Orion Nebula

[stevenc77]

Hi guys, this is my first go at the Orion Nebula, and it is great to finally try something other than the Lagoon! Taken with a Canon 40d and roughly 20 minutes of exposure stacked. I will try to spend more time doing the stacking properly as I just stacked the lot in one hit regardless of exposure and ISO. Any tips? Steve.

http://i481.photobucket.com/albums/rr172/standz18/Autosave8.jpg?t=1222460140

[Garyh]

Looks like you are on your way Steve, only comment is the color seems a bit odd? maybe you have bad LP at you place doing this? Maybe some color balance and level adjustments in PS?
cheers

[Jeffkop]

Yeah Steve, Ive never seen it greenish before and its really easy to over expose the centre of it with those 4 bright stars. Ive taken images with a 40D and at the time, autoguiding wasnt an option for me so I had to take short exposures, like 20secs. I didnt get any of the greenish tinge but rather started to get some deep red and grey colour. So perhaps Gary is right, you may have some serious pollution froma close light to contend with. Point is though, weather permitting, you have the scope out again and get to perhaps change a few settings on the camera and I will just bet the next one will be better ... they always are .. GOOD LUCK

[stevenc77]

Funnily enough i took the images right next to a damn street light, but i tried to block it with a screen! I managed to get the setup to track with good exposures without trails up to four or five minutes (EQ6 Pro). That was achieved by attaining polar alignment using drift alignment with an illuminated reticle eyepiece. What i don't get is why was the camera still on the target five hours later? Surely it would have drifted out of view by then...or does the mechanical error in the drive even out over time to just an average variation? (rendering an unsteady cycle useless for long exposures). Also i have a 12" dob and even in dark skies i can instantly see the green nebula in Orion, so if not light pollution what would cause this? Perhaps I need to get a guide scope and autoguider, and even a main scope of higher quality to answer these questions (but I wanted to do it the hard way first!). So many questions????????

[bojan]

Autoguiding takes care of all errors in tracking... but it is primarily used for periodic errors, which can not be compensated (easily) otherwise..
Long-term tracking speed accuracy of EQ6 is quite OK (crystal controlled, 20ppm typical), so if polar alignment is accurate, there is no reason why scope should not be on the target after couple of hours.
BTW, I found out that guiding (EQ6 basic) is not necessary for lenses 300mm and shorter (polar alignment done with polar scope only).. but for 500mm (and longer) it is helpful (and mandatory for longer).
With guiding, I am guessing the polar alignment is not so critical any more.