Nothing shows when stretching - would love some advice

[Tapion]

Hello Everyone,

For my first attempt at deep sky astro, I shot M51 over 3 nights. I used a Sony 6400 with an ISO of 500 at 10 seconds with a 50mm lens. While I know the math would suggest I use 6 seconds, I sampled several settings with DeepSkyStacker and got the best scores with 10 seconds. I used around 250 images, 25 flats, darks and biases. Stretched them how I have seen other stretch them in dozens of videos and...

...nothing. There is no M51 galaxy in my image. Not a hint of anything being there. I know I had the camera on the correct location. So does it sound like I used enough images? Any idea as to what a possible issue might be? I am really at a loss for where to go next. Also just an FYI, I have seen other people online using filters, but I do not have any. Still I would think something should show.

Any advice would be great on where to consider looking to work on the current problem.

[Rallemikken]

Not sure what equipment you used, but if you shot M51 with a DSLR and a standard 50mm lens, the galaxy would not be bigger than a star. Much to faint, details would drown. Learn to use a field-of-view calculator. To get a detailed picture where you clearly see that it is M51, you need a telescope at least 800mm long. I suggest you have a take at Andromeda, Triangulum galaxy, or the Pleiades if you stick to that lens. Or Orion, if you don't have to much light pollution.

Edited July 8, 2022 by Rallemikken

[vlaiv]

1 hour ago, Tapion said:

...nothing. There is no M51 galaxy in my image. Not a hint of anything being there. I know I had the camera on the correct location.

Hi and welcome to SGL.

Yes, you had your setup pointed to the right location - and yes - it is there in the image!

Maybe not as clear as you've hoped it would be - but it is there:

Here is a bit wider screen shot for reference:

[The Lazy Astronomer]

20 hours ago, Rallemikken said:

Not sure what equipment you used, but if you shot M51 with a DSLR and a standard 50mm lens, the galaxy would not be bigger than a star. Much to faint, details would drown. Learn to use a field-of-view calculator. To get a detailed picture where you clearly see that it is M51, you need a telescope at least 800mm long. I suggest you have a take at Andromeda, Triangulum galaxy, or the Pleiades if you stick to that lens. Or Orion, if you don't have to much light pollution.

50mm lens unsuitable sure, but galaxies need not be only the reserve of long focal lengths - the below was taken at just 250mm. Not an award winner by any stretch of the imagination, but larger scale structure clearly visible on what is a very small target.

[Tapion]

Thanks for confirming that I did have the right spot. Would I just need more data/images to bring it out more? Or is a longer focal length just going to work better?

[Tapion]

21 hours ago, Rallemikken said:

Not sure what equipment you used, but if you shot M51 with a DSLR and a standard 50mm lens, the galaxy would not be bigger than a star. Much to faint, details would drown. Learn to use a field-of-view calculator. To get a detailed picture where you clearly see that it is M51, you need a telescope at least 800mm long. I suggest you have a take at Andromeda, Triangulum galaxy, or the Pleiades if you stick to that lens. Or Orion, if you don't have to much light pollution.

Thanks Rallemikken. So, what would a super wide angle lens, such as the popular 12mm lenses, be used for? Milky Way shots or gas giants? Since I want to shoot galaxies, I guess I will need to save up and get a telescope I can mount my camera to or get a mega long lens by the sound of it.

[Rallemikken]

3 hours ago, The Lazy Astronomer said:

50mm lens unsuitable sure, but galaxies need not be only the reserve of long focal lengths - the below was taken at just 250mm.

That was very nice indeed. I have a ST 80 at 400mm, but  such an image on that scope would be very difficult. Triplet or camera lens?

[Rallemikken]

2 hours ago, Tapion said:

So, what would a super wide angle lens, such as the popular 12mm lenses, be used for? Milky Way shots or gas giants? Since I want to shoot galaxies, I guess I will need to save up and get a telescope I can mount my camera to or get a mega long lens by the sound of it.

I have not done socalled nightscapes or Milky Way shots myself, but that is a good place to start, to get the grips on things. Much technical things to learn. And as you can see above in the reply from the Lazy Astronomer, you can do galaxies with long camera lenses, but for the faintest ones you might need some sort of motorized mount. As mentioned before, Andromeda, Pleiades and Triangulum should be possible without a mount, if you use a lens longer than 100-150mm and shoot many pictures. That's how most astrophotographers start, me included.

[vlaiv]

4 hours ago, Rallemikken said:

That was very nice indeed. I have a ST 80 at 400mm, but  such an image on that scope would be very difficult. Triplet or camera lens?

You can do image of M51 with ST80, but there are several things that you must take care of in order to succeed:

1. do your best to make focuser usable. It is weak link as it will sag and in general perform purely

2. Use aperture mask to tame chromatic aberration. Aim for F/10 or so to minimize it. Possibly use Wratten #8 filter in this role as well. This will create yellow cast on the image so be sure you know how to color correct in processing for that

3. Because you stopped your scope down - use longer exposures and more of them

[The Lazy Astronomer]

7 hours ago, Rallemikken said:

That was very nice indeed. I have a ST 80 at 400mm, but  such an image on that scope would be very difficult. Triplet or camera lens?

It was taken through an Evoguide 50, which is a doublet. I also used an Astronomik L3 filter to cut the extreme ends of blue and red to reduce CA a bit.

[The Lazy Astronomer]

9 hours ago, Tapion said:

Thanks for confirming that I did have the right spot. Would I just need more data/images to bring it out more? Or is a longer focal length just going to work better?

Unfortunately, with your current lens, M51 will never be anything more than a tiny fuzzy grey speck, regardless of integration time. Most galaxies have a very small angular diameter, so will appear very small in images. A telescope with a focal length of 500mm+ would probably be the minimum needed to get decent detail on some of the larger ones*. However, be aware that the longer the focal length, the more difficult (read: expensive!) things get.

*A notable exception here is Andromeda, which is one of largest things in the sky - this would actually be doable with your existing setup. It would still be quite small in the image though, as shown from the FOV calculator image below (https://astronomy.tools/calculators/field_of_view/), but wide shots like this can help to give context to a deep sky object.

I did a quick Google image search for Andromeda through a 50mm lens and found this image, so this is as idea of what you can expect:

The owner of that image stated an integration time of <10 minutes, so I'd imagine more detail could be brought forward with more imaging time.

[rickwayne]

As for diagnosing your image, 2500 seconds of integration time is...not a lot. First time I did M51 (huh -- my profile image, actually!) I got about an hour and a half at f/4.5. I fiddled with that image a LOT in Photoshop to show detail -- a ton of localized Curves to tweak contrast in specific places. My more recent version was four and a half, and hardly needed any manual work. That said, I'm a little surprised that your M51 was quite that dim.

The Antares/Rho Ophiuchi region is up now, and IMO is a great target for 50mm. Orion is another good one, you can get the Great Nebula, Horsehead/Flame, and Barnard's Loop to fit pretty nicely. This is a pretty crude astrophotograph, but shows what a 50mm view would look like.

As for filters...meh. All filters do is take light away, right? In specific cases, such as when you know you have light pollution from gas-emission lights (sodium or mercury), filters can increase the signal/noise ratio considerably. But more often they just introduce color-balance problems and decrease the light getting to the sensor. Unless you're talking narrowband imaging, which is its own specialized thing but does not work well with most terrestrial-type cameras.

Edited July 9, 2022 by rickwayne