First attempts at Orion Nebula

I was out last night and gave it a shot after getting a couple of tips and a lot of reading.

I used the Celestron Nexstar 6se and Canon 7d set on 30 second exposure and 1000 ISO.

I am thinking that 30 secs may be too long for where I was as many of the 30 plus shots I took had a little blur from the slight breeze. Can I get away with less time?


Any other suggestions would be helpful. I did also shoot 3 black frames of 30 seconds.

nice for first try...to get the real Orion Nebula colors you need looong exposure, I suggested 30 seconds because I believe that will be max for unguided shots, stack several of these 30 sec shots to get higher resolution and color.

Thanks Tony.

There's a lot more data in those images than is apparent from the jpeg's you posted. I took one of them and stretched it in Photoshop. Starting with the original full image you should be able to coax a lot more out of it than I could with the small jpeg.

You should shoot in RAW mode in order to be able to stretch the contrast in post processing without introducing artifacts. Leave the images in a 16 bit format until all post processing is done. Don't clip the blacks when you are editing the images or you will lose a lot of the faint details.

Then, figure out how long you can go at your focal length. I assume you were not using the focal reducer for this shot due to the image scale, unless you cropped it. Using the focal reducer will allow longer exposures without trailing stars or field rotation. Unfortunately it will also increase the vignetting due to the 1.25" focuser, but learning to acquire and apply flat frames will minimize the impact of the vignetting.

Finally, once you have the parameters worked out, shoot lots of exposures at the maximum exposure length you can manage, acquire the darks and flats, and apply them with DeepSkyStacker or some other astro-specific processing software.

It's a very respectable first attempt. I think you will be surprised how far you can go before investing in more hardware.

Don

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I did shoot them in raw but converted to jpeg. Will deep sky stacker work with raw?

I did also shoot 3 blacks.

Not sure what flats are.

I would love to get more out of what I shot but just not sure how. Something I should read?

Or someway you can show me with a full raw I could send?

Very different it seems then processing other daytime images.

Also the reducer was not used for this.

I have to take off the eyepiece for that. I think I may try that tonight if the skies stay clear.

I see, so these images were made with eyepiece projection. That explains the scale and probably the low signal from such a bright object. I would definitely recommend trying prime focus, with or without the reducer. You will need to remove the part of your camera adapter that holds the eyepiece in order to get the camera close enough to focus.

DeepSkyStacker does support Canon RAW files, including the 7D, which I believe is what you have.

Flats are simply exposures of an evenly illuminated field, like the twilight sky, made through the telescope with the camera in the same orientation as when the subject was imaged. They contain the vignetting and other anomalies that will be in your subject exposures, and they are used to remove those defects from the images during processing. I take mine by pointing the telescope at the southeast sky, about 45 degrees up, about 10 minutes after sunset, and setting the camera to Av mode. Take several (10 to 15, they're quick), and then put the cap on the telescope and take several more with the same exposure time (using Tv mode) - these are called flat darks (or dark flats, same thing). DeepSkyStacker will produce better results if you include the flat darks.

The results from DeepSkyStacker need to be processed further to produce the final image. What image processing software do you have? Photoshop is what I, and most astrophotographers I believe, prefer.

I'll be glad to process one of your RAW files. If you don''t have a place to put it where I can download it, I can PM you with instructions for putting it on a server I keep in my basement.

Don

Hi Lloyd,

In response to your PM, here are the steps I used for a quick and dirty adjustment of the image you posted. I used the first of the three images, and I used Photoshop CS2. These same steps would be applied to a processed image from DeepSkyStacker, but with different values.

The first step in Photoshop will normally be to apply Levels (press CTRL-L or select Image ... Adjustments ... Levels). Set the black point (left-most slider) and white point (right-most slider) to eliminate data below the "hump" and above the brightest data points representing the subject. Don't clip the blacks or whites - leave some space if possible between the hump and the black point, and between the white point and the brightest data in the subject. For final processing of a "real" image, e.g., the processing result from DSS, doing this in several steps is often beneficial, but in this example I'm doing it all at once:

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Hi Lloyd,

Here's the results of a quick Photoshop tune-up of the RAW image you provided. I used DPP to convert the RAW file to TIFF, then adjusted Levels and Curves in Photoshop CS2. For a single thirty second image it shows quite a bit of detail.

Those two tear-drop shaped anomalies at top center are apparently internal reflections. I see the same anomalies in images made with my 5" Maksutov Cassesgrain. They only show up when there's a fairly bright star (or in this case several fairly bright stars, the Trapezium) in the image.

It's fairly noisy, that's what the darks and stacking multiple images will address. And vignetting is pretty obvious with the dark corners, that's what flats, or cropping after post-processing, will address.

POTN forum member Baz has written a nice step-by-step guide for using DSS to stack images. You can find a link to it in the first post in this thread:

https://photography-on-the.net/forum/showthre​ad.php?t=763083

I would only add that when you save the file at the end of the process, be sure to select "Embed adjustments in the saved image but do not apply them", if you plan to further process the image in Photoshop or any other software. Failure to select this option may result in an image that only DSS can handle well.

Don

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Thanks Don. This will be really helpful. I appreciate your time.