Getting a better pic of Orion etc.

[JOC]

That looks a lot more promising - many thanks for the Gimp tweaks.  OK, I guess I owe an explanation for the non tracking shots.  So it was super moon night.  It looked like being lovely and clear so despite the cold and as I hadn't had a good session for a while I dumped the scope outside ready to play.  I knew Orion would be grabbable early in the evening before it got too icy cold and sorted everything ready to go out after animal feeding.  6 pm and it still looked great out.  Then.......... life happened, daughter wanted support with her 'A' level mocks revision.  8pm came and went and I was still up to my eveballs in biology.  Finally she decided she was done.  10 mins later I had wriggled into my warm observing suit, I grabbed the power box fully intending to Goto and my bag of bits and EPs and hurried outside.  What do I find, 50% + cloud cover, not enough stars left that I knew to callibrate on, Orion right over the yard arm and scarcely in view over the house and the moon beaming out any chance of stars to the east with the clouds.  Well teed off I nearly came straight back in, but then I thought well I did clear out the SD card lets try taking some basic non Goto snaps, the results of which are what you found above.  So all my plans to try and get a decent Goto'd M42 went right out the window and then I forgot I'd need the 400 rule and things went from bad to worse and I wasted all that time and effort and my chance to make something pleasing.  Oh and just to be bloody minded my 5mm Pentax wouldn't play ball on the trapezium and I could still only see 4 stars with my 8mm.  The were 2 rather feint ones a little distance away both on the same side of it, but they seemed just too distant to be E and F

[JOC]

Bump - I'm fishing this old thread out as I thought I might have a bash at a constellation for the latest SGL competition.  I've got a Canon fitting cheap Yongnuo lens to try using.  It's a 50mm fixed focal length (prime?) lens.  Crucially it claims to be F1.8 so this is a lower F number than I can achieve with the short zoom that I have and I hope will be a better weapon - assuming I can fit the bit of sky I want into it.  Unfortunately I've been looking at the dates here and it looks like I was finding Orion in the south during the hours before 12pm during Jan/Feb this year so maybe I won't be able to get a shot of Orion (which is a shame as it's such a nice shape), but I'm going to have a look at Stellarium and see what is in the South and East at the moment. 

[JOC]

Mmmm......I've been outside to do some snapping and appear to have a problem - I've got about 10 + pictures of areas of the sky, ISO 1600, F1.8 and 10 second exposures the trouble is that although the focus may not be spot on (which is something I'll have to work on) I think  the backgrounds aren't dark enough, when I stack them they just seem to turn white - almost as though the whole thing becomes overexposed.  Is there anything I can do with them - example of each set below or shall I just delete them. and try another night at a lower ISO.  NB.  Getting the focus right without the moon up is def. an art.

 

Good grief they look even worse blown up on this display!

[Davey-T]

Focus is out, have you got live view ? if so you can focus zoomed in on a bright star first, manual focus with auto focus turned off.

Shorter exposures look to be possible start with 2 secs and work up.

Have you got a lot of light pollution ?

Dave

 

[Mognet]

The lightness of the background might be having images that are too bright to start with. There is some advice on page 1 of this thread about using the histogram to check initial exposure settings. It could also be from the stacking software settings, depending on what you are using

Sharp focus takes a bit of practice and patience. I generally start using autofocus on a distant bright light, and then switch to manual focus on the stars. From there I make gradual adjustments to the focus, checking the image after capture using the image zoom for sharpness of stars in the centre and corners, until they are as sharp as possible. I do the focussing part with the lens at f1.8, but for capture I usually stop the aperture down to f2.5. This sounds a little odd when supposedly trying to catch as much light as possible, but it helps to get sharper star shapes, control vignetting, and remove some of the lens distortion.

ISO1600 and 10 second exposures should be fine at f2.2 or f2.5

[JOC]

Thanks both, I think I need to go back to basics again.  The problem with the focus was finding a bright star to focus on, but perhaps a distant object as @mgnet says might be a good starting point.  If I could find a bright star and get it in the view finder I've got one of those camera sized Bantinov masks that I could dig out and try, but it was surprisingly difficult to see a single star in the view finder or even in the tiny live view grid on the back of the camera.  Perhaps as mentioned above trial and error is the only way forward. 

I knew I should be looking for the histogram, but I'd gone outside without a torch and couldn't find the right button!

On ‎14‎/‎11‎/‎2018 at 23:36, Mognet said:

but for capture I usually stop the aperture down to f2.5. This sounds a little odd when supposedly trying to catch as much light as possible, but it helps to get sharper star shapes, control vignetting, and remove some of the lens distortion. 

ISO1600 and 10 second exposures should be fine at f2.2 or f2.5

I can try this - anything useful is worth trying.  I was wondering about doing things at ISO1600 - when I was doing manual stuff on film many years ago if you went too high on ISO the images became very 'grainy' as the film got faster - does the same thing not happen with DSLR photography or does it not matter when talking about tiny white points on a (what should be) black sky?  There was probably more light pollution kicking around at ground level than I had when I tried in the earlier part of the thread, but I assumed as I was looking up into a reasonably dark sky it wouldn't matter, however it does look as though it has had an effect - It is supposed to be clear tonight, maybe I'll get out and try for some better results.  An entry in the the current SGL competition must be within my grasp if I can find/identify a set of stars that fits the bill of a constellation or asterism.

NB.  Sorry I had not responded to my helpers sooner - the system hadn't pinged that there had been responses on the thread and I've just spotted the reply watch was set to 'off' which I've now remedied

[JOC]

I've re-read the thread and finally found the simple to use software name that I was getting along with (I downloaded about 4 different ones at the time).  Running Sequator on the images I'm back to a black sky hurray!  However, the images are def. out of focus as we all knew.  Qu.  How do you get rid of aeroplane light trails?  I am on several flight paths to airports and with some regularity get aircraft going through.  They make err...... interesting? light trails on the photo, but rather detract from what I'm after.  I've also dug out the baby Bahtinov mask for the camera to that might be worth a try if I can actually get a star in view that I can see through the view finder.  The battery is also on charge and I've cleaned out all the old images on the SD card. 

Now watch 'life' happen and ruin all these best laid plans!

[Davey-T]

This weekend is looking promising and the Moon being out will give you something better to focus on in live view, there can be another problem with the focus moving when imaging so a blob of blue tack can be used to lock it.

Have you got  a red dot finder to fit in the camera hot shoe ? this is a good aid to find a bright star on live view which can be surprisingly tricky, Altair, Aldebaran, Capella and Vega are suitable candidates tonight, you should be able to set live view to override your settings and get the brightest live view screen.

I've never found a BM much help on a camera, live view works fine as the star gets smaller it will flip between blue and red and zoomed right in you can catch it at it's smallest.

Good luck

Dave

[JOC]

I did try two areas of the sky the other night.  This is no-where perfect and it's nowhere near the standard that I'm happy with, but somehow I've got it slightly more in focus and you can see that Sequator has given me back the black background.  Again I had no way seeing exactly what I was aiming at (as I can't see the stars through the viewfinder or live display (for some reason), but its a 50mm lens pointed somewhat in the rough direction of Pleiades around about 9pm a couple of nights ago  (though I suspect I've missed it entirely).  However, I'm slightly more encouraged that, if I can find focus again,  I can do this.  NB.  If there is a constellation somewhere in this that I've missed and someone wants to point it out at least I will know that I can get a full constellation into this lens.

[tooth_dr]

@JOC

With the Bhatinov mask on the camera try taking 2s exposures of a bright star at a high iso - this will give you good spikes. Adjust the focus slightly then take another 2s exposure. The spikes will move. Decide which way you need to move it. Keep moving it little by little until it’s in focus then remove mask carefully.  Hang the mask using just 1 peg rather then gripping onto the end of the lens. 

[JOC]

3 minutes ago, tooth_dr said:

With the Bhatinov mask on the camera try taking 2s exposures of a bright star at a high iso - this will give you good spikes. Adjust the focus slightly then take another 2s exposure. The spikes will move. Decide which way you need to move it. Keep moving it little by little until it’s in focus then remove mask carefully.  Hang the mask using just 1 peg rather then gripping onto the end of the lens. 

Ooo.....that's excellent thank you - I had no idea how to use it - daft question does the straight line that splits the half into two quarters have to be vertical on the camera?

[JOC]

NB.  Looking at the picture above I am surprised at how many of the stars seem to be different colours - you don't see any of that by eye.

[JOC]

25 minutes ago, Davey-T said:

Have you got  a red dot finder to fit in the camera hot shoe

I like that idea - I didn't know you could get one, but I wonder if there is some way tonight that I could cobble my telescope one onto the top of the camera with some rubber bands!

[Davey-T]

I thought FLO did one but can't find it on their new site.

https://www.365astronomy.com/Blitz-Hotshoe-dSLR-Camera-Adapter-for-Red-Dot-Finder.html

I just filed down an RDF to fit in the hot shoe.

Stars always look more colourful out of focus, I guess it spreads the colour more.

Dave

 

[JOC]

10 minutes ago, Davey-T said:

I just filed down an RDF to fit in the hot shoe.

I've found someone making them on the popular auction site and just ordered one - putting an RDF onto things will make finding a bright star to focus on a whole lot easier.

[Davey-T]

1 hour ago, JOC said:

putting an RDF onto things will make finding a bright star to focus on a whole lot easier.

It also helps when imaging things like nebula that don't show up on live view, you can aim the RDF at their location using adjacent stars.

Dave

[Davey-T]

2 hours ago, JOC said:

.  How do you get rid of aeroplane light trails?

Astro Art has a remove lines tool championed by Olly for satellite trails, don't know if it works for planes, you could ask him.

2 hours ago, JOC said:

If there is a constellation somewhere in this that I've missed and someone wants to point it out at least I will know that I can get a full constellation into this lens.

If you enter your camera sensor and lens stat's into Stellarium it will draw you a field of view on the screen.

Dave

[JOC]

1 minute ago, Davey-T said:

If you enter your camera sensor and lens stat's into Stellarium it will draw you a field of view on the screen.

I'll try that.  ?

[JOC]

14 minutes ago, Davey-T said:

It also helps when imaging things like nebula that don't show up on live view, you can aim the RDF at their location using adjacent stars

I don't know why I didn't think of using a finder, but knowing how it helps with the telescope it makes perfect sense.  I will be able to mount the telescope one when I get this little adapting shoe through the post ?

[JOC]

So how does light pollution work with cameras - if I am, say, in the back garden and the lights of the house are behind me and the back garden is dark, but is not 'that dark' and I have the camera pointing away from the house and up into a fairly dark sky, will the light in the back garden have a detrimental effect on what I am trying to take a picture of when that is far higher up and away from the source of light pollution?

[Davey-T]

Eyes are not the best thing to measure light pollution with, a sky quality meter works better.

Bit of trial and error required, have you got orange street lights as your images have an orange cast ?

Generally I set ISO800 and see how long an exposure I can take before the histogram  falls off the right hand side 

Dave

[JOC]

No orange street lights - in fact no street lights at all - you don't get much for your council tax 'in the sticks' LOL.  However, the factory next doors runs for 24hrs a day and is floodlit at night so what light pollution there is largely comes from that source although there are a lot of trees between them and us and very little direct light intrudes.

[Mognet]

3 hours ago, JOC said:

I was wondering about doing things at ISO1600 - when I was doing manual stuff on film many years ago if you went too high on ISO the images became very 'grainy' as the film got faster - does the same thing not happen with DSLR photography or does it not matter when talking about tiny white points on a (what should be) black sky?

Noise from digital is a bit different to film. With film it was from the particles being much larger in the faster films. In digital photography it's from the mostly random electronic and thermal noise being amplified. The way around this with astrophotography is to take plenty of shots and stack them, averaging out the random noise to an even point leaving the signals hidden therein. I typically take 60 images using an intervalometer to control the camera. The Deep Sky Stacker website has a technical explanation, including the various ways to remove the non-random noise. For now just concentrate on taking the light frames (the star images) and once you've got the hang of that, the flat images.

3 hours ago, JOC said:

Running Sequator on the images I'm back to a black sky hurray!  However, the images are def. out of focus as we all knew.  Qu.  How do you get rid of aeroplane light trails?  I am on several flight paths to airports and with some regularity get aircraft going through.  They make err...... interesting? light trails on the photo, but rather detract from what I'm after.

In Sequator, click on Composition, and click on the 'Select best pixels' radio button. This changes the calculation from average to sigma clipping. It will take care of all but the worst satellite and plane trails. For the worst trails the only thing is to exclude the photo from the stack or delete it entirely. Another way is to take the images later at night as the sky tends to go quieter after 11pm here.

My typical setup in Sequator is:

• Composition: Align stars. Normally I leave the calculation as average, unless satellite trails show up
• Sky region: Full area (default)
• Auto brightness: On. Sometimes turning this on improves the stack, sometimes it doesn't
• High dynamic range: Off (default)
• Remove dynamic noises: Off (default)
• Reduce distotion effects: On, and set to complex. DSLR lenses can cause a pincushion distortion effect. In normal photography it's not that noticable and processing software can take care of it. But when when stacking raw images straight from the camera, the rotation from image to image makes a mess of things towards the edges
• Reduce light pollution: Off for the trial stack, and then on with the uneven setting depending on the results from that. The amount of reduction can be adjusted too
• Enhance star light: Off (default)
• Merge 4 pixels: Off (default)
• Time lapse: Off (default)
• Colour space: sRGB (default)

47 minutes ago, JOC said:

So how does light pollution work with cameras - if I am, say, in the back garden and the lights of the house are behind me and the back garden is dark, but is not 'that dark' and I have the camera pointing away from the house and up into a fairly dark sky, will the light in the back garden have a detrimental effect on what I am trying to take a picture of when that is far higher up and away from the source of light pollution?

Light pollution will cause a gradient across the background of the stacked image, and it gets more noticeable when the image is stretched. What I generally do is to take the stacked image into GIMP, select Colour->Levels from the menu and then click on auto input levels. I call this the 'nasty process'. It's no good for processing images, but it will show up problems like gradients and satellite trails. It's then that I go back and re-stack using the reduce light pollution option until the problem is minimised, and then I can process properly.

[JOC]

There are a lot of clever folks on SGL - I am very lucky to be able to share in this already accumulated knowledge - many thanks all  ? - it is my intention to go and have another go tonight providing life doesn't get in the way.

[tooth_dr]

12 minutes ago, JOC said:

There are a lot of clever folks on SGL - I am very lucky to be able to share in this already accumulated knowledge - many thanks all  ? - it is my intention to go and have another go tonight providing life doesn't get in the way.

Focus is critical to the end result so take time to get it right at the start of the night.  The mask can go on anyway you like, orientation is irrelevant. Get it close by eye without the mask on, then place mask and fine tune it.  Then don’t forget to remove once focused.