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Kendrick Newtonian Heaters
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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.
NEW !!! Primary Mirror and "Red Rope" Heaters: With so many types of Newtonian mirror holders on the market today, we have redesigned our primary Newtonian mirror heaters to accommodate a larger variety of telescope models. Need help chossing the right heater? Refer to the Heater Selection Guide below. NOTE: We can't tell you which model works for every telescope ever made (thousands). But the good news is that you have the telescope in front of you and the Selection Guide will help you pick the right model. |
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 that don't have an exposed back-side suitable for the Elliptical or Split-Ring models.
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 |
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-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" or Elliptical style heaters. 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. Look below and you will see a link to a template that will help you find the perfect fit. New "Universal Fit" Model (3 sizes to choose from)
With so many types of Newtonian mirror holders on the market today, we have redesigned our primary Newtonian mirror heaters to accommodate a larger variety of telescope models. This new style heater can also be used for a variety of other difficult heating challenges and as such, we are also naming these "Red Rope Heaters" which offer a flexible generic solution. The 2023-610 heater is designed to be used with and placed onto the back side of 6” to 10” primary mirrors. The 2024-1216 heater is designed to be used with and placed onto the back side of 12” to 16” primary mirrors. The heater(s) will affix to the backside of the mirror, or wrap around any surface and make direct contact with the glass. There is not right or wrong way to install this heater(s). The design gives you the flexibility to determine what installation method will work best with your telescope hardware. Our 2029-RR "Red Rope Heater" is for more generic applications and offers several ways to connect to your Dew Controller. You can use either the standard wire or the copper foil tape which reduces obstructions in the light path. The heater element (the red section) is quite flexible and can be worked around and through many obstacles which can make the installation of a typical flex heater awkward to impossible. The heater(s) will affix to the backside of the mirror and make direct contact with the glass. There is no right or wrong way to install this heater(s). The design gives you the flexibility to determine what installation method will work best with your telescope hardware. Rope Heater Installation Guide (PDF)
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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.
