USB to RS232D Cable?

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Well-Known Member
Jan 19, 2009
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I have a telescope that needs a software update. I do not have a cable for it to hook up to my computer. The telescope manufacterer sells a cable for $25, but I'd like to see if I can save money. It uses the RS232D with RJ45 type connectors, which is the same connector used with ethernet. My question is, can a USB to ethernet cable be used? Are the pinouts the same as with RJ45 serial?

I am assuming also that I cannot just use an ethernet cable and hook up to the ethernet port on my computer.

Thanks for your help,
RS232 and Ethernet are two entirely different standards, so you can't use an USB to Ethernet cable. It's possible to use a standard USB to RS232 converter (with SUB-D connectors) and an adapter for the connector. However this doesn't look like an opportunity to save much money to me.

In some cases, USB to RS232 converters can be troublesome, depending on the model used (and other factors, like interface timing). With an cable from the telescope manufacturer, this shouldn't be an issue.

The RS232 is an old standard with positive and negative voltages. Its quite possible that the manufacturers cable has some circuitry to change levels. The $25 doesn't sound too bad for an OEM cable.

You also might check out eBay. Used to be a lot of aftermarket cables offered there for telescopes. I picked one up for a Meade scope a while back.

Thanks for your replies. Hmm, I'll have to check out ebay, but I never like dealing with them though.

Guess I'm springing for the $25 cable.