narrowband nebula filter

[Chippy3476 (Danial)]

Hi all,
I am thinking of buying a narrowband nebula filter for my 8" dobsonian, would this ne good for this scope? What difference would I see and would it be worth it?
Thanks,
Dan

[gaa_ian (Ian)]

Hi Dan
UHC filters seem the most popular as they enhance the widest range of nebula's as well as reducing the effects of light pollution.
Their are OIII filters available, but these work on only a few specific nebula.
All filters reduce light, so the bigger and brighter the nebula, the more effective they will be.
The filters I do are in my NightSkySecrets advert here in IIS :-)
Cheers
Ian

[Chippy3476 (Danial)]

Thanks mate,
So in your opinion would 8" appeture be a good size to use one pr not really enough light?
Thanks
Dan

[Renato1 (Renato)]

Orion Ultrablock and other UHC filters are ideal for you 8". They will enhance all views of the vast majority of emission nebulas, and planetary nebula.

They are pretty much essential for detecting the tiny dot-like planetary nebula. You hold the filter in your fingers and either move it left and right across the top of the eyepiece, or hold it over the eyepiece and tilt it up and down 45 degrees - and the planetary nebula becomes obvious.

When the UHC filter fails to pick up the planetary, I go to the O111 filter, which then usually does the trick.
Regards,
Renato

[ausastronomer (John Bambury)]

Hi Danial,

I gave a presentation at IISAC a few years ago about Visual astronomy and the use of filters. A copy of that presentation in PDF format can be downloaded from this thread. This will give you a better understanding on what filters are suited to what purpose. The critical thing to remember is that no filter will make the target brighter. They make the detail in the target more visible against the background by removing all the unwanted wavelengths of light.

For the person owning only one filter I would recommend the DGM Optics NPB filter. This is a Narrowband (UHC) filter with a very tight bandpass. It is the best of all the narrowband filters that I have used which is just about all of them. It works well in both small and large scopes and works well with a wide range of exit pupils. I have used it successfully with exit pupils from .5mm to 6mm. The DGM NPB filter has a high bandpass in both OIII lines at 496nm and 501nm and importantly it has a high bandpass in the H-Beta wavelength at 486nm. This makes it a good option in the absence of a dedicated H-Beta filter on some selected targets with high H-Beta emissions. Some of the other Narrowband (UHC) filters do not have such a high bandpass in H-Beta.The Orion Ultrablock is another good choice, as is the Lumicon UHC. I rate both of these as being slightly behind the DGM NPB.

You can order the DGM NPB filter direct from Dan McShane the owner of DGM Optics. These filters are made for Dan McShane by Omega Optics in the USA.
Omega Optics sometimes have "blems" that get sold very cheap on ebay as Omega Optics NPB filters and there is nothing wrong with them at all, but there are none listed at present.

Cheers,
John B

[Chippy3476 (Danial)]

Would the one advertised in the clasifieds by traveller be a good one as thats the one im planning on buying? Thanks again for all the info.
Dan

[ausastronomer (John Bambury)]

It's not the one I would be buying. At $55 it isn't all that much cheaper than a new filter and IMO it isn't as good a filter as the DGM NPB filter, or about 4 or 5 other narrowband filters you can buy including the DGM NPB, Orion Ultrablock, Lumicon UHC, Astronomik UHC or the Televue Nebustar Bandmate. The Meade Narrowband Filter is designated as 908N and it does have a bandpass in H-Beta but its overall bandpass is quite a bit wider than the DGM Optics NPB filter and that isn't really what you need in your situation with only 1 filter, a smaller telescope (8") and rural skies. The Meade OIII filter designated 908X, on the other hand is one of the best OIII filters available, but that isn't really what you need. If you can afford it and it isn't all that much extra money the DGM NPB filter is the best of the narrowband filters for an 8" telescope under rural skies IMO. Closely followed by the Orion Ultrablock and the Lumicon UHC, but the Lumicon is quite a bit more money than the other two.

Cheers,
John B

[gaa_ian (Ian)]

This UHC 1.25" filter is new and only $40 posted (Same as Orion)
In the interests of disclosure, yes, I sell these :-)

[Chippy3476 (Danial)]

They sound great, thanks mate. That site looks interesting. I guess I just foumd another place to spend some money on my hobby.

[gaa_ian (Ian)]

No worries Dan
I am adding to my product range all the time. I seek to only sell gear that I would be happy to own myself. The Nebula Filters and Ortho eyepieces have been popular with IIS members.