Dew Control

[Paramount]

Hi Steve
I used to use a Premier controller but had continual problems with it cutting out whenever there was a slight variation in voltage and I also found it over complicated and the menu system a nightmare to use, since changing to the digifire 7 I have not had any problems at all, I use it with an AWR 240v AC to 12v DC transformer and it works fine.
Weather wise we have had the wettest August on record and September has started with floods in many areas so I have to grab whatever imaging time when I can but at least I am getting some results as you may see from my postings.
Best wishes
Gordon

[ausastronomer (John Bambury)]

Originally Posted by montewilson

I made mine too with Nichrome wire from Jaycar. I just leave them on all the time with a gentle heat. I haven't had dew on my coke bottle for more than ten years and it cost me less than $5.

Come on Monte tell the truth, it's actually the exhaust heat off your generator that's keeping the dew at bay. I saw you aiming that exhaust port straight at the objective of your Tak when you set it all up. Your dew heater is just for show

Cheers,
John B

[ausastronomer (John Bambury)]

Originally Posted by Paramount

Hi Steve
I used to use a Premier controller but had continual problems with it cutting out whenever there was a slight variation in voltage and I also found it over complicated and the menu system a nightmare to use, since changing to the digifire 7 I have not had any problems at all, I use it with an AWR 240v AC to 12v DC transformer and it works fine.

Hi Gordon,

I also have a Kendrick Digifire 7 fitted to my 18" Obsession. I am sure it is an excellent controller when fed through through a mains supply transformer. Using battery power it certainly has low voltage issues. The low voltage warning light comes on every time the servocat drives are engaged with a fast goto slew and when battery power has dropped a bit, using the servocat drives causes it to cut out completely.

For this very reason Peter Read at SDM Telescopes switched from the Kendrick Digifire systems (7 and 10) to the Thousand Oaks system. The big advantage of the Thousand Oaks controller is that you can disable the low voltage warning light and cutout. The dew heater straps work perfectly when fed a voltage slightly less than 11.8V, which is where the Digifire cutout engages.

I am about to purchase a Thousand Oaks controller to avoid the low voltage issues of the Digifire 7.

Cheers,
John B

[bluescope]

Thanks guys for the input to this thread, I have now ordered the Thousand Oaks controller and DewNot straps from Peter Read and they are being put in the mail tomorrow ( Friday 12th ).

Looking forward to no more dew problems on the FLT110 and being able to image/observe all night long if and whenever I feel like it.

Cheers

[erick (Eric)]

Originally Posted by bluescope

...... being able to image/observe all night long if and whenever I feel like it.

Presuming your battery doesn't run flat!

[RB (Andrew)]

I've been using a 'Dew Buster' http://www.dewbuster.com/ which I bought second hand off a member here and am very happy with it, but not sure if they're still available.
I like this unit because it has an external temp sensor that 'follows' the ambient temp and adjusts itself accordingly.

The Thousand Oaks controller sounds like a great unit and if I am to get another controller I'll be seriously looking at the Thousand Oaks.

[erick (Eric)]

Andrew, my reading says the DewBuster has more desirable capability than the Thousand Oaks - namely the sensor control of three AUTO outlets. I understand that the five AUX outlets are also not so fixed, switching from medium power to full power if the scope temperature differential is high. Also the unit will reduce power consumption if it detects low battery, reducing to zero consumption when the battery hits 10.5 V (at which stage I don't think you'll start your car?)

However, I'm not sure where to plug in an intelligent heater such as the Astrosystems secondary mirror heater. Probably have to power directly from the battery.

I think you have the Rolls Royce unit already!

[RB (Andrew)]

Originally Posted by erick

I think you have the Rolls Royce unit already!

Yes indeed Eric I am very happy with this unit, it has performed flawlessly for me and having 8 outputs total and the external sensor is fantastic.

I only mentioned that I'd consider the Thousand Oaks because I initially did a search the other day to find the unit on OPT Corp but they were not on there, and I heard the guy that makes them was affected by the hurricane and had stopped production.
But according to the web site it now seems he is selling them direct so they should be available again.

[bluescope]

Originally Posted by erick

Presuming your battery doesn't run flat!

I'll be using mains power Eric so no problem in that department. I also have a 17 amp-hour jump starter ... but that's more for starting my car if my battery goes flat when I move to the bush as I will be 12kms from nearest town. When I setup my observatory there it will all run on mains supply again as it does here.

[ausastronomer (John Bambury)]

Originally Posted by erick

However, I'm not sure where to plug in an intelligent heater such as the Astrosystems secondary mirror heater. Probably have to power directly from the battery.

Hi Erick,

I have the Astrosystems Secondary heater fitted to my 18" Obsession as well as the Digifire 7 Dew Heater Controller.

Irrespective of which electronic dew control system you use, it is necessary to power the Astrosystems secondary heater system with a "non controlled" 12V power supply. The Astrosystems secondary heater has automatic temperature sensing which is adjustable with a trimpot on the circuit board. You do have to totally remove and dissassemble the secondary mirror and holder to get to it. The Digifire 7 has 2 dedicated "non controlled" 12V power outlets which are suitable; and the Thousand Oaks controller has one. Dedicated 12V outlets are an optional extra on the "Dewbuster" system. I have the UCA assembly "powered" on my Obsession and just feed the Astrosystems Secondary Heater from +ve and -ve power posts on the UCA. I don't use the power outlets on the Digifire 7 at all. I get the power to the Astrosystems secondary heater by using one of the spider vanes as the -ve power feed and use a thin wire superglued to the top of another spider vane as the +ve power feed.

Cheers,
John B

[bluescope]

My Thousand Oaks controller and DewNot straps arrived today ... they look like good gear but with the weather like it is in Perth right now it's going to be a few days before I can try them out.

[AlexN]

Good going Steve!

I was saying the other night, even the finest apo ever built would be useless if it were not for dew heaters.

[bluescope]

Originally Posted by AlexN

Good going Steve!

I was saying the other night, even the finest apo ever built would be useless if it were not for dew heaters.

Too true Alex ! I'll probably get a strap for my 180mm Pro Mak as well one day.

[AlexN]

mmmm that reminds me I must get one for the C11... Im thinking that hairdryer might be a better option for a corrector plate that big... although, provided you have the dew heater on BEFORE dew becomes starts forming, it only requires a little heat to keep the corrector warm enough... If you put the heater on after dew has formed, it requires a lot more heat to actively remove the dew.... Keep that in mind.

[bluescope]

Originally Posted by AlexN

mmmm that reminds me I must get one for the C11... Im thinking that hairdryer might be a better option for a corrector plate that big... although, provided you have the dew heater on BEFORE dew becomes starts forming, it only requires a little heat to keep the corrector warm enough... If you put the heater on after dew has formed, it requires a lot more heat to actively remove the dew.... Keep that in mind.

The heater will be on as a standard part of setup in my case ! You should get one for your 11" they're not that expensive.

[qld]

Originally Posted by bluescope

The heater will be on as a standard part of setup in my case ! You should get one for your 11" they're not that expensive.

hi team, have any of you tried a cheaper method?
i have an electric blanket that operates on 12volts
which i put over the scope( newt ,maks schmidts refractors).these cost $15.00 from Auto one and used sparingly your 12v battery lasts throught the night,and also doubles up as a genuine blanket when camping out or
asleep in the back seat.They are similiar in design to the normal auto rug/blanket except for the 12v cigarette plug/cord.they work well on truss dobs,particularly if you get a black one as it makes a very good shroud using a strip of velcro top and botom to hold it in place, this consultation was free, and for the affectionardos no global warming contribution ,all warming is limited and usefull.

[AlexN]

yeah that would be a fair bit of weight hanging off the mount man...

[RB (Andrew)]

Originally Posted by qld

hi team, have any of you tried a cheaper method?
i have an electric blanket that operates on 12volts
which i put over the scope( newt ,maks schmidts refractors).these cost $15.00 from Auto one and used sparingly your 12v battery lasts throught the night

Never on a scope since you can't regulate the heat and also it's too heavy, but I have used the 12v electric blanket, plugged into my 240V 'hotbox inverter', stretched out across my accessories table to keep dew of my gear.
I leave it on all night sometimes.

[qld]

Originally Posted by RB

Never on a scope since you can't regulate the heat and also it's too heavy, but I have used the 12v electric blanket, plugged into my 240V 'hotbox inverter', stretched out across my accessories table to keep dew of my gear.
I leave it on all night sometimes.

hi team the blanket is very light and does not pose a balancing problem,i only turn it on for a little while to clear away the mist.my one is made by AUNGER CARCRAFT PTY LTD of 320 Fison Av East Eagle Farm Brisbane
Qld., email www.aunger.com.au you can also control it through a dew controller qld