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Canon 500D 135mm lens no difference in quality even when there is a 200 photo gap.


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Hello, I think I am about to go insane. Yesterday I took 101 photos of the Orion Nebula, processed them with deep sky stacker and photoshop. Today I took 383 photos of Orion and processed them the exact same way. From what I understand I should be getting amazing stuff with around 400 photos, I was extremely confused as to why my images were turning out like this, so I spent 2 hours in photoshop making 3 different versions of the same image, I tried tweaking everything I could but yet no major difference. Please tell me what I'm doing wrong. I understand this is silly but I ask for your help. (the first file is made up of 101 images and the second of 383)

orion good copy.jpg

orion final 1.jpg

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18 minutes ago, happy-kat said:

Hi nice to capture data, it's a good start.

What do you use to help you get focus?

Well I'm not sure exactly what you mean by that but I either use live view or my eyepiece to manual focus on the nebula. Generally, I get better results with my eyepiece as  the live view display is low res and doesn't really capture the nebula well.

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Are you triggering your camera using a remote release, this minimises camera shake and out of focus stars.

I either use and Android device and DSLR controller to focus and set the manual settings up, bigger screen and 10x zoom helps with focus. 

 

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Just now, happy-kat said:

Are you triggering your camera using a remote release, this minimises camera shake and out of focus stars.

I either use and Android device and DSLR controller to focus and set the manual settings up, bigger screen and 10x zoom helps with focus. 

 

Yes I am using a remote trigger device, but I still have a shaky frame for every 5 pictures . I will try tomorrow again but I'll go for 500 photos.

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1 minute ago, happy-kat said:

Focusing on a star will be easier and it will mean the nebula is also in focus. 

I did not know that despite thinking I researched this topic. Thank you I will try because I really think it is out of focus the more I look at it.

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Orion is quite South now in the northern hemisphere means star trails show faster. East and West are more forgiving below 60 degrees for static photos

Focus is key. You could make what is called a Y mask out of cardboard to help focus on say Rigel good bright star in the area of your target.

Maybe focus in the daytime on a really distant chimney or tree (no where near the Sun) then you'd be close for the stars.

When stacking kappa sigma clipping can help tighten stars up. Be encouraged you captured Orion and successfully stacked your images. 

 

Edited by happy-kat
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2 seconds might be too short, if you're not delaying between your frames you might also be getting shutter shadow in the images as the camera captures the shutter not retracting fully. With Orion I've done 5-10 seconds unguided within reason, although the longer the lens the less you can push the exposure time as you've experienced. If you can't, you need to take a lot more frames, with my fast systems I normally have to triple/quadruple the amount of frames to get the same signal as a slower long exposure system.

If you're not using one currently, get an intervalometer which can do the following, you can set exposure duration, number of exposures, delay between images, and once set you only press it once and leave the camera to do its thing.

With a DSLR, if I'm not using computer control I find focusing easy by taking say a 2 second exposure, zooming in to check the star size and repeat. Once they're near as small as can be before they start getting bigger again you know you're near infinity focus, then dial focus back again and repeat. Do this a few times back and forth until you're at a point you like. It only takes around 5-10 minutes to do this process. Or if you want make a bahtinov mask to fit your lens, but based on the above I don't really use one.

Edited by Elp
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I've occasionally captured the odd photos of the night sky using an unguided telescope with a camera attached to the EP holder.  It is incredibly difficult to get things in focus on the night sky.  I've done it using live view through the atached camera, but would second the above advice about focusing on a single point star and then just sliding the camera already in focus carefully across to the nebula and not touching it further.  What really helped me was a cable free remote shutter release - these can be had for not a lot of cash from the usual online sales sites.  Also, the OP must understand that he is not going to capture the marvellous false colour images of the nearly professional imagers we have on SGL who are using far more advanced kit, but it should be possible to capture an acceptably nice B&W image with 30 or 40 exposures if he can get things in focus and use a remote shutter release, as I have managed it myself with similar equipment.  TBH  I wouldn't go down the road of 300-500 exposures until I could get a decently sharp image from just a few exposures so that the OP can learn how to get a nice sharp single exposure.  Crack that and I think you could start the think about stacking more, but there seems little point in wasting time on hundreds of exposures, until you've cracked stacking 10 and getting them sharp, I may be wrong as I haven't done much of this, but I don't think it follows that more exposures = sharper image.  I think its more a case of sharper images in those exposures = a sharpter final output.

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10 hours ago, guywithonequestion said:

but I still have a shaky frame for every 5 pictures

Your camera has a mirror-lock feature which delays the shutter after the mirror goes up to help prevent camera shake and long exposure noise reduction. Which will make automatic dark frame subtraction though it will take twice as long to do this. These features will all help. 

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No, you're right, more images will never make the image sharper, they need to be in focus in the first place.

But more images increases the chances of photons hitting the sensor, thus increases signal and the more frames the more you average out the noise.

But your advice is sound, try it first with a smaller stack, no point in doing hundreds of frames if the focus is no good. A lot of lenses I've used cannot reach infinity focus on stars.

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Hello "guy"

1. Looking at the second image, you will notice that the brighter stars are "comet shaped", one side of each star is flared.

This is a defect in the lens that would never be noticed on daytime "snaps".

Stopping down a lens often improves overall performance, it may improve this "coma".

2. The Orion Nebula is rich in red Hydrogen Alpha (Ha) emissions.

Which are somewhat attenuated in stock DSLRs by filters in the camera that match the camera's spectral response to the human eye's response.

An "Astro Modded" DSLR has one of those filters removed to give better Ha response.

3.  If 2 seconds is the longest you can use without trailing, try one-higher ISO setting and see if the noise in the final stacked image is acceptable.

Michael

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9 hours ago, michael8554 said:

Hello "guy"

1. Looking at the second image, you will notice that the brighter stars are "comet shaped", one side of each star is flared.

This is a defect in the lens that would never be noticed on daytime "snaps".

Stopping down a lens often improves overall performance, it may improve this "coma".

2. The Orion Nebula is rich in red Hydrogen Alpha (Ha) emissions.

Which are somewhat attenuated in stock DSLRs by filters in the camera that match the camera's spectral response to the human eye's response.

An "Astro Modded" DSLR has one of those filters removed to give better Ha response.

3.  If 2 seconds is the longest you can use without trailing, try one-higher ISO setting and see if the noise in the final stacked image is acceptable.

Michael

I am using my max ISO and would like to say that I am currently trying to find a way to open my aperture to 3.5 as for some reason it doesn't let me open it fully in manual mode. But I am using the lowest possible f value I can.

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The wider a lens is open the more evident any imperfections will show, having the lens not fully open often helps the star shapes. If you don't like defraction spikes on bright stars from stopping down you can either use step rings or make a cardboard aperture mask to stop a lens down which is what I've done for a lens I use which needs stopping down (the actual lens under the mask is on the widest aperture).

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2 hours ago, guywithonequestion said:

spend

You could try making a DIY barn door tracker, people have been making them and using them for years. For a more professional start there's the Omegon LX clockwork mount, you'll need an equatorial wedge or something to angle it to your latitude, polar aligning will be an issue but you can do it roughly to start with.

Regarding F ratio, as long as it's within F6 you should be fine, I've shot with my Takumar 200mm at F5.6, but I was autoguiding.

Edited by Elp
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