What settings for....

dc99

my camera to take a astro photo?

Hi, Sorry for the dumb starter question.

I drop in and out here every so often, and can understand some of the jargon here.

I'm an amature photographer for many many years and have a very deep understanding of 'normal' photograph :-)

So can I ask a very annoying question ?

I have a Nikon dslr D7000 and a 18-105vr nikon lens. Also a reasonable good tripod. I also have a nikon remote trigger...)
Could I get any decent night sky shots with this equipment?

If I can get something, - what settings should I start with? (Small apeture? time of exposure?) and will I need to do multiple exposures? (I do not have a tracker or motor mount system).

DO I turn off the VR (I think I heard somewhere that VR on a a tripod mtg'ed camera actually produces a vibration....?)

Will I need the 'stacker' software I see talked about? (is this free to download ? where?)

I usually shoot in RAW. (Is this the optium or should I shoot JPG for night sky?)

I live outside Tralee Kerry, Anytime I have been out with a good sky view it is pretty good and clear (low light polution from the town - I'm west of town and behind a hill).
Thanks for the patience with a complete sky newbe ...:-)

Thanks guys.

Kersh

You have everything there to get started.

Some Nikons have built in software that inadvertently removes stars - A simple median blurring filter is always applied, removing many stars, as they are seen as noise. But that wont worry you too much to begin with.

Your camera will be ideal.

I would start with exposures of 20 or 30s on the tripod, in RAW, and then try various ISO settings, to see which gives best result without being washed out. The defining thing here is, if 30s gives slight star trails over a sample of 4 photos, then reduce exposures to 25s, etc etc. I can get 25s exposures, on a tripod, with a 50mm F1.8 Prime Canon Lens.

Not sure about VR, none of my lenses have it, and it never causes a problem.


Pick a target, frame it in the viewfinder/screen, and snap away. The remote will help here, and leave a small time gap between shots to cool the sensor. Finish taking all these "lights".


Then take darks (same exposures/iso etc but with lens cap on). Ideally while you are outside still, to keep sensor temp consistent.

Then take same amount of BIAS frames (highest shutter speed, same iso).


You then use DSS - http://deepskystacker.free.fr/english/index.html or http://www.astronomie.be/registax/
for the stacking. (I use DSS)

You will be asked to open each type (bias, dark, lights) in DSS, select them all, and press "register".

The software does the rest.

The processing afterwards, some basics of which can be done in DSS, is best done with Photoshop, or GIMP, which is free.

Keep us updated on how you get on.

dc99

Hi,

Brilliant. thanks for the start.

I was wondering about ISO setting. The D7000 is very good at higher ISO settings regarding noise.

Can you recommend an ISO? do I stay around 100 or go the other end of the scale of 800iso?

This will change the exposure dramaticly (the 800 being more sensitive than the 100. - like not getting into it deep, but 25s or 30s at 800iso is of course vastly different than 100iso....)
My instinct says stay at the 100iso end, maybe up to 400? (please tell me if Im completely wrong etc and that it should be up at 800 etc?)

In a series of the 'light' photos, how many? I was looking at the DSS programe - it mantions 10 or 20 exposures for 'flat frames, but I'm missing how many actual star images (the light frames?)???? like how many should I get? (30 by 20 is like 10 minutes plus the cool down time (and write to sd card time). PLUS the Black frames etc...

I also realise that there is movement (ie. the earth is rotating) so each exposure will be a different composition. (ie the stars will have moved). so your mention using a 50mm focal lenth lense - I'm better of around this magnification to allow for the re-framing of each shot (is DSS)? I would recond that even shooting at 105mm focal lenght will work, but my final frame will be far smaller than any of the original frames ....or am I over complicating things for my self.....

Thanks again.

Kersh

I would start higher than 100. Try 400, then check it, then 800.

The M33 I took in post below - http://www.boards.ie/vbulletin/showthread.php?t=2057316992 was at ISO 1600 with a Canon 1000D, 75 second subs, 32 in all. So dont be afraid to push ISO.

Once you do a few test shots, to check for trailing at the settings you are using, I would then, when happy, take a load of lights. Something like 10 to 20.

Ideally you want the same amount of darks, but laziness usually gets me, and I settle for half the amount. In theory 10 darks should do for any photo.

And an equal or more amount of Bias frames, these are important if sensor temp of lights and darks hasnt been exactly the same.


With regard to rotation, yes, the stars will appear to jump ever so slightly between exposures, but even with 20 x 25 second exposures with my 50mm, DSS or Registax will still find align points. If they jump too far after 10 frames, then just re-align them in the viewfinder as best you can.

At 105mm, the stars will move quicker, than at say 50mm, so exposures may not be as long, plus the field of view will be smaller, so they may hop out of frame quicker. Limit lights to 10, darks to 5 or 6, Bias to 10 etc.

Its a matter of what you find works best for you. Keep it simple, try 50mm to begin with, and stick to that til you see results.

Trial and error.