Welcome to the forum.
Most intervalometers are usable. Here is a older thread:
Intervalometer - PentaxForums.com
I own the SMDV controller featured in the thread, but used it only once until now. I bought it, because it shows you all the parameters in one glance.
You can find additional information on other triggers here (you have to search a bit).
Miscellaneous - Pentax Camera Accessory Review Database
I would also suggest to buy an additional cs 205 cable release or it's cheap third party counterpart in case you want to use a smaller manual solution. The SMDV works as such as well, but sometimes the simple solution is all what you need.
If you are not familiar with astrophotography, I also recommend you to get stellarium for your PC as a planning tool and the stellarium phone app for finding celestical objects on the go. With the later one and a tripod with a head with graduation on the vertical axis you can blindfire dim deep sky objects. Horizontal direction is by the O-GPS. And a Petzel head lamp with redlight will be of help too.
Good luck!
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