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11-04-2019, 03:28 AM   #46
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QuoteOriginally posted by MossyRocks Quote
30 seconds @560mm is probably pushing it. I've managed 20 seconds at 400mm.
...
It looks like you weren't tracking at all with the 5 stationary dots but streaks for the stars. I've had the GPS go to sleep if I stepped away briefly and then the next shot I took didn't use it and it turned out bad so I'm wondering if that happened with that one.
Thanks for that explanation.

I understood the thing was supposed to be good for five minutes or so. You figure the focal length changes how long it can keep up?

I think those five dots were keeping up with the movement of the earth, since that's what satellites in a geosynchronous orbit do. Hence, no trails, they were moving at the same rate I was, relatively speaking.

11-04-2019, 04:29 AM - 1 Like   #47
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QuoteOriginally posted by dlh Quote
You figure the focal length changes how long it can keep up?
Yes it does and the estimates it gives I find to be pretty optimistic. Here is the official Ricoh page where they give their best case times. I've found that to get pinpoint stars if I stay under 1/4 the estimate the camera gives me it will usually work but their estimates have always seemed overly optimistic. The other information on the O-GPS1 PAGE on calibrating it would apply if you are using one of the cameras that has the built in GPS as well. There is a video showing how to do the calibration as well there.
02-21-2021, 09:14 AM   #48
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I posted this in photo critiques but those of you more interested might look here. All comments ae welcome. I will repost the text from original below. Also here i post the original no PS. Thanks.




Hello all. This was taken as an HDR 3 image and resolved in camera. Tripod mounted, 3 second timer, no filter, focus to infinity, I had the 3/4 (give or take) moon just off screen. and of course a lot of other light from being just a few miles from Atlanta, my neighbors porch light etc. I had the hood on which seemed to be absolutely necessary.

The image came out with a not so dark sky. I turned the contrast up and maybe the shadows down. I really just thought to make more contrast. Obviously Im not an expert.

The image is take facing somewhat south so South is at the bottom of the screen (my best recollection). I think the Pleides were to the right (east) but in some tree limbs. I tried to get a pic of just sky. In hindsight I will likey include those at the edge so i have an anchor, next time. Im not sure if just my inexperience but I thought the central object was Arigua. However, now that I cannot currently go out and look again - until tonight (fingers crossed)- It is a mystery to me what I took a photo of. I have been looking at star charts and I don't get them to match. So my bet is that I am so wrong that this is not going to help you help me.

So far as the image, I see the edges of the photo the stars sort of double up, which Im guessing is due to the 3 image composite and different colors/wave lengths so some should probably be cropped . But I did not crop so y'all might be able to give more advice for when the next semi clear sky appears. I think we have been overcast for a couple of months until last eve.

I was staying with f1.4 and keeping the ISO 3200 or below on Auto ISO. I tried 2 sec and 1.6 1.3 1.0 .8 .6 .5. This is the one that came out best. Given a better game plan I would like to try shots at f1.4 1.8 up to 2.8 to see if sharpness improves.

Yes I am looking for critical advice. I do not have a astro device currently. Perhaps that would help. The tripod has a 2.5 lb weight hanging and is on concrete. This to say its about as stable as I can think to make it.

My other lens options for primes are the 70 limited 2.4 and the 40 limited 2.8. I have a Tamron 70-200 2.8 from back when it had the macro moniker so that lens might be an option. I have slower lenses but without tracking etc. I think I need to stay below 2 seconds shutter.

Fire Away!

Oh Yes and Thank You all for Your comments ahead of time! I am looking forward to the help.

Risx

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02-22-2021, 01:47 PM   #49
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QuoteOriginally posted by Risxsoul Quote
I posted this in photo critiques but those of you more interested might look here. All comments ae welcome. I will repost the text from original below. Also here i post the original no PS. Thanks.
I looked at your original post. To answer the question you asked there what is in your field of view I passed the URL of your image here to have it plate solve it. The results of plate solving can be found here.

So now you know what is showing in your image. So we can move on to how to improve. When doing astro shooting exposure matters and if you can't get enough in a single shot (you never can get enough) you will need to use stacking software. For those starting out I suggest using Deep Sky Stacker or Sequator as they are free and do well enough for beginners. I would still seek to increase exposure times for each frame.

Since you mention you don't have any tracking (astrotracer or equatorial) your best option is to use the rule of 200. This is a modern variation of the rule of 500 that was used for film but digital doesn't have reciprocity failure and digital is sharper, so because of that you use 200 instead of 500. This rule says that your maximum single frame exposure time should be no more than 200/(focal length) in seconds. So with a 50mm lens it means you can use a 4 second exposure for a single exposure and not have much noticeable trailing. I would say don't bother using the in camera HDR options as they expect things to not move and they do move.

Your images isn't too bad for one's first astro image. it shows noticeable vignetting but with a pushed image shot wide open with one of the 50/1.4 that is expected. It also shows clear coma in the corners, another thing that is common. Finally I see those wonderful purple halos that show up when wide open on most lenses and more so when the focus isn't perfect.

So let's work on solving those problems
First solving the purple halos. This is often caused by the focus being slightly off. There are focusing aids you can get to help you nail the focus and the most common preferred one is a bahtinov mask. You can buy them premade and this one should work pretty well for your short lenses. If you don't have one you can get a very good focus by manually focusing in magnified live view and minimizing the stars and when you get it close look at some of the flickering pixels. You will find that eventually a bunch of those flickering pixels will stay on, these are dim stars and when you get the perfect focus they consistently stay on.

Next will solve the rest of the purple fringing, most of the coma and most of the vignetting. To do this you will need to stop the lens down. Almost every lens needs to be stopped down some to get great when shooting astro. Even legendary astro glass like the Rokinon/Samyang 135mm f/2 UMC, Laowa 12mm F/2.8, and SMC A* 400mm F/2.8 ED [IF]. I also have some 50mm lenses I run for astro, one is the S-M-C 50/1.4 Takumar and the other is the SMC A 50/1.2 and I will run both of these lenses at f/2.8. This removes almost all of the coma, basically all the color fringing (I maybe could count 1 pixel but that might be bad tracking), and basically the vignetting. So I would run your 50/1.4 at f/2.8. Even the modern DFA * 50/1.4 needs to be run at 2.8 for astro shooting.

The bright sky is normal, especially in light polluted areas. This is normal and can be clean up with post processing. But for someone starting out focus on taking shots and getting them stacked using a program like Deep Sky Stacker (DSS) or Sequator. Use a remote release (cabled or wireless doesn't matter) also use the 2s delay as that will cause the camera to flip the mirror up for a couple of seconds before opening the shutter. This allows shake to die down giving better results. As far as tripods go you want the biggest heaviest, most ridged you can find, or in my case build. I also have a Manfrotto 3058 with the 3057 head which is a big sturdy one too. From there I would shoot a few shots and reframe to shoot more and just keep repeating that until you are cold, tired, or sick of being outside.

For more info I wrote this up a few years ago to get beginners pointed in the right direction. It doesn't tell everything as I could probably write volumes on the subject now but is enough to get someone more or less off to taking some good starter images.

If you want better responses go join the astro group, we are friendly and will usually fall over each other to help others grown in ability.

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