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Photographing Comet Hale-Bopp

A Quick and Dirty Guide by Russ Arcuri

This is a guide for people who want to take photos of the comet, but don't have a lot of specialized equipment for astrophotography. All photo.net regular readers will likely have an SLR, a tripod, and one or two fast prime lenses, right? That's all that's necessary for reasonably good pics of the comet.

Equipment

The camera: Any SLR camera with shutter speeds up to 30 seconds and/or "bulb" mode will suffice. If you have a modern SLR that uses battery power to keep the shutter open, pack an extra battery or two. You'll also want a remote shutter release or cable release. You can do without the remote release if your camera has a self-timer.

The lens: My favorite lens for photographing comets is an 85/1.8. This focal length is long enough that the comet won't be a tiny blur on your pics, but short enough that the stars won't trail too noticeably in the exposures we'll be using. (I'll explain star-trailing below.) If you don't have an 85/1.8, don't worry - you can get reasonably good pics with a fast 50, like a 50/1.4 or /1.8. Oh, if you have an autofocus camera, you have to be able to turn it (autofocus) off.

The tripod: Any tripod will suffice, but the heavier, the better. If you don't have a tripod, forget it. Beg, borrow, or steal one if need be.

Other equipment: I'd also recommend bringing along a small flashlight, a stopwatch, and a pair of binoculars.

[Editor's note: Where to buy all of this stuff? Check out the photo.net recommended retailers. Adorama has particularly good selection and prices for binoculars.]

Film

You can pretty much forget about slide film. Anything faster than ISO 100 suffers from terrible grain, and you'll need very fast film for good comet photos. High-speed negative film is the film-du-jour for astrophotography.

I like Fuji Super G 800 and Kodak Ektapress Multispeed 640 (PJM) for photographing the comet. Others have had good luck with Kodak Pro 400 (PPF) and Kodak Royal Gold 1000. For simplicity's sake, take my advice and get the Super G 800. It's probably the easiest to find other than Royal Gold 1000, which I think is too grainy and has a color cast I don't like. Faster (ISO 1600-3200) films are much too grainy, IMO.

Procedure

1.) While still at home, load your film into your camera, and take one picture in daylight or with flash of anything you want. (If you have a gray card, take a picture of that.) This "regular" picture will help the lab when you bring your film in to be processed.

2.) Pack your stuff into a car. If you don't have a car, borrow one. Plan your trip so you'll arrive where you're going about an hour after sunset. If you live in a cold area, dress warm.

3.) Get out of the city. This is extremely important. Find a spot at least 5 miles outside the city (suburbs don't count -- get at least 5 miles outside of the suburbs, to avoid the glow of the city lights.) 5 miles is about the minimum. The sky won't be pitch black, but it will be dark enough for the pics. Be sure you drive out of the city in the direction of the comet - northwest. You don't want to have city lights between you and the comet. If you've got the time and the inclination, go further - 10 or 15 miles is even better. The first couple weeks of April are especially good because there is no moon in the evening/night sky. The moon's glow will drown out the fainter parts of the comet's tail when it is visible.

4.) Find an out-of-the-way location, without much traffic, and a good view of the comet. Look at the comet through your binoculars -- this is absolutely the best view of the comet and tail you will get.

5.) Put the camera on the tripod, and attach the remote release.

6.) Focus the lens on the infinity mark. Be sure the autofocus feature is turned OFF.

7.) Point the camera at the comet. It is bright enough that you should be able to frame it in your camera's viewfinder. You may want to include the branches of a tree, or other natural objects in the frame too.

8.) Set the lens at its widest aperture, and do a series of exposures as described below. If you don't have a remote release, set the self timer on the camera to trip the shutter. The exposure times are: 4 seconds, 8 seconds, 10 seconds, 15 seconds, 20 seconds, 30 seconds.

If your camera does not support these shutter speeds, set it on "bulb" and use the stopwatch to time the exposures. Be sure to shield your flashlight from the lens. (I should have mentioned that a lens hood is quite valuable here.) Be careful not to shake the camera during the exposures.

Every once in a while (between exposures) make sure the framing is still good. The rotation of the earth will slowly move the comet out of the frame if you're not careful.

9.) Now stop the lens down one stop from its widest aperture. Again, do exposures of 4 seconds, 8 seconds, 10 seconds, 15 seconds, 20 seconds, and 30 seconds.

The rotation of the Earth will cause the stars (and the comet) to trail across the film in these long exposures, turning round star images into ovals or lines. However, it probably won't be very noticeable under 20 seconds. It will be noticeable in the 30 second exposures, but you may decide you like the effect. You can, of course, do longer exposures than 30 seconds, but the trailing is much more pronounced over 30 seconds.

10.) If you have other focal length lenses, you can try them as well. Try to keep the apertures at f/2.8 or faster. Slower (f/4) lenses will work too, but you won't pick up as much of the tail. The longer the focal length in use, the more obvious the trailing will be. With a 135mm lens, the stars and comet will noticeably trail in a 15 second exposure or less. With a 35mm lens, you can do 30 or 45 second exposures without much trailing, but the comet will be smaller in the picture.

11.) When you get the film developed, warn the lab that they are comet photos. Tell them that if they have difficulty finding the frame edges, they shouldn't cut the negatives. Explain to them that the sky should be fairly dark, but it doesn't have to be pitch black. If they print the pics for a completely black sky, not much of the comet's tail will be visible. If they let the printing machine "autocorrect" the exposures, it will badly overexpose them, producing a medium gray sky -- yuck. You might also explain to them that the comet exhibits two tails - a bright yellow dust tail, and a dimmer blue ion tail going off at an angle to the dust tail.

12.) If the lab is incapable of producing a reasonably dark sky, try a different lab. A good lab may be able to enhance the dimmer blue tail a bit to make it more visible.

How'd they turn out?

The pics should be good enough to impress your family and friends, especially if any of them tried taking pics of the comet with a point and shoot camera. Even more so if they used the built-in flash. (Don't laugh! One of your relatives did this just last night!)

If you want better pictures than this, you need one or more of the following things:

Have your film push-processed

Fuji Super G 800 pushes well to 1600. Contrast and grain increase slightly, but higher contrast is good in comet photos and Fuji 800's grain is fine enough that it can afford to be pushed.

A darker location

On top of a mountain, hours away from a city would be ideal.

A tracking mount for your camera

These counteract the rotation of the Earth, allowing you to leave the shutter open for minutes at a time without star trails.

If you'd like info about tracking (barndoor) mounts, or if you want to be really envious of some terrific comet photos, see Brian Rachford's excellent Wide-Field Astrophotography Page.

Good luck!

Links

Copyright 1997 Russ Arcuri.

Article created 1997

Readers' Comments


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Ben Yaffe , April 06, 1997; 11:23 A.M.

Hey- I took pictures of the lunar eclipse a while back with my Rebel XS and my 35-80 with a minimum aperature of about 4. Jupiter was barely visible below the moon, but I didn't think that that would be a problem. I made most of the exposures at 20-30 seconds. When I got the pics back from the lab, the first thing I noticed was the large white blotch over the moon! I guess it was jupiter, but I am sure that it was just barely visible. Can you help explain this? --ben yaffe

Russ Arcuri , April 07, 1997; 09:13 A.M.

I've gotten a couple questions via e-mail about photographing the moon and the comet in the same frame later this week (Thursday). Since this relates to the above question, and might be of general interest, I'm posting my answer here.

Here's the problem: the moon is really, really bright -- thousands of times brighter than the comet. So the simple answer is that there is no single proper exposure for both the moon and the comet. The moon is an object brightly lit by the sun - the approximate exposure for it when it's full or nearly full is 1/film ISO at f/11. When it's a crescent the proper exposure is 1/film ISO at f/8. As you already know, the proper exposure for the comet is around 20 seconds at f/2 with an 80mm lens (or longer, if you have a tracking mount for your camera).

The complex answer is this: you can do a double exposure. It won't be technically correct, but it will look cool. Here's how:

First, using the longest lens you have, expose the crescent moon at 1/film ISO at f/8. For example, if you're using Fuji 800, the proper exposure would be 1/800 at f/8. Since most cameras won't do 1/800, you'd pick the closest thing, which might be 1/750 at f/8, or 1/500 at f/11 if your camera can't do 1/750. Place the moon on one side of the frame - be sure that your camera is set for a double exposure.

For the second exposure, change lenses, put the comet on the other side of the frame, and expose for 15 or 20 seconds at approx. f/2. Now you have a picture with both the moon and the comet properly exposed in the same frame.

If you really want to do a single exposure which shows the moon and the comet on the same frame, you have to simply let the moon overexpose.

Russ Arcuri , April 07, 1997; 09:20 A.M.

I also should have noted that the ECLIPSED moon calls for a longer exposure than the normal, uneclipsed moon. I'm not sure of the proper exposure, but it would probably be along the lines of 2-3 seconds at f/5.6. Perhaps someone who knows the correct answer to this question could comment? I'm really just guessing here.

Patrick Chase , July 07, 1997; 02:47 A.M.

I think that comet shots are a great opportunity to "go digital". When I developed my Hale-Bopp shots, I found that I had a reasonable set of photos, but with one common flaw: grain. This was particularly in the sky and in the silhouette of the treeline against the sky. I've seen the same in a lot of other peoples' Hale-Bopp shots, which is why I'm bothering to post this.

Here are two ways to fix such grain in an image-editor, once you have a scan of your image: 1. Slam all of the grainy stuff to black. This is easy to do (by adjusting the input range in the Image:Adjust:Levels dialog in PhotoShop, for example), but very heavy-handed. For example, it would obliterated the treeline mentioned above. 2. Use an agressive noise-reducing filter. I like median filters for this purpose. The problem is that if applied to the whole image, any filter agressive enough to suppress grain would also act upon the stars. The trick here it to create a mask including only the stuff you want filtered (should be everything but stars), and use that mask to control which pixels the filter can touch. The photoshop "Select Color Range" dialog is a good place to start for creating such a mask, though there are a vast number of other approaches. I hope this helps someone!

-- Patrick

Ben Woodruff , November 16, 1999; 04:55 P.M.

Two excellent photoshop ways of killing grain are as follows

A. Either in the scanning software(Nikonscan) or in the Adjust curves, use the set black point tool on a dark area of the image. This will make it a smooth black instead of the grainy black.

B. Convert to CMYK, change to the black channel by hitting CTRL+4. On this channel, use the dust and scratches tool, usually with a 4 to 5 pixel radius, and a threshold of 0 levels. If you find you lose too much image sharpness, hit CTRL+`, to get back to all 4 layers, and unsharp mask.

Hope this helps

Ben

Roy J , December 10, 2000; 03:38 P.M.

This article talks about only simple astrophotos, if you are taking pictures of Orion through a 12 inch telescope, you'll have more problems to worry about. A typical photo of deep space objects are going to last about 30 minutes or sometimes even longer. To eliminate the star circles you'll need a clock drive on the telescope set at the same speed the Earth is spinning at. Because you are not using a lens, you don't have to worry about expensive fast telephoto lenses, but you do need a fast telescope, f4 - f5(f5 on a camera lens is slow, but it's very fast for a telescope), a f10 telescope will take forever. Also, you should use a camera that has a mirror locking feature, a mirror slap can cause an object in space to move thousands of miles. You'll probably want to use a manual camera, since some auto SLRs can't hold the shutter open for 40 minutes, or if it can, the battery will get drained quickly on a cold night.

Tak-Ming Leung , March 09, 2001; 03:25 A.M.

Capturing images of beautiful yet elusive celestial objects is a thrilling experience for me. Like no other form of art, astrophotography empowers its participants to look back in history by taking pictures from photons that take millions of years to travel through the vast universe. Like other form of photography though, it requires both technical skills and aesthetic visions. My passion with astrophotography focuses mainly on capturing dazzling images of galaxies, nebulae or comets etc. on film. There are other areas of astrophotography (CCD-based or scientific-oriented) which I'm not going to discuss here.

Most astrophotos we see on magazines or posters (except those featuring images taken by profesisonal observatories or the famed Hubble Space Telescope) require a camera coupled with a telescope or a long focal-length telephoto lens mounted on a equatorial mount. In general, the focal-length of the telescope/lens depends on the size of the object. The exposure time depends on the brightness of the object and focal-ratio of the optics. A good way to start taking astrophoto is to buy a used Schmidt Cassegrain type telescope (about $400- $800) with 8" aperture (such as the CelesXXon or the MeaXX brand). These telescopes are well suited for basic astrophotography of galaxies, star clusters, comets, moon, some planets and nebulae. They usually come complete with tripod, electronics (guiding system) and accessories (eyepieces). Exposure is usually long (from minutes to hours) and the guiding procedure can be tedious but the results are rewarding. Use fast films (ASA 400 - 800) or better yet, use hypersensitized films. Movements (wind, vibration etc) must be avoided and the atmosphere should be steady and the sky as dark as possible. A good source of reference is the "Sky and TelesXXpe" magazine or the "AstrXXomy" magazine. Have fun star-hopping and picture-taking!!!

The author uses a PXXtax LX body, PXXtax SDHF 100 ED refractor with f/3.6 adaptor and PXXtax MS-4 mount.

Rockne Roll , April 20, 2003; 05:55 P.M.

Have you ever thought about fujipress 1600??? The grain is razor sharp. Or what about b&w??????????????????????

does anybody ever try this with either a 200 or a 300??? you could get some good stuff.

If you are just going for the stars, not a comet or anything, try this. Get some slow film (100-200 should do it). point a short zoom lens (35-70 or 28-80) at the north star, hold the shutter open for 2 min, and as you do, turn the zoom ring. Good times

Rachel Young , January 10, 2007; 08:25 A.M.

This is a simple astronomy tip: use a red filter or a piece of transparent red tape to cover the end of your flashlight. The human eye adjusts more slowly to red light than to white light. This way, after you turn your flashlight off, your eyes will still be adjusted to darkness.

Rafael Canedo , February 21, 2007; 12:46 A.M.

I think this article was written some time on 1997, ten long years ago. I have one question, Can all this be possible with a digital camera?

Jerald Johnson , June 04, 2007; 05:37 P.M.

I wanted to add this as a help topic article, if I posted this wrong, please let me know what to do to change it...

I've been sinking into astro-photography more and more over the past 2 years now, what it has taught me about focal lengths, exposure, on and on has renewed my interest in regular photography. I'm also a member of Cloudynights Telescope Review forum ( www.cloudynights.com ). I'll relay what I have learned about the subject and what others have learned. I'm still a rookie when it comes to regular photography and it's taken several roles of film and many stressful headaches to come up with less than 10 mentionable deepsky photos, and of those I'm only proud of a couple because I guided them correctly. One of the first things that has been found in recent years is the better films for astro. As far as ISO is really concerned, it won't make much difference except in grain and saturation. The biggest factor in picking film is it's red responce down to the "hydrogen alpha" line of the spectrum, approx 656 nanometers. The most popular films currently that can show this red nicely is Fuji Provia 400F, Fuji Sensia 200, and Kodak E200. These films also seem to have a nice response to reprocity failure, although nobody I have dealt with has ever been able to graph it. Print films and high ISO (800+) are the worst films to use if you're trying to gather color across the spectrum. They seriously lack a red response to Hydrogen Alpha, the greens and blues are cut horribly, and the grain gets in the way. Hypersensitive films are used for research, but, they won't bring out color. The color will be washed out in favor of shortened exposure times on distant, very dim objects. Because of the atmosphere, stay away from infrared film.

As far as scopes go. Well, that's a loaded subject, depends on who you ask as to what type of info you'll receive. The basics, on a reflector or catadioptric scopes (newtonian, schmidt-newtonian, schmidt-cassigran, etc) you should aim for 8inch or more aperature, expect the f/speed to be long. One of the shortest is the Meade LXD-75 at f/4, most are even slower at f/11 or more and require focal reducers for reasonable exposure times. With reflectors you won't get the aperature, they more closely resemble the characteristics of long tele-photo lenses but cost hundreds if not thousands more. For more in depth help and step by step on what you will need, want, and how to use it go to this site: http://www.petesastrophotography.com/ the owner has the screen name of clownfish at cloudynights and has taken film astro-photos that could compete with the CCD and DSLR.

You can also work with DSLR. Now, I haven't really wanted to mess with digital purely because of the work invovled after you finally take the shot(s) may take several hours of work with software that you may or may not have access to. Noise is a big problem, no matter the DSLR you use, the built in noise reduction won't help, neither will the noise reducing masks such as Adobe's. You have to take several 'darks' in addition to the shots you take thru the scope or for that matter thru a regular lens. Essentially, if you take 10 2minute sub exposures, you (depending on who you ask) take 3 or 4 two minute dark shots (covering the lens, the scope objective, etc). The darks have to be taken while the camera is at the same temperature as the regular photos were taken to capture the noise to be subtracted later in the software. Once the photos are taken, darks subtracted, then you have to align and combine all the sub shots. I've been told it can be done in Adobe, but it's a long frustraiting way because most comercial photo software isn't designed for this. The most popular is imagesplus, registax, PixInSight. One problem I've found recently and decided I didn't like about using a DSLR is ghosting in long exposures. I did a wide angle shot with my D-80 at Cygnus, the exposure was only 4 min long, one 4 min dark exposure, the shot turned out green, not tinted, it turned out GREEN. All the background detail was there, stars were pinpoint, but the levels showed the red and blue where they were suppose to be but the green was saturating the photo. It was later found that it was the light reflecting off the sensor to the filter and back, at certain angles the sensor appears green on appearance.

No matter which style you choose, digital or film, one of biggest hurdles will be focus. Focusing thru a scope is not the same as the focusing you're used to in normal photography. Stars are point light sources, they will be fuzzy at best in the best of viewfinders and the human eye will compensate for the focus. There a few ways to overcome the problem. The cheapest way is a Hartman Mask, a piece of cardboard (for example) with 2 or 3 holes cut in it. When looking thru the camera's view finder you'll see the stars in double or triplet, move the focus untill you see the doubles or triples merge into one star. You still have human eye error. The most accurate and easy to use that others including myself have found is the Ronchi screen. A ronchi screen uses small blades spaced so that when not in focus there are bars across the image in the eyepiece and in focus no bars are visible. Either you're in focus or you're not, no human eye error. You can find examples here: http://www.stellar-international.com/ .

Here are some examples, not the best, but they are my first semi-successful attempts. I say 'semi' because I was just learning about the focus problems, guiding, and long exposure thru a scope.

M42 (Great Orion Nebula) 15 minute exposure, Minolta X370, Fuji Sensia 200, thru 10 inch Schimdt-Newtonian scope, 1016mm focal length (f/4). http://i136.photobucket.com/albums/q167/jerry_2412/Astro-photos/orion-neb.jpg should be noted, the focus was way off and had to be fixed in Adobe, the secondary mirror was visible in the stars in the original image, even fixed, you can see the focus was off, used a Hartman Mask.

M31 (Andromeda Galaxy), 12 minute exposure (later learned should have been no less than 25 minutes), same camera, film, and scope as the previous photo above. The focus was much better. http://i136.photobucket.com/albums/q167/jerry_2412/Astro-photos/M31.jpg

Both of these photos were manually guided thru a secondary 90mm x 1000mm refractor scope mounted piggy back on the main scope. I have since turned to auto-guiding, using a CCD thru that scope so my laptop can 'see' where the scope is and make small adjustments every second rather than me trying to catch drift movment every 20-30 seconds thru an eyepiece with reticle.

Again, if anyone has questions, I will try my best to answer them, and if I don't know the answer I will find a resource to help answer them.

Jerry Johnson


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