The Astronomy Connection

Astronomy Equipment => Equipment Discussions => Topic started by: mccarthymark on January 17, 2015, 06:43:26 PM

Title: Comet filter?
Post by: mccarthymark on January 17, 2015, 06:43:26 PM
Has anyone had success using comet filters for visual -- in order to bring out more of an ionized tail.  Lumicon has one which is a narrow band-pass filter (25nm) that isolates the 501nm OIII line and both C2 lines at 511nm and 514nm.  Wondering if they're worth having.  Of course I'm assuming they only help from a dark site.

Rogelio Bernal's APOD of Lovejoy makes me wish I could "see" that.
Title: Re: Comet filter?
Post by: Marko on January 17, 2015, 07:59:12 PM
Comets are a fairly broadband light so maybe if those 'comet filters' are really something like a city light suppression filter it may assist contrast.   The green head is about the only spectral advantage to utilize but I think any filter may help the core area but greatly kill the tail.   

Dark skies are the best assist I should think.

With a very dark sky and trained averted vision you can sense a much longer tail (see Albert's recent post) but you will never see it like a camera can as Rogelio is also using his bag of tricks to bring out the tail and your eyes have no such 'bag of tricks' nor do they have the integration time of a camera although to catch a comet that is moving against the stars he would not be able to use really long exposure like for a nebula but even so the camera can integrate much better than our eyes.
Title: Re: Comet filter?
Post by: mccarthymark on January 17, 2015, 10:53:46 PM
I'm sure glad he has that bag of tricks, and can capture such a beautiful image for us!

I suppose some improvement in the tail with a comet filter is helpful.  But as you say a well trained eye may do just as well.  I think for now, I'll spend the money on gasoline to get to darker sites and enjoy what I can of the comet and everything else that's out there.
Title: Re: Comet filter?
Post by: Don Pensack on August 12, 2017, 01:13:37 PM
Many inexpensive O-III filters also transmit the C2 lines, so make decent "comet" filters.
[You'd have to know the spectrum of transmission, and Lumicon will test a filter for free or provide you details
on a filter they've tested.]
And since these typically have much narrower bandwidths than many "CLS/Broadband" type filters, also yield more contrast.
Note that they only enhance the gas tail.  The dust tail is usually full spectrum and usually best without a filter.