Astro Photography?

[JG777]

Hi,

Does anyone here dabble with astrophotography or have any experiences / tips they would like to share. This is something I have been wanting to do for some time and now the dark evenings and shorter daylight hours are almost upon us would really like to give this some time.

In particular I am interested in lens recomendations and usage. I have 3 cameras, a D300 a D5100 and a Canon G12. The lenses I own are the 35 F1.8 / 50 F1.8 ( screw focus version ) 85mm micro, 16-85VR / 70-200 VR1 / 70-300VR / Sigma 120-400 . Various cable releases, tripods and spare batteries!

I am interested in star shots, trails constellation shots and also moon shots. Planets and deep sky I think might be a bit more complex on DSLR set ups but not entirely sure.

So the Qs are

1/ Do I already have the lens in the armoury or is something else better advised?
2/ My lenses all have pro digital clear filters for protection, never noticed any IQ reduction with these in daylight use but could it be an issue at night?
3/ What kind of settings for camera and focus?
4/ Auto white balance? I shoot raw all the time but does WB need some special attention?

Any pointers or general advice much appreciated.

Thanks

[Shadowman]

Hi,

Does anyone here dabble with astrophotography or have any experiences / tips they would like to share. This is

So the Qs are

1/ Do I already have the lens in the armoury or is something else better advised? [ Yes you do but there is always something better. You should be able to get some good shots with each of your lenses, outcome will be different for each. For instance, the 35/50mm can be used for cityscapes with the moon above the buildings. The telephotos will get you some good closeups. ]
2/ My lenses all have pro digital clear filters for protection, never noticed any IQ reduction with these in daylight use but could it be an issue at night? [ Not really but look for double images, scratches, and effects on exposure.]
3/ What kind of settings for camera and focus? [Manual focus, start at ISO 100, various shutter speeds until you get the best exposure.]
4/ Auto white balance? I shoot raw all the time but does WB need some special attention? [Not with RAW.]

Any pointers or general advice much appreciated. [Check threads on this forum for astrophotography, full moon photography. There are at least ten topics on the subject.]

Thanks

[JonathanC]

I used to do this quite a bit, and accumulated a lot of kit in an attempt to be better at it. The first thing you need is a dark site to start with. Not just dark, but so dark that you can't see where you are going. Street lighting within a mile will affect your attempts, as I found out. I have a motorway within half a mile and a busy road junction within 200 metres of my home, so this didn't help.
Some obvious things.
A tripod is almost essential. You can put the camera on its back in extreme cases, but thats not good for framing.
Good focus is essential. The pinpoint star light is extremely dim if it hits more than two or three sensor elemants and it won't show up.
Warm clothing is necessary, not a luxury. It gets very cold at night standing counting the seconds away.

Some observations of my own.
The targets range from small to quite big, in angular size. You can get a Milky Way shot with a wide angle lens, but try the cat's eye nebula or planets and you need something like an 4000mm lens to start off. If you get hooked on this kind of thing, rob a bank.
Star trails are nice, but to get untrailed stuff you'll need a tracking mount. These range from a few hundred GBP to more than is decent.
Once you have the tracking mount you have to aim it so that the tracking is in the correct direction, or you just made it worse.
The moon is a superb target with lots of features that are challenging to photograph, but it is also bright enough (daylight on it) so that you don't have exposure durations of 15 minutes like some other targets. ( Not joking there, some are several days!)

HTH

[Tringa]

As already mentioned a dark sky is needed. Digital sensors are very good a picking up light pollution which if not ruining your shots, will affect them.

Having said that its a good idea to practice a bit somewhere that is not too dark just to get the feel of what you are doing and an idea of what settings work well.

Focussing is often a problem as the autofocus almost certainly will not be able to lock on to stars. A couple of suggestions -

1. See if you can find something distant on the horizon to manually focus on - building, tree against the sky. This can still be difficult is you are at a very dark site.

2. Set the focus ring of lens to infinity. This can have problems as not all lenses focus at infinity when the focus ring shows infinity.


If you want stars to show as single points, so you can see the constellations, then the 600 rule is a good starting point.

Maximum exposure in seconds before trailing occurs =

600/(focal length of the lens x the crop factor of the camera).

On my camera (crop factor 1.5) with the kit lens at 18mm that is about 22 seconds - 600/(18 x 1.5).

This is not an absolute rule as it depends on what part of the sky you are photographing, but it is a reasonable place to start experimenting.

If you want to go further have a look at this bit of free software

http://deepskystacker.free.fr/english/index.html

which allows several shots to be stacked.

Alternatively a mount which tracks the stars as Jonathan has suggested.


If you want star trails, just point the camera at one part of the sky and open the shutter. I have read, but have no experience of, about sensors overheating with long exposures (ie hours). There is also the possibility of the battery running out during a very long exposure. This software (also free) helps with star trails -

http://www.startrails.de/html/software.html

Like the other software mentioned above, it stacks a number of shorter exposures but it preserves the trails.

Along with the warm clothing I'd suggest a chair and maybe a warm drink. These are particularly important if you are taking star trails as inevitably you are going to be outside for some hours. A small torch is also handy, if you can rig a red filter over the light it will help to preserve your night vision.

If you have a pair of binoculars take them. You can see a lot with just a simple pair and it will give you some things to do if you are out for hours.

Hope this helps

Dave

Although a very dark sky is best you can still get something in less than ideal conditions. This was taken about 200 yards from a school and the security lights illuminated the foreground hill, though I was able to shield the camera from the lights. F4.5, ISO 400, 30s

[ajohnw]

Astrophotography is a specialised subject.There is lots of information on the web and various specialised software packages. I haven't had much luck looking for a decent source of information. Most of it is aimed at telescope use.

Shots used to be taken with very long exposure using very accurate guiding systems to prevent star trails but digital cameras allow multiple shorter exposures to be taken and added together with software. Dark frames are used to remove noise from the shots as well. Say a 30sec exposure was taken of the sky, another 30 sec exposure would be taken with the lens cap on. There are all sorts of variations on that. One problem is that the sensor will heat up as the exposure progresses and increase the noise. There are also other types of frames used. Best search for them with google as you come across the terms. Often packages only seem to handle avi's but they will usually handle separate shots as well.

Telescope jargon might cause some confusions. Diameter is the over riding factor hear as it sets the resolution of the telescope and the amount of light captured from a source. The focal length sets the scale of the image. The F ratio it's speed as per photography. There are calculators about that will relate exposure times to lack of star trails.


The most comprehensive software package is probably IRIS. There are tutorials here

near the end of this page http://www.astrosurf.com/buil/us/iris/iris.htm.

More here
http://deepskystacker.free.fr/english/index.html

Those are a bit like throwing you in at the deep end but might be a source of suitable google search terms for more info on various aspects. This tutorial is very straight forwards and uses a different style of image stacking software

http://www.russsscope.net/staxtutorial.htm using this package http://www.astronomie.be/registax/

This video gives a photographers perspective on stars Much simpler. It all depends on how far you want to go really. I suspect the use of camera lenses for this sort of thing hasn't really made a lot of use of some of the facilities available in specialised software unless they have been piggy backed as it's called on a guided telescope.

There are some simple ways of making a camera track the stars.. Some info on here http://www.jlc.net/~force5/Astro/ATM/Poncet/Intro.html The barn door type is linked too of the construction page. Seems they are also called Scotch mounts at times too. People used to make them out of 2 pieces of wood hinged at the end and driven apart with all thread driven with a synchronous motor.

-

[JG777]

Thank you Shadowman, I did search and found some useful threads.

[JG777]

I used to do this quite a bit, and accumulated a lot of kit in an attempt to be better at it. The first thing you need is a dark site to start with. Not just dark, but so dark that you can't see where you are going. Street lighting within a mile will affect your attempts, as I found out. I have a motorway within half a mile and a busy road junction within 200 metres of my home, so this didn't help.
Some obvious things.
A tripod is almost essential. You can put the camera on its back in extreme cases, but thats not good for framing.
Good focus is essential. The pinpoint star light is extremely dim if it hits more than two or three sensor elemants and it won't show up.
Warm clothing is necessary, not a luxury. It gets very cold at night standing counting the seconds away.

Some observations of my own.
The targets range from small to quite big, in angular size. You can get a Milky Way shot with a wide angle lens, but try the cat's eye nebula or planets and you need something like an 4000mm lens to start off. If you get hooked on this kind of thing, rob a bank.
Star trails are nice, but to get untrailed stuff you'll need a tracking mount. These range from a few hundred GBP to more than is decent.
Once you have the tracking mount you have to aim it so that the tracking is in the correct direction, or you just made it worse.
The moon is a superb target with lots of features that are challenging to photograph, but it is also bright enough (daylight on it) so that you don't have exposure durations of 15 minutes like some other targets. ( Not joking there, some are several days!)

HTH

Thanks Jonathan much appreciated. Did you really mean to type 4000 or was that 400? lens? I think I can get to somewhere with darker skies than where I live and street lighting not an issue. I guess the orangery light polluted areas and the possible overspill to my location will be a significant issue.

[JG777]

As already mentioned a dark sky is needed. Digital sensors are very good a picking up light pollution which if not ruining your shots, will affect them.

Having said that its a good idea to practice a bit somewhere that is not too dark just to get the feel of what you are doing and an idea of what settings work well.

Focussing is often a problem as the autofocus almost certainly will not be able to lock on to stars. A couple of suggestions -

1. See if you can find something distant on the horizon to manually focus on - building, tree against the sky. This can still be difficult is you are at a very dark site.

2. Set the focus ring of lens to infinity. This can have problems as not all lenses focus at infinity when the focus ring shows infinity.


If you want stars to show as single points, so you can see the constellations, then the 600 rule is a good starting point.

Maximum exposure in seconds before trailing occurs =

600/(focal length of the lens x the crop factor of the camera).

On my camera (crop factor 1.5) with the kit lens at 18mm that is about 22 seconds - 600/(18 x 1.5).

This is not an absolute rule as it depends on what part of the sky you are photographing, but it is a reasonable place to start experimenting.

If you want to go further have a look at this bit of free software

http://deepskystacker.free.fr/english/index.html

which allows several shots to be stacked.

Alternatively a mount which tracks the stars as Jonathan has suggested.


If you want star trails, just point the camera at one part of the sky and open the shutter. I have read, but have no experience of, about sensors overheating with long exposures (ie hours). There is also the possibility of the battery running out during a very long exposure. This software (also free) helps with star trails -

http://www.startrails.de/html/software.html

Like the other software mentioned above, it stacks a number of shorter exposures but it preserves the trails.

Along with the warm clothing I'd suggest a chair and maybe a warm drink. These are particularly important if you are taking star trails as inevitably you are going to be outside for some hours. A small torch is also handy, if you can rig a red filter over the light it will help to preserve your night vision.

If you have a pair of binoculars take them. You can see a lot with just a simple pair and it will give you some things to do if you are out for hours.

Hope this helps

Dave

Although a very dark sky is best you can still get something in less than ideal conditions. This was taken about 200 yards from a school and the security lights illuminated the foreground hill, though I was able to shield the camera from the lights. F4.5, ISO 400, 30s

Dave, thank you for the comprehensive reply and links. I can see this is going to be big learning curve. I cant see your image from my work PC but will look later. I never heard of the 600 rule so this looks interesting.

[JG777]

Astrophotography is a specialised subject.There is lots of information on the web and various specialised software packages. I haven't had much luck looking for a decent source of information. Most of it is aimed at telescope use.

Shots used to be taken with very long exposure using very accurate guiding systems to prevent star trails but digital cameras allow multiple shorter exposures to be taken and added together with software. Dark frames are used to remove noise from the shots as well. Say a 30sec exposure was taken of the sky, another 30 sec exposure would be taken with the lens cap on. There are all sorts of variations on that. One problem is that the sensor will heat up as the exposure progresses and increase the noise. There are also other types of frames used. Best search for them with google as you come across the terms. Often packages only seem to handle avi's but they will usually handle separate shots as well.

Telescope jargon might cause some confusions. Diameter is the over riding factor hear as it sets the resolution of the telescope and the amount of light captured from a source. The focal length sets the scale of the image. The F ratio it's speed as per photography. There are calculators about that will relate exposure times to lack of star trails.


The most comprehensive software package is probably IRIS. There are tutorials here

near the end of this page http://www.astrosurf.com/buil/us/iris/iris.htm.

More here
http://deepskystacker.free.fr/english/index.html

Those are a bit like throwing you in at the deep end but might be a source of suitable google search terms for more info on various aspects. This tutorial is very straight forwards and uses a different style of image stacking software

http://www.russsscope.net/staxtutorial.htm using this package http://www.astronomie.be/registax/

This video gives a photographers perspective on stars Much simpler. It all depends on how far you want to go really. I suspect the use of camera lenses for this sort of thing hasn't really made a lot of use of some of the facilities available in specialised software unless they have been piggy backed as it's called on a guided telescope.

There are some simple ways of making a camera track the stars.. Some info on here http://www.jlc.net/~force5/Astro/ATM/Poncet/Intro.html The barn door type is linked too of the construction page. Seems they are also called Scotch mounts at times too. People used to make them out of 2 pieces of wood hinged at the end and driven apart with all thread driven with a synchronous motor.

-

John, thank you for taking the time to respond with this and the links. There is indeed a lot of information to take on board. Guess it is head down this week reading and form a plan for an evening out under the stars. Having the info and technology is one thing but also tying it up with a dark clear sky in the UK in available time is another!

So I maybe OK camera and lens wise, just technique and application to consider more.

Thanks

[ajohnw]

John, thank you for taking the time to respond with this and the links. There is indeed a lot of information to take on board. Guess it is head down this week reading and form a plan for an evening out under the stars. Having the info and technology is one thing but also tying it up with a dark clear sky in the UK in available time is another!

So I maybe OK camera and lens wise, just technique and application to consider more.

Thanks

You should be ok with shorter focal length in the wide angle range on a tripod. The vimeo link I posted makes some good suggestions about how to take photo's that way. Just wish there was a few web pages that gave straight forward information. How much of that is needed really depends on how far you want to go. My main experience in this area is visual through telescopes. Light pollution is a problem but varies from place to place even within towns. Near by hills help and the best time for clear skies is usually winter. It's possible to buy light pollution filters but as far as I'm aware these only come in sizes to suit telescope eyepieces. 2in max. I suspect people have forgotten that shots can be taken with camera gear on very simple stands that could be suitable for bolting onto a rigid photo tripod. Probably down to people wanting instant gratification with self aligning telescopes and computerised goto etc. I've had more fun is some ways just browsing round the sky often not having a clue what I'm looking at. The go to becomes useful when insufficient stars are visible to get a reasonable idea of where things are - the usual result of light pollution. On the other hand in a dark sky showing the milky way clearly there are so many stars visible aligning the go to can be a trial.

I have a bit of a thing about lighting. As a species we are perfectly capable of seeing well in moonlight so why do we for ever try to create sunlight at night rather badly.

-

[JG777]

Thanks John will check the link out properly this week. Like you my main experience was with telescopes where I once owned a very good 5 inch refractor, this was pre digital camera days or just about when that technology was getting going. Light pollution was a problem then. Locally orange or murky skies was pretty normal, not a great deal has changed. I got some excellent information from Robin Scagels book Astronomy from towns and suberbs which although a bit dated now is still very relevant in his assesment of town lighting and ways to still observe through it. He called it knowing your enemy!

Agree over the whole lighting issue, but maybe there is a way forward now that some areas are switching off street lights at night to save money. That and full cut off street lights that direct the light down rather than up and all around. It seems we still have to rely on the best atmospheric conditions for a dark sky. I will have to factor this in of course and it may be the difference as to how far I might experiment with astro photography.

For finding stars google night maps on a smartphone does a reasonable job!

[JonathanC]

Thanks Jonathan much appreciated. Did you really mean to type 4000 or was that 400? lens? I think I can get to somewhere with darker skies than where I live and street lighting not an issue. I guess the orangery light polluted areas and the possible overspill to my location will be a significant issue.

Yes 4000mm focal length. 200mm aperture at f/10 with a 2X Barlow lens (=Teleconverter).

The angular diameter of a planet is so very small that HUGE magnification is required. Most people use a webcam (no kidding!) to capture images. You take off the lens (they unscrew) and screw in an adapter to fit the telescope. Software then post processes the stream of images in the AVI file into an averaged (think focus stacking, but not quite) photo.
See stargazerslounge.com for loads of stuff and a forum similar to here (friendly and helpful)