Astrophotography and Scanning

[lovethismoment]

I�ve just had my first foray into astrophotography � nothing fancy,

basically just an attempt to capture the stars as points using 24

f2.8 and 50 f1.8 lenses and Fuji NPZ. After reading up a little bit

(doesn�t seem nearly enough now) I left the aperture at f2.8 on both

lenses and had shutter speeds between 6 and 30 seconds. The area I

was in was reasonably dark, no moon, but there was a little bit of

light pollution from one direction.

 

I get my prints done on a Fuji Frontier and was very disappointed

with the results. I was well prepared for out-of-focus stars or

completely black prints, but what I got was a sky that is a murky

grey-dark green colour and so grainy you can only just tell the

difference between the stars and the gain. I assume this is a result

of the very thin negatives and the scanning process but the question

is what can be done about it?

 

I have a Canon FS4000 scanner at home and have been attempting to get

something resembling an attractive scan from my negatives. Mostly

they turn out looking like the prints, sometimes they look worse. I

have tried using Vuescan and grain reduction, but maybe I just don�t

know how to use it properly because it seems to do a worse job than

Canon�s software. I�ve gotten better results scanning them in as

positives and adjusting the exposure on the scanner, but still can�t

seem to get anything that really resembles what I would expect to see

(ie. a dark sky and stars).

 

Does anyone have any tips about how to scan thin negatives without

all the grain? It must be possible since I�ve seen some great photos

on the web with really dark skies�or are they just from scanning the

prints? Would I be better off using slide film for astrophotography

and scanning? Can I get good prints from the Fuji Frontier or should

I forget digital processing? Or is it just a crummy photographic

technique?

 

BTW, examining the negatives shows there is certainly not much there

except for the stars, so maybe I just need more exposure???

 

Any help would be greatly appreciated.

[NK Guy]

Sounds to me like the images were terribly underexposed, yes.

[arniemilowsky]

A few suggestions. Your exposure times are too low. You should test exposure times using ISO 400 slide film, and start out with 30 seconds and increase by 15-30 seconds per exposure (30 sec interval is preferrable) depending on the amount of light pollution. You will get star trails as the exposure time lengthens, but you will get an idea where you need to be at. When you get the slides developed, tell the lab what you are doing, as they will not be able to recognize where the frames end, and will always cut your best shot in half. I always left my slides uncut. If you want to cut down exposure times, which is a real good idea, as light pollution limits exposure, use gas hypered film. Do a Google search on gas hypered film and start reading. Lumicon sells single rolls of gas hypered film (color and B/W), but their website is down now. You can get their phone number off the internet, and they sell directly. They are also great to talk with, and will help guide you in the right direction. Other Lumicon distributors exist, but you may be required to buy more than a few rolls at a time. Gas hypered film helps significantly.</p> You should know that astrophotography is not one of those areas in which you will go out on the first night (or several) and get several great shots; it takes some time to figure out exposure times, how to deal with light pollution (there are filters available; google search on LPR filter). If you stick with it, you can get really neat pictures. If you find you need long exposures, and don't want star trails, you may want to look into getting an equatorial mount motor to move the camera with the rotation of the earth. You should also know that if you really get into it, and want to try different things, astrophotography is the ultimate money pit, but the rewards are there. (I wound up using a cooled CCD camera mounted in the prime position a CST scope).

[peter nelson]

I'm an experienced astrophotographer (see: http://studio-nelson.com/scinat.htm ) and I disagree with the other posters. The Fuji NPZ that I know is ISO 800 and a 30 second exposure with ISO 800 should be <B>plenty</B> to pick up stars at f/2.8. Indeed, with a 50mm lens, at a declination of 0-degrees (i.e., shooting the celestial equator) the longest exposure you can do without trails is 26 seconds. In other words, you CAN'T keep the star on the same point on the film longer than 26 seconds in order to make a longer exposure without a motorized mount even if you wanted to! So using an exposure of several minutes would cause the star to trail across the film but no point on the film would be exposed for more than 26 seconds.<P>

 

The "graininess" you've seen is because the automated exposure system at the film lab tried to compensate for the "thin" negatives. <B>IT</B> doesn't know these were astrophotos - it wants the average density to be the same as a snapshot of Aunt Martha in front of the Statue of Liberty on a sunny day.<P>

 

Don't make the same mistake on your own scans. Set your scanner exposure manually so black is black and thin is nearly black. The stars themselves will be denser. When you examine the histogram it will be all bunched up on the low end but there should be SOME scores a bit higher - those are the stars. Use your levels adjustment in Photoshop to spread it out so the black is still down at the bottom but the stars are at whatever level of "white that looks reasonable to you.<P>

 

<B><U>Editorial Comment</B></U> These automated exposure systems at mini (and some pro-) labs make my blood boil. They're smart enough to make histograms in all three channels but not smart enough to recognized what the subject is. So they try to "fix" things by autobalancing density and color. The result is that if your negative has a predominant color it subtracts it, and if it has a predominant density it adjusts it to 18% gray! I had a Portra NC shot of a model - a closeup of a belly-button ring surrounded by just skin. The lab system "balanced" out the skin tone to neutral so I ended up with a black and white print with a colored belly-button ring! I couldn't have done it better in Photoshop if I tried!

[scott_eaton]

Yo peter,

 

I managed to 'blow out' the core of the orion nebula with a 135mm F2 Nikkor wide open mounted on a fixed tripod with a 30second exposure with Konica 3200. Wish I could find the print.

 

There was of course some minor star streaking, but I just couldn't believe how sensitive that film was.

 

My advice to to Lisa is to skip the print film because it will just result in a grainy mess with such low density exposures. Get a roll of Provia 400F or Sensia 400, shoot wide open at 1.8 for 30seconds, and do your own scan. They'll come out on the green side, but there will be less grain in the background and you can easily correct the color cast.

[dave_mueller]

"Astrophotography Prints from One-Hour Labs" by Jerry Lodigruss

 

http://www.astropix.com/HTML/I_ASTROP/I12/I12.HTM

 

This (and the rest of Jerry's site) should answer almost all of your questions.

[bernhard]

2 years ago I tried to capture the leonid showers, one camera with NPZ, one with Provia 400F. What you describe with NPZ is like a deja vu, I got EXACTLY the same crap, the negs were just too thin, I didn't even attempt to scan them. Provia 400F however came out pretty decently exposed and I didn't even push it. So Scott's suggestion is right on the money.

[peter nelson]

<I>I managed to 'blow out' the core of the orion nebula with a 135mm F2 Nikkor wide open mounted on a fixed tripod with a 30second exposure with Konica 3200. Wish I could find the print. </I><P>

 

That makes sense. I blew out the core of the Orion nebula (I assume we both mean M42) with a 5 minute (guided) exposure using a Nikkor 180 f/2.8 on Kodak Royal Gold 1000. It's a very bright nebula.

[lovethismoment]

Thanks heaps for everyone�s responses. Living in Australia I don't know how easily I'd find hypered film, though if the suggested store has a website that might be an option. I've got some Sensia 400 so I'll have a go with that when I next find an opportune night. On the bright side I did at least get some reasonable photos with the NPZ of a friend�s band playing a gig, so all was not lost :)

 

As an aside, can anyone recommend a good book on astrophotography, ranging from the basics to the more advanced techniques?

[lyle_aldridge1]

Lisa, this isn't much help for dealing with what you've already shot, but some of your problem may be caused by the low magnification from your relatively short lenses, especially the 28mm. The comment that your dark sky has too much grain suggests that you have actually OVER-exposed those parts of the image. Using such wide lenses, you're picking up a lot of light reflecting off what your naked eye perceives to be dark sky. You're concentrating light from large areas of sky onto the film, and that will kill the contrast you want.<p>

Increasing the magnification (just jumping up to a 105 or 135mm lens, for example) will pump up the contrast between the stars and the dark sky. This is sort of hard to explain, but basically, the stars are point sources of light, while the sky is a reflective body. When you magnify the sky, you are spreading the light from it out, so that it exposes the film less. But since the stars are point sources that show up only as points of light, no matter how much they are magnified, they don't go dim from magnification the way the sky does.

[peter nelson]

<I>while the sky is a reflective body. When you magnify the sky, you are spreading the light from it out, so that it exposes the film less</I><P>

 

Is this true? Say I paint the broad side of a barn 18% gray, and meter if to be be 1/250th at f/8 with ISO 200 film. Are you saying if I shoot it with a 50mm lens and a 105mm lens, both at f/8, the two focal lengths will produce different densities on the negative?

[lyle_aldridge1]

Well, Peter, you got me there! The films in your hypothetical get the same exposure and have the same resulting density, because �both at f/8� means you didn't just change magnification, you also changed the physical aperture of the lens to account for the magnification change. Telescopes don�t have that luxury feature, so when thinking in "astro mode," I tend to forget all about it. Lisa, forget everything I wrote until you get yourself a Schmidt camera :).

[scott_eaton]

Increasing your focal length also decreases the amount of time you can use in your exposure before stars begin to visibly streak.

 

Amen to that Schmidt camera rec.

[imaginator]

Splenders of the Universe, by Terence Dickinson and Jack Newton. It's big, hardbound, and full of wonderful images and ton's of advice for beginners, including camera on tripod, tracking mounts (commercial and homemade ones) shooting the moon, stars, planets, comets, and much much more! I've done a few "camera on tripod" shots, using Fuji 800 print film that were OK, but it's really hard to get good images without a subtle trailing effect (I used a 50mm f/2) Right now I'm building my own tracking mount, but I'm the inventer type, so most others would be better off buying a commercial one. Guess what? They are now making smaller setups that are much more affordable than many expect, and for a little more you get a motor drive! Since you will be using normal or wide angle lenses, the camera/lens won't weigh much, so check out <A HREF="http://www.telescopes.com/detail.asp?PID=14377">this affordable mount</A> Add a ball-swivel (ball-head) so you can aim anywhere in the sky. If you really like this astro stuff, then consider checking out a local astronomy club in your area. They might even let you "piggyback" your camera on one of the big guided telescopes (a ball head is great for this too!) Here's one I took using the Fuji800 and "camera on tripod" method.<div></div>

[lovethismoment]

I just thought I'd (finally) do a follow up to this question. I tried star trails with Sensia 400 and was very happy with the film and pretty happy with the photos (need to take more)...except for the fact it was the first time I shot with my EOS 10 and I didn't realise it put the date right in the frame (doh). I won't make that mistake again (dare I ask why anyone would want a date right in the middle of the frame?). Anyway, definitely go slide film all the way. I'd put up an example but I can't use my laptop at the moment (damn dodgy technology).

 

In a few weeks time I'm off to the Northern Territory, Australia for 3 weeks holiday and so will have ample opportunity to try more...along with lots of other photography of course. I love holidays!