I have never purchased a filter before. Would these be 2 inch filters I should be looking at to avoid vignetting on an APS-C sensor Canon 20Da?
H-Alpha filter with DSLR cameras
Posted 08 April 2021 - 02:31 PM
Since you're using lenses, you'll need a clip-in filter.
Beware that some lenses have such a short flange distance that they can't be used with clip-in filters, they bump on the filter. Most notably EF-S lenses IIRC have that problem.
- Reece likes this
Posted 08 April 2021 - 04:57 PM
Which filter were you using that caused this problem? I don't have any experience with clip filters yet, but the round filter is a bit of a hassle with mounting to the front of a lens. The filter drawer would fix this for sure. Was it with full frame or APS-C sensor?
The OIII will be affected by moonlight for sure. But it'll be useable data versus unfiltered during the full moon. Your H-a data will be great. The emission nebulae I've shot during full moon with the l-enhance filter have been decent.
It was my full frame 6D. I've generally heard good reviews with clips and the APS-C so the issue might be primarily ff and the tighter space it fits into. It still works but requires a bit extra cropping, which kind of defeats some of the purpose of using the ff vs crop sensor. Hopefully I can go to 2" filters in the lens to be able to swap cameras more easily. I just picked up an old canon lens that was suppose to originally come with a holder for 48mm filters, but it must've been swapped for a gel holder. And now I can't find any replacement drawers for 48mm filters. Darn! I may just unmount the filter and see if the gel holder will hold it.
Posted 09 April 2021 - 09:35 PM
I have done some reading on filters.
It appears that the L-Extreme works better with slower lenses as there is some loss of light transmission when using it with fast lenses such as my Canon 200mm F/2.8. The L-Extreme would allow wavelengths of light which might reduce it's usefulness under a bright moon. It is also more expensive.
The L-Enhance filter appears to work fine at F/2.8. One buyer of this filter who seemed quite knowledgeable claimed it suffers considerable loss of light transmission at F/2 however.
Astronomik makes a 12nm h-alpha filter. This lens has a wider passband at the h-alpha wavelength than the L-Enhance or L-Extreme. It would presumably be less susceptible to the reduced light transmission effect of the fastest lenses. It would be strictly h-alpha. I am not sure of the significance of this in practice for the imaging of nebulae and planetary nebulae.
Baader appears to make filters specifically for fast telescopes such as the RASA. I have been unable to find a DSLR clip filter from them for fast camera lenses unfortunately.
I may wish to purchase a Sigma 85mm 1.4 at a later date. It would be frustrating to purchase equipment now which would be sub-optimal with future equipment purchases.
Edited by Reece, 09 April 2021 - 10:10 PM.