Flats with no scope

[tingting44]

Hi, its been a long time since i had a scope to do flats, now i have a barn door im looking at doing flats again, are there any methods that work good just for dslr camera and lens with no scope? i use to use a light board which was great for the telescope but no longer have either now, would love to hear what some of you guys are using

[geordie85]

I'd just stretch a plain white t-shirt over the lens and point at a clear sky

[tingting44]

Yes but unlike a telescope the focus can be moved and will be moved if I go putting a t shirt over the lens is the only problem, any shift in focus and the flats will do more harm than good 😭

[happy-kat]

I use an Android app Lightbox and use my tablet as a light box and just rest  that on the lens to take flats.

I have also used notepad on the computer screen but I needed to place a large white envelope over the monitor as the camera was capturing flicker.

[stevewanstall]

I aim the telescope at a piece of white card about about half a metre from the front of the telescope. I have also used an app on a tablet to give a white screen , reduced the brightness as much as possible and put that right against the telescope (so there were no reflections)

[tingting44]

Happy kat I like the idea of covering the screen instead of the lens or telescope! Nice one, I'll have to start experimenting

 

Thanks Steven I'm trying to get flats with canon kit lens so even if u breath or look at it wrong it changes focus 🤣

Edited April 28, 2020 by tingting44

[ollypenrice]

Focus needs to be reasonably close to the point used for the capture but a small deviation won't matter.

Olly

[Macavity]

I've had some rather good results using an entirely artificial polynomial FIT
for the background "flat" using the IRIS Software... I sense this is the "same"
gradient removal algorithm used in some commercial software as well? 😏

http://www.astrosurf.com/buil/iris-software.html

With basic (wide!) star [only] fields I don't need to bother with "masks" even.
IIRC this was taken with a 24mm "Pankcake" (+ my APS-C chip Canon 100D):

Even with a fair bit of sky gradient + vignetting the simple fit works well... at least as a start? 🙂

Edited April 28, 2020 by Macavity

[tingting44]

thanks olly  ill have to start tinkering

 

Thats very interesting Chris, i will look more into that software today, thank you

 

edit, im actually shocked how good your image has come out! very nice indeed

 

Chris is this the feature you used in IRIS? cant find any tutorials for this software any where online, keep getting iris payrol lol

Flat-field extraction from science images

 

EDIT, i cant get my head around IRIS, its so strange lol, will have to do some proper research 1st i think lol

Edited April 28, 2020 by tingting44

[iapa]

10 hours ago, tingting44 said:

Yes but unlike a telescope the focus can be moved and will be moved if I go putting a t shirt over the lens is the only problem, any shift in focus and the flats will do more harm than good 😭

masking tape around the focuser?