Aluminum Vs Carbon Fiber
WHICH TUBE - ALUMINUM OR CARBON FIBER?
Stellarvue offers a 102 mm apo triplet in either an aluminum or carbon fiber tube and dew shield. Many prefer the "sexy" appearance of the carbon fiber tube while others like the classic look of the aluminum tube. We get a number of questions from customers wanting to know which is best. This page will help you decide by giving you the real pros and cons.
Cool Down: Aluminum tubes adapt to the night air rapidly. Carbon fiber tubes may retain heat and depending on the size and how they are made, this may be an issue. In the case of the 102, there is actually very little difference. We observed that different carbon fiber tubes retain heat differently. In the 102 we use a relatively thin carbon fiber tube without any interior lining and this permits faster cool down. Given the success of the 102 tube we are investigating using a specifically designed carbon fiber tube in larger telescopes but first we will continue testing tubes we develop against the same size aluminum tube.
Durability: Aluminum tubes are powder-coated and carbon fiber tubes are plastic coated. Tightening the rings too tight on a carbon fiber tube can create tube marks. Light marks can be buffed out, deep marks cannot. Keep this in mind when deciding on which tube you prefer. Ring marks from over-tightening are not considered a defect. Paying a little attention when tightening will make a difference.
Aluminum tubes are threaded to accept aluminum fittings. The connections are solid and maintain perfect alignment. Carbon fiber tubes have aluminum fittings bonded to it using epoxy. There have been cases were import telescopes on the market have had issues with parts falling off and much of this is due to improper cementing. For this reason, we bond these parts together here in Auburn using an epoxy specifically created for bonding aluminum to carbon fiber and this increases durability. Our bonding process includes ensuring alignment of parts during the process. So once again, there really is no reason for concern with carbon fiber Stellarvue SVX telescopes as they are bonded here using the proper materials.
Solar Work: White tubes do not get as hot outside in daylight so many consider them better when used for solar work. For occasional solar work this is not really an issue.
Thermal Expansion/Contraction: Some say they prefer Carbon Fiber since it does not contract when temperatures drop. They justify it as they believe it maintains focus better. What they fail to recognize is that lenses shorten in focal length as they cool down. So there really is not an advantage here to carbon fiber tubes. If optics were not affected by temperature change there would be but that is not the case. We are not saying aluminum is better in this regard but we are saying that one should not select carbon fiber thinking they will never need to adjust focus as the telescope cools down. Refocus is required for all telescopes as the temperature drops.
Weight: at 8.8 pounds without rings, the carbon fiber SVX102T-R weighs one pound less than the aluminum SVX102T which is 9.8 pounds. This is a real practical advantage to carbon fiber tubes, they are lighter.
The Bottom Line
You should select the tube type based on your personal preference. Carbon fiber tubes are lighter and aluminum tubes may cool down a little faster (we have sold over 1000 refractors with carbon fiber tubes and to date no one has complained about thermal issues). Carbon fiber tubes cost a little more. Other than that there really are no practical differences.