6 replies to this topic

[tazer]

I have a modified Sony NEX-5 and have been imaging with an Astronomik UV/IR cut filter for a while now. Wanting to do more observing in my green zone front yard I decided to pick up an UHC filter. I debated between the Lumicon and DGM filters, but due to price and availability I opted for the Astronomik UHC filter. It's a bit less aggressive than the other two, not by much though, but I felt it should greatly enhance my experience nonetheless. Since I primarily image I couldn't help but throw it in the imaging train last night for a test.

 

A few weeks back I had taken a 10-minute exposure of M27 with just the UV/IR cut filter. The moon was around 8-9% illuminated and 45 degrees below the horizon and the Milky Way was visible. My test image last night was with the moon at around 85% illuminated and around 45 degrees above the horizon (almost at culmination.) There was no hint of the Milky Way and only the brightest stars were visible with the naked eye. There was a large difference in humidity between the two tests and a little bit of a temperature differential too.

 

Below are the results of the test and I'm very happy with the results. Post-processing was minimal, white balance adjustments in FITSWork and a slight level adjustment on the UHC image (the background was slightly darker than the non-UHC image.) The filter really seems to reduce the fainter stars bringing more focus to the nebula itself. It's much easier to discern the fainter portions of the nebula and it appears to have had an impact on moon-glow as well (which I wasn't fully expecting.)

 

Not only does it seem to be great on nebulae, it will also increase the number of nights that I can image.

 

[Samir Kharusi]

Your passbands encompass Hb and OIII on the blue-green side, plus Ha and SII on the red side; and even though the passbands are fairly wide, you do get to shoot two narrowband images simultaneously, very useful for any nebulae with Ha and OIII regions, more explained here and here.

 

[whwang]

Hi Tazer,

 

Thank you for sharing.  I also got an Astronomik UHC filter recently for 

exactly the same purpose.  I chose Astronomik because its bandpass

around OIII and H-beta is the narrowest one among other similar filters,

meaning that it can more effectively suppress light pollution and star

light.  I had some doubt about its transmission at H-alpha, but your

picture shows that this is probably not a problem.

 

Cheers,

Wei-Hao

[tazer]

Samir, thanks for the links. I actually referenced your site while I was making my filter decision. Thanks for putting it up, it's very useful.

 

Wei-Hao, I was surprised at how effective it was. I definitely didn't notice it having an impact on Ha. It's rated to pass it at 96%, so any effect it did have was small.

[Puck Ja]

Interesting comparison.  The color in no-filter images looks more pleasing to me.  However, you may be able to bring the filtered image to the similar color tone with some more processing.

 

I am heading the same investigation with the targets in front of lots of stars.  I am using Orion SkyGlow and IDAS LPF-V4 in this study.  The interesting part of LPF-V4 is that it has much narrower Ha band than "traditional" LPF.

 

I found the similar result.  The background stars can be reduced by LPF slightly.  They can be reduced even more effectively with "narrowband" LPF-V4.  The contrast of nebula features increases proportionally with narrower passband.  The color, on the other hand, became more "artificial" due to the narrow passband.

[tazer]

Here are 100% crops of the camera generated JPG's with no post-processing (color or otherwise):

 

1) With just a UV/IR cut filter:

 

 

 

2) With UV/IR cut & UHC:

 

 

It does look like focus was off in the UHC test even though the FWHM was a bit lower. It's obviously a lot more blue, but that's easily corrected. Filter reflections are also decreased though there does seem to be some red halos around stars (both images were taken with a Mak-Newt) but perhaps that's due to focus.

 

Overall I do like the contrast enhancement. Hopefully I'll get a chance to spend some time on it with proper focus, stacking, and post-processing.

[Starfishey]

Did u use a canon dslr for these pictures if so did u use the custom white balance feature? I have a modded 600d with the low pass filter 2 as my ir cut (97% block) and i use a astronomik uhc aswell. But this night i didnt use the CWB i got lost in the world of guiding just wondering cause my pics looks like ur 10min subs..

Skickat från min SM-G965F via Tapatalk