First Attempt DSO Images

[Langy]

Well I've just been to the RSPB Geltsdaleand as the Border Astronomical Society were there with a couple of telescopes as the RSPB site has been awarded a Dark Sky site. Amazingly we had some good views with the nice clear skies. Even my 10yo daughter enjoyed herself, just cold feet to deal with.

So when I got home the sky was still reasonably clear with the odd thin whispers of cloud. I decided to get the camera out and have a go at getting some images for stacking.

I have a Canon EOS 300D which must be at least 7 years old now which I think its only around 6MP which is low compared to todays cameras. Mounted on a tripod with a 300mm lens I used my remote time control (excellent buy off eBay as you can set it for number of shots, and various times).

The Orion Nebula had moved in a less favorable position with the light pollution where I live and I didn't expect to get much recorded. I set the camera at ISO 400 (more like forgot to check that bit) F5.6 and 1.6 seconds and started the timer taking 10 images at a time with a gap of 10 seconds between each one as the 4GB card isn't quick and the camera takes a while to save the RAW images. Checking the alignment after each batch I managed to get around 60 images.

Downloaded to one of the computers and installed the DeepSkyStacker software. Quickly reviewed the Astrophotography without a star tracker video on YouTube to walk me through the process. When I finally adjusted the levels I was amazed by the content.

A little cropping here to show the subject

Further cropping here to highlight it better

Now had I been out at the RSPB with my camera I think I would be quite amazed as to how much more I could get.

Cold feet now but a great evening.

[Thalestris24]

Well done Paul!

I'm very much a newbie and started astronomy/AP with my 1100d + 75-300mm zoom + tripod back in November. It's amazing what you can do with just a dslr. I put a few images on Flickr - http://www.flickr.com/photos/108862926@N05/10905532963/ I started with Jupiter and of course had a go with Orion too. I did a uni-based intro to astronomy course Sept-Dec which kindof got me into it. Anyway, I quickly got the bug and bought a mount, then a cheap frac (ST-80) and just this last week upgraded to a 150pds and a finderguider. Where will it all end?!!

All the best

Louise

[Langy]

Thanks Louise, I see you're just up the road from me.

Yes you soon get the bug. It was nice and clear to start with last night, but by the time I got home to take the images the whispers of thin cloud had started. I can't wait to get out and try some more. I may even have to go back (10 mins drive) to the RSPB car park for the darker skies and pick up more detail.

How nice it would be to have deep pockets. 

[Leveye]

It depends on the camera and it's sensor. For my Canon 5DMKiii it is iso 800. That's what dark,dark flats, bias frames and dithering are for to lower the noticeable noise introduced from  using these higher iso settings.

[Ryan_B]

Hi Paul

Nice work! I did the very same a couple of days ago, albeit with a 550d, using a 300mm lens. I don't have a programmable shutter release so I was stood clicking away with a wired remote shutter release! I got about 70 lights, 25 darks and 20 bias frames, shot at 1.3s, f5.6 iso 1600-3200.

After stacking and a bit of adjustment later and I got this

As you can see they are very similar, and if that was your first attempt then I think you will have great success in the future!

[Langy]

Great image Ryan. Yes I needed to increase the exposure time to compensate for the low ISO setting. With a 300mm lens I'm sure either a 2 or 3 second exposure will start to collect more data on the chip.

[Ryan_B]

Great image Ryan. Yes I needed to increase the exposure time to compensate for the low ISO setting. With a 300mm lens I'm sure either a 2 or 3 second exposure will start to collect more data on the chip.

But any more than 1.3 seconds will start to show trails.

Rule of 600 : 600/(focal length x crop factor) = longest exposure time before trails

With both of our cameras there is a crop factor of 1.6 so:

600/(300x1.6)=1.25

This is why I kept my frames to 1.3s. Just need to collect more data, more frames!

[Langy]

Thanks Ryan, never heard of that but at least it gives a good guide.

So I would guess that if using something like DSS software it doesn't matter too much if you increase the gain from the preferred ISO 400 to 800 or 1600 to try and bring in more data onto the chip as the software should take care of a lot of the noise generated with the gain.

[Ryan_B]

Hi Paul,

The article linked by IanL on your other thread:

This explains about ISO and long exposure imaging:

http://www.blackwaterskies.co.uk/2014/01/do-high-isos-make-dslrs-more-sensitive.html

TL;DR: You won't get any more light in your image using a high ISO, digital is not film.  You will increase the appearance of noise however, and potentially lose detail in bright parts of the image. So use a low ISO (depends on the camera model, but ISO 400 is usually a safe bet).  Stack your image, then if it is still too dark use a histogram stretch to bring out the details.  The only good reason to use high ISOs is if you need to see the image on the back of the camera immediately (i.e. not using a laptop for camera control).

Seems to suggest a lower iso, however I haven't tried this yet myself, that would require a clear night! I do plan on trying this at the next opportunity, but I think the results will be much lower in detail when using a 300m lens, especially since mine has a max aperture of 5.6 at 300mm!