First attempt at AP (and some DSS questions)

[wouter]

Hello all,

Last Sunday night was a clear night here.

Despite the very high air humidity and the almost full moon high up in the sky, I decided to make an attempt at putting what I've been reading and studying about AP into practice.

I dedicated the whole night at M42.

Following is the equipment I used:

-Celestron C9.25 at F10 on a CG-5 mount with a (poor quality) polar finder scope from my old Helios telescope.

-Canon Eos 550D in prime focus.

This is the final result I came up with:

An important note to add:

This morning I just received my f/6.3 focal reducer, Orion mini Guidescope with QHY5V guide camera, 9mm illuminated reticule eyepiece for drift allignment and a Bahtinov mask for more accurate focusing.

So, this means that the image above was taken at very slow F10 speed (thus very narrow FOV), no precise polar allignment and not perfectly focused. (I focused through the live view Eos utility app.)

Despite these handicaps I'm quite satisfied with my first AP image.

However I am running into trouble with stacking.

The image above consists of 12 light frame .jpg!! images.

I couldn't do it with my canon RAW files.

I was unable to use the 5 dark frames I had taken either.

originally, 10 out of 21 subs were taken at ISO 100, 60sec exposure, 1 at ISO 200, 30sec, 4 at ISO 400, 30sec and 1 at ISO 800, 60sec + 5 dark frames at ISO 100, 30sec.

All these images taken in RAW format.

Now when I use DSS with my RAW images, no matter what settings I try, I always get the following error:

I have played around with the star detection tresshold, used the Median filter, but nothing comes out.

The dark files cannot be used because they were not taken at the same ISO and exposure time.

Do they really have to be?

Anyway, for all those ISO 100 images, I always get 0 detected stars, no matter what tresshold or filter I use.

After that, I noticed there is a manual star selection function in the program.

Using that I could find in all the pictures at least 15 stars minimum, and the score I saw in the table was all above 5.

So then again I tried to register and stack the raw files again, but I got the same message "only 1 frame out of 16 will be stacked..."

This time I chose to continue and the result I got was this:

Not a really pretty picture, but at least some more detail is visible in the nebulosity, poor alligning though...

What I tried next was to convert one of my ISO 400 images into a TIFF 16bit image and bring it into Gimp, seems Gimp doesn't support 16bit yet, so it was automatically converted into an 8bit file.

I played around with color levels, contrast, etc... and I could get this out of it:

This proves there is a lot more data in there that I should be able to stack and process further to get a much nicer rendering, no?

This is what the original image looked like:

What I want to ask is if there is any (possibly better) software available, preferebly freeware or demo version with good tutorials?

I am a real noob to image prcessing and I don't really have the budget to buy a Photo Shop CS 6 license.

I was thinking about trying out Nebulosity 3.0 which is only $80, but I'd like to hear how well that goes for image aligning, callibration and stacking as well as the ability to process 16bit images.

Is this a user friendly, not too steep learning curve and fit for my needs piece of software?

I hope there are good tutorials available for it as well.

I've also upload all the original RAW files to my dropbox.

If there would be somebody who wouldn't mind to take a look at them and try to get something out of it and give me some advice, I would be very grateful.

Please let me know your e-mail address then so I can share the folder with you.

Thanks in advance, hope to get some good feedback here

Wouter

[Catweazel]

Not an expert on software but have you had a look at Gimp http://www.gimp.org/

It may not be up to the tasks you require it for, and support is a bit flaky, but it's FREE so may be worth a look.

[Bizibilder]

Your "Star detection threshold" should be up around 70+% or there abouts, then click on "compute the number of detected stars" ant DSS will calculate and show the number of stars detected. if there are only a few then lower the threshold (60%) and try again. You need to detect around 20-100 stars. Change "select the best 80% of pictures" to 100% and always use 100% - you can manually reject the poor images before you put anything into DSS.

Try those settings and see how you get on. BTW only attempt to stack one set of images with the same ISO and exposure to start with or DSS can get confused. I just noticed that you have image exposures of 1m 0s and 1m 1s - these must be stacked seperately as DSS will not stack images of different exposure time within one stack. Try all the 1m 0s images in a single stack.

[wouter]

Thank you for your advice Roger,

I have tried what you told me, but still there are no stars detected.

The strange thing is, when I use the .jpg for stacking (I shot those pictures in RAW+jpg setting, so I have both types) DSS detects over 30 stars for each image.

Is it possible that DSS has difficulties with EOS 550D RAW files?

I've read somewhere that the 550D RAW files are well known to give conflicts with certain somewhere. I'm not sure that is the case with DSS...

Hope someone has a solution or an explanation for this...

[Bizibilder]

That is quite possible - Have a look on the DSS site and it may tell you which RAW images it will accept or not.

[wouter]

I double checked it again and it appears there was a problem with the EOS 550D RAW files, but that it was resolved in the latest beta version, which I am already using.

I read through the FAQ on the DSS homepage on the topic "why can't I stack my images?"

It seems the stars that are in my images are too bright and a little oval and are not detected as stars by DSS...

It would be sad if there is no other software which can handle this.

I guess I better wait for a clear night and take all new subs.

Thanks for the help anyways!

More advice or opinions are very welcome!

Wouter

[allcart]

It seems there is not enough data in the iso 100, 30s subs. If I raise the exposure by 2 stops I can barely count 8 stars. DSS cannot alter the exposure so cannot see any stars in the original raws. I would not use ISO 100 unless you have guiding good enough for at least 120s. I don't think there are many targets that are so bright they require ISO 100. Most people seem to favour ISO 400.

The darks have to be the same exposure time and ISO setting as the lights. I take mine when I am packing the rest of the gear away. I just set the camera on a timer with the lens cap on and leave it to it.

I'm still downloading the rest of the pics so I'll let you know what happens.

[allcart]

No luck I'm afraid. I managed to stack all the images, and just a few selected images, but DSS will not align them. The most stars I could find was 14 and thats with a threshold of 2%.

I think that processing just 1 single sub will give you the best that you are going to get.

I would try to take more subs and start again. This time use ISO 400 and do batches of 20 subs from 30s to 120s. Try to get your focus better and keep your times accurate.

What are you using to control the shutter?

[wouter]

Allan,

Thank you so much for all the help and the effort you took to evaluate and trying to improve my images, I really appreciate it! and thanks for the suggestions!

I also thought an ISO 100 setting was too little, but when I previewed higher ISO settings, I thought they were overbright with too much noise.

Anyway, I am going to give it a shot again with my focal reducer and (hopefully) better polar alignment.

Hope the snow will stop soon and give us some more stable weather

Thanks again

Wouter

[Bizibilder]

You could even try ISO 800 - you will get a bit more noise but, if you take a lot of frames, this should be manageable. Maybe go for an hour or more of 60sec exposures - you may have to discard a few but at least you should end up with 50+ to stack.

[Pete Presland]

i would say 400-800 ISO is a minimum setting you will need if your exposures are going to be quite short.

[boabsta]

Being a noob and learning this myself I also done iso 100 and found that it was way too low. 400 is probably the minimum now and 800 average. It will seem like there is a lot of light and possibly even blown out in places but that is where the darks come into play. DSS uses them to calibrate the images so the noise and a fair chunk of the light polution is removed leaving you with a nice dark image.

As has been mentioned, only try and stack images and darks of the same exposure time. The resulting images can then be stacked in gimp and blended so you can get the best part of each image as you need it. That however is where I have no clue yet. A lot to learn and a family and job stopping me from doing so.