Confessions of a Frustrated Amateur Astronomer

I just couldn’t get a break from the weather these past 2 months! You think that Hawaii, of all places, would have lots of clear blue skies.

NOPE!

I’ve been socked in for the past 2 months. I’m looking out the window as I write this and it is completely clouded over. The few days that had clear skies where during the weekdays. So that’s not helpful. It was pouring rain during the normal monthly star parties so I didn’t even go.

On the bright side, I took some pretty non astronomy related pictures with my new camera.

I have been mulling over a new camera since I borrowed the Canon XTi and took some photos at the dark site.  It was a tough decision since this will be the most expensive item I’ve purchase so far for this hobby.  Finally, Amazon dropped their prices on the Canon XSi and I decided it was just time to get one.

Of course it didn’t end there, getting the camera is only the start.  I had to get a good, fast lens to match.  So after yet even more hair pulling, I decided to get the Sigma 30mm f/1.4 lens.  When I took the picture of the Milky way a couple of months ago, I was using a 17mm F/4 lens.  This means that my new lens is 3 full stops faster than the one I used for the previous photo.  That should make a really big difference in the amount of light I could gather.  I could lower the ISO setting to 400 in order to reduce some of the noise in the old picture.

Next outing for the Hawaii Astronomical Society is in 2 weeks.  Until then, I guess I’m going to use to the camera and just take some pictures.m

 I’ve darken the picture a bit because it seems to show more detail.  The picture is definitely kind of crappy.  There are hardly any details visible other than 2 brown bands.  What I need to figure out is whether the poor quality is due to something I did wrong or that I’ve reached the limits of my 6″ scope.  It could be that I didn’t focus the scope as well as I could have.  It is not easy to focus a dobsonian scope with the webcam.  If you play the video, you would notice that Jupiter goes out of frame in about 20 seconds.  So that’s the amount of time I have to adjust my focus before I have to move the telescope.

Other reasons could be the light pollution.  Maybe I could get a better picture if I’m at a dark site.  Also I’m not too sure about the seeing of the night.  The video didn’t show too much bluring so I think the seeing was pretty good that night.

I’ve been spending some time reading about techniques for post processing digital images.  There are certainly a lot of information about digital filters and their effect on the picture.  But there is not that much information on the net about which filter to apply to an astrophoto that will make it look more “pleasing”.

I guess for astrophotography, the ultimate goal is to capture the sky as sharp as possible and with as much detail as possible.  So when I processed the pictures I took from the last star party, I simply tried as hard as I could to bring out as much detail as possible.  However, the more I look at the picture, the more “busy” it looks and everything just looks messy.  When I looked back as some of the constellations pictures at astropix I realized that Jerry had used a diffusion filter on his pictures.  Actually, he said in his tutorial that a fog filter will soften the picture and bring out the bright stars of the constellation better.

I couldn’t really just take another picture with a fog filter so I decided to see if I could simulate the effect in photoshop.  After a lot of trial and error (there are a lot of filters in photoshop, and none of them is labeled diffusion), I found that the effect I was looking for is call the soft focus.  Soft focus is used mostly in portraits to give the subject a softer look.  A softer look reduces the effects of harsh lines and intensifies colors.  To simulate the effect in photoshop (no, there isn’t a soft focus filter like they should have), you have to use the Gaussian blur.  Here is a great tutorial on how to properly use the Gaussian blur in photoshop to simulate a soft filter.

I applied a very strong soft filter to the image I took last star party and here is the result:

Scorpius and Sagittarius with heavy soft focus applied

As you can see, a lot of the background stars have been wiped away.  But this is different than simply turning down the brightness because the bright stars kept their brilliance and is much more pronounce than before.  You can now very easily pick out the major constellations in the picture.  The star’s color shows up much better now that it is not fighting with the background as much.  Overall, I think it looks pretty good.

Hawaii astronomical society held their monthly public star party at Dillingham Airfield near Kaena Point last Saturday.  Dillingham is a very dark site, one of the few left on Oahu.  The airfield only has 1 runway for light aircrafts.

Usually, about 15-20 club members and about 30 or so general public will show up at the star party.  Most of the telescopes there during a public star party are dobsonians ranging anywhere from 6″ (mines) to 18″ (someone else).  Most of the telescopes last Saturday was on Jupiter as it is very high in the sky at this time of the year and a good target for any size telescope.  However, last Saturday I was on a mission, I was there to take my first, good, picture of the sky.

Most of the club’s members are old school amateur astronomers and do their work visually.  There were only 2 other members doing astrophotography besides myself so I setup my equipment, which amounts to a the canon XTi on a tripod, near them.  One member, Steven, was set up with a 8″ f/4 newtoian on a Vixen sphinx mount.  Some of the pictures he took was pretty amazing.  The other was doing the same thing I was, wide angle fixed tripod astrophotography.  Turns out he was just starting out too.

But enough of that, I was there to take pictures.  So after some camera fiddling I manage to take this picture:

Canon XTi, 17mm focal length, f/4, ISO 1600, 30 seconds exposure

I couldn’t stop smiling when I saw the picture on the camera’s screen.  It was hard for me to believe that I was able to capture so much of the Milky way core in a single 30 seconds exposure with a fairly slow lens.  The picture was pointing South towards Sagittarius; the same view as the picture I took from my balcony.  The difference, of course, is that this is from a pretty dark site.  I was so excited about the success that I completely forgot to take any dark frames or bias frames for later.  I did remember to take several pictures from the same angle for stacking.  Unfortunately a cloud moved in and ruined all but that 1 picture.  I guess I should be happy that at least 1 picture turned out good.

contrast and color adjust of the Milky way core

The picture looks pretty good, the Milky way core has lots of detail.  You can easily pick out M6, M7 and the Lagoon nebular in the picture.  There are also a lot of colors that you could see.  Star trails doesn’t seem to be a problem at this focal length and exposure time.  In case you’re curious, the mountains at the bottom is the Waianae mountain range, 1 of 2 mountain ranges on Oahu.

The person who loaned me the camera had some dark and bias frames from an earlier shoot and he wanted to see what the picture would look like when both are subtracted from the light frame.  He also adjusted color, contrast and ran the image through noise ninja to tone down the noise.

dark frame and bias frame subtracted, color and contrast adjusted, noise ninja'ed

The picture has much better contrast especially at the center of the Milky way.  The red shows up very clear.

I wanted to see at which focal length star trails becomes apparent.  That was harder than I though because I could not see the setting on the lens in the dark and I don’t have a red flash light.  So I guessed at it and took a picture.

Canon XTi, 53mm focal length, f/5.6, ISO 1600, 30 seconds exposure

The stars are trailing very badly at 53mm focal length.  So that limits the types of pictures I could take on a tripod.  Especially when facing away from the celestrial poles.  As a test, I took a picture of the North celestrial pole to see the star trails.

Canon XTi, 53mm focal length, f/5.6, ISO 1600, 30 seconds exposure

I was off the mark a little bit.  The little dipper is off camera to the left but I did manage to capture all of Cassiopeia.  However, there isn’t very much else in the picture so it is pretty boring.

I would call Saturday a complete success.  I was able to recreate some of the picture I’ve seen on the Internet using their suggested settings.  I was able to prove to myself that the camera I plan to get, and the dark site available to me are both adequate for astrophotography.  This gives me some confident now to spend money on a DSLR carmera and mount.