OIII filter & bits

Cumbrian · #1 21-03-2013, 10:05 PM

Hello again all. This cloud is killing me it's just seems to go on an on day after day. I was in WA last weekend and by the looks of the forecast I may just have missed Brisbane's best nights. Sorry, I'm going off topic...

I want to buy a OIII filter for my Guen Sheng 10" DOB.

Now firstly, do I want a 1.25" or 2" or does my scope have the capability to take either?

Secondly, I'm looking at either Andrews 2" at $99 or the 1.25" at 59,
http://andrewscom.com.au/site-section-10.htm

or the Televue 2" at $180 (TeleVue Bandmate OIII 2 Inch Telescope Filter) or even the TeleVue Bandmate NebuStar Filter - 2 Inch. To be frank I don't have a clue what the difference between them all is but I want to look at Nebulas!
http://www.telescopes.com/telescope-...ilter2inch.cfm

I also want a t-ring to attach my camera to my scope. I'm aware the scope's probably not the best for this but I'd just like to take a snap or two.

I'm picking up some 10 x 50 Nikon a211 binos. tomorrow - which I'm excited about.

But you all know that I've just wrecked the Brisbane skies for the next few months.

Thanks in advance for your words of wisdom

barx1963 (Malcolm) · #2 21-03-2013, 11:16 PM

Hi Cumbrian

Whether to get 1.25" or 2" is dependant on your eyepieces you intend using. As I gather from your sig you only have the stock EPs that come with your scope and they are all 1.25" then there is your answer. In case you are not aware the filters screw into the bottom of the EPs, they are threaded to take them.
The next question is which filter. OIII filters are primarily used for Palnetary Nebulae which ususally emit stringly in the OIII wavelength. They can also help with some details of emission nebs such as Eta Carina, M42 etc but I have found the UHC filters work better as they admit more of the other wavelengths from these nebs.
For a start, I would go the UHC filter, or with the Televue, the Nebustar. I have found that cheaper filters have an annoying habit of causing the stars in the field to be split with a little red dot nect to all the stars. I would imagine that the better quality filters (TV, Astronomik etc) do not do this, but I have no first hand knowledge that this is the case.

Remember that filters will not make nebs brighter (you need a bigger scope to do that!) but will increase contrast and block some of the light pollution from city lights.

Malcolm

wavelandscott (Scott) · #3 22-03-2013, 01:27 AM

Quote:

Originally Posted by barx1963

Hi Cumbrian

Whether to get 1.25" or 2" is dependant on your eyepieces you intend using. As I gather from your sig you only have the stock EPs that come with your scope and they are all 1.25" then there is your answer. In case you are not aware the filters screw into the bottom of the EPs, they are threaded to take them.
The next question is which filter. OIII filters are primarily used for Palnetary Nebulae which ususally emit stringly in the OIII wavelength. They can also help with some details of emission nebs such as Eta Carina, M42 etc but I have found the UHC filters work better as they admit more of the other wavelengths from these nebs.
For a start, I would go the UHC filter, or with the Televue, the Nebustar. I have found that cheaper filters have an annoying habit of causing the stars in the field to be split with a little red dot nect to all the stars. I would imagine that the better quality filters (TV, Astronomik etc) do not do this, but I have no first hand knowledge that this is the case.

Remember that filters will not make nebs brighter (you need a bigger scope to do that!) but will increase contrast and block some of the light pollution from city lights.

Malcolm

Good comments...depending on your intended targets you will get some different benefits frm different filters. I am quite partial to the DGM Filters both their NPB and OIII.

As noted above, any filter will block out unwanted light so only the wavelengths you are looking for get through. If you have never looked through a filter before, try to do so before you buy one as you may not like the views...some folks don't.

As to size, most users either screw them into the bottom of their eyepiece or use a multiple filter slide or wheel so get the size that best fits your gear. I like to use my OIII filter to "blink" (holding it in my fingers between eyepiece and eye) and find my fat fingers do this better with a 2 inch filter...

There are many good bits of advice for filters on-line so do a search here and on Cloudy Nights website...

Clear Skies!