Best filter for general astrophotography

[Christopher Spencer]

Hello everyone. I am just starting out with astrophotography and have an Orion ED80T CF mounted on my Orion Altas EQ-G. I plan to use my unmodified Canon Xsi for imaging.

Does anybody have any recommendations as to the best general purpose filter for astrophotography and which brands make the best filters? I am only wanting to spend the money on 1 filter for now. 

Thanks in advance!

Christopher

[VigdisVZ]

With an unmodded DSLR, don't bother with a filter.

[Tinker1947]

This may help a bit.......

http://www.firstlightoptics.com/uv-ir-filters/baader-uvir-cut-filter.html

[Christopher Spencer]

Well, I know there are filters for light pollution, and Ha filters and other narrowband filters etc. But I was wanting to get one now. I have been looking at an LPR filter or an Ha filter. Does anybody have any thoughts???

I want to get an OIII and a SII later on down the road.

[Bizibilder]

Narrowband (Ha,Olll and Sll)  filters are not really suitable for DSLR cameras (modded or unmodded).  You need to decide if you have any light pollution and, if so, what the source of that pollution is.  In the UK we have sodium streetlights which emit strongly in the yellow part of the spectrum and you can get away with a simple and cheap light pollution filter that blocks these yellow wavelengths.  If you have a different light source then you may need a different filter.

[Christopher Spencer]

Narrowband (Ha,Olll and Sll)  filters are not really suitable for DSLR cameras (modded or unmodded).  You need to decide if you have any light pollution and, if so, what the source of that pollution is.  In the UK we have sodium streetlights which emit strongly in the yellow part of the spectrum and you can get away with a simple and cheap light pollution filter that blocks these yellow wavelengths.  If you have a different light source then you may need a different filter.

Ok, thanks. I will look into the light pollution near me.

Would you mind explaining or pointing me to a link that explains why narrow band filters don't work well with a DSLR? Thanks!

[Bizibilder]

Should have said - they will work but...A DSLR is far less sensitive than a dedicated Astro camera and it is "colour" so you are only using 1/4 of the sensor with most narrowband filters.  Therefore you need very long exposure times (or large numbers of subs) to get a decent amount of signal. You then need to go through the whole process again (twice usually) to get a colour image.  It can be done but is not really worth the hassle when you can take "one shot colour" easily enough with a DSLR camera.

[Christopher Spencer]

Thanks for the information!

I think I will skip the filters until I get a dedicated CCD camera. 

[ronin]

LPR filters are getting difficult. Used to be a relatively easy choice when it was mainly Sodium Yellow LP, but now the spectrum cauing the pollution consists of many more wavelengths that it gets difficult or impossible.

You would probably still be half sensible to get a simple Sodium removal one, there is still a lot of Sodium lights around when you think of it . Although just recalled you are in the US in Mo, Missouri. I have no idea if Sodium lamps are prevelant out there.

You will have to remember that a filter removes in effect a colour, so if you block Yellow there is a shift in overall colour.

If reading filter curves makes sense thry this site:

http://www.astrosurf.com/buil/filters/curves.htm

Makes interesting reading for what gets removed and reduced.

Looking at the Canon+Nikon standard filters in a DSLR then 80% or 90% of the Ha is already blocked.