flat frames

[gonzostar]

As i am taking photographs using the astronomik cls filter, should i take flat frames with the filter still inside the camera.

Ta

Dean 

[swag72]

Yes - You take flat frames with everything the same in the imaging train, including the same focus, filters and orientation of the camera. 

[graemlourens]

Hi Dean.

Yes, as there could be dust on the filter, or other optical imperfections that distort the resulting image, if you would make flats without the filter, it would not correct the image correctly (maybe it would, but thats just luck )

Kind regards, Graem

[MarsG76]

yes

[Scott]

And thats a yes from me too

[gonzostar]

Thanks everyone. I thinks thats an absolute yes! 

[Garethr]

Yes.

Just snap away at the end of the session whilst everything is still in place that's the key.  Flats don't take any time at all, darks are the the pain.

Gareth

[gonzostar]

So you can do flats in the dark? 

[graemlourens]

Nooooo

To make a flat you need to illuminate the optical train evenly, so your resulting flat will have the optical imperfections.

You can take lots of things to do that, i was using ipad's when i was mobile. You can also use laptop screens.

There are flatboxes giving you the 'perfect' illumination, but they're not cheap. My ipad always worked fine, just get some kind of bright screen app that displayes you pure white and adjust so that you're flats do not take too long and are also not too short, for broadband filters my flats are at around 0.2 s.

The 'optimal' exposure is different from camera to camera.

I have seen a lot people talking about a third of the full well capacity and for DSLR's around a third of the histogram. But others say half. My experience showd that both works.

Kind regards, Graem

[gonzostar]

Thanks for that. Yes i have being looking at flat boxes. I am still putting white tea shirt over dew cap and pointing at zenith 

Dean

[PeterCPC]

If you set your camera to AV it should give a well exposed flat. You can use a laptop or I now use a Tattoo box.

Peter

[gonzostar]

Thanks Peter

[ollypenrice]

Using a flat box (in my case an illuminated panel) I find it far better to do them in a dark environment than a daytime one. I usually get gradients in flats when I use the panel in the observatory by day, even though it is reasonably dark. I find this odd but... that's what I find.

Olly

[gonzostar]

Thanls Olly Lots of good ideas i need to try out. Trouble is waiting for decent clear nights!

Dean