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Filter for star light & videocam

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#1 dragonslayer1

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Posted 22 January 2013 - 11:18 AM

Have a videocam VSS+ I purchased a couple months ago but weather, work and schedule have not cooperated at all. Last night was finally able to get it to work on a non planetary item (M42). Is there' a filter that would work just to specifically tone down the lights from the stars? It was 5* and scope iced up before could really play with settings but it seemed no matter what I did the stars were really bright beams of light. I have seen some other pictures of video captures that seem to have the same thing going on. Any advice would be greatly appreciated, thank you. Kasey :question:

#2 Dwight J

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Posted 22 January 2013 - 12:14 PM

Hi Kasey: I have seen Astronomics UHC filters and 12Nm Ha filters in action and they seem to attenuate the starlight somewhat. Additionally, while watching NSN, some broadcasters were using Virtualdub (freeware) that had a filter that made the stars smaller although I forget what specific filter in Virtualdub. As it is freeware give it a shot...

#3 dragonslayer1

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Posted 23 January 2013 - 11:48 AM

Thanks Dwight, I am not the sharpest knife in the drawer, but I have a UHC, are all UHC filters the same? I haven't tried it but will when I get a chance to use scope again. thanks Kasey

#4 mclewis1

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Posted 23 January 2013 - 12:14 PM

Kasey,

All UHC filters are not exactly the same. For visual use there's not too much of difference but when imaging the sensors in the cameras have a wider range of sensitivity and then some of the differences in the filters start to become apparent.

For video viewing the Astronomik UHC filter is very popular because it also passes quite a bit of IR light, and this helps when viewing galaxies (which often have a significant IR signature). Most other UHC filters don't pass as much IR and when compared to the Astronomik filter the galaxies don't show up quite as well.

On objects other than galaxies there's not much of a difference between UHC filters. If you don't have an Astronomik model I wouldn't worry. I'd go ahead and get used to using whatever UHC filter you have (which will with longer exposures open up a lot more potential viewing under skies with lots of light pollution). If you then find that your spending a lot of time viewing galaxies then perhaps the additional investment would make sense.

#5 dragonslayer1

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Posted 26 January 2013 - 01:51 PM

I found a really indepth study on filters in the yahoo mallincam site (Jim Thompson: Astronomical filters part 7, how to choose an LP filter).. Mark you are probably aware of it from your visits there. It appears to be a very long ehaustive hands on study covering everything from A-Z... He gives the Astronomis UHC very high marks as well. I think from reading it that one would want a IR CUT filter to also cut down on star brightness?? A way to take the visual output of videocamera and turn stars from bright headlights on a dark night to something that would blend in a little better as they look in real time so to speak. Did I interpet that right??

#6 plav1959

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Posted 26 January 2013 - 02:12 PM

I have an Astronomiks UHC filter but rarely use it with my MCX viewing from a dark site. Star bloat can also be caused by bad seeing, high AGC, etc. The Orion nebula is probably not a good test object for this. If you're looking to see the trapezium stars individually in M42, you would have to turn sense off and switch to shutter to get individual points of light, but then you would lose most of the detail in the nebula. Other nebulae like M8, 16, 17, 27, 57, etc. would give you a better idea about how much you would need a UHC.

#7 dragonslayer1

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Posted 26 January 2013 - 04:05 PM

Thank you very much and your probably right about my settings and conditions. Star bloat is a good term also. It has been so cold and terrible viewing here that trying to learn camera is a mad dash,, get everything set up and try it out before ice covers everything and have to shut down.... :tonofbricks: I know I need more use of camera to learn it and play with settings,, :foreheadslap:

#8 plav1959

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Posted 26 January 2013 - 04:31 PM

Better winter test objects would be the Flame nebula (NGC2024), Running Man nebula (NGC 1977), or M1. NGC 253 is a great galaxy if you have enough southern exposure.






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