M27 from 30/09/2011

[Whirlwind]

Hi All

It seems an age since I was last imaging...so I was finally relieved to get some done.

This is M27 in 3nm NII (30mins), Ha (90mins) , OIII (60mins) (Red, Green, Blue) using the FLT98 at F6.3 with Flattener in 30min subs (Guided with Lodestar). Would have liked more time but it went behind trees by 1am.

This was the first real test with the new Mach1GTO but at this point I am suitably impressed. There does appear to be some issues with the camera not being straight in the focuser and/or the spacing to the flattener being slightly off though. (No flats were taken either).

http://www.flickr.com/photos/58451625@N08/6222905870/in/photostream

Thanks

Ian

[Ags]

Very good - you caught a lot of the outer structure.

[Ags]

I just noticed you imaged using NII - what filter did you use? I have not seen NII filters on sale anywhere. I understand NII is near Ha and broader Ha filters will include NII, but a dedicated NII filter is new to me.

[Whirlwind]

Astrodon sell NII filters (I got mine from Ian King Imaging). You are correct in that NII is very close to the Ha emission lines. That's why they are only 3nm filters. A 5nm Ha filter would include NII - they are that close together.

There are distinct differences in the images though - i have attached the Ha and NII images for reference.

Ian

[Ags]

It looks like you get more detail in the NII image. Can NII filters be used on a wide variety of targets or are they mainly for bright planetaries?

[riklaunim]

If you have strong data you could try checking if you have such shell - Twitter

[Whirlwind]

Yes there does appear to me more detail in the NII part, I can assume that this is down to Ha being 'everywhere' in M27.

There seems very little info on the web about NII and what images well. Images are relatively sparse of some of the more common targets. As such the NII is a bit of an experiment for me to see what's out there. I'm hoping to get some time on objects like M42 later this year to see what happens.

Thanks for the link on twitter - I shall have a play!

Ian

[riklaunim]

For planetary nebula you can use this database: Gallery of Planetary Nebula Spectra - you will be able to check if it has N II or only H-a. M42 has some [N II] but less than H-a. Rosetta seems to be only H-a.