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Old 27-04-2013, 09:49 PM
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Joshua Bunn (Joshua)
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HA flat field times?

Hi all,

Im trying to capture some flats for my ha data which was through a 5nm filter and im at 10 min exposures and the adu is only at 6000, a long way off the 30000 that im aiming for. Is this normal, should they be this long?
using the same light box, my flats for Lum are 2.5 sec.

Is it ok to capture the flats binned 2x2 and them re sample to 1x1?

thanks
Josh
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Old 27-04-2013, 09:54 PM
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Tandum (Robin)
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What sort of bulbs are in the light box? LED's ?

To be honest I don;t normally do flats for Ha anyway.
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Old 27-04-2013, 09:55 PM
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Joshua Bunn (Joshua)
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Yep, white light LED's
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Old 27-04-2013, 10:00 PM
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Tandum (Robin)
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I guess it depends on the LED's. I seem to remember doing 20sec exposures last time I did Ha flats but I'm using Baader filters an I think they are about 12nm not 5. Try combining without flats.
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Old 27-04-2013, 10:03 PM
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Joshua Bunn (Joshua)
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Thanks Robin,

Maybee... then again, i may need a stronger light box.

Josh
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Old 27-04-2013, 10:07 PM
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Tandum (Robin)
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My homebrew box has 4xled's, one in each corner pointing up. They are just bright white LED's from jaycar, nothing flash?

I do run it off my dew controller so I can turn it down.
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Old 27-04-2013, 10:42 PM
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OK, as long as they do the job. Ive got 9 evenly spaced pointing straight down with some diffuser material in between running off about 2.8 volts, don't think they can take much more than that. Its the small square ones with 4 studs, although i only need two of the studs.

I looked at the 600sec exposure again and it produced an ADU of 17000 not the original 6000, but still short of where i want to be. Maybe i need to point it at the sky at midday to get some light through . Ill try that - away from the sun.

Josh
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Old 07-05-2013, 05:58 AM
stevous67 (Steve M)
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Hi Josh,

I use occassionally a self made EL panel, and Ha flats take about 45-50 sec, as opposed to a luminance thats only a few sec. Normally I use sky flats.

Cheers

Steve
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Old 07-05-2013, 11:18 AM
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Joshua Bunn (Joshua)
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Hi Steve,

Thankyou, Yea sky flats were the answer for me too with the ha filter. Did it late in the day when the sky brightness was changing, so using the stl with 26 sec downloads needed the exposure time increasing by about 1 sec every other exposure or so. but, still Blasted it in 5 sec .

CS
Josh
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