Modified Canon Cygnus Widefield

[MarkS]

A widefield of Cygnus taken by the modified Canon EOS 300D with a Nikon 50mm prime lens at F4. 
19 x 5min exposures. 
I used a CLS filter and also an IR filter to prevent unfocused IR coming through (no pox this time!).



I''m not yet happy with the processing, so it's in my "works in progress" folder.  I've also cropped this image to show just the "interesting" stuff.  The two main stars in the picture are alpha (on the left) and gamma (to its right).

Interesting question - looking at the diffraction spikes (which are genuine) how many blades do you think the lens has?

[Mike]

Lovely image Mark.

[RobertM]

Great image Mark, focus looks spot on - something I still have to work on.

I assume it's not a 50mm F4 lens, so why did you stop it down so much - sharpness ?

[JohnP]

Hi Mark - Looks a lot better - Well done on curing your 'Pox'.... John.

PS - Did you seriously post that at 3am...?

[Ian]

I don't know if it's the reason you stopped the lens down a little Mark, but in general camera lenses are not at their sharpest at full aperture. I usually stop down my lenses by at least one click. The reason (as I understand it) is that accurate lens manufacture gets harder as you get towards the rim.

Mark, I would say the diaphragm on your lens has several segments

[Rick]

Cracking shot. I've gone cross-eyed trying to count spikes, but I'm guessing the lens aperature mechanism has seven segments...

[Ian]

I counted 14 spikes, but that might mean 14 segments or 7. I think 3.5 is probably pushing it a bit though...

[Rick]

Yeah, either seven or fourteen, but I'm guessing (from past experience taking mechanisms apart) that seven is the more likely.

[MarkS]

Thanks for your comments.

Robert,  it's a 50mm F1.8 lens but is much sharper at F4.  Ian correctly said lenses tend not to be optimum at full aperture.

John, yes I really did post it at 3am.  Definitely need an early night tonight -  no observing however clear it is!

Ian & Rick, you both correctly deduced that the lens iris has 7 blades.

I need to reprocess this because
1) I forgot to take some flats, so there is some vignetting in the original (but not too apparent in this cropped version)
2) I need to perform a better removal of an annoying blue background gradient in the original - you can see the North American and Pelican Nebulae (on the left) still have a slightly purple hue remaining.

[Fay]

Mark, really nice, I watch wiith great interest.

You 're not a creature of the night are you? (re: your early postings)

Will have to wear garlic next time I see you!



Fay

[Mac]

fantastic image,

Is that blue gradient, not the sensor picking up more of the blue now that the UV/IR filter has been removed?
your sensor is also more sensitive in the UV region as well which will appear more blueish.

only the blue also appears on the right hand side, and dosent seem to be a gradient type hue?

Mac

[MarkS]

I've now re-processed the image.  It brings out a bit more of the H-alpha.

[Later Edit:  Image details as before- modified Canon EOS 300D with a Nikon 50mm prime lens at F4. 
19 x 5min exposures.  CLS filter + IR filter to prevent unfocused IR coming through ]




The full-size version is here:
http://gallery.orpington-astronomy.org.uk/albums/userpics/10046/cygnus290608v2.jpg