M42 first attempt (and all the warts) 10.12.09 Back garden

[Carole]

Spent most of the evening and early hours last night doing this.  Not the greatest image but its a start.
60 x 30secs subs unguided (see problems below), darks, flats and Bias, and CLS filter
Stacked in DSS and post-processed in photoshop.
See post number 8 for the 45 x 60 sec version



Problems, new lessons learnt and queries:
I did also do 45 x 60 sec subs (just to see what difference the longer exposure would make to the nebula), but for some strange reason DSS would only stack 1 out of 45 images saying "only 1 frame will be stacked, check/change star detection threshold to detect more stars)", I even tried stacking just a couple but got the same message, and yet it stacked the 30sec subs done on the same set up, same evening with no problems at all....why?

I could not see the Orion nebula at all on live view and had to do a 15 sec sub to identify it, only to find it was wildly out of focus, despite having sorted out a parfocal ring system albeit with an elastic band, but this was on a land object, so may be different at infinity, must get some proper parfocal rings and do this again.  

It therefore took me a further 30 images (using the Focus mask to achieve anything like focus).  

Having done that I went to start up guiding which I had set up, but could I find a flippin star!!??  Could not see one, through the SC3 camera which ever way I pointed the scope, or focussed, so thought I'd better use an eye piece.  However by that time the side by side bar was vertical (Guide camera below), cameras, and cables (and the position I had to have the table because my camera interface cable is too short and am having difficulty finding a longer one), were all in such a position that it was impossible to look through the eyepiece, unless I had the body of a serpent and could wind myself over the table and under and through the mesh of wires and cameras.  So I will have to practice all that another night and see if I can get that longer Interface cable!!!!  Might also try swapping the Guide scope to the opposite side.  

This was the first time I had used the CLS filter and could immediately see the difference.

Lastily, I have posted a small crop of the stars in this image and wonder whether you can tell me why most of the stars appear as rings.



Sorry this was so long.

Carole

[Mac]

I did also do 45 x 60 minute subs

Wow 45 hours,

The reason for the rings around the stars is that its out of focus.
Mac.

Nice image though for your first attempt at M42.

[Carole]

Hi Mac,

Yes, whoops, I realised my mistake before I read your posting, and have now amended it.  Yes I wondered whether it might be out of Focus, but as you probably read, getting focus was quite a challenge not being actually able to see what I was focussing.  But I guess you all have the same problem, so will just have to learn, there's probably no easy way of doing it.

Any ideas why DSS would not stack the 60sec subs?

Carole

[RobertM]

Did you use a focus mask Carole ? It's more accurate than just looking at the size of the stars on live view.  The only trouble is that you may need at least a magnitude 2 or 3 star and because of that it can be best to focus first then aim the telescope.  Always check the first full length frame for problems before continuing.

Don't use DSS so I'll leave that for someone else to comment on.

Hope that helps
Robert

[Carole]

Yes I did use a focus mask.  I used the one Mac told me to make, but I thought so long as you got triple stars merged into one you were in focus. 

Always check the first full length frame for problems before continuing.

, Yes I did look at the image, but didn't understand why it was like it, and having taken so long try to merge the triple stars did not want to chance unmerging them again by fiddling further with focus. 

Re DSS:  Hold your horses every-one, I have just had another go at stacking the 60sec subs on my desk top DSS and so far so good (am doing a few at a time trying to weedle out if there's a rogue file causing the problem.  So far have managed to stack 12 light subs successfully and it's already looking like an improvement on the image above.  I am wondering whether I have a different version of DSS on my laptop, will look later.

So hopefully a further M42 image to post.

Carole

[Carole]

focus first then aim the telescope

.  Yes I've done that before, I'll try to do that next time.

So many new things to think about!!!

Carole

[RobertM]

Write them down like a recipe and follow those steps; refine it further as you get proficient.

[Carole]

Write them down like a recipe and follow those steps; refine it further as you get proficient.

Good idea. 
I do have some things written down, like which USB port to plug each item into, and which settings to use on the camera, etc, and I wrote down what I did as regardings what subs, and darks I was doing, times and temperature etc, and shifted the different length ones into folders as I went along so I would not get confused afterwards.

I am about to post the 45 x 60sec image which has processed this time on DSS (no idea what the problem was before).

Carole

[Carole]

OK.  Here is the 45 x 60 sec version.  Unguided (for reasons previously explained).
Lights, darks, flats, Bias, . 10.12.09 back garden Bromley
Canon DSLR 450D unmodified + CLS Filter


Carole

[Ian]

I reckon there's more faint detail there that could be brought out in the processing. Try a simple histogram stretch to start with.

BTW, focussing is the biggest P.I.T.A. in imaging. I read a website once that went into the maths of focussing and the incredibly small tolerances we have to work with when moving the focusser.

[Mac]

That is very good, you can start to see the faint nebulosity.

As for the focus, hmmmm, as Ian said, PITA.

Use the live view on the camera with the focus mask, and zoom into a brightish star using the live view. use the mask to assist the focus,
once thats done remove the mask. and then start taking the images.

set the iso to the highest setting on the camera whilst focusing.
and dont forget to reset it when you've finished focusing.

Mac.

[MarkS]

Carole,

It's a real shame about the focusing because, otherwise, that is an excellent attempt.  It shows that you have got everything else right.

There may well be more detail there waiting to be stretched out.

As you said, the CLS filter has made a lot of difference.  Once you begin guiding - that will make even more difference.

Mark

[Carole]

Thanks every-one for your advice and comments.

Try a simple histogram stretch to start with.

Now histograms are something I am not sure about.  Would this be the histogram in DSS or a histogram in Photoshop, if so where do I find it and what's it supposed to look like? How do I stretch it?  I did try using curves in PS but that did not make any satisfactory improvement.  I mostly used levels and brightness and contrast, and colour adustments to bring out the red and keep the sky dark. 

Does any-one who owns a Canon 450D use the interface cable, and if so how long is theirs?  Any thoughts on getting a longer one?  I have found the cable on the internet, but it's trying to actually obtain it as it seems to be currently out of stock with no expected date of delivery. 

I'll keep trying in case I can find some-one with one still in stock.

Carole

[MarkS]

Colour stretching in IRIS is the same thing.  You might be able to simulate it using multiple applications of PS curves as long as your black point is set correctly.  You might find that DSS has set it too high and already lost your faint stuff.

Do you mean the USB lead?  They are far too short - I use a USB extension cable with mine to give another few metres.

Mark

[Carole]

One more question:

The image is very grainy especially if I try to enlarge the image any more.  Can you tell me, is it longer subs or more of them (or both) I need to do to get a smoother image.  

Do you mean the USB lead?  They are far too short - I use a USB extension cable with mine to give another few metres.

It is the cable that plugs into the DSLR camera and then into the USB on the laptop.  Would you mind bringing it to the Xmas meeting (I'll bring my DSLR and Laptop) so I can try it out.  Or I could pop over. 

Thanks

Carole