Photographing with just a camera and tripod no telescope

What settings do you use to photograph stars, moon, etc.. ex: f-stop, exposure length, iso, lens size mm..

I have everything from 15mm - 400mm so I dont know if zooming is better or a wider focal length.. I've seen some pretty cool pictures people have taken and they are not on a specific object but a wider view with just the digital camera and a tripod.. just something to experiment with but i would like to hear what other people are using for settings.

Marc

Hi Marc, from my recent experience in shooting the moon (during the eclipse!) you want to get the longest reach you have, so put that 400mm lens on! Exposure and aperture differs from moon phases but from what I used on a full moon was f11 and about 1/125 to 1/200 sec exposure on ISO100. There is some sunny f16 rule to follow when shooting the moon but I find it easier and practical to just shoot and review, make adjustments and shoot again. Rinse and repeat if necessary! Now for stars I don't know, hopefully someone else will chime in!

For stars on just a tripod it depends on what you are after. If you want star trails showing the earth's rotation, point it toward the pole. Though not necessarily centered on the pole. It depends on the effect you are after. F stop depends on lens quality and how dark your skies are. For very dark skies, open the lens all the way. Exposure time again depends on how dark your skies are. I like like to go several hours in dark skies. The longer the exposure the longer the trail. Use a wide angle to standard lens. If your skies are bright and you go a long time then stop it down. At least with digital you can erase and try again. Exact settings of ISO, f stop and exposure time are all interdependent on your sky conditions and how the others are set. You'll want to find the settings that work best for your skies and the length of trail you want. Defocusing the camera a tad will often increase star color and make a more colorful picture. Bright stars show the most color but if they burn in the color is lost. A slight defocus assures they won't burn in, at least around the edges giving them their correct color instead of white.

If you want to capture constellations then you have to go with short exposures. About 15 seconds with a normal lens, wide angle can go longer, say 30 seconds. If you can tolerate more trailing of the stars then use longer exposure times. Here, due to the short exposure you will want to open the lens all the way unless the lens has problems with point sources at the edge of the field. ISO setting needs to be fairly high as well, as high as noise allows. If shooting near the pole at say Ursa Major then you will likely get 30 seconds before the stars trail too much. How much is too much is an individual thing of course. Again, the longer the lens the shorter the exposure must be. A star at the celestial equator moves a the rate of 1 degree every 4 minutes. That's two moon diameters. As you move away from the pole the rate varies with the cosine of the declination. So at 40 degrees declination you'd multiply 4*0.766 (cosine of 40 degrees) to get 3 degrees motion per minute. Cosine of 60 degrees is 0.5 so north of that you can expose at least twice as long as at the equator.

Simple inexpensive equatorial mounts will carry a camera allowing longer exposure times. How long depends on how accurately you polar align them. But even a rather crude alignment should go 5 minutes with a "normal" focal length lens. One such is offered by Orion. You'll need one of the two electric drives so the cost is $90 for a basic drive, a bit more for a better one. If serious about this go for the better one.
http://www.telescope.com/control/pro...oduct_id=09055

It also comes in a tripod version which may be better unless you have a stable table to put the little one on.
http://www.telescope.com/control/pro...oduct_id=09011

Of course, in this hobby there's always the ridiculously expensive solution as well.
http://www.astrovid.com/prod_details.php?pid=3397

For that price you can get an entire equatorially mounted scope and just piggy back the camera on it!

Exposure for the moon is same as the exposure in daylight here on earth. Moon is lit by the same sun at about the same distance so expect about the same exposure. Full moon has no shadows so is more like a beach scene exposure while a thin crescent has lots of shadows (you don't see them but they are there) so you will need to open up a stop or two depending on how thin the crescent. It will be a lot smaller than you expect.

Rick

Rick gave some wonderful advice. I may add that there is a simple rule for moon exposure for a full moon. 1/ISO @ f11, then bracket from there. As for shooting stars, there is no test of lens quality better than shooting point sources of light. In other words, whatever flaws a certain lens has will show glaringly when shooting the stars. Especially shooting wide open. Depending on your particular lens quality, a good idea is to stop down 1 or 2 stops for star shots.

I am in the same position. I have a Canon Rebel XT, 18-55, 50 f1.8, and Sigma 70-300 APO.

I usually shoot at ISO 1600 when trying to shoot stars or DSOs without trails.

At 300mm the longest you can shoot without bad trailing is 1.6sec. Shooting M42/43 at 2 or 2.5 secs you get a lot more nebulosity, but trailing. Here's a stack of 54 1.6 sec shots at 300mm.


At 70mm you can get decent shots at 5-10 secs. At 50mm, I think the 8-15sec range is decent. when you go down to 18mm, you can shoot for 30 secs. I think that when I shoot for 30 secs, I have to reduce the ISO because of the noise pollution in my area.

Here are a couple of other shots that I've taken with a camera and tripod.

Sirius with M41


Andromeda galaxy
http://home.swbell.net/smasraum/andromeda_M31.jpg

Cluster NGC2362
http://home.swbell.net/smasraum/unkclustercrop.jpg

Wow thank you for that great information. I dont know how i missed the replies to this thread I must of missed the email reminder.

So what would be the best way to practice on the moon. I am just starting to understand what stacking images is all about but i have yet to try it. How far apart in time are the images taken and how many do you take ? I have the software that everyone seems to be using to put images back together but im waiting to find out about time and all that good stuff.

Photographing the moon is completely different than photographing other stuff like stars, clusters, constellations, nebulas. So if you want to practice shooting that stuff, don't practice on the moon. If you want to practice on the moon to shoot more of the moon, then go right ahead.

For the moon, I don't know how many shots you'd need, but usually the more the merrier. At 300mm, I can get a decent image out of 1 single shot. I've tried stacking moon shots and that seemed to work well too. I used registax and stacked 5 or 10 images. For the moon, your shots can be anywhere from 1/640 - 1/200 of a second. It's good to keep them short because at 1/60, the motion is evident. On the moon, I get the best results when the "seas" are fairly dark in the shot. It's really easy to overexpose the moon.

When stacking, I shoot the pictures one after the other.

Stacking for planetary work is very different than that for deep sky.

Planetary it's best to use a web cam that can capture 30 frames a second (AVI movie). After you have a thousand or so let Registax pick out and stack the best of the bunch. How many depends on your seeing. Average seeing it might be 200 or so. That gives you a lot of data to work with so the wavelet and other processing can often bring out detail far beyond what was in any single frame. Pefect tracking is NOT desired as you want to eke out detail smaller than the resolution of the CCD by this process. If the exact same scene hits the same pixel this isn't possible. Registax or K3CCD tools (some prefer it) will align the tracking errors when it stacks them. You just don't want such lousy tracking the image is blurred by it. Usually not a problem at 30 frames a second. Work at about f/30 with a typical web cam.

Exposure time is simply the correct exposure for what you are taking. That depends on f ratio and the object. Phase of the moon if that's your target also enters in. As it gets toward full shadows too small to see get smaller so it gets brighter and you need less exposure. Watch the results as you change the exposure and gain settings and adjust for the best image on the monitor.

Deep sky is stacked for an entirely different reason. The one beginners usually have is that their mounts can't track accurately for more than a few seconds, maybe a minute if they are lucky. Smasraum isn't even using a drive so he is limited to VERY short exposures. Stacking these is needed just to build an image. It will be too faint to even see on one frame. By adding many together you get something like one long exposure. Of course you have to align the frames which software does easily. There is a limit to this as each time you read out the data noise is added. After enough frames the noise starts to build faster than the signal and you gain nothing by further stacking.

Those with drives and or guiders that will allow them to shoot for hours don't do so. A CCD or film will over expose bright objects in the frame if you go too long. But even if there's nothing bright enough to be a problem you still likely don't go all that long. 30 minutes is my limit. The reason being if something goes wrong, hours of data can be lost if you take one 2 hour exposure. If you take 12 10 minute ones then the glitch robs you of 10 minutes of time and you still have a usable image rather than 2 totally lost hours. Some things that have happend to me: A bright satellite flies through the frame; An idiot fisherman shines his spotlight onto me trying to figure out what I'm doing; Clouds, power glitches. hitting the wrong key on the computer are more common glitches. Then there was the neighbor kid years ago that leaned against the scope afer 90 minutes on film and asked, "What you doing?" I saved his life by not killing him. Also if the temperature is changing the focus needs to be adjusted fairly often. So most of the time, unless I'm using narrow band filters, I'll limit my exposure time to 10 minutes if nothing bright is in the frame, if it is the time will go down to 5 minutes or even 2 in a few cases. Then I can stack images building the faint detail but not over exposing the bright stuff. Again there's some read noise added so you use the longest frame time that suits the subject and filters you are using balanced against the risk of Mr. Murphy showing up.

While a CCD can record extremely faint things in only a few seconds the image will be very noisy. The longer the exposure time the less the noise. It goes down by the square of the exposure time. So a one hour image won't go any deeper than a 1 minute one (well maybe a bit). What you do get for the added time is a much cleaner image with far less "grain" (noise). After an hour the noise is reduced 7.75 times over a 1 minute image. Going to 4 hours will reduce that noise in half. Another 16 hours will cut that in half. Notice you soon reach a point of little gain for hours of work.

It matters little if that data is collected in one hour frames or 10 minute ones unless the camera has a lot of read noise. So we go with short frames stacking only those that pass muster. Saves a lot of wasted time and over exposure of bright regions.

Stacking can be done by various mathematical routines, each has its advantages and disadvantages. Sigma reject is great for rejecting satellites, meteors and random noise. But it also rejects asteroids! One might be a new discovery. So I don't use it unless I have a nasty satellite or something similar. Simple addition, if it will use more bits than 16 of the CCD, can be used when stacking images of various exposure times. This helps bring out really bright detail in faint objects, like the Trapezium area of M42. I might stack 30" images for the stars, 2 minute for the bright nebula region and 10 for the rest. When added by a good add routine it will preserve the detail in the bright regions yet bring out the faint. Saves a lot of processing time. For darks I usually use Median Combine as it removes random noise and cosmic ray hits that would ruin a dark.

Sometimes a simple average combine is all that's needed. Just depends on what I'm working on which method I use.

In the data with the images I post, like for: M51 Re Re processed
you'll see:
L=6x10', RGB=2x10'
That means I use 6 10 minute stacked images (sigma reject after finding satellite trails in 4 of the 6 images) for the luminosity image. I used 2 10 minute frames for each color; 2 red, 2 green and 2 blue all 10 minutes long. These were combined using a simple average combine. Those resulting 4 black and white images are imported to photoshop and turned into the color image that was posted. The luminosity image provides the detail the RGB images provide the color but not the detail.

I think Rick pretty well covered, well, everything!

Wow that is amazing. I had no idea it was so complex. I cant wait to get that point where i have equipment good enough to take decent photos.

Rick:

[quote=RickJ;1180883]

Simple inexpensive equatorial mounts will carry a camera allowing longer exposure times. ...
One such is offered by Orion. You'll need one of the two electric drives so the cost is $90 for a basic drive, a bit more for a better one. If serious about this go for the better one.
http://www.telescope.com/control/pro...oduct_id=09055

Has anybody actually tried this device ($50 for the mount + $40 for the motor) with a DSLR and a lens with a reasonable focal length, say 100 mm?

I am looking for something like this to take star picture on dark sites not accessible from roads. Obviously it is not as good as a regular tracking tripod, but since the total weight (camera + lens) being moved is not much ( maybe 2 lb) it may work for a sequence of 30 second exposures.

Any experience with this?

hha

[quote=hha1;1186302]Rick:

It will work fine at that focal length if accurately polar aligned. The tripod version can carry a short 3" telescope easily so 2 lb camera it wouldn't notice. I know several who use the tripod version for cameras. The little one needs a very solid base to set on and then should be fine. The key to all this is your polar alignment. As long as that is good it will work fine at 100mm. I'd limit the exposure to about 5 minutes at that focal length if you just eyeball the alignment -- does the axis look like its pointed at Polaris? -- type of alignment.

For longer times you'd want to drift align it. Put a small scope on it with a cross hair eyepiece and follow the procedure for drift alignment (Google it). Then you'll get up to 20 minutes or so out of it at 100mm. Much beyond 400mm and the periodic error will likely start to hurt. I'd consider that the limit.

I home built something similar years ago (50's) in which the polar axis was a hinge. It is known as a barn door tracker/mount/platform (take your pick). I powered it with a wind up alarm clock modified so the minute hand gear turned the screw that did the tracking. A small telescope was also on the platform which I used to make minor corrections as needed. That tracked a 400mm f/6.3 $35 lens for 30 minutes. It would be far inferior to this mount with a dual axis drive on it. I've attached the result. It would be far easier to achieve with this mount an the dual axis corrector if you use a guide scope like I did. I checked it every 5 minutes or so. It ran at 40x as I recall. I lost the system in a move in the late 60's. I still regret that! The photo was taken about 1963 I believe, give or take a year.

If you use a guider get the dual axis drive for longer imaging.

Rick

Attached Images

m31.jpg (131.3 KB, 13 views)

I want to see the rings of Saturn with just my 35 mm camera and tripod. I used 400 mm FL and all I get is a dot. If I use 1600 mm FL I can't see a damn thing through all the lenses stacked together!

Am I better off just photographing through my 8 inch scope for Saturn?

That's like asking; "If I want to fly to Paris should I flap my arms or take a plane?

With an 8" with barlow to extend it to a 6000mm focal length you should get good results photographically with a web cam. Though without a drive you may need to cut that back and settle for a pretty small Saturn. Visually it will be spectacular in an 8" scope of reasonable quality.

Though I did once attach a 10mm eyepiece to the 400mm lens that took the M31 shot I posted in this thread. It showed a very tiny Saturn at 40x with a heck of a lot of color fringing. Color correction wasn't up to that task. I could see the rings however.

Rick