[Pete_XL]

Edited in Photoshop. I still need to get better at comps!

Very nice result though!

Compared to the last photo of mikeSF there is some trailing in the edges. I also have problems with this using wide lens and think it occurs because the sensor shift is off-axis in respect to the earth axis.

Why does the picture of mikeSF not show trails instead?

[SirTomster]

Very nice result though!

Compared to the last photo of mikeSF there is some trailing in the edges. I also have problems with this using wide lens and think it occurs because the sensor shift is off-axis in respect to the earth axis.

Why does the picture of mikeSF not show trails instead?

My guess is that he is taking multiple shots just and merging into a panorama so then the whole shot is all parts taken from the center of the lens and not its edges, he crops the sides where the trailing occurs. I plan to try that when I go out next to shoot the stars.

But if mikeSF wants to tell us all his secrets, I will not argue

Another thing I have realized is that in these comps the images are not taken at the same spot. Or I should say my theory is that the sky images are taken with nothing in the way to get a full image of the sky. Then an image of the foreground is taken by itself. So an example is that awesome image of the bridge mikeSF did. Instead of all shots taken at the same spot. You have one picture of the bridge, then you move to a spot where you can see the whole sky and take your sky photos and them combine in post. Up until now I had always taken both pictures at the same location which causes its own issues. Eventually I will get smarter

Hey a reminder to all. The Geminid Meteor Shower is next Monday morning! The 14th. Best time is between Midnight and 4 AM on the 14th (Sunday Night/Monday Morning) I really hope the weather works.

[interested_observer]

Very nice result though!

Compared to the last photo of mikeSF there is some trailing in the edges. I also have problems with this using wide lens and think it occurs because the sensor shift is off-axis in respect to the earth axis.

Why does the picture of mikeSF not show trails instead?

I am certainly not mikeSF - not nearly as talented, but in the two years (well two Milky Way seasons - Feb to Oct) I have been using the GPS unit, I have found (through trial and error - a lot of error), that time (shutter) is a critical parameter in all of this. Initially, I thought that 5 minutes (300 seconds) - go for the max, was the way to go. Optimize / maximize you exposure time to light (collect as much as possible). Then I started to see the stars trailing around the edges of the frame. Initially, I thought that it was coma, but the lens I was using - the FA 31Ltd and Sigma 18-35 are noted for their lack of coma. At the same time, I was also experimenting with ISO - and have settled on no higher than 1600. [note - changing two items, shutter time and ISO, just prolonged the agony of discovery.]

Anyway, back to time. I also considered just abandoning the GPS unit and just going for a single image containing both the landscape element and the sky (MW). The 500 rule (500/focal length) was being pushed a lot on the web. Another poster over on Reddit (RClark - who does some really magnificent MW shots and processing) made an off hand remark (working through the math on the pixel level) that to eliminate trailing a good approximation is the 200 rule (200/focal length). This got me thinking earlier this year, and I backed off of 5 minutes to 4 minutes and was able to capture a really nice shot, but I still was capturing some trailing - essentially "sensor shift is off-axis in respect to the earth axis", as you described it.

• https://www.pentaxforums.com/forums/12-post-your-photos/299560-landscape-milk...-mountain.html

So, now my rule of thumb is no more than 2 minutes (120 seconds) with the GPS unit, and when not using GPS tracking 10 seconds (the 200 rule with an 18mm lens). Unfortunately, earlier this year, I kept missing opportunities - with business travel back east, and then later in the year, the MW rotated a bit too high over the landscape elements. So, I missed it - there is always next year!

In terms of stitching, one evening after being kicked out of the state park (upon closing) - I went up to a slightly different area with a poorer view of the landscape and did some stitching - with just the body and lens - no GPS. Even using 20 seconds and doing about 50% overlap, I did not get any real trailing (center of the lens and center of the sensor). This was essentially a throwaway shot at the last minute, before heading home.

• https://www.pentaxforums.com/forums/38-photographic-technique/299474-gps-astr...ml#post3311528

So, this year has been filled with the frustration of discovery (the hard way), missed opportunities, and just plain making stupid mistakes. But I have learned quite a bit overall. Then, there is this unity discussion over on the Astrophotography group here on PF - that a number of you are also on....

• https://www.pentaxforums.com/forums/groups/135-astrophotography/4340-how-avoi...sos.html?pp=15

The main thrust is that there is an ISO level that is optimum in terms of capturing light photons - and anything over this ISO is just adding noise. So, for my K5IIs it appears to be either 800 or 1600. Reading the posts after recovering from surgery has not done a lot for my full understanding - I need to go back and re-read them. My question is now 800 or 1600?

So, my take away is that ...

• in terms of both shutter speed and ISO - less is more. Somewhat counter intuitive.
• in terms of stitching, you can get away with more with a lot of overlapping - which essentially forces the use of both the center of the lens (and sensor). This I really did not expect until I really looked at that stitched image I was going to toss.

[mikeSF]

Very nice result though!

Compared to the last photo of mikeSF there is some trailing in the edges. I also have problems with this using wide lens and think it occurs because the sensor shift is off-axis in respect to the earth axis.

Why does the picture of mikeSF not show trails instead?

Hi - I avoid using ultra wide lenses because i find plenty of smearing at the adges with my DA15 and wider. Instead, I typically do a pano strip using the FA31 and the individual frames are great.

---------- Post added 12-06-2015 at 04:59 PM ----------

My guess is that he is taking multiple shots just and merging into a panorama so then the whole shot is all parts taken from the center of the lens and not its edges,.

yes, exactly.

---------- Post added 12-06-2015 at 05:02 PM ----------

Another thing I have realized is that in these comps the images are not taken at the same spot. Or I should say my theory is that the sky images are taken with nothing in the way to get a full image of the sky. Then an image of the foreground is taken by itself. So an example is that awesome image of the bridge mikeSF did. .

No, I always compose the foreground with the sky and they are lined up just like that when I shoot them. I have never aimed the camera to a different part of the sky, but i'm sure it can be done. That bridge image was a tremendous amount of preplanning to get the perfect night and then hiking around under the bridge to line it up. As such, the milky way lined up with the bridge in a favorable way, but I had to wait a couple hours for it to get in place.

Covered Bridge & Milky Way

And wouldn't you know THAT example was a single frame(not a pano)with the 10mm and has stars smearing all over the right side of the frame...sheesh!

---

Last edited by mikeSF; 12-06-2015 at 06:04 PM.

[mikeSF]

Here's a star frame from that night, showing actual alignment of the milky way to the scene.

[SKYGZR]

Recent K5ii "project" of mine here: Trapping the Trap - DSLR & Digital Camera Astro Imaging & Processing - Cloudy Nights

[Aaron28]

I typically do a pano strip using the FA31 and the individual frames are great

when it comes to the MW this is the approach I am now taking with the ogps but with a 28/2.8 or 50/1.7 and like what I am getting........if I am doin a time lapse vid or star trail I use my 14/2.8.........the big thing holding me back from a very nice finished product is my post process skills they are terrible (pretty much non existent but improving slightly)

Here's a star frame

that is a typical frame I would get (with a little more light pollution but close enough) and confirms that my PP sux!


but this forum has helped me tremendously in improving and an inspiration to get better......thanks so much!

[SirTomster]

Hi - I avoid using ultra wide lenses because i find plenty of smearing at the adges with my DA15 and wider. Instead, I typically do a pano strip using the FA31 and the individual frames are great.

---------- Post added 12-06-2015 at 04:59 PM ----------



yes, exactly.

---------- Post added 12-06-2015 at 05:02 PM ----------



No, I always compose the foreground with the sky and they are lined up just like that when I shoot them. I have never aimed the camera to a different part of the sky, but i'm sure it can be done. That bridge image was a tremendous amount of preplanning to get the perfect night and then hiking around under the bridge to line it up. As such, the milky way lined up with the bridge in a favorable way, but I had to wait a couple hours for it to get in place.

Covered Bridge & Milky Way

And wouldn't you know THAT example was a single frame(not a pano)with the 10mm and has stars smearing all over the right side of the frame...sheesh!

So my question is when you are taking the longer exposures how do you handle the foreground blurring? For me, I imagine it would be easier to take some shots of the bridge then move up the hill so you can see the whole Milky Way with no obstruction and nothing blurring.

Maybe shorter shots with the O-GPS1? When I do longer shots around 5 minutes I have significant blurring of the foreground which makes it harder to then comp in correct foreground.

Oh and thanks for the reply.

[Aaron28]

the foreground blurring

no ogps.....a stand alone static shot and a separate ogps shot composite/blend together.....which I have a terrible time doing

[Pete_XL]

Hi - I avoid using ultra wide lenses because i find plenty of smearing at the adges with my DA15 and wider. Instead, I typically do a pano strip using the FA31 and the individual frames are great.
.....

Chapeau mikeSF!

....and the more I think about it.....it must be impossible to avoid trailing stars in the edges of wide angle shots by just moving the sensor in x- and y-axis (as O-GPS does it as I think). In the projection of every uncompensated astro photo frame the stars all have a different (angular) velocity that is depending on each ones position relative to the earth's rotation axis. And you cannot compensate different speeds by doing a single-speed movement of a sensor that is determined by the center direction the sensor is aiming at. Best example: If the camerra is aiming at Polaris the sensor stands still in the ideal case. So Polaris finally will be nearly a pinpoint but all the others arround will show uncompensated trailing. The same effect - more or less heavy depending on focal length and pointing direction must happen in every photo shot with O-GPS.

I do not know if it would lead to a solution of this geometric problem if one could realize a combination of X/Y-shifting and rotation in the sensor movement....blows my mind if I think about this here in the early morning

[mikeSF]

when it comes to the MW this is the approach I am now taking with the ogps but with a 28/2.8 or 50/1.7 and like what I am getting.......
that is a typical frame I would get (with a little more light pollution but close enough) and confirms that my PP sux!

just keep at it and the processing will come. i use curves to pry apart the bright stars from the sky, and then just keep tweaking sliders here and there to dial in what i want.

---------- Post added 12-07-2015 at 09:00 AM ----------

So my question is when you are taking the longer exposures how do you handle the foreground blurring? For me, I imagine it would be easier to take some shots of the bridge then move up the hill so you can see the whole Milky Way with no obstruction and nothing blurring.

Maybe shorter shots with the O-GPS1? When I do longer shots around 5 minutes I have significant blurring of the foreground which makes it harder to then comp in correct foreground.

Oh and thanks for the reply.

i've never gotten an exposure longer than 2 minutes without trailing and in fact, i tend to go for 1.5 minutes or so. This works fine for me and the terrestrial objects that smear over the starfield is less pronounced, such that i can usually lay in the separate terrestrial exposure without any issues. occasionally i will have to clone a messy overlap but not a big deal.

There is another technique i have used before to catch sky and fg all in one, but only if the FG is completely unlit and you are lightpainting. This involves opening the astrotracer exposure and letting it run half of its duration then very quickly popping the foreground with the lightsource, whether from a strobe or some quick flashlight sweeps. then turn off all light and let the star exposure run to the end. The amount of terrestrial smearing is minimal and for the most part, a clean SOOC result can be obtained.

---------- Post added 12-07-2015 at 09:03 AM ----------

Chapeau mikeSF!

Merci!

---------- Post added 12-07-2015 at 09:07 AM ----------

....and the more I think about it.....it must be impossible to avoid trailing stars in the edges of wide angle shots by just moving the sensor in x- and y-axis (as O-GPS does it as I think).

yes. i certainly cannot speak mathematically about it, but a fanning out of the stars becomes evident with increased wide angle distortion and will certainly counter the "correction" course of the O-GPS1.

---------- Post added 12-07-2015 at 09:14 AM ----------

And folks it looks like I won't have any more images to contribute to this thread as I am selling my K5 and O-GPS1, replacing them with the K3II. Good luck everyone and do pm me offline if i can answer any questions - in case i dont check in here as often as before.

[colonel00]

I've been following this thread but I too am looking at a K3II so perhaps it's time to start a similar thread.

[SirTomster]

And folks it looks like I won't have any more images to contribute to this thread as I am selling my K5 and O-GPS1, replacing them with the K3II. Good luck everyone and do pm me offline if i can answer any questions - in case i dont check in here as often as before.

Please post some pictures of how the K3II does. Might just push me over upgrading. Doubt I could save up for the FF any time soon.

---------- Post added 12-07-15 at 10:32 AM ----------

I've been following this thread but I too am looking at a K3II so perhaps it's time to start a similar thread.

It looks like this thread: https://www.pentaxforums.com/forums/172-pentax-k-3/242797-k-3-astrophotograph...t-session.html

Will be the K3 version of our thread here.

[Aaron28]

letting it run half of its duration

brilliant and simple approach! gonna try that out!

[stanzhou]

Moonrise and Meteor with The Milky Way of Southern hemisphere


and Aurora Australis