4 hours ago
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Re: Star trails and an Orion shot with a few questions
In reply to Team Thor Expeditions,
4 months ago
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Team Thor Expeditions wrote:
Esteemed list members:
I recently purchased an Astrotrac with pier. I have only used it 3 times, but so far I am quite pleased. Just last week I had to take a trip to Tucson, AZ and being in the desert I expected good viewing conditions. Only one of the 2 nights was sufficiently clear to make photos worthwhile and that night there was tons of light pollution. I have 2 photos to share and a couple of questions.
The nebula came out better than expected (posted photo is at 1k X 1k pixel size) with regard to tracking and slurring, but less good on color rendition. I did PP with PixInsight and did stretch the histogram to get the details. But, given the other really good Orion photos posted recently, what am I missing on color. I do recall that one of the posters stated that he had a 60a camera that is missing the low-pass filter. Is that the only reason on color or should I be seeking another cause?
Bill, that image above is a commendable first attempt. You got some nice color and details in the nebulae. As for color, those of us with standard (non-astro-modified) cameras have got to work with what we have. I notice that you did pick up some of the pink colors in M42. You can likely bring up more of those colors in post processing. I have limited experience in digital imaging of nebulae. And having only Photoshop Elements 2.0 to work with limits the adjustments that I can make. But what I did to bring out some of the colors in M42 that my Sony NEX-5N struggled to record is as follows.
In PS Elements:
Another method that I haven't explored much in adjusting Levels is to choose the Red, Green or Blue Histogram to stretch and adjust mid point. I just recently realized that Elements had that capability.
I did notice that my ability to focus the Oly lens was impaired. The fully manual lenses seem to focus better; it may have something to do with the gearing that connects the focus mechanism to the stepper motors, but I am not sure.
Here's what I do to focus when the camera is attached to my telescope. The 'scope is just a big, glorified manual focus lens. The same technique may also work when using a standard camera lens. I use a Bahtinov Mask to achieve close to perfect focus. There are plans online to make your own, but it looks to be a lot of work. They are available on-line for a wide range of camera lens and telescope diameters. Here is one source:
http://www.kendrickastro.com/astro/kwikfocus.html
What works for me is:
I have noticed that sometimes the spikes as shown above are faint and hard to see. So selected the brightest star available, like Rigel which is close by M42. Sirius would be even better if its up.
The second photo ate up the whole night, but was done in parallel with the normal star photos.
This shot was a stack of 72-3 minute exposures. I was rather annoyed by the light pollution, but this part of the city is bigger than I recall as a kid when I lived there. The real annoyance were the plane light trails as there was a fellow testing for his IFR rules and doing loops. Also note the police helicopter light trail near the horizon.
Very nice star trails! I notice they are without any breaks in the trails. The airplane and helicopter lights add an interesting element to the overall scene. In the magnified view, the airplane lights have a lot of details. Thanks for sharing both images.
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Best Regards,
Russ
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