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Double_Grapefruit_55 t1_ja387xu wrote

What type of telescope do you need to see this? I am curious how powerful it needs to be.


Zanhard t1_ja3kwny wrote

Nothing crazy actually, however it is much easier to capture if using a tracking mount which follows the movement of the night sky, allowing for longer exposures.


Double_Grapefruit_55 t1_ja3mykj wrote

I have a telescope , but it isn't too strong. I can see stars and see the moon close up, but that is the extent of it.


Zanhard t1_ja3snxj wrote

There's generally a difference between telescopes used for visual use and astrophotography.


J3RRYLIKESCHEESE OP t1_ja5mo7h wrote

I used a 10" goto Dobsonian for this image, but I'm sure you can get similar results with an 8. A goto or tracking setup will make your life easier but it isn't necessary especially if you have a larger camera sensor


Double_Grapefruit_55 t1_ja6liax wrote

I have a Celestron 70az. I don't know anything about telescopes. So I am not sure how strong this is.


J3RRYLIKESCHEESE OP t1_ja7a0na wrote

This is enough to see the moon, planets, and some of the brighter dso's, but not enough for photos like this sharp. The aperture is 70mm, which is just under 3 inches, compared to 10 inches which is 254mm. The light-gathering power is incomparable


Tonyhillzone t1_ja2suu4 wrote

Giving James Webb telescope a run for its money!


J3RRYLIKESCHEESE OP t1_ja4ija0 wrote

A clear night gave me the chance to test my new camera out once again! This time I tried to focus on one target and gather a lot of data for a nice image. It could use more data, but here is my take on M51 last night with my 10" GoTo Dob and my new Uranus-C camera.

Details: 3600x1s exposures (1 hour) using Sharpcap livestacking of 12x5 minute frames, then using deep sky stacker to combine the livestacks. Processing done in SiRiL and GIMP.

Gear: Skywatcher 10" GoTo Dob and Uranus-C + UV/IR cut


747-8F t1_ja3v08n wrote

That is Beautiful and Amazing! Wonderful Shot!! Thank you so much for sharing!!πŸ€™πŸ½πŸ––πŸ½


J3RRYLIKESCHEESE OP t1_ja5k9r9 wrote

Thank you sir! I'm hoping to shoot more data when the weather clears up


pramarama t1_ja3qu4b wrote

Is this picture one of the 3600 that happened to be the sharpest one, or is this a composite made from all 3600?


dcw259 t1_ja3rz2i wrote

There's no way to get a single 1-second exposure to look that good with any amateur telescope, maybe even any man-made telescope at all


Zanhard t1_ja3sw3q wrote

It's a combination of all 3600 pictures assembled together using a method called rejection stacking in order to reduce noise.


throughawaeladdie t1_ja3xcmo wrote

could someone explain how these exposures work? I'm not big on photography so i don't understand it very well but as far as i know, it's 1 second compressed into a single image and 3600 of those superimposed onto each other right?


KntKoko t1_ja4y6ya wrote

OP took 3600 pictures of 1 second exposure each ( the sensor capture light particles for 1sec for each picture )

Then OP takes all 3600 pictures to a stacking software ( we don't know which one OP chose, but there are many like SiriL, DSS, etc )

The software will align all the pictures using the stars. Then it'll average out every single pixel ( ie. pixel in the same location in the sky, hence why it needs to align the pictures )

The stacking process will reduce the noise created by the camera sensor ( and there is a looooot of it ), and keep what we call signal ( so the actual light from stars and galaxies and stuff ) at roughtly the same level.

When seeing a 1sec exposure, you will think there is litterally no light from the galaxy that reached your camera, but it did ! It's so low that it's almost black ! Keyword here being ALMOST black, so it's there !

Once the noise has been removed by stacking, you take your stacked image ( only 1 file usually in .tif/.fit format ) and process it in a software like Photoshop, gimp and so on.

Now you just need to carefully use "level adjustments" and "curve adjustments" ( not sure about my grammar of adjustments ) to bring all the data in the near-black to the grey/dark-grey zone, and you're basically done !

Hope it helped ! I didn't go too much into the explanation because I tried to keep it as simple as possible ! Astrophotography is a really nice ( but becomes expensive ) hobby, I suggest you to take a quick look into it !


throughawaeladdie t1_ja6aykg wrote

i definitely want to all of this sounds really interesting. thanks a lot for explaining


KingRandomGuy t1_ja4x3uu wrote

Whenever you take a photo, the image sensor is exposed to light for some amount of time. The duration of this time period where the sensor is capturing light is called "exposure time" or "shutter speed." By increasing this duration, the sensor receives more light, which is useful for taking photos of dim objects (for example, a 2 second exposure gets twice the light as a 1 second exposure). However, this has a tradeoff - if the camera or object moves before the exposure finishes, then there will be blur in the image. This is why photos taken under low light tend to be blurrier, since there is more of a chance that camera will shake in your hands or the subject will move.

When you take photos in daytime, you usually use a shutter speed of from 1/8000th of a second to 1/30th of a second. However, at night photographing dim objects, these kinds of shutter speeds will not give you any reasonable signal - more or less just a black frame. As such, you take exposures of 1 second or more to gather as much light as possible without incurring blur from the sky rotating (tracking mounts help with this).

However, for dim objects like galaxies, even 1 second exposures don't capture enough signal compared to the overall noise level of the camera. As such, we can take many 1 second exposures and stack them together by aligning the frames (done by aligning the stars in the image together) and then adding the pixel values. This results in an increased signal to noise ratio, allowing us to make a more detailed image once properly edited.


throughawaeladdie t1_ja6bbvq wrote

so if op had chosen to do 2 second exposures instead, the pre-stacked photos would have more noise right?


KingRandomGuy t1_ja6fed5 wrote

No, they would have less noise. A longer exposure means that more light hits the sensor, so you get more signal for the same amount of noise. In this case, assuming that the ISO (sensitivity) of the camera remained constant, doubling the exposure time would double the brightness (signal) while having the same noise level. In turn, the pre-stacked images would have a higher signal to noise ratio.


throughawaeladdie t1_ja6fkcp wrote

ah i see where i went wrong. thanks for explaining this to me!


KingRandomGuy t1_ja6fsxk wrote

No problem! I'm happy to answer any other questions too.

Astrophotography is quite a technical hobby but it's really rewarding IMO. I'd recommend giving it a try if you have the time and resources.


DPanzer17 t1_ja73gl9 wrote

I'd love to try too, there's just one thing unclear for me. Why 1 second exposure? Wouldn't 10 seconds exposures have allowed him to take 1/10th of the photos to get approximately the same result?

But I guess long exposures are not always a good idea, I tried 30 sec and the result wasn't satisfying (but I might have got the focus wrong there)


KingRandomGuy t1_ja74wh7 wrote

So the downside to long shutter speeds is that if any motion happens during the duration of the exposure, then you will get blur in your image. This is why photos of people in lowlight often aren't sharp - people moving a little bit during the long exposure makes them have visible blur.

For astrophotography, the problem is that the sky is slowly rotating. This is barely perceptible to us, but it's enough rotation that a 10 second exposure may result in star trails - basically stars will appear like streaks instead of points.

So, as you've correctly identified, we want to maximize our exposure time, but you can't go too long or you'll get blurry images. This can be alleviated by star trackers, but that's an extra piece of equipment. One rule that can help with this is the 500 rule, which states that anything over 500/f seconds, where f is your lens's focal length (full frame equivalent), will cause motion blur. Do note that you'll often need to be well under this number to avoid blur, but it's a nice rule of thumb.

Clear skies!


Total-Oil2289 t1_ja7api5 wrote

What's the difference between this and so-called "lucky imaging" where my understanding is that you're taking lots of short exposures and keeping the ones that are least affected by atmospheric turbulence? Is it just the same solution for different problems?


KingRandomGuy t1_ja82qp1 wrote

It's a similar solution to lucky imaging, but lucky imaging specifically requires that your exposures are short. You can still stack very long exposures for deep sky objects and get a great result (assuming you are tracking).

The concept is similar though; in both cases you are stacking to increase the signal to noise ratio, and you should throw out bad frames.


KntKoko t1_ja4ydgq wrote

Nice pic OP ! You might wanna try the Andromeda galaxy if you want to top your own Sharpest galaxy record !


Ukulele_Maestro t1_ja94cbb wrote

The perspective of other galaxies like this shot blow my mind.

100's of million stars, planets all in that one little field of view. We could be looking at a million earth like planets right there for all we know. Does this galaxy have a name?

the vastness is just a total mind fuck.


Dipping-Grizzly t1_jabgpza wrote

Very nice....who keeps saying we can't do DSO AP with a dob? ...this proves otherwise.

I'll have to try this out on my dob, but can only get about one quarter second subs since i only have the regular old school mount.


OkRadish11 t1_ja6jddt wrote

That's wild. Are the points of light on the periphery 1) stars in that galaxy, 2) stars in our galaxy, or 3) different galaxies entirely?


tanman729 t1_ja6tc99 wrote

What are the spots that look darker than the rest of the space?