DSLR Widefield Imaging..... Gathering Data

[Mav359]

Hi guys

My DSLR is mounted to the top of my OTA on an EQ mount which is tracking, i can control the Camera over USB and i have watched a really good explination on camera setup. I have had a plan and am happy i know how to capture the data...... great!

What i am unsure of at this point is what data to capture, a single shot is easy but what about.....

Do i capture multiple subs?

Is there a best exposure time or just as long as i can?

I haven't heard anyone metion stacking?

If i have a foreground to my image but am exposing for 2mins wont the foreground appeared to have moved?

And if i am controlling over the USB and software whats the best software to use? Canon's EOS is ok.

Cheers

[Mav359]

Oh and can i use my C9.25 at the same time for imaging or will the shutter vibration be picked up?

Cheers

[Knight of Clear Skies]

Do i capture multiple subs?

Is there a best exposure time or just as long as i can?

I haven't heard anyone metion stacking?

If i have a foreground to my image but am exposing for 2mins wont the foreground appeared to have moved?

And if i am controlling over the USB and software whats the best software to use? Canon's EOS is ok.

Yes, you'll get better results by stacking exposures, improving the signal-to-noise ratio. Exposure time and ISO level need to be tuned to the speed of your optics and the local sky conditions. As a guideline if you check the camera histogram try not to get the peak over 40%, this will help avoid overexposing any bright areas of the image. You can also zoom in on the image to check for trailing and coma.

I can recommend APT for laptop control, it has some nice features such as a focussing aid and is very cheap.

If you're shooting with a foreground it will blur noticeably. Some people take a single short exposure for that and then paste it in front of the final stack.

What lens will you be using please?

[Mav359]

Its a Canon 1000d & for now just the stock 18-55mm lens that came with it. The chap in the vid recommended a Rokinon 14mm lens whicl retails for about £250, might treat myself to that after christmas.

I was playing with the stock lens at 18mm at F4.0 and variable ISO settings to try and accomodate the LP, which is terrible here. Still i was getting a reasnoble starfield.

[Mav359]

oh yeah and do i still do darks, bias & flats as normal?

[bruno]

If your mount is polar aligned, just take a single shot at say three mins & see if you get any star trails if you do just reduce the time if not then take as many subs as you need with your darks,bais & flats & stack them in Deep sky stacker .

If you divide your focal length of your lens by400 then that will give you roughly a time scale of exposure ie:- 400 divide by 18mm lens = 22.2secs that calculation is of more use when shooting from a tripod, but if you are struggling with pa then that will give you a base from which to work from

[Physicist13]

if you only plan to capture the sky, then the standard procedure of stackin, using darks, flats and bias as per normal AP. If you intend to use foreground...often giving the most pleasing widefield views then multiple subs is less often used as the forground movement can be too severe. you just have to play with the exp length and settings to get what pleases you. Sometime even half sidereal tracking rate is used as a sort of compromise balance between star trails and foreground movement. Why use a laptop? use a remote (wireless) interval timer to control the camera...much simpler!

P

[Mav359]

Hi guys

@Bruno - PA isn't an issue, I'm good up to about the 20min mark

@Physicist13 - I want to do both, get some shots of the milky way but as you say the foreground can really make the picture. Everything on my imaging rig is already connected to the USB hub on the tripod and in turn connects to the PC in my Obs/Van, i have a remote shutter release for the PC but might invest in an intervelometer if i start trying this from the tripod as well

Cheers guys

[Physicist13]

look forward to seeing the images!

[Dave Lloyd]

I bought an aputure(sic) intervalometer. Works really well and cheaper than a marque brand.

[symesie04]

Lots of questions. My opinion is the exposure length should be as long as possible given tracking. I.e as long as poss without star trails. However this does depend on target, Orion for instance is bright and doesnt require such long exposures especially for the core. ISO generally is reagarded to be best set to 800 but light pollution may dictate otherwise. 

Regarding camera control yes you can do it with a timer but a timer doesnt help you focus or frame your subjects. Both APT and backyard EOS are excellent products and inexpensive. Both provide focus and frame aids with APT providing auto focus on later Canon EOS cameras. Free stacking software DSS for one and there are many others.

Multiple frames are definately the way to go, they make a huge difference to data. Also yes use darks and flats they also make a huge difference. With regards to using a foreground subject its a little complicated. It depends on the brightness of the target, light pollution and speed of lens. I.e if you have a f2 lens in a nice dark site and a eye visible milky way over you subject then yes with short focul length you could do a single 20sec or so frame. If not your have to take multiple frames of the sky and a single frame of the foreground subject. Stack the sky frames and then paste the foreground over the top. Photoshop is ideal to achieve this and process your stacked images but its not cheap. There may be others but many of the tutorials your see will be centred around PS.

Possible targets could include Orion, Rosette, M31, Pleides and the Cygnus region to name but a few. Hope that helps.

[Mav359]

Lots of questions. My opinion is the exposure length should be as long as possible given tracking. I.e as long as poss without star trails. However this does depend on target, Orion for instance is bright and doesnt require such long exposures especially for the core. ISO generally is reagarded to be best set to 800 but light pollution may dictate otherwise. 

Regarding camera control yes you can do it with a timer but a timer doesnt help you focus or frame your subjects. Both APT and backyard EOS are excellent products and inexpensive. Both provide focus and frame aids with APT providing auto focus on later Canon EOS cameras. Free stacking software DSS for one and there are many others.

Multiple frames are definately the way to go, they make a huge difference to data. Also yes use darks and flats they also make a huge difference. With regards to using a foreground subject its a little complicated. It depends on the brightness of the target, light pollution and speed of lens. I.e if you have a f2 lens in a nice dark site and a eye visible milky way over you subject then yes with short focul length you could do a single 20sec or so frame. If not your have to take multiple frames of the sky and a single frame of the foreground subject. Stack the sky frames and then paste the foreground over the top. Photoshop is ideal to achieve this and process your stacked images but its not cheap. There may be others but many of the tutorials your see will be centred around PS.

Possible targets could include Orion, Rosette, M31, Pleides and the Cygnus region to name but a few. Hope that helps.

APT is installed and ready to go and 10+min exposures should be an issue, nor should darks or flats. I'm only using a stock lens for now so its F3.5 @ 18mm

I'm away to Galloways on Friday so i'll have a play with both and report back for more advice, usually on the bits ive done wrong :-)

Cheers for all the advice guys

[symesie04]

Good stuff, did you buy APT or have you downloaded the trial version? The only reason i ask is that im not dead sure if the auto focus will work with the 1000d, it still has a focus aid though. But good luck and from my experience i can tell you it takes a bit of patience but dont give in persist  Look forward to see how you get on.

[Mav359]

APT's bought, I have bought an AC adaptor for the camera as well but I don't think it's going to arrive before I go away.

[Knight of Clear Skies]

You'll probably want to stop the kits lens down a bit, to f4.5 or f5.0. The coma is quite bad when wide open.

[Mav359]

You'll probably want to stop the kits lens down a bit, to f4.5 or f5.0. The coma is quite bad when wide open.

Will do