10 replies to this topic

[Maui-Jim]

I expect lots of opinions and welcome them all.

I live in N. California and high humidity & early dew are a plague.

I've an 8" SCT (Meade LXD75) on a GOTO mount.

I've also a good dew shield that fits over the front - but....

 

Even with the shield on (and it is NOT heated), dew starts to form around the secondary mirror obstruction.

It grows like a little algae bloom concentrically and works its way out to the outer perimeter.

I've grown good at estimating real dew point at about 5 degrees above the weather channel posting.

But sometimes it sneaks up on me - really frustrating.  Question: what is recommended to keep dew at bay.

I'd prefer something I can plug in to 120V since I'm stationary in my backyard observatory. Thanks in advance.

 

[Bob4BVM]

When I'm at home, standard hair dryer is my goto. A few swipes is all it takes for corrector plate, mirrors, EP's whatever.  Also great for occasional shot up under the jacket on these cold nights !

Pretty simple, very effective !

[daveb2022]

I expect lots of opinions and welcome them all.

I live in N. California and high humidity & early dew are a plague.

I've an 8" SCT (Meade LXD75) on a GOTO mount.

I've also a good dew shield that fits over the front - but....

 

Even with the shield on (and it is NOT heated), dew starts to form around the secondary mirror obstruction.

It grows like a little algae bloom concentrically and works its way out to the outer perimeter.

I've grown good at estimating real dew point at about 5 degrees above the weather channel posting.

But sometimes it sneaks up on me - really frustrating.  Question: what is recommended to keep dew at bay.

I'd prefer something I can plug in to 120V since I'm stationary in my backyard observatory. Thanks in advance.

Yeah, I'm in central Ca and high humidity can be an issue at the cooler temps. I use a few different dew heater controllers. The strips work well for me. I've found they can cause some issues with image stability YMMV.

I've got the Celestron dew ring but have yet to try it. Their smart controller is supposed to regulate the levels for best results. My old 25 year old Kendric??? controller is small and easy to operate and has 4 ports. A strip on the front has always worked for me keeping it clear. I also use strips on my finder, finder EP and observing EP.

Actually the observing EP is prone to fogging over more than anything else.

With the finder, it depend how much I need to use it. If I can just keep it capped most of the time, I won't outfit it with strips.

Everything I have is 12v. I use a battery supply under the tripod for power.

If you have a go-to scope, cord management can be critical.

 

The majority of the time my dew shield is good enough, but there are times I get overrun. The worst is near freezing when it's foggy at ground level. Everything above 40 degrees (alt) to zenith is clear, but the scope is pointing right up into the moist air. Kind of a balancing act trying to maintain a low enough heat to keep turbulence down and anticipating how heavy the moisture will be.

 

I've had my front corrector do as what you describe but turns to ice. It happened because I didn't turn the dew strip on the front corrector high enough to keep up with the dropping temps. 

 

BTW, my SCT OTA is wrapped, but I generally don't wrap the shield. I haven't found a need to wrap the shield and don't know if it would help for colder temps, but I intend to try. The last couple years, the weather has been a bit drier but it has returned to the regular December fog lately. A couple nights ago the humidity was 94% at 39 degrees.

 

Hope you find the solution. Probably differs widely from site to site.

[Mike Q]

I run heaters and a dew shield on my SCT.  Its pretty much mandatory for me unless there is a breeze.

[Patrick]

I expect lots of opinions and welcome them all.

I live in N. California and high humidity & early dew are a plague.

I've an 8" SCT (Meade LXD75) on a GOTO mount.

I've also a good dew shield that fits over the front - but....

 

Even with the shield on (and it is NOT heated), dew starts to form around the secondary mirror obstruction.

It grows like a little algae bloom concentrically and works its way out to the outer perimeter.

I've grown good at estimating real dew point at about 5 degrees above the weather channel posting.

But sometimes it sneaks up on me - really frustrating.  Question: what is recommended to keep dew at bay.

I'd prefer something I can plug in to 120V since I'm stationary in my backyard observatory. Thanks in advance.

Take a look at a heated dew shields.  I've used them many years with no dew issues, even in heavy dew.  See Here: AstroZap Flexi-Heat Dew Shield

 

You will also probably want a dew heater controller:  Here's one:  Pegasus Astro Dew Heater Controller
 

You would need to figure out how to convert to 12v from 120v.

 

Patrick

Edited by Patrick, 04 December 2024 - 07:30 PM.

[havasman]

All the astro gear dew heater hardware I know of runs on 12vDC because that's what most have at their sites and probably use to run their other systems. That's the biggest restriction here. Get around that and there are good applications for all dew conditions. That AstroZap is effective. I have seen it work for others on a field with heavy dew conditions that night. I use controllers from R-Sky as they're a bit less $ and have always worked  well. I have some of their strips too. All the strips work in any controller and the "RCA" plug/socket is the standard. The best controllers read ambient temp and maintain a setpoint relative to it.

 

Insulating and moving air are both sometimes effective.

 

Inverters can be expensive but should be reliable. AC-powered dew control systems could be configured. 

[Mike Q]

All the astro gear dew heater hardware I know of runs on 12vDC because that's what most have at their sites and probably use to run their other systems. That's the biggest restriction here. Get around that and there are good applications for all dew conditions. That AstroZap is effective. I have seen it work for others on a field with heavy dew conditions that night. I use controllers from R-Sky as they're a bit less $ and have always worked  well. I have some of their strips too. All the strips work in any controller and the "RCA" plug/socket is the standard. The best controllers read ambient temp and maintain a setpoint relative to it.

 

Insulating and moving air are both sometimes effective.

 

Inverters can be expensive but should be reliable. AC-powered dew control systems could be configured. 

Overall, how is the stuff from R Sky?

[ABQJeff]

Try insulating your scope and dew shield (in addition to a dew strap).

[havasman]

Overall, how is the stuff from R Sky?

It's as good as any I've ever used. Their controllers have developed to include controllable setpoints matched to ambient that it measures. I recommend it and the folks that make it w/o reservation.

[Napp]

Add a dew heater to your configuration and you should be good.  That's what I use here in high dew point Florida.  An sct is unusable here without a dew shield and heater.  I do not recommend a heated dew shield.  If you decide to add a rail to your scope tube to add an accessory you will not be avble to add a notch to the dew shield if needed.  Cutting a notch means cutting the heater element.  Your better off to just add a dew heater and use your existing dew shield.  You will need a controller.  You can buy a basic controller and adjust the heat applied manually or you can buy a controller that can automatically control  the heat applied.  That kind of controller needs an additional temperature sensor.

[Mike Q]

It's as good as any I've ever used. Their controllers have developed to include controllable setpoints matched to ambient that it measures. I recommend it and the folks that make it w/o reservation.

I have one of their heater bands and it seems that it is of pretty good quality.