Hi Anyone out there got there Newt setup with Dew Heater can you post any photos please of your configuration on the secondary mirror.? Does the primary mirror really need a heater?
I am thinking about picking up the below heaters not sure which is best for my GSO 8 inch.
It's not ideal to add any heat into your telescope system, because it induces tube currents which degrades the image you see in the eyepiece. Unfortunately though the alternative is dew on your optics and an early night.
In a Newtonian the secondary is quite prone to dew as it's close to the end of the tube. I added a removable 12" light/dew shroud onto the end of my tube. It may have helped a bit, but my secondary still gets dew on it without the dew heater.
Heating the primary is not recommended. Lots of people go to great lengths with fan systems to cool the primary mirror so its temperature is closer to ambient. The boundary layer of hot air that sits on top of the mirror is what is responsible for the degraded images when a telescope is first set up. Cooling the mirror with fans helps clear this layer. So adding a dew heater to the primary defeats the purpose of having cooling fans. Fortunately I find the primary rarely suffers from dew problems as it's at the rear of the tube and somewhat protected from the cool air. I run my fan system constantly while observing which forces air up the tube and out the top. This I think also helps prevent dew problems.
I have a dew heater attached to the back of my secondary with silicone. I have attached copper strips to each side of a spider vain. They are a bit hard to see because I painted them black. I then soldered the heater wires to each copper strip. At the tube end I soldered wires from the copper strip to an RCA type plug that I fitted through a hole I drilled in the tube.
From the outside this is the lead running from the dew controller to the RCA plug. Any of the heaters you have linked there from Bintel will work fine and have all the bits there to do the same as I have. Except the RCA plug, I got that from JayCar.
I used one of the wrap around heaters on my old GSO 12" (ie one of these http://www.bintel.com.au/Accessories...oductview.aspx )
Worked fine. Just check with Bintel whether you need the 1.25" or 2". From memory the 2" was OK on my scope and the 1.25" is OK for an 8" scope, but check anyway.
I can pump out a lot of heat. I accidentally put mine on full blast one night and the air current were so bad i couldn't see anything clearly. Usually only ran it at the lowest setting.
The heater controller is fine. I have one and it works OK. Just be aware you will need a 12v power source. I found a battery was best solution as I could mount it on the base of the scope.
I second what Allan said about not heating the primary. If dew is a problem on that (which would be rare, it has never happened to me and Colac can be dew central in winter!) the fan is usually better to create some airflow.
Malcolm
PS. One issue I found with the secondary heater is it is held on with just a rubber band, so you have to regularly check it is not perishing, even the low heat required seemed to cause it to deteriorate, so I changed it every 6 months or so.
I used one of the wrap around heaters on my old GSO 12" (ie one of these http://www.bintel.com.au/Accessories...oductview.aspx )
Worked fine. Just check with Bintel whether you need the 1.25" or 2". From memory the 2" was OK on my scope and the 1.25" is OK for an 8" scope, but check anyway.
I can pump out a lot of heat. I accidentally put mine on full blast one night and the air current were so bad i couldn't see anything clearly. Usually only ran it at the lowest setting.
Be especially careful with this, I ran mine flat out one night by accident and melted the secondary holder!
Be especially careful with this, I ran mine flat out one night by accident and melted the secondary holder!
I would believe that. The amount of heat was simply amazing. I use the Kendrick Digifire 7 (http://www.bintel.com.au/Accessories...oductview.aspx ) and plugged it into one of the outputs that run a the full 12v. My secondary holder and spider were still warm hours later!
I only usually ran it a the lowest setting which was 10% and that was more than enough.
I use the fan on my Bintel f/4 newt, I use the one that came with the scope, but have removed it, and reattached to a foam baffle which is velcro wrapped to the base of the scope, it pushes air up the tube, and has kept the secondary dry so far.
The fan, as supplied, was screwed into the primary holder, and vibrated the mirror mercilessly....
I use the fan on my Bintel f/4 newt, I use the one that came with the scope, but have removed it, and reattached to a foam baffle which is velcro wrapped to the base of the scope, it pushes air up the tube, and has kept the secondary dry so far.
The fan, as supplied, was screwed into the primary holder, and vibrated the mirror mercilessly....
I also have the GSO Newt with the same fan setup. I didn't realize there is a gap between the mirror backing and the tube to allow air flow up the tube. Could you please post a pick of your foam Mod?
Funnily enough Mario it was I who actually developed the new style split heaters you see there with Kendrick in 2012, in order to fit the large stalk mounted secondary on my 12" F3.8 Orion Optics UK Astrograph...but I haven't actually fitted it yet
I have found I actually don't need it, so while I intend to fit it I haven't got around to it. I wanted it for when I moved from Newcastle (as in the link above) to Canberra, I actually thought the colder climate in winter here would require one but in actual fact I never had a problem, even when outside all night, probably because I run my three rear cooling fans all night, which suck air down the tube and out the back of the OTA (rather than blowing on the back of the mirror)..? Now under a dome, the secondary heater is even less necessary it would seem...?
In any case... yes! I thoroughly recommend the new Kendrick split style heaters if you are having secondary mirror dew problems
Funnily enough Mario it was I who actually developed the new style split heaters you see there with Kendrick in 2012, in order to fit the large stalk mounted secondary on my 12" F3.8 Orion Optics UK Astrograph...but I haven't actually fitted it yet
I have found I actually don't need it, so while I intend to fit it I haven't got around to it. I wanted it for when I moved from Newcastle (as in the link above) to Canberra, I actually thought the colder climate in winter here would require one but in actual fact I never had a problem, even when outside all night, probably because I run my three rear cooling fans all night, which suck air down the tube and out the back of the OTA (rather than blowing on the back of the mirror)..? Now under a dome, the secondary heater is even less necessary it would seem...?
In any case... yes! I thoroughly recommend the new Kendrick split style heaters if you are having secondary mirror dew problems
Mike
Thanks Mike good point on the fan orientation no need for air to push against the secondary mirror when the real problem starts at the top of the scope for a lack of temp equalisation.
P.S Just when i thought, im spending too much I see youre rig.
I also have the GSO Newt with the same fan setup. I didn't realize there is a gap between the mirror backing and the tube to allow air flow up the tube. Could you please post a pick of your foam Mod?
Sorry - meant to post these earlier....
This was assembled as a bit of a prototype, but seems to do its job well, so I haven't redone it, I haven't even filled the gaps around the edge of the baffle.
I haven't done any testing of mirror temp, but have noted no more fogging of the secondary, it produces a gentle air current up the tube, mostly noticeable when putting the dust cap on while the fan is running. I run the fan with a little PWM motor speed controller, even full speed produces no effect on image sharpness, as measured by HFR specs....
Sorry - meant to post these earlier....
This was assembled as a bit of a prototype, but seems to do its job well, so I haven't redone it, I haven't even filled the gaps around the edge of the baffle.
I haven't done any testing of mirror temp, but have noted no more fogging of the secondary, it produces a gentle air current up the tube, mostly noticeable when putting the dust cap on while the fan is running. I run the fan with a little PWM motor speed controller, even full speed produces no effect on image sharpness, as measured by HFR specs....
it was I who actually developed the new style split heaters you see there with Kendrick in 2012, in order to fit the large stalk mounted secondary on my 
