapes are kinda weird. Can you post a photo of where it protrudes? 

Ray

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I think the main issue is the fact it is not a knife sharp edge like the secondary holder Ray. Sort of fluffy uneven edge. Will also check collimation tonight if weather plays nice.

 

Shane

DSCF2039.JPG

DSCF2040.JPG

DSCF2041.JPG

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Interesting. Yes, it probably is the heater causing irregular star shapes. Does the secondary dew over much being facedown? Theoretically speaking, you could probably ward off dew by having that heater around the outside of the main tube at the front. I found that I needed a tiny amount of heat coming off my main tube to ward off dew on the corrector plate. 

Ray

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Yep the secondary does dew up pretty easily mate, I might have to look into a strap around the end of the main tube to see if that works.

 

Shane

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I had someone tell me that it is possible to have the dew heater too warm and distort the secondary, so tried with it turned down really low tonight and there was a small improvement, also checked secondary collimation which is good(might need a very slight tweak but I am happy that it is the same as before),clouds have now rolled in so that's it tonight. If I get time in the next day or so before going away for the weekend, I will try trimming the edges back. If that doesn't work I will most likely remove the heater and live with it as I have for the past.

I am rather disappointed with the quality of this Kendrick secondary heater overall.

 

Shane

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Hopefully it is just a heat problem mate. Fingers crossed. Be annoying if the material is causing that star problem, you'd think this would be something they would have removed during the design process.

Ray

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Tried trimming today and no can do, next solution, black electrical tape so at least it is a sharp edge and not fluffy. Hopefully will be able to test tonight.

 

Shane

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Well another fail:(. Not good enough for me so I will be removing the heater, which will be a chore as it is glued to the back of the secondary. Then I'll need to collimate again.:(

 

Shane

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Update: heater came off reasonably easy, so I thought I'd have a crack at trimming it while it was off. Took to the inside with a dremel and made the ID a bit bigger, now there is no overhanging fluffy edge. I will re do secondary collimation and try it yet again when the opportunity arrises. Kendrick state that these heaters are not able to be trimmed, with a knife or scissors I agree with a dremel it works and I have tested that it still operates. It's a pity that they couldn't get the sizing correct in the first place. fingers crossed.

 

Shane

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All is good in the world once more, after a trim all looks good with round stars. I tried slightly different temperature settings as well and all still looks good, now I have to wait for our Lunar friend to bugger off so I can get back to imaging.

 

Shane

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5 hours ago, poppasmurf said:

after a trim all looks good with round stars.

lol, mate what an annoying little problem that was. Nice fix buddy.

Ray

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