imaging problems

[viperwhite33]

hello, i have been trying to image m42 with a nexstar6se, 6.3 focal reducer and meade ccd camera. if i do a 10 of 15 second exposure i get good nebulae and color but the sars are too bright they join up as a blur, do i need a filter to filter out the star light allowing me to do a longer exposure, and then add the shorter exposure on to it with only stars on it. any help really appreciated. see image of probs im having. i have tried to adjust contrast etc but to no avail.

[RobH]

Hello Viperwhite.

M42, although an obvious target when you start imaging, is actually rather tricky to get right, because, as you have found out, there is a very great difference in brightness between the core and the outer nebulousity.

The standard way to approach this is to shoot one set of exposures to get the core detail, without oversaturating the stars, and then shoot longer exposures to capture the outer nebulousity, then merge these together in a program like photoshop.

Adjusting the contrast won't really work....once an area is saturated, any information is lost and no amount of adjustment will bring it back!

It is possible, as long as the core isn't overexposed, to bring out a lot of the faint stuff without blowing out the core by using the CURVES tool in Photoshop, but this takes a little practice to begin with and will only work so far. A combination of layering and curves is the best approach for really good results.

Cheers

Rob