Bias frames, how many?

[Vega]

Can anyone recommend a good number for creating a Master Bias frame? I mean how many exposures?

30, 50, 100, A gazzillion ?

Thanks

Matt

[James]

Until the experts correct me I've assumed it's just a statistical thing - the more the better but the returns diminish as the number of frames grows. As they're virtually instant subs for me it's no big deal to rattle of 80-100 - that may not be applicable in other setups.

James

[Dann]

I keep 50 for each ISO I use and retake them every 6 months or so. I have no particular reason for taking 50 other than following what some others on the forum do.

[Psychobilly]

I usually use 40-50 their quick to take ...

[johnrt]

Yup. About 80-100 as they are so quick to take.

Why would you need to re-take every 6 months? Will the bias signal in the camera chip change over time?

[Vega]

Looks like the general consensus is 50+ and as many as you are bothered to chuck in there onwards

I might go for a nice round 97 LOL

Matt

[Psychobilly]

If your using DSS you can speed things up by using the Master Offset tiff for subsequent images..

Bias can change with time so they should be refreshed periodically...

DSS will need at least one light to "stack" before it will go on to produce the master's I often copy one of the bias files and use it for the dummy light... I do the same for Darks, flats etc...

[Vega]

I use ImagesPlus but I think the same rule applies... I'll need to create my MasterBias frame with a light frame. I've recently acuired a new modded DSLR so I'll be doing plenty of experimenting to make my MasterBias with ;-)

Thanks for reminding me

:-)

[todd8137]

take them ans save them s suggested a range of iso`s 200,300 ect i save them up saves time some times

[ollypenrice]

Yup. About 80-100 as they are so quick to take.

Why would you need to re-take every 6 months? Will the bias signal in the camera chip change over time?

Yes, I think it probably will. I've read, also, that simply changing cables or USB connections can change the bias, too.

Like a good few others I use bias frames only as darks-for-flats and for no other purpose. I shoot them when I've finished the flats since it takes so little time. Minimum of fifty, I'd say.

Olly

[Vega]

Just processed 80 bias frames in ImagesPlus and there was no need for a light frame. Just used the bias frame tab in automatic image set processing and it converted them, did a whole load of checks and created a masterbias.. great stuff... but to be expected for the price of the software!

Cheers

[steppenwolf]

I don't take more than 20 but that's just me! I do refresh them a couple of times a year though as the sensor 'ages' and any change in the cabling should be considered as good cause for a refresh - at the end of the day, a BIAS frame is a representation of the readout noise so any changes in the sensor or the means of downloading should be compensated for.