Very over exposed looking subs and particularly poor final image :(

[TiffsAndAstro]

1 hour ago, dciobota said:

So a full moon and fast lens indeed will give you that result even at 30 sec.  As far as exposure compensation, as long as you shoot raw and stack the raw files it shouldn't matter.  That's only for jpegs or using the camera settings when you bring the file in say Photoshop or use the Adobe converter to make raw into tiff.  Only the iso affects the raw data.

So to correct myself.  If you shoot manual exposure compensation is ignored actually.  If you set the exposure and f stop manually yourself then ec has no effect.  EC is only used in modes where it can control aperture or exposure time like av or tv.

The brightness of the background will affect your dynamic range.  You were able to rescue a good bit of it but as pointed out, when the sky is this bright I would either stop down a bit or better yet reduce exposure or iso.  On some cameras you can shoot a lower iso and maintain the cameras best dynamic range.  I would try a combination of iso400 and stopping down a bit as suggested.

Best solution of course is to wait for the moon to get out of the way.  But that won't be for a while.

 

ty so much for this.  Av is the next position on the selector wheel next to manual. Its more than possible i accidentally changed it to Av mode and more than possible after i did, i did test shots and changed the shutter speed via the roller for speed - which also might have changed the exposure compensation to +3. Because im pro

 

630 to 1030 going to be clear according to my new favourite weather app. With such faster replies on here (who knew ireland had internet? ) i might post an update in a few hours showing my skills or begging for more assistance

 

ty all again !

[Guest]

Lol no worries, I don't know how many times I've done that myself.  Btw, the EC will move around as yu change exposure or aperture or iso in manual mode.  Pay no attention to it tbh, it's an indication of overall scene brightness.  Best to look at the histogram after you take a test shot if you really need to.   That's usually more useful but even than I kinda tend to ignore it sometimes.  For astro work it can be misleading a bit especially with small faint objects in a dark wide starfield.

[TiffsAndAstro]

6 hours ago, dciobota said:

Lol no worries, I don't know how many times I've done that myself.  Btw, the EC will move around as yu change exposure or aperture or iso in manual mode.  Pay no attention to it tbh, it's an indication of overall scene brightness.  Best to look at the histogram after you take a test shot if you really need to.   That's usually more useful but even than I kinda tend to ignore it sometimes.  For astro work it can be misleading a bit especially with small faint objects in a dark wide starfield.

had a frustrating time dodging cloud and rain. 30 seconds at iso400 look promising, but its frustrating doing this through clouds

[Guest]

I feel your pain my man.  This is a hobby for masochists for sure.

[900SL]

19 hours ago, TiffsAndAstro said:

hi there, hoping for some thoughts on the 'final image' ill post below (not a lot more than a quick stretch) and an example of my exposures.

Im thinking the answer is high thin cloud that i can't see with my eyes is reflecting light pollution? if this is the case - if i see a test exposure in future like my example below - just try another night?

30sec subs iso800 canon 600d/t3i (unmodified) and an old  pentax m 50mm f1.7 shot wide open because im a noob.

anyway result is here:

 

 

 

and an example sub here:

 

thanks in advance for any insights anyone can provide. 

 

 

What is your location/bortle class for light pollution? 

What does your exposure histogram look like? 

What did you use to stack, and what type of stacking? 

There's some bad lens artifacts there, coma etc

[TiffsAndAstro]

10 hours ago, 900SL said:

What is your location/bortle class for light pollution? 

What does your exposure histogram look like? 

What did you use to stack, and what type of stacking? 

There's some bad lens artifacts there, coma etc

bortle 6 backyard

never looked but i checked how to access it and will try and remember

er i think this one was siril with drizzle.

lens was wide open at 1.7, i was trying last night with it at 2,8 and iso 400 its  an old pentax m 50mm f1.7 on a 600d

here's a test shot i did last night. 30sec iso400 f2.8 couldn't really do much more cos clouds

 

 

IMG_5291.CR2

 

[alacant]

3 hours ago, TiffsAndAstro said:

i think this one was siril with drizzle

Hi
Still a little overdone perhaps.

eos600d? So as a starting point maybe try:

RAW, ISO800, 5s, f8, no drizzle; leave the aperture wide open and place a M6 washer over the front of the lens.

Cheers and HTH

Edited February 22 by alacant

[Elp]

Canon 600D I usually shot at ISO1600. That gradient is strong, how high in altitude are you imaging (altitude of the target in centre)? If it's not that, you've got a very bad source of light out of shot.

But that's the whole point of using background extraction as per the above. It will transform your images, especially if you're imaging RGB/OSC in LP areas.

[TiffsAndAstro]

ty both for this.

what's an M6 washer ? also, i could do 5sec exposures on a tripod no tracker

would a bedroom light from behind blinds 30ft away create that gradient? 

 

[alacant]

17 minutes ago, TiffsAndAstro said:

what's an M6 washer

For example...

Edited February 22 by alacant

[mackiedlm]

There is something going on between image capture and saving the image as CR2. Are you sure you disabled any in camera processing.

Taking the last image you uploaded from last night IMG_5291.CR2;

When I open in Photoshop camera raw, I get this

 

Note the histogram , data in middle. The image is still very bright. A properly exposed astro CR2 will be very dark.

 

If I open that same image in Pixinsight and debayer, This is what I get without any stretch applied;

 

This is exactly what a reasonably well exposed unstretched astro image should look like, Note the histogram way to the left (on a moonless night it would likely be further to the left.

If I apply an automatic stretch with STF I get this

 

Again this is exactly what I'd expect from this camera, lens, no filters, a bright moon, 30s @ISO400 - based on what I get with my 700D, The gradient is almost certainly from the moon and other LP and would be easily handled in the stack using any form of gradient removal.

 

In my opinion, there is some processing imbedded in the .CR2 which Photoshop uses to produce what it does. PI does not understand that imbedded information and opens the true "raw" image.

You need to work out what is happening in camera and stop it. Or else try stacking the subs in pixinsight.

But as long as you shoot with that camera and fast lens un filtered, in full moon conditions, you are going to have live with those terrible gradients and the other issues related to the bright moon LP

Also, I'd just note that stopping down has done little to improve the coma/abberations from the lens. They are still very bad. this is a zoom in to the top left corner.

 

HTH

Edited February 22 by mackiedlm

[TiffsAndAstro]

2 hours ago, alacant said:

For example...

why would i place that over the front of a lens ?

[TiffsAndAstro]

38 minutes ago, mackiedlm said:

There is something going on between image capture and saving the image as CR2. Are you sure you disabled any in camera processing.

Taking the last image you uploaded from last night IMG_5291.CR2;

When I open in Photoshop camera raw, I get this

 

Note the histogram , data in middle. The image is still very bright. A properly exposed astro CR2 will be very dark.

 

If I open that same image in Pixinsight and debayer, This is what I get without any stretch applied;

 

This is exactly what a reasonably well exposed unstretched astro image should look like, Note the histogram way to the left (on a moonless night it would likely be further to the left.

If I apply an automatic stretch with STF I get this

 

Again this is exactly what I'd expect from this camera, lens, no filters, a bright moon, 30s @ISO400 - based on what I get with my 700D, The gradient is almost certainly from the moon and other LP and would be easily handled in the stack using any form of gradient removal.

 

In my opinion, there is some processing imbedded in the .CR2 which Photoshop uses to produce what it does. PI does not understand that imbedded information and opens the true "raw" image.

You need to work out what is happening in camera and stop it. Or else try stacking the subs in pixinsight.

But as long as you shoot with that camera and fast lens un filtered, in full moon conditions, you are going to have live with those terrible gradients and the other issues related to the bright moon LP

Also, I'd just note that stopping down has done little to improve the coma/abberations from the lens. They are still very bad. this is a zoom in to the top left corner.

 

HTH

ty so much for all this. i think it possible i had exposure compensation on, possibly. im pretty sure i have it off now. its been clearish here for a few hours. i took orion again while i could see it, some pleides first too, also playing with a mirror lens as i type this.

my tracking times have been a bit variable though, sometimes star trails at 10sec, sometimes at 30sec - especially with the mirror.

i've tried to take in what everyone here has suggested, hopefully some of my efforts from tonight will turn out well. i just want to see an improvement from using a triped and a gazillion 5sec exposures.

im taking all the calibration frames for both lens and exposures etc - will do my mirror flats when clouds arrive. im assuming the mirror will be bad but it looks nice

 

 

 

[mackiedlm]

Make sure Auto ISO is turned off too.

[alacant]

9 hours ago, TiffsAndAstro said:

why would i place that over the front of a lens ?

It gives you a circular aperture, helping control aberrations around stars, particularly those caused by the non circular edge of the lens diaphragm.

Edited February 23 by alacant

[Elp]

Or use step down rings

[alacant]

1 minute ago, Elp said:

Or use step down rings

Really? A step down ring to 6mm?

 

[Elp]

7 minutes ago, alacant said:

Really? A step down ring to 6mm?

 

Ah I see. But 6mm seems unusually a small aperture to stop down to for DSO imaging, what is it equivalent near F10?

A lot of lenses (the majority) just aren't built for astro I've found, you'll inevitably get edge distortion/CA/loca etc on a lot of them, usually you'll have to crop out the really bad issues.

I kind of like the star diffraction patterns cause by aperture blades, it shows that they were imaged with real photo lens equipment.

Edited February 23 by Elp

[happy-kat]

Processing I find is easier without lens  deffraction spikes 

[Elp]

True, but for a beginner it won't matter. It's only an issue if you plan to process starless for nebulosity stretching. You can still get decent short total exposure time images processing the image with stars/diffraction still left in the image.

Edited February 23 by Elp

[alacant]

17 minutes ago, Elp said:

F10?

I suggested f8:
50/6 = 8 and a bit

[TiffsAndAstro]

1 hour ago, mackiedlm said:

Make sure Auto ISO is turned off too.

do you know where this feature lives? would it function even in manual mode?

[mackiedlm]

7 minutes ago, TiffsAndAstro said:

do you know where this feature lives? would it function even in manual mode?

In the ISO setting window. Yes it will function in manual mode. This from the 600D manual

There is indication that, despite what the manuals say, Exposure Compensation will also function in manual mode in some specific Canon Models - I've seen specific reference to this in the 6D but dont know how true that is or if any other models also show this characteristic.

[TiffsAndAstro]

2 hours ago, mackiedlm said:

In the ISO setting window. Yes it will function in manual mode. This from the 600D manual

There is indication that, despite what the manuals say, Exposure Compensation will also function in manual mode in some specific Canon Models - I've seen specific reference to this in the 6D but dont know how true that is or if any other models also show this characteristic.

wow ty for this. definately never enabled this intentionally. i've generally used 800iso but did try some iso400 last night maybe with better results. 

playing with processing now, stacked with background extraction looks ok, but it seems almost monochrome will have some more tries at it. 

 

 

here's one i made earlier - i think its better and worse at least more red. this is all good practice for me though, apologies

these are both from 107 x 10 sec subs f2.8 iso400 50mm on 600d moon up to the left and almost full, no lens hood and probably poor PA. if its clear tonight ill try again but do a Polar Align, Start Align and then try a 2 star polar align. Maybe with a 135m that has a hood. 

also, tempted to try my 18-55 kit lens for comparison's sake. its a lot slower though. 

Edited February 23 by TiffsAndAstro

[Elp]

You really need to spend more time on target, the above is an improvement. You can see the flame nebula in your above and that's from 17 minutes. Spend up to 3-5 hours and you'll see a lot more, even the horse head nebula next to the flame. You can stack your unstretched stacks per session (as the simplest method, they have to still be in linear state) to combine your multiple session exposure time.

Adding more and more time will help lower the read noise in the stack but won't eliminate it completely, all DSO smooth images have had a noise reduction applied to them post process.

Edited February 23 by Elp