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Author Topic: Bias frames  (Read 228 times)

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Offline clive

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Bias frames
« on: 15:25:07, 24 December, 2017 »
Have we got to take bias frames with all 4 filters say  red green blue  lum cheers

Offline chris.bailey

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Re: Bias frames
« Reply #1 on: 15:41:15, 24 December, 2017 »
Nope. No light involved so no need to do them by filter IN FACT I highly recommend taking Bias frames in total darkness as any light leak ruins them and those pesky photons have a nasty habit of sneaking through the tiniest gap. As they are zero length exposures they are quick to take so take plenty (I take 200) and they remain valid for quite some time (I last did mine a year ago). Temperature does have a VERY small impact with some CCD's so worth taking them at your normal set point temperature.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline clive

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Re: Bias frames
« Reply #2 on: 15:47:12, 24 December, 2017 »
Ok chris i only took about 25 when i imaged m33 it looks very red looking i dont know why  may be not enough bias frames then with my dslr i used about 25  so with filters so i need a lot moor then

Offline chris.bailey

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Re: Bias frames
« Reply #3 on: 10:23:28, 25 December, 2017 »
Clive

The bias frames should not affect the colour balance but yes 25 is a bit mean. It only takes a few minutes to take a load and get a nice clean master bias so why not? Depending on your calibration routine the bias is used for the lights and flats (and darks if dark scaling) so potentially three times and each time you add the noise component from the master bias. To me its a no brainer to get the master bias noise component as low as possible.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline clive

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Re: Bias frames
« Reply #4 on: 12:16:17, 25 December, 2017 »
Ok cheers chris

 

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