LooseFur

14 hours ago, Uranium235 said:

Im using the KAF8300 sensor - its just very slightly smaller than APS-C

aaah ok - Yes, I am using full frame so you are not using the edges of the lens that I am...

2 hours ago, Uranium235 said:

You have the same lens? Try 2/3rds, but moving the star towards the affected corner.

yes, same lens but I am on full frame so I am not sure how much of the lens area you are using with your camera ? Is it full frame?
Though I am very new to all this so I have a lot to learn! 
I opened a thread about this on CN actually (https://www.cloudynights.com/topic/734450-issue-with-asymmetry/). I can't seem to get both corners sharp (top right, bottom left)

cool! I am struggling to get good stars across the image of my modded canon 6D at f/4. I can get the lower left corner good, but the top right suffers, and vice versa. Painful!

Very nice, what aperture did you set the lens to? 

How are you getting on with this lens? I have one too, on a modified Canon 6d. Not had a lot of time to test it yet but I did discover that it's tricky to get a flat field across the frame at f/4. I need more time to test though, cloud permitting of course! 

Hi all,

I hope you are well.

I recently got an iOptron skyguider pro and since have had only one night for testing it so far.

However, I noticed some odd artefacts in an image I took (100% crop):

Ignore the green stars, I am aware that Nikon have this issue but I am seeing some strange line artefacts too. 

200% crop:

I shot this at f/4, 100mm lens (100mm focal length, 50mm aperture) - 64 seconds, ISO 400. 
I have an old version of the firmware, I'll probably update it tomorrow (1.11 - current is 1.14, I think). Camera is unmodded.
I'd love to know what you guys think that is all about!?
PS I didn't use dark calibration, this is just one image. I did use in camera long exposure noise reduction.
Are they just hot pixels? In RawTherapee they do seem to vanish when I adjust the 'hot pixel' removal slider.

PPS it was windy and I am not 100% sure I nailed the polar alignment.

thanks a lot!

On 31/08/2020 at 18:52, toxic said:

and if you use photoshop you can get a free set of plugins from google called NIK collection they are very good i used it on your image as well as HLVG as andy r said.

Hi Toxic, 
I was looking at the nik tools last night and I couldn't figure out which tool you used to increase the saturation here - it looks really good! Can you please let me know which one you used?

Thanks for all the info guys, you are very helpful!

Yep - I am an old time user of cs2, I also have many 'actions' under my belt for landscapes already. I am loathe to pay for new software that doesn't really bring anything new to the table, especially these 'pay monthly' schemes. I'd rather spend the money on new hiking boots or a new lens etc. Of course, software is a large part of imaging but as you said - you can do most things in CS2, you just need more knowledge of the tool. 
Anyway, I got the plugins working, I'll have a look later. Thanks again all!

Thanks Toxic, I'll have a look at that - I hope these plugins work in Photoshop CS2 as I don't have a later version - do you know if they do?

1 minute ago, Philip R said:

The re-edited image is a lot better. Thank you for sharing. 

Thanks very much!

I am just learning this really. 

I used Pix Insight in the end, yes it looks better now after the SCNR. Thanks a lot for the tips guys.

Thanks guys, that's the sort of feedback I was hoping for - I am not an astrophotographer per se, though I am a veteran landscape photographer - what applications do I need to perform SCNR?

Just now, fwm891 said:

'FX' is full frame 'DX' is the cropped format

silly me, my head is not screwed on - I knew this haha. I'll edit the post

Hi all!
I hope you guys are well. 
I was doing a night hike yesterday morning (started at midnight the previous night). I like to shoot landscapes/sunrises on mountains so usually that involves me hiking in the dark for many hours until I arrive at a predetermined location. But I've been looking to the heavens increasingly lately, mountains are usually great dark sky locations so when the head torch is off - the skies are amazing.
Anyway, I got sidetracked (from the hike) because as the moon set the sky lit up with stars (and the milky way) so I opted to take a few long exposures of the Cygnus region using a nikon d810 and zeiss 35mm on a static tripod. I should note that I used the lens in 'dx' mode, even though the D810 is full frame - so 1.5 x crop factor. The lens is amazing stopped down but even at f/4 the corners are still not great for stars. f/5.6 gets you there though but without tracking, I need more light. 'dx' mode was the compromise, plus I get a bit more magnification.
This is what I came up with (12 images stacked in DSS, f/3.2, 4 secs each ISO 6400). No tracking, or guiding - just a static tripod. This was my first real attempt at any sort of wide field shot. I used in camera long exposure noise reduction and took darks but did not use them in the stack (I might try the stack again later with darks).

I was quite happy with it but I think there is probably some noise and I am not too sure about the colour balance, I'd like to get more accuracy with the colour balance - so tips are most welcome! Obviously there is room for improvement, more frames would have been better (but I was again 'balancing' between getting to my spot for sunrise in time vs shooting the stars - life is ALL about compromise!). Without tracking, I can't get away with much more than 4 seconds exposure either. 

I think I know what it is, I think my suspicion was correct - it's shutter shock (not mirror slap shock). Electronic Front Curtain only works in Mirror up mode on the D810 - not on the quiet modes (although the mirror is indeed raised in this mode). 

48 minutes ago, The Admiral said:

I really wouldn't like to say, but it's interesting that there is colour associated with it, with a light green on the right 'bump' and magenta on the left 'bump', with white in between:

I would just make the comment that aircraft navigation lights are red on the left of the aircraft and green on the right and white at the rear. Quite often than these are strobed. I'm not sure that this explains the sequence of colours though, unless perhaps the left and right lights are strobed alternately, but it is food for thought.

Ian

Yes, I noticed the colour too. I thought perhaps it was some mild chromatic aberration or colour fringing. It's very odd. I am not stressed about it, I am curious however.

23 minutes ago, tooth_dr said:

I was wondering if it was possible to do mirror lock up.  I have a nikon d800e and havent worked it out yet. 

It could be that actually, using the quiet mode DOES lock the mirror up but there is still vibration from the shutter mechanism itself (hence the Electronic Front Curtain feature, only engaged in Mup drive mode). But I am still confused why the satellite trail in the above image doesn't 'wobble'.

7 minutes ago, tooth_dr said:

It could be a tumbling satellite.  I did recently experience this and my stars also looked ok, but it was concluded that it was the wind shaking the scope.  The stars appears slightly elongated in line with the oscillations, so perhaps it is shake?  The mirror clicking up might cause this?

maybe you are right. I was using 'quiet continuous' drive mode on my nikon d810, which I had _thought_ locked the mirror the up prior to exposure. Maybe I am  wrong. Strange, though - because other images using the quiet mode show satellite trails as straight lines. Puzzling, but interesing! See below:

I did a quick stack, using only the frames with the line in it - it's very noisy actually and it has a lot of what I think you guys call 'walking noise'? PS I did no dithering, this was taken on a fixed tripod (no tracking/guiding). I was just experimenting with a 200mm lens I have.

15 minutes ago, Tomatobro said:

There are some websites that show pictures of tumbling space junk or other stuff.  That's moved quite a distance for a tenth of a second and you say the other frames show the object moving in a straight line frame to frame. You are right though in thinking that usually sats produce straight lines on the frame.

I wonder if it appeared mid frame and disappeared the same way. Could be interesting to stack just those frames to see what it looked like

 

yep, it moves in a straight line, frame to frame but always 'squiggly' like that. Similar shape each time too.

42 minutes ago, tooth_dr said:

It could be a satellite but with some vibration/movement with the telescope during capture, so it’s recorded as oscillating.

I too was suspecting camera shake actually, but on closer inspection - the stars themselves do appear sharp (at least to me, see below - a different frame with the line near some stars) . Shutter speed was 1/10th of a second

25 minutes ago, Tomatobro said:

try "heavens above" to search for satellite

Thanks, I'll have a look. Strange that it's so wobbly though - I thought satellite trajectories were quite linear/straight. But I am not expert by any means!

Hi all,

A quick question - I am sure someone here has seen this before, but what is it?
In about 10 frames (of 100+) I see the below 'squiggly line'. What on earth (or space!) is it?

It clearly moves from the top of 1 frame to the bottom of tenth (ish) frame. I assume it's not an aircraft? Drink flying?

Thanks

14 minutes ago, Seelive said:

Yes, just using 1 dark frame will be worse than using none.  You really need to stack several dark frames (I always try for at least 20 to 30) for them not to effect the noise in the final image.  The more lights you stack, the lower the final image noise will be (in theory reduced by the square root of the number of lights) so just keep adding to them (up to a point anyway, the law of diminishing returns comes into play!).  

Is LENR the in-camera noise reduction?  If so, you could test the results with and without using it but I think the general census of opinion is to turn it off, it can give more problems than it solves, and just use darks.

The star images certainly look sharp but I think I would be tempted to open the lens up by a least a stop or two. With a F1.4 lens, I would try F2.8, you will get considerably much more detail in the images for the same exposure time at the expense of some distortion in the corners, but you could always crop the image. 

Thanks for the reply. Yep, LENR is in camera noise reduction. I will turn this off next time, at least I'd be able to take 2X more images now! I will take more lights/darks instead.

Yeah I tried a few test shots at f/2.8 and f/4 but I really wasn't pleased with the corner performance. I think I would have to crop a lot. This is with a £2k 35mm lens. I am (and so is the nikon d810) very demanding! I tried a few other lenses too (I have the Sigma art 35mm f/1.4 too, it's not an even a comparison if I am honest).
I made a conscious decision to trade noise (use a smaller aperture and therefore higher ISO) for edge to edge detail. Maybe cropping might have been better, but to be honest I can pull the exposure up quite a lot in lightroom with the D810 - it has a good dynamic range latitude. 

Thanks for the very knowledgeable replies everyone, still finding my way a bit and I don't get many clear nights where I live.