Help with whole sky shots

[Hughesy94]

Hi there, Im trying to take photos of the night sky using just my Astro modded camera on a camera so i can practise with some foreground and background shots. It seems that no matter how short i keep the shutter speed i get star trails. I'm using an 18mm-55mm standard kit lens, and at 8 to 10 seconds I'm still getting star trails when i zoom in. Following the 500 rule i should surely be well in my limits taking 10 second exposures? 

Ive attached some images i took tonight whilst trying to image what i could of the milky way bands and also Mars and Neptune together, but none of them seem really clear or in focus and when i zoom in they all have trails?

Whats the best technique? In the second photo you can barely see where the bands of the milky way should be, but if i increase the exposure time any more the trails become too obvious.

 

Cheers

Alex 

[old codger]

I got almost identical results DEC.3rd. using my Cannon 600D with 30s exposure at ISO 1600 and stacking 3X 30sec in Nebulosity and stretching in Photoshop. The best way to get good focus is to zoom in first, focus and if you can magnify the image on your camera ( mine lets me do X5 and X10) to get the most accurate focus then zoom out and your camera should still be in perfect focus .When you then zoom in again it should remain in focus. I believe some people put a bit of 'Bluetack' on the telescopic part of the camera to keep it in focus.

Old Codger

CYGNUS LYRA. 3DEC 2018 30S. ATISO1600.tif.tif

[almcl]

Have a look here:

http://beltoforion.de/article.php?a=untracked_astrophotography&p=camerasettings

The much quoted rule of 500 may need to be modified a bit with a crop sensor.  

If you are handy, a barn door tracker will allow a considerable extension to your imaging time without too serious trailing and doesn't cost much to make.

 

[happy-kat]

With what is often termed a crop sensor using 400 is better. Also where you point in the sky can also effect how soon star trails appear, point to the east or west and not too high is best for minimising trails.

400/ focal length of lens is a rough guide for how long the exposure can be in seconds. I built a manual barn door and can easily get 3 minutes using a 40mm lens on the 1100d that I use.

I personally set the camera to back button focus this I find minimises lens focus slip.

If stacking foreground with sky then Sequator is good to use.

[Jojo204]

Ah something I can reply to!

Here are some quick and simple considerations before going into the more complex stuff:

1. Have you got a solid tripod that doesn't vibrate with the shutter?

2. Are you using a remote shutter or timer?

3. Have you taken into account the crop factor? (if you have a crop sensor) Note, APS-C usually has a crop factor of 1.6 meaning you'd have a new rule called the '312.5 Rule' ?

Ok now if you've done all of this, it gets a little harder to understand the problem. Try shortening your exposure to a small 4 seconds and see if stars still trail. If they still do (at 18mm) then that's a problem

with your setup, the sky doesn't move that quickly! Make sure you zoom in on a star using digital zoom too, and try to get the star as small as possible to reach focus. 

Apart from this there's really nothing much else I can do but recommend stacking shorter exposures or buying/building a cheap tracking mount. This will really improve your results and they don't need

to be expensive ones unless you want to start taking DSO or Planetary shots or zoom right in.

[Hughesy94]

Hi everyone, sorry about the late reply ive been manic busy! So i tried keeping my exposures well within the exposure time i got from the 500 rule, i was using a really stable photography tripod and had my camera focused and pinned. 

i just thought i should be able to get longer shots without trails, because i feel my sky is underexposed. Kinda bummed out seeing as the camera is astro modded and can produce awesome shots when attached to a scope. 

Ive never even heard of this barn door method, i'l look into it!

I tried to stack about 20 photos from the milky way shots with some dark frames just to see what they came out as. I used DSS which I've never used before and the photo i saved seems annoyingly close to showing some kind of milky way band through the middle, but seems really whited out and like the exposure needs fiddling with. IS this image worth chasing to bring something out do people think, or should i write it off as practise and try again? 

Its for an astro portfolio I'm creating at university but I'm new to image processing software and taking images of the whole sky and no matter what i read about milky way shots i just cant seem to crack it! 

Cheers

Alex

milky way 29-11-18.TIF

[happy-kat]

There's a link to my barn door build in my signature.

With a camera lens you want to ideally focus on a star where a third intersects. It evens out lens focus.

I'll look at your image in a bit.

 

[Hughesy94]

1 hour ago, happy-kat said:

There's a link to my barn door build in my signature.

With a camera lens you want to ideally focus on a star where a third intersects. It evens out lens focus.

I'll look at your image in a bit.

 

I did not know that! Il use that next time, thanks! 

For some reason when I clicked the image I sent it was very zoomed in. The Milky Way should run down the middle and it’s not the brightest part, would just love to have an image for the portfolio of the observatory with the Milky Way in the background! 

[happy-kat]

There is the Milky Way there but very some strong gradients.

I would next time make a lens shield, I have one I made from a plastic flowerpot that I flocked.

Make sure the light histogram is clear of the left hand side, check on the back of the camera.

There were a lot of stacking artifacts too. This suggested there was quite some time between the frames taken and used in DSS.

I use 400 and not 500 as the camera I use is not full frame.

If you want to keep foreground in the shot like your mentioned with the Observatory, then either use Sequator to stack or DSS and add the foreground as a single file as a layer on the final process in photo Shop or GIMP etc.. (ah just twigged you were talking about a photo for the observatory not one with it in the foreground)

To show the milky Way I think you need to have more image files in your DSS stack, 10 is not very many if the area is light polluted. But you have to have a go to make a start which this is ?

 

[Hughesy94]

40 minutes ago, happy-kat said:

There is the Milky Way there but very some strong gradients.

I would next time make a lens shield, I have one I made from a plastic flowerpot that I flocked.

Make sure the light histogram is clear of the left hand side, check on the back of the camera.

There were a lot of stacking artifacts too. This suggested there was quite some time between the frames taken and used in DSS.

I use 400 and not 500 as the camera I use is not full frame.

If you want to keep foreground in the shot like your mentioned with the Observatory, then either use Sequator to stack or DSS and add the foreground as a single file as a layer on the final process in photo Shop or GIMP etc.. (ah just twigged you were talking about a photo for the observatory not one with it in the foreground)

To show the milky Way I think you need to have more image files in your DSS stack, 10 is not very many if the area is light polluted. But you have to have a go to make a start which this is ?

 

Thanks for the help! 

Yeah i took a separate photo of the observatory to use as the foreground, just wanted to try and get the Milky Way looking as good as possible! 

I’m not too sure what you mean by making sure the light histogram is clear and stacking artifacts? 

All images that were included in this image were taken within a 1 hour time frame, is this too much? 

Also nice edit on the photo, what did you do? Would you mind if I used it to try and make an image with the observatory just for practise? Sorry about the questions! I’m super new to this and feel like I’ve jumped in at the deep end! Strangely find imaging from the scope so much easier!

cheers

Alex 

[happy-kat]

You are welcome.

Stack artifacts occur when the earth rotates and subsequent images don;t align the same exactly as the sky shifts but your tripod does not as it is static, the artifacts are at the edges when the frame are overlaid but obviously not exactly one on one.

I opened it in DSS so I Could save it again as a tiff. Then loaded in StarTools and cropped (removed the edges and worst gradient banding on the right) and then binned the image 50%. I then developed it manually (stretch) then wipe for the gradients then contrast then colour balance. Saved as tiff then opened in PSP to save as jpg for upload speed/ease.

1 hour is fine but 1 hour for just 20 photos of less than 30 seconds, I would personally have given a 6 second gap only between frames.

When you take you first image with the ISO you start with and exposure time look at preview then look at the histogram, the peak needs to be clear of the left hand edge, if it is not clear you are losing data if it is too far to the right (stay to the left of middle but really just proper clear of the left edge) then the image is over exposed/saturated.

[Hughesy94]

1 hour ago, happy-kat said:

You are welcome.

Stack artifacts occur when the earth rotates and subsequent images don;t align the same exactly as the sky shifts but your tripod does not as it is static, the artifacts are at the edges when the frame are overlaid but obviously not exactly one on one.

I opened it in DSS so I Could save it again as a tiff. Then loaded in StarTools and cropped (removed the edges and worst gradient banding on the right) and then binned the image 50%. I then developed it manually (stretch) then wipe for the gradients then contrast then colour balance. Saved as tiff then opened in PSP to save as jpg for upload speed/ease.

1 hour is fine but 1 hour for just 20 photos of less than 30 seconds, I would personally have given a 6 second gap only between frames.

When you take you first image with the ISO you start with and exposure time look at preview then look at the histogram, the peak needs to be clear of the left hand edge, if it is not clear you are losing data if it is too far to the right (stay to the left of middle but really just proper clear of the left edge) then the image is over exposed/saturated.

Ahh okay, thanks for the tips! Il try and take all this into account next time and see if I can get something better out of it. What kind of programs would you recommend? I downloaded DSS but need to get some image processing software too ? 

[happy-kat]

GIMP is free and pretty good. PaintShopPro is fairly inexpensive and will generally run Photoshop plugins and do what Photoshop does (sometimes available for very little beer tokens), then astro related I like StarTools as very competent but very accessible price. For stacking DSS. I personally don't do enough to warrant any further outlay then the above.

[Maxrayne]

Just to show what is possible with an APS-C camera, this was taken with an unmodded Nikon D5300 in my kids back yard under Bortle 5 skies. Consists of 195 seconds total exposure time, using 15 second subs at 18mm. No darks or flats. ISO was 12800, all untracked on a "bog standard" tripod with an intervalometer. Stacked in Sequator, processing done in Lightroom only.

Did this using the principle of ETTR (or exposure to the right), which is where you push the exposure as far right as you can without clipping the histogram. There's some very good tutorials on YouTube about imaging this way. Although granted, this is primarily used for quite light polluted skies. I'll see if I can dig out the link for you.

[Maxrayne]

 

[Hughesy94]

25 minutes ago, Maxrayne said:

 

Thanks il have a look! i have the problem that the observatory is right on the end of campus and as you can probably tell i get huge amounts of light pollution! 

[Maxrayne]

44 minutes ago, Hughesy94 said:

Thanks il have a look! i have the problem that the observatory is right on the end of campus and as you can probably tell i get huge amounts of light pollution! 

Hopefully that will help in that case. I know my own processing "skillz" are the major suk but they're not as bad as they used to be lol

[Jojo204]

18 hours ago, Hughesy94 said:

i just thought i should be able to get longer shots without trails, because i feel my sky is underexposed.

Don’t be afraid to increase the ISO to 6400 if needed!

[Hughesy94]

Hi all, just an update! So i finally got lightroom and had a tinker with it last night and this was the result of restacking my image, editing in lightroom and then layering with an image of the observatory! just wanted to say thanks for everyone's tips and tricks, would of liked a more developed milky way but for a first attempt i'm pretty pleased to be sticking this in my module portfolio!

Thanks all!