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ADVICE SOUGHT RE FILTER PROBLEM

Started by Kevin Barker, 08/07/2002 03:30AM
Posted 08/07/2002 03:30AM Opening Post
Hi,
I have a wee problem that some of you folks may be able to help me with.

I am attempting to take some 35 mm slide photographs of Southern celestial targets from my back yard in a light polluted city. I am using an excellent clock drive that allows exposures of up to 8 minutes or more with perfect tracking.
I am using 800 ASA slide film.

Results so far have been very encouraging. I would however like to introduce a broadband filter to reduce sodium vapour light pollution.

The scope I am using is a 130 mm f7.7 refractor. The scope's photographic accesories use a Zeiss M44 thread.

I have a M44 to T adapter and use Olympus cameras for prime focus. Does anyone know where T threaded broadband filters are found??

Also what other alternatives are there for filtering. Perhaps a female T thread to male 2 inch adapter and a female 2 inch to male t threaded adapter are possible??

Also are two inch filters like say Lumicon's deep sky filter male and female threaded???

Thankyou for looking.

Kevin Barker
Posted 08/07/2002 04:54AM #1
Kevin,
I have a 2" deepsky filter and yes it is male and female threaded. The filter screws onto my off-axis guider at the camera end and then the camera t-ring screws onto the other end of the filter. I hope this is of some help.
Steve
Posted 08/07/2002 02:24PM #2
Kevin, Steve again,The 2" filter has a 42mm female thread on one end that screws onto your T-adapter and a 42mm male thread on the other end which you screw your camera T-ring onto.Their is also a 48mm male thread over the top of the 42mm female which must be for 2" eye pieces,I've never used this thread so don't quote me on that part.
The clear aperture is about 39mm.
One other point,If you are not going to expose the film for more than 8 min then I cant see how you will have much to gain by using this filter.I think you would need to expose for at least 30min before you would see much benifit.I would be inclined to get an Off-Axis-Guider so you can expose longer before getting the filter.
Just my 2 cent worth.At my exchange rate that's about 0.9c US.