[AZ-Observing] Re: LapTop
- From: Andrew Cooper <acooper@xxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Sun, 21 Aug 2005 11:54:59 -0700
Stan Gorodenski wrote:
>I am considering getting a laptop for my LXD75 to be able to use Meade's
>LPI that came with the telescope, as well as possibly the DSI if I
>decide to buy it at some time in the future. At one time I knew much
>more about computers than I do now, and I have not kept up with changes
>in technology. Can anyone recommend one that is relatively inexpensive?
>Cost will be a factor on whether I will even get one. I would be using
>Windows2000 as the OS. Some of the things I would like to know are
>
>
I currently use a couple old (Dell Latitude Pentium 2, 300MHz) laptops
for field use. I have a modern high end HP that is my primary computer,
but I rarely use it in the field. The old Dell's are just fine, they
don't chew much power, and I don't panic if they get a bit dusty or dew
covered in the night. (I had one time my mouse was frozen to the table!
I had to pry it loose.) The smaller hard drives (10Gb) are sufficient
for CCD with a USB memory stick used to transfer the few hundred
megabytes I can generate in a night. The drives are a bit small for
webcam imaging where the AVI's can get very large, very fast. These
machines were sold at an employee auction by my company as surplus, a
lot of four for $20. I got two working by stealing parts and memory
from the others and buying a couple new hard drive and batteries.
Surprisingly they run windows XP pretty well, one you shut off and
de-install all the junk windows comes with.
>1. Are there differences in how they are powered? I remember years ago
>laptops were pretty heavy because of the battery weights. Now they seem
>pretty light. Are there less desireable batter power sources?
>
>
Certainly look at battery lifetime as one criteria, but no laptop
battery will get you through a whole night. 2-6 hours is normal, but
heavy processing tasks (like webcamming) will cut into that. I use an
external 17Ah 12V battery pack that will run the camera and laptop all
night.
The issue here is voltage, if you find a laptop that will run on 12V it
is great, but I haven't seen any modern laptop that does. 18-20V is the
usual input voltage, so if you use a standard 12V field battery you will
need to boost the voltage.
Avoid using a 120V converter and the standard laptop supply, these are
horribly inefficient. The 120V converters are usually less than 60%
efficient, and the standard laptop supply is probably around 80%
efficient, the remaining power is just wasted as heat from the
conversion process. Run through both and you are now throwing away half
your power.
Look into buying a laptop travel charger, this will convert 12V straight
to the 18V your computer needs at about 80% efficiency.
>2. What is a reasonable minimum processor to get? I know getting the
>current most advanced technology processor is more on the safe side if I
>plan on using the laptop many years, but it probably would be much more
>expensive.
>
>
The latest processor will certainly benefit you down the road, but you
can save a lot of money by not going with the highest possible clock
speed, staying just a couple steps back. The only time you will really
notice is when you are processing a stack of images, such as webcam
imaging. The other issue here is power, the higher end processors chew
a LOT of power. I don't generally use my big HP laptop (which I am
typing on right now) in the field because it's 3+ GHz Pentium 4 is very
power hungry. But on the other hand it chews through 1000 frame AVI's in
Registax like butter.
>3. Any manufacturers to stay away from because of hardware problems?
>
>
Stick with a mainline manufacturer, Dell, HP/Compaq, Sony, or similar.
Quality is usually a little better, but the real determination is the
availability of replacement parts, batteries, memory and such down the
road. If you choose a very popular laptop the after market parts will be
around for many years. When I rebuilt those couple Dell Latitudes that
were 6+ year old machines I could still get anything I needed very easily.
>4. What kinds of external ports should it have for a telescope?
>Stan
>
>
At least four USB 2.0 ports, when you start connecting the telescope,
webcam, camera, a mouse you will use these USB ports up quickly. You
can use an external USB hub to get more ports, but that is just more
cable rats nest to setup/wrapup and it could need power as well. An old
fashioned serial port is nice as many things in astro still use standard
serial, but USB/serial adapters a readily available and work well. I
run a Nexstar 11 through one with no problems at all. Most laptops
still have a traditional printer/parallel port standard.
Hope this helps!
Andrew
Andrew Cooper
----------------------------------------------------
http://www.siowl.com
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