Anyone use a minus violet filter

DavidU (Dave) · #1 31-07-2009, 01:40 PM

I have a large achro and was wondering if anyone uses a minus violet
filter.

jjjnettie (Jeanette) · #2 31-07-2009, 01:51 PM

I used one on my 120mm refractor and it did make a big difference, but there was still some fringing.

rogerg (Roger) · #3 31-07-2009, 02:12 PM

I have a 2" one I used to use on my Megrez 80 SD. It helped a lot, although it made the images generally less blue which meant things like Jupiter and the Moon weren't such a nice colour. For visual and photographic work I used it almost 100% the time on that scope.

pmrid (Peter) · #4 31-07-2009, 05:08 PM

Hi David. I use one on a 5" refractor with an achromat from Surplus Shed. The lens is good for visual but for photographic work, the blue/violet fringe was pretty powerful. I tried a fringe killer filter and I have to admit it did reduce the violet but did not eliminate it. It also gave a general yellowish tint to the image. I imagine that the quality of my objective was such that this level of improvement was as much as I could reasonably expect. Perhaps a better lens might make better use of the filters available. But for now my achromat is relegated to visual use only - at which it does a fine job.
Peter

renormalised (Carl) · #5 31-07-2009, 05:45 PM

Instead of trying to take colour shots with the achro/filter combo, why not just do B&W shots. They can look just as good and in some case they're better than colour piccies. The colour fringing won't matter so much and even if you lose a bit of resolution due to the fringing it won't matter so much

DavidU (Dave) · #6 31-07-2009, 05:48 PM

I only use the achro for visual work.

renormalised (Carl) · #7 31-07-2009, 06:01 PM

Quote:

Originally Posted by DavidU

I only use the achro for visual work.

That they're good at, especially if they have good lenses. But if it's a nice size it seems a shame not to have a go with an imager

pmrid (Peter) · #8 31-07-2009, 06:40 PM

Quote:

Originally Posted by renormalised

Instead of trying to take colour shots with the achro/filter combo, why not just do B&W shots.

Thaqt's not a abad suggestion. I'll have a run at it and see where it takes me.
Peter

renormalised (Carl) · #9 31-07-2009, 07:16 PM

Quote:

Originally Posted by pmrid

Thaqt's not a abad suggestion. I'll have a run at it and see where it takes me.
Peter

Let us know how it goes.

DavidU (Dave) · #10 31-07-2009, 07:39 PM

Quote:

Originally Posted by renormalised

Instead of trying to take colour shots with the achro/filter combo, why not just do B&W shots. They can look just as good and in some case they're better than colour piccies. The colour fringing won't matter so much and even if you lose a bit of resolution due to the fringing it won't matter so much

Great idea BTW. I must try it.

renormalised (Carl) · #11 31-07-2009, 08:03 PM

You will probably still have a bit of fringe in the shot, but it's not something that will adversely affect the look (not unless it's very prominent). There are plugins for Photoshop and other image software that will reduce the fringe nearly altogether.

allan gould · #12 31-07-2009, 09:57 PM

The best filter for this is the Baader semi-apo.