Assignment 7: Slow it Down -- Congratulations travischance

[mattsartin]

Now Jon that's not fair to everyone else!

[Jon Ruyle]

Wow, Jon, those are beautiful.

Thanks!
I've been in to astronomy and photography for some time, but only
recently have gotten interested in astrophotography.

Now Jon that's not fair to everyone else!

Hmmm... I always think it isn't fair to me when you guys with actual skill post your photos... [:P]

[Ghosthex]

[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.33.12/western-fair-08-1086-2.jpg[/img]

[HiFiGuy1]

Jon,


That is a great shot of the Orion. What is stacking? Are you taking multiple exposures and somehow combining them? Is it like HDR, or something totally different?

[MattG]

[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.39.55/palm.jpg[/img]

[Dumien]

Sorry guys, I had to post another one


Canon Rebel XSi - 450D
Canon EF 24-70mm f/2.8L
5 sec
24mm @ f/8.0
ISO 100






The only post I did on this was lowering the black level so that the people in the foreground got "blacked-away"...unfortunately, when I printed it (a 50*75 cm print) they popped out a little again...but it still looks good to me


Andy

[Stephen Probert]

Gosthex, is this image really a second or longer exposure? Looking at the blurred lights, that ride must have been turning less than once every 30 seconds for it to be a 1 sec exposure. Cool shot though!

[Stephen Probert]

Made this shot for my wife as a part of a "Digital Anniversary Card" for our 2nd anniversary.


<span class="photoQExifValue"]Canon EOS 5D|<span class="photoQExifValue"]24 mm|<span class="photoQExifValue"]f/9|<span class="photoQExifValue"]30 sec|<span class="photoQExifTag"]ISO<span class="photoQExifValue"]800

[musickna]

Made this shot for my wife as a part of a "Digital Anniversary Card" for our 2nd anniversary.

I love it! I hope your wife was suitably impressed! []

[Jon Ruyle]

That is a great shot of the Orion. What is stacking? Are you taking multiple exposures and somehow combining them? Is it like HDR, or something totally different?

Thanks


Yes, by stacking I mean I just took multiple exposures. Deep Sky Stacker alligned the images (they were very close to start with) and added them up.


This does allow more dynamic range like HDR, but not much (to get detail at the center of the nebula I would have taken a very short exposure, ie the standard HDR technique).


The main reason for multiple exposures is that tracking the stars is not perfect. The Mach 1 mount I was using is very accurate, but tracking accuracy is limited by how well you align the axis of rotation of the mount with the axis of rotation of the sky. It must be done almost perfectly for long exposures. Pointing the mounttowards the north star will give enough accuracy for an exposure of only a few seconds, (the North Star is not exactly North, of course). I used a polar allignment scope (with different markings for the position of Polaris for different years since Polaris moves slowly in the sky), which allowed about 8 minute exposures. The elongated stars at the corner of the frame are due to the optics (I wasn't using a field flattener), not tracking.


I *should* have used an autoguider, which is another small telescope and ccd which detects star movement and actively corrects for errors, thus allowing exposures about as long as you want (I've done single exposures of up to about 45 minutes wile using an autoguider), but I didn't have time to set it up so I just went with the shorter exposures and stacked them.