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02-04-2022, 08:12 PM   #1
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Another Astrotracer thread (I'm a newbie at this)

Here's the story. Just a few nights ago I finally figured out how to use Astrotracer and got some useable results with my K-1ii at 450mm, f/5.6, 20 sec, 1600ISO (aside they were a hair out of focus.) Fast forward a few cloudy nights to a partially clear one, I decide to try it again. Instead of running my 150-450, thought I'd try my new D FA* 70-200/2.8. So I calibrate and set it up. Max running time says 2:20. so I think I'll try 1:00, f/2.8, ISO 1600. Similar settings when I had a real tracker and could run 1:30+ minutes subs. Well, focus seemed good (used a Batinov mask and checking diffraction spikes. So I let it run for a minute. Everything was way overexposed and there was streaking. OK, back off the exposure to f/4, 400 ISO and it looks more like it should other than the streaking. I calibrated the camera before I started shooting, had a good GPS signal, so I thought I'm good to go.

Was I just running it too long? 30 or 40 sec subs instead of 60? Obviously I running everything too hot as it was overexposed.I was using a two second self timer, SR was off, e-shutter was being used to minimize camera movement as much as possible. No wind and I was no where near it. Very sturdy tripod was used. Trying to figure out the streaking. If you look at how the streaks are, it looks like something else is going on, some kind of camera movement (lmagnify the photo and you'll see the jerks) that I can't figure out. Ideas? I've done some astro before with and without a tracker, so I'm not totally new to this. Look at the EXIF. What am I doing wrong, besides overexposing? Am I just trying to run AT too long?

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02-04-2022, 09:25 PM - 1 Like   #2
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This is a common discussion point over on the Astrophotography social group but the general consensus is that the "advised" maximum times with Astrotracer are far too optimistic.

I have settled on maximum 20 second exposures with the DA*300 on an aps-c. Others claim that 30 seconds is OK but never come across someone claiming success beyond 30 seconds. Guru deep space image makers like Mossyrocks uses his 400 mm at 20 seconds. I think most are pulling up at about 30 to 40 seconds with a 135 mm to 150 mm. Wide lenses can go much longer and 90 seconds on the DA15 or 10-17 FE seems OK but some have shown wide angle images out to 2.5 minutes that seem perfect. When you go wide, there is issues with stars in parts of the frame being affected by the stretching of rectilinear lenses. It's a bit trial and error but this should give you some start points.

Bear in mind that every frame is not exactly the same in terms of tracing performance so if you are stacking, there is a balance between going as long as you can and getting as many usable images as you can to provide a quality stack if that makes sense.

Hope this helps. Check out the Astrophotography social group, there is a lot of good advice and experience there.
02-05-2022, 02:53 AM - 1 Like   #3
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I am just learning to use Astrotracer - as last night was clear I had a go at the Orion nebula using a KP with 150-450 image below is the first I took. This is from my back garden so not entirely clean view of the sky - there is also a lot of light pollution. I have 3D printed a Bahtinov mask to help focus but only figured out how to zoom in live view in a later set of photos so I don't think I had the focus quite right. Unless you zoom in live view I struggle to see whether the focus is correct. Later photos exhibit trails but I think that is from the elevation clamp on the tripod breaking and the whole assembly slowly sagging.
I thought I had set the lens to 400mm (the EXIF is saying 160mm? ) and set the timer to 20 seconds. With the image The only thing I have done is open the .PEF in Affinity and save as a JPEG.
[IMG]

Last edited by MJ43; 02-05-2022 at 02:59 AM.
02-07-2022, 12:45 PM - 3 Likes   #4
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Hi im new dslr in general picked a K50 up in December and added the GPS for astrotracer for astro pics and had good success. I've found 30 seconds to be the limit for 135mm focal length on my aps-c sensor. I've found I'm getting trails on anything above that focal range at 30secs or above.

The lens I'm using is a vintage 135mm takumar f2.5. Non smc k mount version. You can pick em pretty cheap.

The Orion photo is 51 x 30sec @ 3200 iso at f/2.5 (The colours need a lot of work still)

Andromeda is 29 x 30sec @ 3200 iso at f/4

both had 20 darks/flats/biases.

I stacked them in siril and finished in lightroom.

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