Sagittarius star cloud widefield

[luka]

My first image post in this forum
I am still a beginner so any suggestions and comments for improvement are welcome, especially for the post-processing.

Nikon D80 on a tripod, no tracking, 50mm f1.8 lens at f3.8, ISO 800.
50 x 10s exposures stacked in Iris, 10 dark frames subtracted.
Post-processing in Iris (stretching), Photoshop (curves and levels) and SBNRG (noise reduction).

The colours are probably not right as I am not sure how to do RGB balance in Iris for my camera:
http://www.iceinspace.com.au/forum/s...ad.php?t=21161

Some minor star trailing and coma in the edges is visible, need shorter exposure and smaller aperture. Or tracking would even be better

[ballaratdragons (Ken)]

Luka, that's a nice widefield.

Here are some of the many, many objects in your image!!!!

[luka]

Wow, now I like it even more :-)

I am just starting in astronomy/photography and still saving to get my 1st telescope...
I had no idea how many objects are in the photo. Thanks a lot for the labels, I'll be learning what is what now.

The sky is really a beautiful place.

[[1ponders] (Paul)]

Nicely done luka. Great job for only 10 sec subs. You are doing all the right things, lots of exposures, subtracting dark frames. Keep up the good work.

The trailing at the edges might have more to do with curvature in the lens rather than real star trails. At that focal length your should be able to expose for around 14sec before you start to see any sort of trailing and even then it will only just be starting. Try going for the 14sec next time and see if it get worse or stays the same. If it's the same then its likely your lens.

[luka]

Thank you for your comments. Greatly appreciated. It is good to know that I am going in the right direction
I have taken quite a few wide-fields in the last several months and this is the best one so far.

Regarding the lens, the crop is 1.5 for my digital camera (due to smaller CCD size than 35mm film), so I am effectively using a 75mm lens compared to film. I did some test shots and at 10s trailing becomes just visible at full camera resolution.
The posted image has been reduced in size and you can't see much of trailing. In the full size, the middle shows only minor, hardly noticeable trailing, but all edges show elongated stars towards the centre of the image (coma).
I have to step down the lens more to hopefully get rid of it but then I will be losing light.

[jase (Jason)]

Great wide field image Luka. The next logical step is to obtain some form of tracking to increase your exposure times. This will in turn improve your S/N ratio. I enjoyed Ken's diagram pointing out the individual objects. Certainly puts an interesting perspective on the field of view.

If you are daring, put a Ha filter in front of your lens once you've got tracking sorted. Though I suggest you crawl before you walk or run.

Looking forward to seeing more of your work in the future.

[luka]

Yes, tracking is the next step. I am looking at making a barn door mount or getting a cheap 2nd hand EQ1/EQ2 mount or something similar if I can find it.

Long term plans are getting an 8" or 10" dob and mounting it on EQ6. And ED80. One day...

[rogerg (Roger)]

Nice shot , from Perth too which makes it all the better

only 10 sec subs! amazing colour visible for that short exposure time.

[ballaratdragons (Ken)]

Originally Posted by luka

Wow, now I like it even more :-)
I had no idea how many objects are in the photo.

I only marked a few. That is only about 40% of the objects in your image!!!

The sky is full of stuff

[jjjnettie (Jeanette)]

You're an inspiration.

I'm going to go out and have a go with my little camera and see what I can come up with.
Thank you for posting your image.

[luka]

Thank you all. I did not expect such positive comments. This is a definite encouragement to keep going even harder.

I have been trying hard since I got my camera few months ago. First images did not turn out well but trial and and error has thought me much.

By the way, I used f3.5 and not f3.8 as stated above.

Jeanette if you will try taking some shots, here are some hints:
1: avoid background light gradients
- Make sure there is no moon in the sky.
- This was taken from my backyard and I am close to the light polluted Fremantle - the solution was to wait to have the target straight up in the sky (2am).
- Iris can help with gradients but don't expect miracles. Avoid them if you can in the first place.

2. Find maximum exposure so you don't get star trails:
- put camera on tripod and shoot several photos while increasing exposure. Look at the photos on the computer to find maximum time before you get trailing.

3. Step up the lens from the minimum f-number to remove coma. Use same procedure as in 2 to check it. However, if you set f-number too high you won't see anything unless you use very high ISO. I have tried stacking 200 f6 photos without any success.

4. Finding the target in the sky:
- set highest iso that you have, point the camera and shoot a long exposure. You should be able to see fuzziness in the screen so you can recompose the shot for real shooting.

5. Postprocessing - the most important step. Use Iris with dynamic range and colour. Try, try and try. Initially, after stacking, there was not much to see in this image.

Sagittarius cloud is a perfect target this time of the year. You can use Jupiter for autofocus of the camera.


I can't believe that 2 months ago I did not even know where Sagittarius is

[luka]

Thank you all. I did not expect such positive comments. This is a definite encouragement to keep going even harder.

I have been trying hard since I got my camera few months ago. First images did not turn out well but trial and and error has thought me much.

By the way, I used f3.5 and not f3.8 as stated above.

Jeanette if you will try taking some shots, here are some hints:
1: avoid background light gradients
- Make sure there is no moon in the sky.
- This was taken from my backyard and I am close to the light polluted Fremantle - the solution was to wait to have the target straight up in the sky (2am).
- Iris can help with gradients but don't expect miracles. Avoid them if you can in the first place.

2. Find maximum exposure so you don't get star trails:
- put camera on tripod and shoot several photos while increasing exposure. Look at the photos on the computer to find maximum time before you get trailing.

3. Step up the lens from the minimum f-number to remove coma. Use same procedure as in 2 to check it. However, if you set f-number too high you won't see anything unless you use very high ISO. I have tried stacking 200 f6 photos without any success.

4. Finding the target in the sky:
- set highest iso that you have, point the camera and shoot a long exposure. You should be able to see fuzziness in the screen so you can recompose the shot for real shooting.

5. Postprocessing - the most important step. Use Iris with dynamic range and colour. Try, try and try. Initially, after stacking, there was not much to see in this image.

Sagittarius cloud is a perfect target this time of the year. You can use Jupiter for autofocusing the camera.


I can't believe that 2 months ago I did not even know where Sagittarius is

[jjjnettie (Jeanette)]

Thanks for the help.

The camera I use, the Canon Powershot, while not a DSLR, it has some pretty good manual controls and a 12x zoom.
It's max exposure time is 15sec, which is why I am excited about the pic you took. It may be within the capabilities of my little camera.
I built myself a Haig mount (barndoor, scotch etc) a while ago and have used it to take some shots of Orion that turned out OK, some nice colour in the neb, but I think I only stacked a couple of images to get that.
I should have persevered and taken heaps more.
I'll go out tonight, if clear, and have another go, and if I get anything worthwhile I'll post it.

BTW.
A barndoor mount is quite simple to make and costs very little. Even a girl can do it.LOL
Once I had all the gear assembled, it took me only a few hours to put mine together, and most of that time was spent laquering and gold trimming it to make it look purty.

[davidpretorius]

well done Luka and Thanks Ken

[Garyh]

thats a fine first effort for sure!!!
shows what can be done with a standard lense and a fixed tripod!!!
cheers