Robostar: adjusting gain & offset for broadband vs. narrowband filters


Just started using CMOS camera. I understand that we need to use different sets of gain when taking pics with broadband vs. narrowband filters, but how do I set it when calling robostar? Currently I believe when setting at a normal/low gain for broadband filter, robostar with narrowband will not have enough signal to identify the star for focusing. Is this a problem for any other CMOS users or I am wrong with the concept?



If you are referring to autofocus with narrowband filters, you can choose the duration of exposure required for focusing: Setupform - Autofocus - Robofire Configuration Center - Localfield Mode - Manage Focus Bin and Time for Ccd with Filters. I use 10/15 sec. Bin 2 x 2 with my CMOS without any problem.

Hi Roberto,

Thanks, but I am refering autofocusing with narrowband filters with RoboStar, not Localfield. I believe the settings you refer to only affect Localfield? I understand Localfield can be performed with longer exposure duration, but that’s rather slow and I want to utilize RoboStar if possible.

The potential problem is: with a camera gain set for broadband filter use (usually low), the signal when using narrowband filters would be low; when executing RoboStar, default exposure for RoboStar (within reasonable range) is not long enough to detect stars.

For robostar work the magnitude of star … probably you are using wrong magnitude

All the best

Someone arrive before me but I remember to you that Voyager manage offset and gain for each slot, so overall in camera setup set offset and gain for good response for focus and plate solving and leave voyager using the combination of dedicated offset and gain in the sequence slot.

Anyway a check in mag for RoboFIre is necessary

OK clear. Understood, set the “general” gain for general purpose, and let sequence handle the specific gain & offset duration data acquisition.

Yeah we checked mags. It’s set 2-4 for narrowband, should be fine.

if your pixel is really small and filter really narrow probably you must choose more bright star mag, we have introduce up to 0 mag for CMOS for this kind of situation

OK, I’ll give it a try if I have to. It’ will limit the # of suitable stars though…

generally if you do narrow you are over the milky way or really near … this help you to find near what needed