Sh 2-125/IC5146

[icpass]

Hi all

Over the last few clear nights i have been gathering subs on the Cocoon nebula.

21x10 mins at iso 800 and cls filter with moded 350d,and 10x10min darks.

flats are a bit of a grey area for me,and so far have had no luck doing them.

Stacked in Dss and procesed in cs5.

Ian

[NickH]

Ian...given that you are imaging from the Centre of Bath, with a DSLR, that is an extraordinary shot...well done

[glennbech]

Hi Ian,

Great effort. Im a real fan of sticking with one target/night. 21x10 minutes deserves respect! :-)

As for flats; Take a white t-shirt, cover your scope. Point it at the sky, take photos and check the histogram so that you're around the middle. Brighter is better than too dark in my experience. Take 19-21 images. Add them as flat frames in DSS. Cover your scope. Take the same number of frames in "darkness" these are your flat-darks.

This is by no means a scientific aproach to flats, but it works for me :-) Try stacking both with- and without. You'll be able to stretch your images way more after aplying flats!

[NickH]

Yeah..I think Ian's already tried that...is this the FLT Ian or the 66 btw? If it's the 66 I have an EL panel you can borrow to try out?

[icpass]

Nick

Its with the FLT,but i didnt know about checking the histogram,i just illuminated and took exp's.I think i will build a light panel for it.

Will give it another try later.

ian

[NickH]

cool

Flats will really help...and don't obviously move anything until you have done them

[icpass]

Are flats better done at the end of the session,rather than any time

[NickH]

If you lock everything down...in your setup you can do them whenever you like...as it aint moving

[icpass]

ok i get you,why when i do them do i just see a white screen.!!!!

[NickH]

exposure too long or histogram auto adjusting..

[glennbech]

Any flats are also better than no flats. In 2008 i took images of the leo triplet and forgot to take flats. The next morning I set up the equipment again, and did flats with a tshirt.

The tshirt had an ink stain, and the flats were taken at a slightly different camera position, but they really helped take out the vignetting.

Maybe a photoshop plugin (gradient xterminator?) or Pixinsight are better than very primitive flats? Any opinions on that?

[ollypenrice]

Best to take proper flats but they can be darned awkward. I can't use daytime T shirt flats because light gets in everywhere and creates gradients. An EL panel is certainly the easiest way.

Olly