First attempt at stacking Orion

[evacguy]

Thought I'd have a go and stack some images I took of Orion earlier this year. This is my first attempt at stacking and I'm only using PS rather than an astro stacking software package. To be honest, I don't really know what I'm doing as I'm a complete newbie with PS. The first image is a single frame from the stack, its the last one in the stack. The other image is a stack of 15 images taken with my Sony A7iv and Sony GM 70-200mm f2.8 OSS II. I was using a 1.3 s exposure at ISO 400, at 200mm f2.8. I also did a bit of stretching of the stacked image in Lr. Clearly, I need to work on this!

• ILCE-7M4
• FE 70-200mm F2.8 GM OSS II
• 200.0 mm
• ƒ/2.8
• 1.3 sec
• ISO 400

• ILCE-7M4
• FE 70-200mm F2.8 GM OSS II
• 200.0 mm
• ƒ/2.8
• 1.3 sec
• ISO 400

 

[Gaz]

I haven’t done stacking yet but I’m thinking about it! Going by yours, the results are obviously worth attempting.

Is that the galaxy with the new supernova that we can’t see from Sydney!

No tracker - The 500 rule that I read suggests that you can shoot for up to 2.5 seconds at 200mm without trailing stars. (500/200=x). I got good single shot results using Sony 14mm for 30s, but galaxies are tiny so I was thinking about using 135mm F1.8 next time.

Looks promising.

 

[evacguy]

Thanks Gaz. Yes, my image is promising, but it needs a lot more work. I have more frames I can stack, but I'm not 100% sure I know what I'm doing so I may spend a bit of time over the weekend trying to improve my stacking workflow and also my stretching of the stacked image. So, what I've captured is the constellation Orion, it's visible from Australia in the summer months while we see it in winter. You see it upside down (because you are down under) and so the constellation is often called the Saucepan in Australia as the sword, where the nebula is, is located at the top of belt rather than below it, as seen in my image. The nebula is called M31 or the Orion Nebula, with the naked eye, its the second star in the sword, but with the longer exposure with the long lens, you can see that it is not a star but a nubula.


I don't currently have a tracker, this will be my next purchase when I get around to it, so I am forced to take short exposures so that my stars appear spherical rather than stretched star trails. The 500 rule that you mention is a very rough rule of thumb, anything you calculate using the 500 rule is unlikely to work very well, you probably need to take a half or a third of what the 500 rule gives you.
A better rule is the NPF rule (you can find it on the web). This is more complex and so you will need to use a calculator to work it out. There are actually two versions of the NPF rule, a simple version that only uses the lens focal length, f number and camera sensor pixel size and a more complex version that also includes the angle altitude of your target star.

Using the more complex version of the NPF rule, for my 200mm lens, at f2.8 and with my A7iv with a pixel size of 5.12 microns, an exposure of 0.7 sec will produce no star trails at all, while an exposure of 1.3 sec (what I used) will produce a barely noticeable star trail.

For a 135mm f1.8 lens, using my camera you can get away with a 1.7 sec exposure to produce a barely noticeable star trail. I worked this out previously as I've been thinking of getting the new Samyang.

Also, this is not the constellation in which the supernova is currently visible. The supernova is in the Pinwheel Galaxy. The galaxy is located near the border separating Ursa Major (the Big Bear or the big dipper) from Boötes the Herdsman. It’s near the handle of the big dipper. But I'm not sure you can see this in Sydney.

 

[Gaz]

I’ve been eyeing off a tracker but didn’t want to lug it to the northern hemisphere (hoping to see that supernova from somewhere near KL on my next work trip).

Thanks for the calcs. I’d have gotten that horribly wrong!


Currently scouring from the beach to photograph hump back whales migration.