"luminescence" filter for planetary nebulas

[riklaunim]

I'm planning to hunt some small planetary nebulas and I'm looking at various filters that would be good as luminescence filters - that get all the nebulosity, and cut all the glow as much as possible. It would have pass O-III, S-II, H-alfa or even N-II.

I have Baader UHC-S, which isn't that narrow as for example Astronomik UHC (and this one has bigger band at H-alfa and other red friends).

So what can you recommend?

[Doc]

I use the Baader O111 and I've managed to detect quite a few little planetaries. The bigger PN's are quite easy to detect but the way to spot the tiny ones that appear stellar is to blink the O111 filter over them and if they do not dim thats the nebula as the stars around the nebula will dim.

[Merlin66]

Planetaries emit Hb and OIII ( with some other stuff...) so either of these filters would help.

Get a small prism (or 100 l/mm grating), hold it behind an eyepiece while viewing the suspect planetary; a normal star will show a smear of spectrum whereas the planetary will still be seen as a stellar point albeit fainter. Makes it much easier to identify them.

Ken

[Doc]

Planetaries emit Hb and OIII ( with some other stuff...) so either of these filters would help.

Get a small prism (or 100 l/mm grating), hold it behind an eyepiece while viewing the suspect planetary; a normal star will show a smear of spectrum whereas the planetary will still be seen as a stellar point albeit fainter. Makes it much easier to identify them.

Ken

Ken where would one buy one of these prism's? Any websites on them?

[Merlin66]

Mick,

For this sort of low res work almost any prism would work - an old 45 degree for old binos; a 60 deg prism is the best and you can pick them up on ebay and sometimes at the hippy saturday markets - "Suncatchers"

( A 100 l/mm grating - Star Analyser - which can also be used for basic spectroscopy cost around 80 gbp) - there are some cheaper versions on the Paton-Hawksley site "education" gratings - not very good for serious spectroscopy but great for identifying Planetaries!!!

Ken

[riklaunim]

I've got the H-alfa and O-III for M42 some time ago

Both UHC filters (Astronomik and Baader) pass O-III and H-alfa (and beta). Astronomik also looks like it passes S-II, N-II better.

Looking at some nebs:

narrow UHC should be good for all of them, and O-III better for some of them that have mostly O-III

This is interesting too. H-alfa and friends seems to be the strongest (but the CCD may be red/ir-sensitive)

[hawk eye]

I read on another thread on this forum and several other sites that the DGM Optic NPB surpasses some of the best filters for this purpose including Lumicom, Orion and Meade. They are hard to find but I found a direct link on Ebay so have ordered one which came to £59 inc US postage

DGM Optics items - Get great deals on Select Astronomy, Astronomy Filters items on eBay Stores!