The Butterfly Nebula in Cygnus

[steppenwolf]

Having acquired my primary target (the supernova in M51) last night, I realised that there was still plenty of relative darkness left and Cygnus was now nicely place so I took some 5 minute subs. of the Butterfly Nebula (a diffuse nebula near the star Sadr) in Ha to finish off the evening.

[peter shah]

superb detail steve:cool:

[johnrt]

Oh now that is smashing!

[AndyUK]

Yes - Absolutely fantastic detail...!

Exactly how do you get such tight focus? I have a Bhatinov mask and then try to use the FWHM window in Artemis capture to fine tune even further, but for some reason, since I've started using a CCD, the stars aren't as tight / round as they were when I used the DSLR .

I know there's other variables that could be involved (collimation, polar alignment to name but two), but I don't think either of those are really that far out. Also I don't suppose there's any chance you could post an unprocessed sub (just so that I can get an idea of what one looks like that can produce images as detailed as this?). Obviously you have a different camera, but I've been asuming that I'd need 10 or even 15 minute subs with an Ha filter (Atik 314L+), yet this has come from a stack of 5 min subs... (Blimey, this is confusing...!)

[steppenwolf]

Thanks for your comments folks.

Andy, I only use a Bahtinov Mask for focus (best invention ever!) but I am very critical in how I use it and I allow for any change - which there is - when I lock the focus tube. Other factors include the optics, of course, although with narrowband, doublet or triplet is not that important.

Here is a subframe straight out of MaximDL with only a BIAS subtraction applied:-

[AndyUK]

Thanks for that Steve - I think I've learnt two things here:

1. Stick with the Bahtinov mask for focusing and

2. Explore how to use Maxim for capture / framing and alignment / stacking.

I only have Maxim on trial at the moment, but I'm rapidly coming to the conclusion that I may have buy it!

[steppenwolf]

Maxim certainly isn't the only 'kid on the block' but I have to say that apart from an early flutter with Registax when I did DSLR imaging, I have only ever used MaximDL for my own work. It has just so may features (although I really only use it for alignment, capture, calibrations, stacking and preliminary stretch) and seems to just get on with the job solidly.

I hope the single sub is of some use - 15 of them were used in the final image with the transparency conditions deteriorating somewhat towards the end of the session.

[Sparrow]

Lovely image Steve - don't know how you managed to find time to image M51 and that last night - it was all I could do to get M51 - I finished my run on it at 2am by which time the subs were already beginning to look lighter.

The Butterfly is a beautiful nebula which deserves more attention than it seems to get. I'm working on a widefield round Sadr and would love to go in closer on the Butterfly.

Can't wait to see the colour image.

Regards

John

[steppenwolf]

Can't wait to see the colour image.

I captured some OIII as well but it was pretty grainy with the mushy transparency and daylight just round the corner! This region does respond well to colour though.

[Beyond_Vision]

Very nicely done Steve a great amount of detail picked up. Here's hoping you get chance to grab the colour data soon.

Regards

Kevin

[Uranium235]

Cygnus rocks

So much going on there, jobs a good-un!

[Coco]

Whoa.... thats fabulous mate... wonderful detail..

very nice indeed.....

.

[ollypenrice]

Lovely stuff. What an incredible region this is, too.

Bahtinov versus FWHM? I go for FWHM for the final tweak. The B Mask, which is so fast, gives a very slightly different result and maybe out of force of habit I trust the FWHM for the last microns. No science here, just a gut feeling. Steve, when you say you are very critical, what are you looking for? I find my two central 'cat's whiskers' to be slightly offset and try to average their position between the others.

Olly

[AndyUK]

Cheers Olly

Bahtinov versus FWHM? I go for FWHM for the final tweak

I think I may have been struggling with seeing perhaps when I tried it - With the camera on a 5s loop, a single slight tweak on the fine focus adjuster resulted in some figures within a range(ish). A second tweak resulted in a different range which crossed-over with the first range but after a few loops I could see which way I'd gone and then tweaked again, but after a while I got the feeling I was chasing my tail! I'll give it another whirl next time, but when it's where I think it should be, I'll recheck with the B mask and see where the central line is...

[steppenwolf]

Steve, when you say you are very critical, what are you looking for? I find my two central 'cat's whiskers' to be slightly offset and try to average their position between the others.

As well as the 'cat's whiskers', I also get some small circular 'blobs' of light on each whisker so I check the distance from the edges of these from one another too as this can be easier than determining by eye whether the two acute angles match or not.

I used to use FWHM but found that the numbers jumping around in the seeing could lead to unnecessary extra tweaks and once near the sweet spot you could play a guessing game - rather like looking at several weather forecasts and choosing the 'best' one!

[antimorris]

Great image Steve!!