Some astrophotography basics

After researching the ability to save custom settings on the T7 I found that you would be limited only to saving single menu items to the “custom” menu in the camera. Apparently you are not able to save full profiles on any Rebel camera. This sucks but I think you can handle manually making the adjustments noted below. I think the menu profiling can be overridden by replacing the Canon camera OS with MagicLantern but that is something that I would not recommend. While it does add a lot of functionality to just about any Canon camera the interface is beyond difficult to navigate. I did it once. For less than a week.

ISO

Crop sensor cameras are noisy. You cannot avoid that but you can do a few things to make up for it. I would recommend using ISO 3200 to start with and if you see that the images look way too dark bump it up to 6400. I would not go any higher as the noise will add way more “stars” to the sky than there really are. Also for each composition shot take multiples. Three to four of any one composition of the night sky will permit stacking the images in post (there are a few good sky stackers out there) which will align the multiple images and, as noise is not a fixed part of the image, they do a good job of cancelling out the majority of the noise. What noise is left over is pretty easily handled in post. If worse comes to worse I have a few of the Topaz AI apps that are pretty good (once you get past the steep learning curve) at refining images and fixing noise.

Saving images

You mentioned shooting to RAW so you are good there.

Tripod

This one is obvious.

Time Delay

Unless you want to use a remote to trigger the camera you will want to set it to delay the shot for 2 seconds once the shutter button is pushed. As your camera is a DSLR the mirror movement can cause unwanted vibration that will render your image blurry. I will give you some info on how to easily make this happen.

500 Rule

With the 10-18mm lens on a crop sensor camera you would divide 500 by the focal length to determine an approximate exposure time. This rule is actually pretty dubious as all of the sources that cite it never define the ISO setting nor the aperture setting to go along with it. So using this rule with the wrong ISO or aperture would mean under or overexposing. That being said the rule gives you a place to start.

Your lens has a maximum aperture of f/4.5 at 10mm and f/5.6 at 18mm. Despite the edge distortion that comes with wide open shooting I think you would be disappointed if you stopped down to f/8 (most lens’ sweet spot for sharp focus across the lens) and had to bump the ISO up to account for that.

At 10mm the exposure time would be 50 seconds and at 18mm it would be 28 seconds. With the built in maximum exposure in all camera shooting modes (other than Bulb mode) being 30 seconds you would not be wrong on using a lower ISO setting and letting the camera max out the exposure time. This eliminates one setting that to worry about.

I grabbed some images of your camera and lens and will add annotated images using them to assist. If I manage to figure out the custom profiling for this camera they might not be needed but at least the manual approach would be available.

Manual Focus

You will have to switch your lens from autofocus to manual. In the dark autofocus simply does not work as it will endlessly hunt for something to focus on. And stars in the sky are impossible to get it to recognize. To get sharp focus on the stars with manual focus your best bet is always to use your rear screen, tap the magnifying glass icon, zoom in and them manually adjust the focus. Trying to focus on tiny stars without being zoomed in is a crap shoot and you have no guarantee that they will be sharp.