bwana Loc: Bergen, Alberta, Canada

And why exactly would crop factor come into play in the 500 Rule?

The sky moves at 15°/hr and in any given amount of time moves across the same number of photosites on a crop mode sensor as it does on a full frame sensor, assuming the photosites are the same size; thus, the same trailing.

bwa

LoneRangeFinder Loc: Left field

A sample would be helpful to know what you mean by “eliminating glare”. For longer exposures, you should cover the viewfinder with a piece of (gaffers) tape or a dark cloth. This helps to eliminate light entering through the viewfinder.

PHRubin Loc: Nashville TN USA

Because blowing up an image by any factor increases all movement within the image frame of subjects by that amount. This holds true for crop factor as well. Increased movement requires faster shutter speed.

bwana Loc: Bergen, Alberta, Canada

At full scale the movement is exactly the same!

bwa

PHRubin Loc: Nashville TN USA

HUH? By definition, crop factor changes scale.

bwana Loc: Bergen, Alberta, Canada

Crop factor is simply a crop; nothing more, nothing less. If the sensor photosites are the same size in both a full frame or crop mode camera, the star trailing for any given lens will be exactly the same; one or two photosites on both sensors.

Crop mode does not change the fact a 200mm lens is still a 200mm lens. It doesn't change the magnification of the lens. It is exactly the same as taking a crop out of a full frame image or setting a full frame camera to capture in crop mode.

Star trailing impacts the same number of photosites on a crop mode camera as it does on a full frame camera. This is not rocket science!

bwa

IR Jim Loc: St. Louis

If you reply with your type of camera, lens, and if you have a tripod or not, it would help everyone be able to provide information pertinent to your gear. Specifically, we could inform you on the limitations of your gear.

The 500 rule for stars and the Looney 11 rule for the moon are real and do work. I would however suggest you google them as this thread has delved into crazytown. You'll find sites with tables you can print for both crop and full frame cameras, depending on what you have. (yes it matters)

As for stars being out of focus, if it's happening on the edges of the picture it's likely due to the quality of your lens. If all or most are blurry, have swirls, or look like V's it's probably camera shake. If have have a tripod and it's cheap, try not extending the legs at all. A sturdy tripod, remote shutter release, and mirror lockup (beginner cameras usually don't have this feature) can help mitigate camera shake.

Focusing on stars can be very difficult but don't give up. If the moon is out, autofocus on that then turn off autofocus. If it's not out, manual focus is the way to go. If using a zoom lens, decide on your focal length and don't change it (or it will change your focus). Do your best to focus on a bright star in the center of the frame and take a shot. Zoom in on image preview and make a very small adjustment, take another shot and check out the preview again. If it got worse, focus the other direction. If it got better, keep making minor corrections until the stars are sharp.
If you only see a handful of fuzzy objects but most of the stars are sharp then congratulations. You likely photographed galaxies and/or comets!

IR Jim Loc: St. Louis

If you reply with your type of camera, lens, and if you have a tripod or not, it would help everyone be able to provide information pertinent to your gear. Specifically, we could inform you on the limitations of your gear.

The 500 rule for stars and the Looney 11 rule for the moon are real and do work. I would however suggest you google them as this thread has delved into crazytown. You'll find sites with tables you can print for both crop and full frame cameras, depending on what you have. (yes it matters)

As for stars being out of focus, if it's happening on the edges of the picture it's likely due to the quality of your lens. If all or most are blurry, have swirls, or look like V's it's probably camera shake. If have have a tripod and it's cheap, try not extending the legs at all. A sturdy tripod, remote shutter release, and mirror lockup (beginner cameras usually don't have this feature) can help mitigate camera shake.

Focusing on stars can be very difficult but don't give up. If the moon is out, autofocus on that then turn off autofocus. If it's not out, manual focus is the way to go. If using a zoom lens, decide on your focal length and don't change it (or it will change your focus). Do your best to focus on a bright star in the center of the frame and take a shot. Zoom in on image preview and make a very small adjustment, take another shot and check out the preview again. If it got worse, focus the other direction. If it got better, keep making minor corrections until the stars are sharp.
If you only see a handful of fuzzy objects but most of the stars are sharp then congratulations. You likely photographed galaxies and/or comets!

PHRubin Loc: Nashville TN USA

For 2 cameras of the same megapixels (which we all understand we are talking about), the field of view of a crop camera is smaller than that of a full frame, which dictates smaller pixels. So NO, it is NOT the same as cropping a full frame image. Any subject movement is magnified (covers more pixels), hence the need for faster shutter speeds.

bwana Loc: Bergen, Alberta, Canada

No, we are talking about two cameras with the same sized photosites, not the same megapixels!

But I'll let you believe what you want, even if wrong.

bwa

JayRay Loc: Missouri

A camera with a crop frame sensor has a smaller field of view than a full frame sensor camera.
Therefore, in a crop frame sensor camera the time for a star to traverse the sensor (15 degrees per hour) is less than in a full frame sensor camera. Hence the apparent motion across the sensor is proportionally greater in a crop sensor camera and this needs to be proportionally accounted for in the equation to eliminate motion blurring of the stars. You can Google this topic for further insight and explanation.

bwana Loc: Bergen, Alberta, Canada

Yes, the "apparent motion" across the sensor is greater; no disagreement on this point. BUT the actual photosites impacted by star movement, i.e.: the actual star trailing, is identical for a crop sensor vs. a full frame camera with the same lens and same size photosites. Very simple to prove... Just compare the star trailing at full scale and you'll see it is the same.

bwa

armandoluiz Loc: Oppland, Norway

I have a Nikon D3400 with lenses 18-55 and 70-300.

How should I do for night sky, stars and the moon?

Thanks

bwana Loc: Bergen, Alberta, Canada

I'd start with the 18-55 @ ~35mm, wide open, tripod mounted. Do an autofocus on the Moon as a start and lock it.

Choose the star field you want to shoot. Shoot 10-15 sec. shots @ ISO1600 and see what you get.

For the Moon, mount the 70-300, set to 300mm, wide open. Do an autofocus and lock it. Set an ISO of 100, camera mode to Program(P) mode and try some shots. Once you get a few shots that you like, check the settings, switch to Manual(M), set the previous settings and adjust shutter speed or aperture while shooting until you get the perfect image.

Using a digital camera is about trial and error. It doesn't cost you anything to shoot several hundred images...

Another thing to remember about astrophotography is that those miles of atmosphere over your head is the last lens in your setup! You might think you have shot 20 identical shots BUT you'll find some of these will be better than others simply due to atmospheric motion / distortion.

bwa

Jupiter in Motion

armandoluiz Loc: Oppland, Norway

Wow, thank you, I'll try it soon when is not so cold to be outside at night