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Posts Made By: John Centala

April 27, 2004 11:37 AM Forum: Film Astrophotography - Imaging and Processing

NGC 2403

Posted By John Centala

I just compared your picture to one I took on Jan 16, 1999. My 4x6 print has a neutral dark gray background, and presumably shows everything recorded on the negative. I used an AP 130 "f6" with field flattener, and Kodak Royal Gold 400(-2) film, 45 minutes exposure. The actual focal length is exactly 900 mm. Mine does not have the bright blue color, more grayish but with a hint of pink in the tiny knots in the arms of the galaxy. I assume these are H2 regions. My picture has a bit lower contrast than yours. The resolution of mine is exactly the same as yours, except that I have slightly elongated star images due to field rotation around the guide star. I guided mine manually with a 60x700mm Jason refractor, 12mm eyepiece; AP400QMD mount. The 2 bright stars in your picture, to the left of the galaxy, are slightly orangish in my print. My limiting magnitude is possibly a bit fainter than yours, but not significantly. But I'm not sure it's fair to compare my print to what I happen to get on my computer screen. Since your sky background is so dark, you can probably get fainter stars by printing it lighter.

April 27, 2004 11:53 AM Forum: Film Astrophotography - Imaging and Processing

M-51

Posted By John Centala

I did M51 on April 22, 1998, same film (even the same emulsion number), exposure, optics, etc as in my comments on NGC 2403. My tracking was perfect this time, so my star images are rounder than yours. My limiting magnitude is clearly better than yours, but perhaps this is due to your mistracking. The big difference is in the color. Yours looks like it only recorded blue light, except for a hint of red in the companion galaxy. In my print, the two galaxy cores are clearly yellowish, while the spiral arms look purplish, due to the mixture of blue stars and red hydrogen gas. I greatly prefer the color of mine, but then it might not look as good if it were scanned.

April 27, 2004 12:05 PM Forum: Film Astrophotography - Imaging and Processing

M-81 & M-82

Posted By John Centala

I did this one on April 18, 1998, same data as before. My print is unfortunately too yellow. Limiting star magnitude of mine is at least as good as yours, perhaps a tad better. But M81 has very detailed spiral arms in my picture. I think that my lower contrast helps a lot to show both the bright and faint parts well. The reduced contrast makes M82 less detailed, but mine has a red "fog" (of hydrogen?) around the nucleus. I greatly prefer the performance of Royal Gold 400 to your Fuji film, especially considering you used a 6 inch scope. Too bad they don't make it anymore. Have you compared a real print to your scanned images? Maybe the scanner is not picking up the faint stuff.

April 27, 2004 12:12 PM Forum: Film Astrophotography - Imaging and Processing

M-101

Posted By John Centala

I took mine on April 22, 1998. Mine does not show the spiral arms any better than yours, unlike the case with M81. But mine has a better range of color, with a yellowish core and some hint of pink in the arms. My lower contrast seems to be a disadvantage in this photo. My resolution and limiting magnitude appear identical to yours.

May 20, 2004 07:13 PM Forum: Antique/Classic/Vintage Optical Instruments

RE Brandt Lens

Posted By John Centala

Long ago I looked through one, but only at rather low power for such a big lens. The image quality was very good except for the very noticeable chromatic aberration.

June 13, 2004 05:33 PM Forum: Celestron

Help me find a Glass Solar filter

Posted By John Centala

For best performance and a white solar image, get the Baader AstroSolar film. But such a filter is very fragile. The Thousand Oaks filter is much more rugged, gives an orange image, and has decent image quality.

July 13, 2004 08:53 AM Forum: Deep Sky Observing

M51 with binocs?

Posted By John Centala

It's not a big deal. All the Messier objects can be seen in binoculars, although for a few, like M76, M98, etc, you may need 15x70's or bigger. With my 20x100's, M51 is a very obvious double galaxy. With my 10x50's the companion galaxy is not obvious. Incidentally, the Astronomical League has an "observing club" called the Binocular Messier club, which you can check into at www.astroleague.org.

July 26, 2004 08:20 PM Forum: Telescope Making

Need Refractor Tube Source

Posted By John Centala

There is absolutely no need to have an adjustable cell for an F9 lens. Such a lens has a wide field of good image quality. Just cut the tube off as square as you can, and it will be good enough.

September 23, 2004 06:41 PM Forum: Deep Sky Observing

NGC6888

Posted By John Centala

I haven't looked at NGC6888 recently, but when I first saw it in my 17 inch Dob with an OIII filter, in about 1987, I thought it looked like a potato.