m31 help

[cardconvict]

hi can anyone please tell me what this banding is , now i have stretch'ed this a little bit, that is to stand the banding out a little bit more also there is a dust spot on the top off m31 which i'am aware of, it was taken with a ED80 through my 450d also i was using a 2 inch skywatcher filter.the subs where at 300 secs long.

[roundycat]

apart from anything else I would say the picture is way over stretched. The core is burnt out and the background too light. Start again and be more careful with the stretching, in particular do not shift the white point. With the background set to about 12-15% brightness or 28-30-33 in RGB levels (approx PS measurements) and it should improve a lot. The stripy effect may be a bias artefact which may disappear with a darker background.

Dennis

[cardconvict]

hi dennis thanks for responding i know about me overstrtching it because i did that on purpose to show the banding more as i i'am confused in what it is. is it because of my new filter and now i'am doing lengths off 5 miniute's creating loads of noise ?

[blinky]

I think it's noise, the good news is it should be easy to get rid of! Take some flats and BIAS shots, the bias ones should get rid of it.

[cardconvict]

cheers blinky thinking that myself i have just reshot some more bias frames at 60 of them. when you are shooting lenghts of up to 5 mins would it be better to have lets say 60 darks would that help the image

[blinky]

No I would not bother with 60 darks, I usually find between 10 and 20 darks is plenty. Also not that Bias frames only need to be taken once, so get a large number of these and make a 'master bias' frame in DSS.

[cardconvict]

yeah ok thanks i knew about the bias that i only needed one set for everythink but i only kept about 15 so i have decided to raise that to 60 maybe more ?.

also the problem i'am getting is that when i start to stretch it in photoshop it does'nt take alot to start to show alot of noise. i don't know if i'am doing anythink wrong as this is the first time that i'am adventuring to the five miniute mark for the exposers.

[blinky]

5 min exposures should be OK, I have a 350d and routinely take 5 mins exposures. Careful stretching is the way to go!

[cardconvict]

ok also i have noticed that soon as i go into photoshop i don't have to set the black point because the graph is all over to the left already which is the first for me as because normally i can set the black point first then on to the curves

[roundycat]

have a look here for some ideas on how to use PS for the best advantage.

Astrophotography

For my money 20 bias will be enough but bias does change with time so don't rely on one master bias for all time.

Dennis

[cardconvict]

ok does anyone want to have a go at proceesing this see what they make of it here is the link to a tiff Autosave.tif

[Cloudwatcher]

ok does anyone want to have a go at proceesing this see what they make of it ...........

Heres my effort................ still reckon it looks better when flipped vertically.

[cardconvict]

wow you really have got some really good processing techniques