my First 30 second photo without tons of star trailing! fixed star tracker

[realflow100]

Not a super interesting section of the sky or anything but I finally fixed my star tracker enough that 30 second exposures are feasible!

50mm canon STM F1.8 lens
iso 100
F2.2

Canon 500D camera
ioptron smartstar E8500 R goto alt-az star tracker

full size image and 45% scaled down below

[jrkirkham]

Every milestone is cause for celebration. Stretching a 50mm lens to 30 seconds is certainly a milestone. Good job. I noticed your ISO is at 100. I wonder what you would come up with if you jumped it up to 400 or 800 with that 30 second exposure?

[Star Dad]

Yeah, my thoughts. I'd go up to at least 800, maybe 1600. Typically Canons start to get more noisy at 1600 or greater.

[realflow100]

It would be over exposed at a higher iso. due to light pollution effects!
The whole image would be clipped to white and the stars and even the background sky would be white.

iso 100 is already very bright at 30 seconds at F2.2!

here is unedited jpg converted from raw image with nothing enhanced. all default/zero settings except for white balance


ALSO NOTE: website seemed to die for a while. dont know what happened but im able to edit my message. seems the whole website froze really bad.

[realflow100]

I cant see a higher iso having any benefit when the light pollution is this bad to begin with.

[Star Dad]

Take a bunch of images, stack them, take some darks,flats, etc. You may be surprised at the quality. My most successful images with my tracker were 60 - 1 minute images stacked and processed. Individual images were nothing to rave about - but the total result was well worth the effort. Besides, the natural next step is to start processing images. Your results may vary.

[JayTee]

I cant see a higher iso having any benefit when the light pollution is this bad to begin with.

DSLR AP is always a trade-off between ISO and exposure duration when you're dealing with LP. 30 seconds @ ISO 100 = 15 seconds @ ISO 200 = 8 seconds @ ISO 400. All of those exposure times will give the same level of background LP illumination. You will get better results by using a higher ISO in terms of lower sensor noise (for Canon sensors). Additionally, shortening your exposure times gives the added benefit of less time for errors to occur and be recorded by the sensor, namely star trails because of poor tracking. Final benefit is that you can just about squeeze in 3 exposures at ISO 400 for a single exposure at ISO 100. It's more efficient.

So give it a try, go out and see if using those different exposure times with their corresponding ISOs give the same background LP illumination. If you keep extrapolating you could also try 4 seconds @ ISO 800! Then do what Star Dad says above about multiple images.

Cheers,
JT

[realflow100]

I'd have to do stacking with shorter exposures if I want to use a higher iso because of the insane light pollution.
the light pollution makes exposing for longer than 30 seconds at iso 100 not possible without stopping down. but stopping down would reduce the light I get so it would cancel out any gains.

my only option would be stacking a lot of shorter exposures. but that takes a lot of work and the programs ive tried are so bad at stacking my images because of the noise or because of not enough stars visible because of all the light pollution!

[Graeme1858]

I'd have to do stacking with shorter exposures if I want to use a higher iso

Yes! That's exactly what JT is saying. Then you can capture a lot more exposures in a shorter time and stack them to improve the signal to noise ratio. Shorter exposures with higher iso will not show the light pollution any more than your images above.

Image stacking isn't particularly onerous. That's no reason not to try.

Try it, then post back.

Regards

Graeme

[realflow100]

there is one benefit from lower iso though dramatically less hot pixels. the noise is more soft looking and less chunky and harsh looking. like the noise is smoother.