Serial and USB temperature Data Loggers
These products are imported and adapted by Duchek Consulting Services
Temperature data loggers (devices to record temperatures while not connected to a computer, but can download the data to a computer) can be very useful to amateur astronomers.  One can record all sorts of useful information that can improve the performance of your equipment.  Gary Seronik and Bryan Greer have websites discussing the advantages of having your newtonian mirror at thermal equilibrium when observing and photographing.  Of course all telescopes need to be at thermal equilibrium to perform their best.   Anthony Wesley of Australia has done extensive studies of his mirror cooling and come up with some ingenious solutions to cooling his mirrors.  After reading his series of articles, I wanted to get some quantitative information on my telescopes and on my storage shed that houses my OTAs.  Certainly one way of getting a scope cool faster is to not have it as hot in the first place.  It turns out Anthony made his own Temperature data loggers and while he describes the project, I felt I had lots to do already.  When I tried to price commercial industrial data loggers I found the decent ones expensive. There are some cheap ones that will record a single temperature, but I felt I needed to simultaneously record two or more.   After several months I located a couple of bare circuits that did just what I wanted.

These can operate independently of a computer using 3 AA batteries.  They will record approximately 520 data points in each of 4 data channels.  How long that lasts you depends on how often you take a data point.  That is user controllable and can be varied from 2 - 3600 seconds (1 data point/hour) so that the devices have a range from slightly less than 3 hours to 3 weeks.   Once the data is in memory the device can be downloaded using a free terminal program (included) as a CSV (comma separated variable) text file.  These are easily imported into Excel or any other spreadsheet for analysis.  The devices come as shown below --bare circuit board mounted on a 3 AAA battery box.  The box has an on/off switch built into the bottom for convenience.  Power is supplied to the board in one of two ways.  When operating independently, the pin choosing Fahrenheit or Celsius is removed and the 3 pin adapter from the battery is placed on those pins (using the correct polarity).  When connected to a computer, power is supplied from the computer. 

I have 2 pdfs describing these products and how they work in more detail.  They are available without cost by email.  Send a request for the TDL documents to

Serial Data Logger.   This is a slightly older design than the USB version.  It does not have the onboard start button that the USB version has.
It does allow for use of a second type of temperature probe, which I do not carry as the type I carry are very good with these units.
USB Data Logger.  This version has button on the circuit board that allows the user to give it simple commands like start/stop/erase when not connected to a computer. 
Serial Temperature Data Logger with HTerm CD  $30
 (No probes or batteries included)
US shipping is included.
USB Temperature Data Logger with HTerm   $50
 and driver software CD (No probes or batteries included)
US shipping is included.
The circuit board comes mounted on the 3 AA battery compartment.  I have also glued a jumper holder (seen on the right) to hold the F/C pin when one is powering the unit from battery.  Otherwise they would be easy to lose. 
Note:  The data logger is sold with NO PROBES.  The probes are expensive, and I have no idea how many a buyer will need.  In many cases two may well suffice.  (one as an external environmental control, and one for measuring the desired temperature.  Thus, in order to use these a buyer needs to select the desired probes. 

Note also: They are also sold with no batteries included and do not come with serial cables or USB cables.  

I have two different temperature probes available with these device. Both work on the same chip(18B20), but one uses the chip itself as the sensor and the other has a metal cylinder around the chip and the manufacturer claims it is water resistant.  The probe is somewhat larger, and somewhat cheaper to buy.  Both probes have 1 meter (39") wires attached to them.  Both have connectors appropriate for use with the boards above.  The chip is accurate to 0.1 degree

One stainless probe, water resistant (larger probe, stiffer cable) $12. US shipping is included.
One smaller more flexible temperature probe $18.   US shipping is included.