Posts Made By: Stephen Lloyd

August 7, 2002 12:13 PM Forum: Film Astrophotography - Imaging and Processing

Posted By Stephen Lloyd

I have a 400mm f5.6 telephoto lens and have found that
1 1/4" filters fit quite nicely into the rear of the lens.
I was considering buying a 1 1/4" deepsky filter and giving it a try rather than buy a 72mm filter for the front which is 4x the price.The only problem I can see (apart from the filter falling into the camera)is if the light passing through the filter is on to much of an angle and I get colour changes near the edge of the photo.
If anyone has had success at this I would love to hear about it.
Cheers Steve

August 7, 2002 09:24 PM Forum: Film Astrophotography - Imaging and Processing

ADVICE SOUGHT RE FILTER PROBLEM

Posted By Stephen Lloyd

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.

August 8, 2002 11:49 AM Forum: Equipment Talk

Another filter question

Posted By Stephen Lloyd

Chris,
Hutech Astronomical products make a skyglow filter in the 52mm size you want for $189.00. It's called an IDAS LPS filter. Alot of reviews prefair this one over Lumicons Deep Sky filter and it's abit cheaper too.
They are not recomended for Focal lengths less than 100mm though as they cause a colour shift towards the edge of the film due to the light rays passing through the filter at an angle and therefor passing through a thicker amount of the filter. Hopefully you have a longer lens.
Good Luck,
Steve. PS this is there web site http://www.sciencecenter.net/hutech/filters.htm