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Kendrick Newtonian Heaters
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We have Primary Mirror Heaters for 10" to 16" mirrors. They are very effective in the prevention of dew on Newtonian telescope optics, particularly for those who have Dobsonian telescopes with open truss tube designs.
There are many types of holders for Newtonian secondary mirrors on the market and we have attempted to address many of these and their various sizes with Standard Elliptical, Split and Wrap-around styles. Standard Elliptical Heaters are very effective at preventing and/or removing dew and frost from your secondary mirror. Our Split Heaters are designed to be used with larger secondary mirrors that are attached to mirror stalks (as opposed to being inside a secondary mirror holder). As the heaters are flexible, they can easily be placed around a mirror stalk. Wrap-around Heaters are an elegant solution to the problem of the dewing over of the exposed secondary mirror on Celestron, Meade, Orion, Sky Watcher and other dobsonian telescopes that have exposed secondary mirrors that are glued to a stalk.
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Primary Mirror Heater Elements |
We have primary mirror heaters for 10" to 16" mirrors. They are very effective in the prevention of dew on Newtonian telescope optics, particularly for those who have Dobsonian telescopes with open truss tube designs.
These are installed behind the mirror in between the mirror and the mirror cell and are held in place by putting a thin skim of silicone caulk (easily found at any hardware store) onto the heater and allowing the heater to dry to the back of the mirror. We do not recommend using heaters that would wrap around the outside of the optic as the thickness of Newtonian primary mirrors make this method ineffective due to the mirror mass. It is much better and much more effective to heat a primary mirror from behind.
The heaters require the use of a Dew Controller. Any Kendrick Controller model will work great. These heaters can be used with a temperature sensor on some models of our Elliptical and Primary mirror heaters, when used with our our DigiFire FX-PRO Controller (#2001-FX-PRO).
It is recommended that the Primary Mirror heaters be used at a low controller setting (ie: 15% to 20% in order to prevent optical distortion. The high wattage is built into the heaters to help clear dew or frost that is already on the optic. Once cleared reset your controller to a lower setting.
| Primary Mirror Heaters Electrical Specifications (all heaters are 12 volts) | |
| #2024 10" Primary Mirror Heater (heater diameter is 9.1"/231mm) | 0.9 Amps, 11 watts at 100% Controller setting. |
| #2112 14" Primary Mirror Heater (heater diameter is 12.25"/311mm) | 1.6 amps, 20 watts at 100% Controller setting. |
| #2026 16" Primary Mirror Heater (heater diameter is 15.1"/383mm) | 4.75 amps, 60 watts at 100% Controller setting. |
| SKU | Description | Price | |
| 2024 | 10 inch Primary Mirror Heater | CAN $168.00 | |
| 2112 | 13 inch to 15 inch Primary Mirror Heater | CAN $215.00 | |
| 2026 | 16 inch to 18 inch Primary Mirror Heater | CAN $298.00 |
Secondary Mirror Heater Elements | |||||||||||||||||
 Standard Elipticle heater |
 Split heater |
 Wrap-around heater |
Our Standard Elliptical heaters fit behind the secondary mirror and work best in Newtonian telescopes that have the removable type of secondary mirror housing.
The Split heater is also meant to be attached to the back of a secondary mirror but is to be used with larger secondary mirrors that are attached to mirror stalks. As the heater is flexible, it can easily be placed around the mirror stalk and then the heater is glued to the back of the mirror.
The Wrap-around heaters can be used with secondary mirrors that are attached to stalks* or can be wrapped around the outside of a mirror holder**.
*Some stalks connect to the secondary mirror using double sided foam tape. This tape will insulate the stalk from the mirror, making it difficult for the heater to do its' job.
**Using a Wrap-arpound heater on a typical secondary mirror holder will increase the size of the secondary mirror obstruction but it will be very effective. If your secondary mirror is larger than 1.83" in width, we recommend using the Standard Elliptical heaters.
Which one fits my scope?You will need to study how your secondary mirror assembly is constructed and take some measurements. As much as we would like to have one of every telescope in our shop, well, we can't do that. Manufactureres also don't share CAD drawings or even dimensions. Here are some basic guidelines to steer you in the right direction. NOTE: Heaters CANNOT be trimmed to fit (it will sever the heating element)!
Guide to choosing the right secondard heater We make several styles of secondary mirror heaters. Ideally, a heater that is able to make direct contact with the back-side of the mirror works best with lower power consumption:
- Elliptical heaters work for models that have the mirror sitting inside a hollow tube. They are usually stuffed with synthetic wool as the method of keeping the mirror (and an Elliptical heater) in place.
- "Split" heaters work for mirrors that are glued to a "stalk" and have the back-side of the mirror exposed around the perimeter.
- Wrap-Around is for those mirrors that have no means to affix a heater in direct contact with the back-side of the mirror. These wrap-around the "stalk" and in turn transfer heat to the mirror. They work quite well. Generally, set the Dew Contoller a bit higher as the heat does need to travel to where the mirror is attached.
More information on these various heaters can be found below.
Standard Elliptical Secondary Mirror Heaters |
These heaters are very effective at preventing and/or removing dew and frost from your secondary mirror. Using your Kendrick controller, you may turn the power up high to quickly clear the optics of moisture if they are dewed or frosted over or you may use a very low power setting to keep the optic barely above air temperature and prevent the formation of dew or frost.
These heaters work best in Newtonian telescopes that have the removable type of secondary mirror housing pictured here. They can also be used with secondary mirrors that are attached to stalks. To use them in this situation, the mirror will need to be removed from the stalk, the heater glued to the back of the mirror and the mirror (with the heater) glued back onto the stalk. If you do this, be careful that the mirror is firmly attached to the stalk again as you will not want it falling off onto your primary mirror!
Installation Sheet Instructions for S2, S3, S4 Heaters (PDF)
| FITTING DIMENSIONS | |
| Diagonal Mirror Heaters Fitting Specs | |
| #2016 S2 | Fits minor axis of 1.83" to 2.14". (Heater dimensions: 1.75" x 2.625" or 45mm x 70mm) |
| #2017 S3 | Fits minor axis of 2.60" to 3.50". (Heater dimensions: 2.5" x 3.625" or 63mm x 90mm) |
| #2018 S4 | Fits minor axis of 4.00" and up. (Heater dimensions: 3.75" x 5.5" or 95mm x 140mm) |
| HEATER SPECIFICATIONS: | |
| Diagonal Mirror Heaters, (All are 12 volts) | |
| #2016 S2 | 0.16 amps, 2 watts at 100% Controller setting. |
| #2017 S3 | 0.25 amps, 3 watts at 100% Controller setting. |
| #2018 S4 | 0.25 amps, 3 watts at 100% Controller setting. |
Split Secondary Mirror Heater |
Our Split heaters are designed to be used with larger secondary mirrors that are attached to mirror stalks (as opposed to being inside a secondary mirror holder). As the heaters are flexible, they can easily be placed around a mirror stalk. The heater is glued (glue not supplied) to the back of the mirror.
These heaters have plenty of power to clear a fogged over secondary when set to high power. Under normal operation, they should be run at 30% to 50% controller setting, depending on conditions.
Kendrick 2029-M Split Ring Secondary Mirror Heater Installation Sheet (PDF)
Specifications (note: All electrical specs stated at 100% controller setting):
| 2029-S Wire length: 610 mm (24") Connector: RCA plug Wattage: 4 watts Center hole dimensions: 34 mm x 46.5 mm Minor axis dimension: 60.5 mm Major axis dimension: 87 mm |
2029-M Wire length: 610 mm (24") Connector: RCA plug Wattage: 5.5 watts Center hole dimensions: 37 mm x 51.5 mm Minor axis dimension: 67 mm Major axis dimension: 96 mm |
R200SS Wire length: 380 mm (15") Connector: RCA plug Wattage: 2 watts Center hole dimensions: 50 mm x 72 mm Minor axis dimension: 71 mm Major axis dimension: 100 mm |
2029-XM Wire length: 610 mm (24") Connector: RCA plug Wattage: 7 watts Center hole dimensions: 45 mm x 64 mm Minor axis dimension: 80 mm Major axis dimension: 110 mm |
2029-L Wire length: 610 mm (24") Connector: RCA plug Wattage: 8 watts Center hole dimensions: 45 mm x 66 mm Minor axis dimension: 85 mm Major axis dimension: 116 mm |
2029-XL Wire length: 610 mm (24") Connector: RCA plug Wattage: 8 watts Center hole dimensions: 81 mm x 112 mm Minor axis dimension: 108 mm Major axis dimension: 148 mm |
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Wrap-around Secondary Mirror Heater |
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These heaters are designed to work with Newtonian/Dobsonian secondary mirrors that are attached to a "stalk", but don't have enough exposed mirror to use our "Split-Ring" style models. The heater warms the stalk, and that heat is then conducted to the mirror. How to choose the right model for your telescope? It's easy! You just need to make a few easy measurements. We can't help choose because we don't have your telescope in our shop and there are literally thousands of models and "eras" of these telescopes. Even models that have been in continuous production for decades frequently change the mirror assembly design, so we don't want to suggest a model that might not work. The good news is .... you have the telescope in-hand, so a few quick measurements is all it will take to find the perfect fit. 2 Styles To Choose From
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All models include easy electrical connectors and a neoprene wrap-around insulator which greatly enhances the performance of these heaters as it prevents the warmth generated by the heater from dissipating into the atmosphere.
