Getting a better pic of Orion etc.

[JOC]

As some of you will have spotted I had a bash at taking one of those star-field pictures with my DSLR on a tripod the other night when I had very little time.  I found some instructions here https://darkartsastro.ca/how-to-shoot-the-milky-way-and-night-sky-with-a-dslr-camera/

I've also done some digging around here and found an old prime focus 50mm Pracktica lens that has an independent f-stop ring built into it that goes to f1.8 - this seems in line with the recommendation in the article - I've got an adapter ring that will let me fit it to my DSLR and since the rest of the settings come under manual I assume that it might be worth experimenting with it as opposed to continuing with my 18-55 zoom which only allows an f-stop of F5.0?

So I've done this rule of 500 thing that it mentions and come up with an exposure of 10 seconds?

I can set an ISO up to 800/1600/3200 or 6400 on manual mode - 1600?  So I avoid as much graininess as possible?

I also have a live view and could try focussing on a zoomed in bright star to get that better.

So is this a better setup please?  :-

Practika 50mm lens set at f1.8

ISO setting 1600 (or more???)

Exposure of 10 seconds?

Focus using live view zoomed on a bright star and then don't touch it

Any white balance adjustment needed???

 

[knobby]

F1.8 will capture the light much faster so it's definitely worth trying.

Where did you take photo ? a dark site would help massively (as would a break in the clouds )

[happy-kat]

Best to use raw mode so no need to worry about wb. With a canon I love using dslr controller with my android tablet phone.

Iso 800 or 1600 aim for the histogram to be clear of the left edge but before the middle.

If you focus where the thirds intersect it will spread focus sharpness.

Take lots then stack in DSS or Sequator if there is foreground subject.

 

[JOC]

@knobby if you mean these ones below - they were taken in a very quick experiment on my field (back yard) when it was clear last week and I had very little time to experiment.  I was less than impressed, but they suggested that the possibility of getting a better image existed.  I shan't be travelling to improve this, so it's either do the best with where I am or don't try.

@happy-kat histogram?  I've occasionally pressed the wrong button and seen one on the display, but I wouldn't know what to do with it.  When I process I know that I can sometimes improve the colours in the shots if I close the range and get rid of those bits of the histogram with no content on the blackest and whitest sides - beyond that they baffle me. 

31 minutes ago, happy-kat said:

f you focus where the thirds intersect it will spread focus sharpness.

Woooshhh....................did you see that go right over my head!!?  Sorry!

[knobby]

I think what Kat meant was to focus using a star about 1/3 into the frame as the feild isn't particularly flat on a camera lens and dSLR, that way you'll get more of image in focus.

When I said about dark site I was looking at the link you posted about milky way imaging ... And got side tracked !

Orion should be fine in your garden .

[JOC]

55 minutes ago, knobby said:

I think what Kat meant was to focus using a star about 1/3 into the frame as the feild isn't particularly flat on a camera lens and dSLR, that way you'll get more of image in focus.

ahh....OK, I can cope with that level of explanation :-D

Of course I'm all set up - 50mm lens in place on the camera, all manual settings already dialled in tripod ready and...............yup........it's wall to wall cloud outdoors tonight! 

I shall be very interested to take a photo with this very old lens just to see if it works on the camera, I've never used a lens on any camera that didn't come with it from new.

[happy-kat]

As Knobby said

When you take a photo you can then review it, pressing the disp button cycles through displays and one is the light histogram you are aiming for the peak to be fully clear of the left, crudely like this and can be further to the right but probably best to not go further then the left side of half way. Hope this helps. 

[JOC]

@happy-kat the focussing - I see, yes, that's clear, I am not sure why it gets more of the photo in focus than focussing in the middle, but that isn't important - I will certainly give it a try.  The histogram - I've given the buttons a try and would you believe it, up it popped just as you described when I looked at one of those Orion shots.  However, it isn't as you draw above - there is just like a single white line up the very left hand side of the graph.  I obviously need to have a bash with these new settings and see if I can actually get a peak with width to it and in the right place on the graph!

[happy-kat]

Try a higher iso with your 10 second exposure. All lens are generally sharpest in the middle but at cost to outer areas, focusing on a third intersection helps centre and edged focused. Stopping the lens down even to f2 is likely to help star shapes across the frame, you will need to test that if you find wide open star shapes are not stars around the edges. 

Have fun. 

[SilverAstro]

6 hours ago, happy-kat said:

 Sequator

Thanks! I've not met that one before, looks interesting.

 

[SilverAstro]

5 hours ago, JOC said:

However, it isn't as you draw above - there is just like a single white line up the very left hand side of the graph.

That is how it should be, kat's sketch was just a freehand illustration of the separation between the black level of your camera (far left) and white level (far right), the shape is not important at this stage.

The high peak represents the millions of darkish pixels that are most of the image,

{the few bright or white star pixels are way few in number and are thus below datum in the usual histogram display  ( we could talk about linear and log display at this stage but there may be a whoosh factor! involved)  }

provided that your histogram peak of those dark pixels has a gap [ which it does have YEA ok ! ] from the far left margin you are well on the road. The important thing is not to move that peak too far to the right else you will crush the bright/white of the stars such that they all become similar blobs! the whites (few as they are) need room in the right-left space of the histogram to exist.

Dont worry about the whoosh factor ! just ask !

So, to illustrate the above :-

pic1 let us look in detail at the sword of Orion ( M42, dont worry about the trapezium yet)

 

On the left below, the two red arrows show the sort of gap that you need to aim at and achieved ( a little more might be good but that is for later )  the proof of the pudding is on the right, the red arrow here shows the faint weak signal that you captured and can build upon (by stacking- a whole new topic!)

however, importantly, the yellow arrow on the right shows that you have not crushed the white level in this exposure.

{ the yellow on the left shows that those few  white pixels are below the scale of the linear histogram }

 

For further interest / research/ conversation of a whoosh level ! The following pic shows a log histogram plot of where all your brighter  stars are (yellow arrow) and how close  ? you came to bottoming out (red arrow) of your dark nebula and lost data. Green is where your limiting magnitude is .

There is much more that other experienced imagers could explore and help us with.

 

[JOC]

@SilverAstro I had no idea that a histogram could explain so much.  It seems to make sense when someone like yourself explains it in the equivalent of 'words not exceeding 2 syllables', but I am quite sure at the moment that I couldn't have drawn those conclusions myself.  I am quite surprised at how much you have seen by zooming in - I assumed that my image, overall, wouldn't be sufficiently in focus for any useful information to be gained, yet as you've zoomed in you've spotted the light from fainter areas that I hadn't even noticed.  I see that you've used GIMP to do the analysis, I've already got that downloaded - I shall have to get to grips with the use of it.  I am an analytical chemist by training and experience - the concept of sensors for light measurement, baselines, signal to noise ratios, wavelengths of light for measuring certain elements (even why that works!) I can cope with.  Photography is something I've dabbled with since childhood, and I've owned SLR/DSLR since I was 18, but I've never got to grips with what I guess you call post-processing.  I can load up a pic. into software and adjust the overall levels to get a better colour balance and I can play with some of the RGB sliders and pull the lines on the graphs in and out until I get a picture I like, but I don't really understand what I'm doing at a technical level.

The fancy shots of things like the M42 nebula itself I'll leave for the moment, whilst I work on a set-up which will give me a fair wider picture of a constellation in the night sky itself with just my DSLR.  Such photography will be educational in it's own right.  Then, as you mention above, once I get a single decent exposure maybe I can take several and attempt this stacking process.  I know it does all shift in sky relative to me, but there must be settings on the camera which will give me sufficient light on the sensor in a short enough exposure to get rid of most of the movement.  That's what I'm working on at the moment.  On the shots so far I set the ISO (800 IIRC) and the aperture (I think it was f5.6 as that was as far as the lens allowed) and left it to the camera to determine exposure (I don't know what it was taking, but it felt around the 10 seconds mark) - I'm hoping that the 50mm and its allowed f1.8 will let sufficiently more light in that the exposure becomes less and the action more 'frozen'. 

I'll leave this thread for my next attempt at Orion, which will rely on another clear night and time on my hands, but this morning I've been out and tried that 50mm lens - I think I've got a photo and I'll still it in the photo section of the non-astro boards.

[happy-kat]

You'll come to love M manual mode on your camera as already you are using an ISO 800 and exposure of 10 seconds and will have a manual lens you will set at f1.8 that's it all that is left is tell the camera to take raw+jpeg.

The sky moves 'field rotation' after taking multiple pictures and stacking them you just crop the edge of your picture to remove the field rotation artifacts.

[SilverAstro]

2 hours ago, JOC said:

  I am quite surprised at how much you have seen by zooming in Pixel peeking as it is known in the fraternity

sufficiently in focus for any useful information to be gained, Yep, you have captured a fair bit in that brief time, if you had done another 1/2doz or more we could have got into stacking them and then you would have been well amazed !

used GIMP to do the analysis, I've already got that downloaded - I shall have to get to grips with the use of it.  It is good (and free!) but a steep learning curve, I have fallen off a few times but no Sirius injury.

signal to noise ratios, Ah! Good!! all set to understand stacking then The stars and stuff are signal and the more pics you have the more they add up, the background dark noise is random and the more pics you have the more it averages out of the way.

but there must be settings on the camera which will give me sufficient light on the sensor in a short enough exposure Yes, you just did ! If you increase the duration you will introduce a trail, movement, to the stars and/or saturate, white crush, the stars. The duration and thus the movement that is allowable is governed by the focal length of the lens. The longer the lens the shorter must be the exposure,

another clear night and time on my hands, How we all wish good luck.

PS. Your focus was good enough to have stacked several of those, to get a "look- see" practice and a feel for stacking things

 

[JOC]

@SilverAstro you make it all sound much more positive than I thought it was  thanks for all the support - I can see me having another go with the existing setup just to see where I end up (I've got infinity focus problems with the 50mm at the moment - see other thread).  Perhaps I'll give the battery a charge in readiness - mind you I'm always amazed at how long I get per charge - I'm on 2/3rds at the moment and it's been ages since last doing it - good batteries on all my canons even my baby ixus.  Maybe I'll dig out the electronic shutter release gadget too so I don't need to touch things.

[JOC]

1 hour ago, happy-kat said:

all that is left is tell the camera to take raw+jpeg.

It's already doing that - I've got the RAW of that image - I set it up to take them by default and I just go through occasionally and delete what I don't need.

[JOC]

1 hour ago, happy-kat said:

The sky moves 'field rotation' after taking multiple pictures and stacking them you just crop the edge of your picture to remove the field rotation artifacts

Ah, so I don't move the camera to try to keep the image in the middle if I'm thinking about stacking then - instead I let everything move and crop the image later, yes?

[happy-kat]

Yes, let the sky move them crop the final stacked image, helps remove bad corner stars if the lens doesn't create nice one right to the edges.

[SilverAstro]

33 minutes ago, JOC said:

see other thread).  

the electronic shutter release gadget too so I don't need to touch things.

I must have missed that one. Some ebay? sellers of adapters dont always spell out "reaches infinity focus"

That would be a good idea, but if you cant find it on the night there is a work-around :-

Hold your hat (hand, card etc) in front of the lens but not touching, open the shutter with your other hand, pause a mo. to let vibrations subside, then remove your hat aka dummy shutter   Do in reverse at the end.

37 minutes ago, JOC said:

Ah, so I don't move the camera to try to keep the image in the middle if I'm thinking about stacking then - instead I let everything move and crop the image later, yes?

Yes -  if you dont take too long about it, but if spread over an hour or few (clouds interupting) then you can re-frame / re-point the camera to bring it back to the middle and carry on shooting.

 

[SilverAstro]

20 hours ago, JOC said:

 18-55 zoom which only allows an f-stop of F5.0?

That will be at the 55 end. It should be wider at 18

[JOC]

2 minutes ago, SilverAstro said:

That will be at the 55 end. It should be wider at 18

That's magic!  I hadn't even considered that it would change (though if I dredge my old photographic knowledge I suppose it should!), but you are right, if I wind it in one direction at 18mm I get down to f3.5 if its up at 55mm it won't go below f5.6.  Therefore I can use it to get f3.5 when I take a picture of the sky and benefit from a f3.5.  We'll stick that down as one of today's things learned!

[SilverAstro]

On 1/23/2018 at 12:10, JOC said:

That's magic!  I hadn't even considered

and benefit from a f3.5.  We'll stick that down as one of today's things learned!

  /

I have lost my way to the original post so I forgot what exposure time  and focal length you used ?

A little clarification may be in order : when we said you dont need to move the camera between shots - it all depends ! the longer you shoot for ie. the more shots you take, the greater chance of bits drifting out of view, between shots, so the usable bit of the final stack will become smaller.

This is ok if you are at the wide angle end, where the constellation that you are after will all be within each frame. However at the telephoto end bits drop out the sides quickly ! Like you lost Orions outer bits  even in the single shot and if you stacked several of those you would only have, perhaps, the sword and M42 remaining after cropping out the stacking artefacts.

In other words, the longer the focal length, the more you will need to re-frame between shots or group of shots, which is where a tracking alt-az (part of GoTo) * comes into play, it just saves you the bother of re-pointing manually shot by shot when the stars are moving quickly in the field of view.

I need to wave my arms around and a blackboard ,,, am I making sense ! ?

So yes, open up to f3.5 at fl18mm, we can discuss ISO later when clouds allow you to try various,, and have another bash,  getting all of Orion in several frames and then  (tear your hair out as you learn how to) stack in DSS  ( )

** ding ! You have a tracking GoTo dob ?? mount your camera on that ! Dont bother with the scope optics ie. not through the eypiece etc. just use the tube as a mount. Edit : xxed in post with h-k having the same inspiration !

 

[happy-kat]

You have a go to telescope mount your camera with lens piggy back style then at least orion will be kept in your field of view so no need to reposition. 

[SilverAstro]

2 minutes ago, happy-kat said:

You have a go to telescope mount your camera with lens piggy back style then at least orion will be kept in your field of view so need to reposition. 

Snap, great minds etc see edit at end of my post above

[happy-kat]

You can get camera flash hot shoe mounted red dot finder from astroboot.