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01-24-2011, 05:02 AM   #136
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QuoteOriginally posted by outpostbob Quote
Thanks, Angus! I am encouraged, since the stacked image does indeed show a fair amount of red. Were ALL the exposures 0.3 seconds as you data showed? How many such subframes did you stack?
This was done with around 20 exposures, I need to have another go as I took 49 in total - some at 12,800 and some at 25,600

QuoteOriginally posted by outpostbob Quote
My 2.5 second exposure suggestion was based on a rule from Michael Covington's "Astrophotography for the Amateur." The original rule as published (for 35mm frames) was Max Exposure = 1200mm-sec, so a 300mm lens would allow 4 seconds to meet "no obvious trailing of stars" parameter. (More is possible if you are far from the celestial equator but that is irrelevant for Orion.) For APS-size frames, this would be reduced by the lens factor, so you want to keep the exposure below 800mm-sec. 2.5 sec x 300mm = 750mm-sec, so you should be OK. Now, since you were in a light polluted area, with a fast (f/2.8) lens, I can imagine that there was simply too much light to avoid washing out the entire frame with longer exposures than you used, especially at highest ISO.

I will look forward to seeing what you get from a dark location! Let us see what the most extreme frames look like, if you would. $1500 is a big enough purchase for me that I want to be VERY sure I will like the outcome.... and you're our only hope, Obiwan Kenobi! <G>

Bob
I tried getting away with longer exposures but I guess my Orion was too close to the horizon as I was already getting oval stars at 1/2 second exposures - the light pollution would have allowed a little more. Keep your fingers crossed for clear skies this Saturday, then I might be able to deliver - will try my new toy a 300/2.8 A* as well...

01-24-2011, 07:10 AM   #137
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Do you know any light pollution reduction filter that could be directly used on the lens (sky photo with camera and lens only, no telescope)?
01-24-2011, 08:05 AM   #138
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I don't believe there is a such of filter. The solution is to go outside of the city where the sky is dark and clear.
01-24-2011, 02:57 PM   #139
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QuoteOriginally posted by oliver939 Quote
Do you know any light pollution reduction filter that could be directly used on the lens (sky photo with camera and lens only, no telescope)?

Hutech Filters and Accessories

01-25-2011, 11:26 AM   #140
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QuoteOriginally posted by Raybo Quote
Good suggestion Raybo. I use the Hutech IDAS 48 mm Light Pollution Filter almost all the time. It fits Telescope 2 inch eyepiece holders directly, but with adaptors will fit most lenses. For example I just mounted my IDAS to a DA Pentax 50-200 using 52-49 and 49-48 step down filter adaptors. The adaptors are cheap enough for me to acquire a collection so I can put filters on most all my lenses. If you go way down like my 19 mm Vivitar which is threaded for 62 mm down to a 48 mm IDAS you may get some vignetting, but I've done it.

Hints: The 48 mm adaptors are not common in camera stores, I have a Kalt 49-48 and use the 49 end to go to all other sizes. Be aware some companies are not consistent as to what direction Step Down is or which number appears first on their web sites. I've bought a couple that, "went the wrong way."

If you live in a city with visual MAG 3-4 sky like me, you gotta use an LPR filter.

Here is a dark site image with a filterless K110D and a Sigma Zoom at 210mm, I don't think I had the IDAS filter at the time. 30 seconds * 25 images. NGC 2024 & B 33 & NGC 1997 & M 42 & M 43 in Orion.
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Last edited by LeoTaylor; 01-25-2011 at 11:27 AM. Reason: added "dark site"
01-25-2011, 02:22 PM   #141
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Easy Photoshop light pollution fix

I use CS5 but other photo software may have the same features. Disregard the stacking and cropping parts of the artical. I use it for single wide field shots to get the red out.

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01-28-2011, 09:16 AM   #142
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swapped the pics

Hi all together,

I put new pics into the post with hte two pics, one a straight ooc shot slightly with a slightly too long exposure and a stack of 26 pics worked on - all without any tracking!
02-11-2011, 03:24 AM   #143
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I finally had a chance to try my Kx this winter. Stock 18-55 lens set at 55mm f/3.5, tripod mounted, ISO 1200, 16x 20 exposures w/dfs.
Images stacked with DSS, levels and curves in PS CS5.
The stars show signs of trailing at 20.
As soon as the temp gets out of the teens, and I have a clear sky, Im going to try my 300mm riding on my scope.

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02-11-2011, 06:49 AM   #144
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QuoteOriginally posted by phatbob02 Quote
I finally had a chance to try my Kx this winter. Stock 18-55 lens set at 55mm f/3.5, tripod mounted, ISO 1200, 16x 20” exposures w/dfs.
Images stacked with DSS, levels and curves in PS CS5.
The stars show signs of trailing at 20”.
As soon as the temp gets out of the teens, and I have a clear sky, I’m going to try my 300mm riding on my scope.
The kit lens doesn't do to f3.5 at 55mm, I think it's only f5.6. You need a faster lens really for this sort of shot. This was 50mm f1.7 15s ISO 3200, single exposure:

02-11-2011, 08:02 AM   #145
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Ok, that is impressive.
02-11-2011, 08:22 AM   #146
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Wow, you must have had a pretty dark sky with little light pollution for that, right?
02-11-2011, 08:28 AM   #147
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Indeed, nice shot.
02-12-2011, 12:20 AM   #148
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QuoteOriginally posted by krp Quote
Wow, you must have had a pretty dark sky with little light pollution for that, right?
Yes, this is about as clean skies as you'll get - camping on a sub-antarctic island.
02-12-2011, 04:03 AM   #149
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My bad! It is 5.6 @55mm. Im glad it worked out as well as it did. I dont have the luxury of dark skies. I have the glow of a shopping mall to the north and the city of Syracuse to my southeast, hence the red sky glow. I have to limit my exposures to 20/30 and Im trying to learn the camera, DeepSkyStacker, and Photoshop CS5.
Im old school and this digital AP is all new to me.

Photo is 1997 Hale-Bop shot from my driveway. Pentax Mx, 135mm f2.8, Lumicon Deepsky filter, Hypersensitized Fuji 400, 20 guided.
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02-12-2011, 04:08 AM   #150
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Very nice. Congrats!
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