Image taken with the Omega Optical 394nm filter as a blocking filter
next the Omega Optical filter as a blocking filter. As you can see, no vignetting, but not as much contrast as the PST BF, and a suspicious alignment running about '1 o clock - 7 o clock' in this image
19-JUL-2012
Blocking filter comparision : PST Bf Vs Omega Optical 394nm filter
This comparision has been cropped and the vignetting of the PST's BF isn't visible and the mentioned alignment of the Omega filter isn't obvious either, but it shows the contrast differences. (same proc. throughout)
29-JUN-2012
Image with the Omaga Optical filter as the BF
Again this image shows astigmatism with the Omega Optical filter as a BF. In this case an alignment running about 45°, about '10 o clock - 4 o clock'in the image shown can be seen. If you're not used to spotting it minor astigmatism like this might be difficult to recognise but with practice it becomes obvious. It looks similar to aligned rice grains or polished stainless steel.
The image may show astigmatism, but in this case the Ca K filter also picked up minor flaring in the active region AR'1515. Flare activity is more usually picked up in Hydrogen Alpha (Ha) images, but can also be seen in the light of Ca K.
Other blocking filter candidates
Looking at the spectral response curve this filter the 8nm Baader Calcium K line filter would make a good blocking filter I'm sure. And being Baader there would be no questions about it's quality. The problem was it's price : US$ 329 for the 1¼" filter at the time of writing. At that price I might just as well and go out and buy a Ca K module straight from Lunt.
Another blocking filter candidate - the Baader 'U' (venus) filter
OK the spectral response curve of this filter isn't quite as good as the K line filter. It has a much wider passband compared to the K line filter, but the good news was that I already owned one of these though I'd loaned it out at the time I bought the Omega filter. For comparision purposes it's US$ 274 at the time of typing, But I already owned it so I made use of what I had.
08-JAN-2013
Completed Ca K module
This photo shows the completed module (to date anyway !) with the IDAS Type IV UIBAR filter up front as an ERF. Next is the step adapter - used because I already had the M46 threaded aluminium adapter. Then the Ca K filter from the Ca K PST, then an adapter to 1¼" female nosepiece, and lastly the Baader 'U' 'venus' filter (which is screwed on to the camera nosepiece).
14-JAN-2013
20130111 05 13 hrs UT CaK PST with 100 1242mm with Baader U BF.jpg
12-JAN-2013
20130111 04 46 hrs UT CaK PST with 100 1242mm with Baader U BF.jpg
14-JAN-2013
20121311 04 19 to 04 30 hrs UT Ca K PST 100621mm with Baader U BF.jpg
25-FEB-2013
Ca K module with longer tube
Further to my comment of 26 Jan I've now made & flocked a longer spacer tube between the ERF & etalon. The length of this tube has been calculated to work with scopes as fast as f6 and I don't think I'd be wanting to go faster than that. I tried it out this evening and it works OK. I did take an AVI, but the sun was close to the western horizon and was 'boiling'. I did think about including that proc. jpg, but I'll take another AVI in better seeing earlier in the day. The AVI I took today was with a scope of 1600mm FL, so I'm going to have to have good seeing conditions than I was able to get away with when using the f6 621mm FL scope that I've used previously.