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Old 04-09-2008, 11:35 PM
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beren
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Flat Darks Bias frame combinations

Hi finally have flat capability and just need to know if theres any right method in the number of flat and bias frames taken. Should you match the number of lights/darks or maybe double etc ? any thoughts....cheers

Stuart
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Old 05-09-2008, 02:00 AM
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RB (Andrew)
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I usually combine an odd number of flats (say 13 for good luck ).
My usual is anything between 11 and 15 flats and combine into a master flat.
Also I change the orientation of the flats slightly as I go to eliminate any 'errors'.

So Stuart did you build a flat-'machine' or bought one made up or something?
I'd love to see a picy or two mate.
I'm thinking of building one soon.

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Old 05-09-2008, 06:34 AM
Dennis
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Hi Stuart

I usually take a minimum of 6 Darks and 10 Flats based on suggestions picked up from general reading.

The Flats are easy because they are usually to 2 seconds so I can zip through them in no time. However, taking 6 x 3 minute Darks can be a bit of a chore sometimes as I take Darks for each session as I don’t have a permanent set up and standardised operating temperature, etc.

Cheers

Dennis
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Old 05-09-2008, 08:11 AM
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beren
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Cheers RB/Dennis, I usually equal the number of darks to the lights taken I'll have to organise a library or something its not fun taking 10+min darks on a frosty night.
RB embarrassed to write I took the easy way with a Light box from Astro-handy with adapters to fit my scopes. Used it for the first time the previous night with the C9.25 and a F6.3 fr, added a pic of M83 with 5 exposures at 5mins, first dso taken with this scope
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Old 05-09-2008, 08:55 AM
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RB (Andrew)
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Quote:
Originally Posted by beren View Post
RB embarrassed to write I took the easy way with a Light box from Astro-handy with adapters to fit my scopes. Used it for the first time the previous night with the C9.25 and a F6.3 fr, added a pic of M83 with 5 exposures at 5mins, first dso taken with this scope
LOL nothing to be ashamed of, I'll probably go that route after I build mind and find it doesn't work.
The 'flat boxes' look great Stuart !

M83 looks awesome, first light, congrats mate !
Have a quick look in PS and try this, see if it improves the image on your monitor.
Go Image|Adjustments|Channel Mixer and punch in:

+6 constant for each channel, (last item in menu).

This will lift the background sky and bring out a bit more detail in the spiral.
Anyway see if it makes a difference.

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Old 05-09-2008, 09:24 AM
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Terry B
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I take somewhere between 7 and 15 darks and flats depending on my patience. You should use an odd number if you median combine them as the maths works better with an odd number.
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Old 05-09-2008, 12:52 PM
Dennis
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I remember reading that a minimum of 6 Darks provides an optimum “Master Dark” for a “Median Combine”, but I just cannot find the reference to that recommendation now.

Thanks for the tips Andrew & Terry on taking an odd number of calibration frames for the Median Combine function – I’ll factor that into my workflow now.

Cheers

Dennis
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Old 05-09-2008, 07:06 PM
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beren
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Thanks Terry.....thanks RB for the tip thats great cheers mate
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