Shooting the Stars in Wyoming

How the hell did you not get just a solid streak across the sky with a 240 second exposure?!

Those are fantastic!

Exactly... When i first read it was a 240 second exposure and saw the pictures I knew something didn't add up. When I try to take pictures of stars just with 120 seconds i begin to get streaks..

Please explain...

Very nice images - are you doing any flatfielding or dark subtraction? I need to buy one of those equatorial mounts. I've been using my 20D to take 30 second exposures on a regular tripod which does great (with my favorite 24mm f/1.8 lens), but that is about the limit before trailing becomes apparent.

Jim.

rcfury wrote in post #5876646
Exactly... When i first read it was a 240 second exposure and saw the pictures I knew something didn't add up. When I try to take pictures of stars just with 120 seconds i begin to get streaks..

Please explain...

Well, he did say he has an RA drive on the mount.... it's supposed to keep the telescope (in this case camera) centered on one star. Notice the stars are fairly sharp, but the barn in the lower right is blurred from drive movement.

Awesome!

Nortelbert wrote in post #5876772
Well, he did say he has an RA drive on the mount.... it's supposed to keep the telescope (in this case camera) centered on one star. Notice the stars are fairly sharp, but the barn in the lower right is blurred from drive movement.

Ooooh! That's really freaken sweet! I want one of those!

Those are wonderful! Is an "equatorial mount" related to keeping the camera in motion with the stars as well" or is that soley the responsibility of the "RA Drive". First time I've heard these terms. I knew mounts existed for telescopes to keep them locked in place countering earth's rotation, but didn't expect that they could be as affordable as that. $107?! You have peaked my interest

BigBadBrain wrote in post #5874735
Curt,
Did you try any longer lens photography with that setup? I've always wanted to capture Andromeda but that would require a considerable amount of zoom compared to these images (which are fantastic by the way).

Thanks Brian. About Andromeda, I observed it with my naked eye during the nights that my Milky Way and Cygnus images were shot. Being the closest neghboring galaxy to us it is very large in the sky. Your eye can only sense the bright core, but if you were able to see all of its glory it would appear about three times the width of the moon from our perspective.

Shooting Andromeda is challenging because it requires an effort similar to HDR. The core will easily blow out if you expose for the faintest reaches of the spiral sturcture, so you have to shoot two different sessions and then merge them in post-processing. The same problem exists with several other popular objects, such as the Orion Nebula. As an example, here's an image that I shot over the course of three different nights of the Orion Nebula. Exposure lengths of 15-seconds, 30-seconds, and 2-minutes all had to be incorporated for the bright center of this complex not to be completely blown out while still preserving the faintest details around the perimeter. I shot it through the 800mm telescope that is linked below.

Byte size: ZERO | Content warning: NOT AN IMAGE

What kind of mount are you thinking of using? The reason I ask is because the ONLY reason I was able to get away with using an EQ-1 for astrophotography is the extremely short FLs I'm working with here. Autoguiding is necessary for practically all long-exposure work on deep sky objects if you really want to get good results. This is where it gets complicated very quickly. For example, here's my imaging rig set up at a monthly star party I attend. Most of my astrophotos are shot with this equipment:

http://picasaweb.googl​e.com …photo#517363694​4844661410

I'm not sure how much detail I should go into since this forum isn't focused on astrophotography. Most of the discussions that I've participated in take place on the Cloudy Nights forum where they have several rooms dedicated to the various methods of astrophotography (DSLR, cooled CCD, film, webcam, etc). I'm small potatoes in that arena though, still very much a beginner. There are guys with images that will completely blow your mind. When I first got interested in astrophotography I was astonished that people were capturing images with ground-based equipment when at first glance you'd just assume it was shot with the Hubble.

Hopefully the moderators won't mind this subject popping up in the Canon forums too. Keep the questions coming if you have them. I'm happy to help.

Bill Pham wrote in post #5875011
geez some very impressive shot. wish i can get shot like those one of this day. as soon as i figure out to do it.

Bill 1

Go to www.cloudynights.com and start asking questions. You might need to save up some money too

imhotep wrote in post #5878975
Go to www.cloudynights.com and start asking questions. You might need to save up some money too

thanks for the link. and what more money oh geez

Bill 1

rcfury wrote in post #5876646
Exactly... When i first read it was a 240 second exposure and saw the pictures I knew something didn't add up. When I try to take pictures of stars just with 120 seconds i begin to get streaks..

Please explain...

Disclaimer: This is a whirlwind tour of a huge topic that could easily eat up several months of research to fully explore. It certainly did for me

In my experience 60 seconds is long enough to get small streaks (i.e. my milky shot from Canyonlands last year). Generally speaking there are 2 broad catagories of telescope mounts - Alt/Az and German Equatorial (GEM). A GEM allows you to aim the optics at a target and then you only have to nudge one of the axes in order to keep it in view (that being the RA axis). If you install a motor that is designed specifically to match the earth's rotational speed, also none as the sidereal rate, you can in theory keep any target of your choosing in the FOV all night long. The mount will gradually turn at the same rate the earth does.

I say "in theory" because it depends entirely on how accurate your polar alignment is. The RA axis has to be perfectly in line with the north celestial pole, otherwise some amount of error will be present in the form of streaked stars. The NCP is about a degree off from polaris. In reality this is practically impossible to do for a variety of reasons. So rather than worry about obtaining a perfect polar alignment, serious astrophotographers use other methods to eliminate the error.

I'm afraid I'm confusing people. The morale of the story is don't go out and try this with a 400mm lens on the same EQ-1 mount I've used thinking it'll work the same way. When a human being attempts to aim their equatorial mount at the NCP there will ALWAYS be some amount of human error. At focal lengths under about 50mm that error is so small that it often is less than your DSLR pixel size even after a multi-minute exposure, so you get nice tight stars in the resulting image. Once you start wanting more and more magnification you have to bring in additional technologies to get the job done. Same goes for fainter objects which require longer exposures.

Curt:
Standing ovation!
The pictures are really fantastic and the work you did to get them is awesome. Thanks for sharing the pics and the setup. You rule!

Luigi

jscotti wrote in post #5876759
Very nice images - are you doing any flatfielding or dark subtraction? I need to buy one of those equatorial mounts. I've been using my 20D to take 30 second exposures on a regular tripod which does great (with my favorite 24mm f/1.8 lens), but that is about the limit before trailing becomes apparent.

Jim.

It depends on the situation. I almost always shoot dark frames so I can create a hot pixel map and have the benefit of dark subtraction. Even today's DSLR's are still very noisy compared to the cooled CCD cameras that are gaining popularity as well as market share in the AP community. The temperature in Wyoming was in the mid 40's when I shot these images so I wasn't too conerned about thermal noise. Hot pixels are always a problem though.

I shoot my flats with a light box that is made specifically for my 8" scope. So far I haven't made one for my camera lenses.

Triptoph wrote in post #5876985
Those are wonderful! Is an "equatorial mount" related to keeping the camera in motion with the stars as well" or is that soley the responsibility of the "RA Drive". First time I've heard these terms.

Thanks Triptoph. See some of my previous answers about equatorial mounts and let me know if I've muddied the water beyond recognition.

I knew mounts existed for telescopes to keep them locked in place countering earth's rotation, but didn't expect that they could be as affordable as that. $107?! You have peaked my interest

Ok, let me clarify some things. Nic already emailed me about this so I want to make sure I haven't given anybody a false sense of the expenses involved.

For $107 I bought the following items brand new:
http://www.telescope.c​om …ssories/~produc​t_id=09055
http://www.telescope.c​om …rollers/~produc​t_id=07826

Notice that there's not a full-size tripod included. That's because the "Min-Eq" is simply an EQ-1 mounthead minus the tripod legs. This is extremely cool IMHO for us terrestrial photographers because many of us use the Bogen/Manfrotto system and the EQ-1 will screw straight onto the 3/8" bolt on Manfrotto tripods. This is what I did.

But again, this setup is EXTREMELY low-tech on the spectrum of astrophotography equipment. My first computerized GEM that was capable of receiving autoguiding commands from a laptop cost about $500 used or $700 new. The mount I'm currently using is Orion's Atlas EQ-G which retails for $1500. It's rated to sling around up to 40 pounds of equipment. That's arguably the limit for purely visual observing though. The total weight of my current imaging scope, guidescope, and both cameras is around 22 pounds.

One of my AP buddies shoots with a $9k mount, a $4k telescope, and a $5k temperature controlled CCD camera. That doesn't even begin to cover the adapters, software, filters, and other support technologies. That's not to say that you have to drop $20k to give astrophotography a try though. Far from it. The EQ-1 for SWA imaging is a great place to get started and see if you even like it.

Very cool shots!