MnAstro Forums

Hello,

Last night, for the first time.. I saw the Orion Nebula and the Trapezoids with my telescope. It was amazing, but as you know, it looked like a fuzzy cloud around it. I wonder if using filters for blocking lights can improve the appearance of the clouds? I used a Agenta 25mm eyepiece ... Can using a filter get you closer to what astrophotography images look like? At least provide better color contrast?

Any suggestions will be appreciated.

Luis

Hi Luis,
What telescope are you using? For a nebula like this, to see more contrast in the clouds, you generally need more aperture or a time exposure. Also to the naked eye, the colors are pretty hard to pull out. A time exposure with a camera is usually needed to see much color. There are various filters, such as a nebula filter, or a sky glow filter that might help with the contrast but only between the nebula and the background sky. These filters don't really help bring out color.

Also, your choice of eyepiece is good. Using a lower power, or a longer focal length eyepiece, will make the image smaller, but brighter and with better contrast. Depending on your telescope, you might even try a longer focal length like a 40 mm or such.

Thanks for the very valuable feedback! I have a XT6 Orion ... I will try to find some filters ..

Hi Luis,

The best filters for the Orion Nebula will be an OIII or a UHC. Neither will bring out colors like in a photograph. This is because our eyes cannot detect enough light in most deep sky objects to bring out much color. Though in the Orion Nebula i can usually detect some green and red... However, these filters will make the nebula explode with further detail, nebulosity and contrast. Definitely worth getting them...

Suresh

Thanks for the recommendation! Any good value Nebula filter? What's the difference between OIII and UHC? Also any city light filter that you recommend?

O-III is a narrowband filter that only passes the green light of double-ionized Oxygen. It darkens the field of view a lot, but lets the light of the nebula through. It is especially useful for the Veil nebula (and virtually necessary to view it).

UHC is "Ultra High Contrast" and is similar, but not as narrow band as O-III. It works almost as well for nebula like the Veil, but doesn't provide as much contrast as it lets more wavelengths through. It, I believe, is slightly less expensive than an O-III.

For viewing in suburban skies, you may also want to consider a skyglow filter. They cut out the wavelengths of high pressure sodium lights that are sometimes still used for street lighting. Honestly, though, I'm not sure if they are still as effective as they used to be, since the transition to LED street lights. I haven't tried mine in quite some time. Too many of those darn LED street lights things have a color temperature of 5000K or 6000K, about the same color as stars!

Suggestion: Bring your scope to ELO or CGO when we have a public night or a star party and borrow one of the filters there to try them out before buying your own.

Hi Luis,

Steve gave a great explanation of the differences between OIII and UHC filters.

I know many observers who absolutely love their UHC filters, and use them all the time. I'm partial to my OIII, particularly for emission nebulae. As Steve mentioned, the UHC is a broader band filter than the OIII but still provides excellent contrast and detail.

Per your next question, there are several reputable makers of these filters. I am partial to Lumicon (now owned by Farpoint Astro). I believe that Lumicon was the first to market narrowband and broadband filters, back in the 1980s. I have the OIII, UHC, H-Beta (for the Horsehead and California nebulas), Comet and Deep Sky Filter. The Deep Sky filter is a broadband filter that works well in urban lighting. It's pretty good at blocking out Mercury and Sodium based lights... but just know that there aren't any good LPR (light pollution reduction) filters yet for LED lights, as it's too broad across the spectrum to be easily blocked.

Other very good makers of these filters are Baader Planetarium and Astronomik.

Orion, Celestron, Meade and Antares also make them, but these are usually lower cost and not quite as good as the ones from Lumicon, Baader and Astronomik.

Another thing to consider is the filter size. You can get these as either 1.25" or 2" filters. If you can afford it, get the 2" versions that will screw onto your 2" eyepieces. Seeing the detail in the Orion, Swan, Omega, Lagoon, Trifid, Veil, Helix and other nebulae thru a wide angle 2" eyepiece with an OIII or UHC filter is truly unbelievable. Beginners usually gasp the first time they see them thru these filters. Also, since these filters only let in particular wavelengths related to nebulae, and block out everything else, they improve the view in urban areas as well.

See here for a list of these filters and prices: https://optcorp.com/collections/visual-filters

Also, here is a very good article from AgenaAstro, explaining how these filters work: https://agenaastro.com/articles/guides/ ... lters.html

I suggest that you come out to a B-SIG observing event and see these filters in action before you buy...

I hope this helps!

Suresh

Hi Luis,
I had another idea for you which might be helpful. Under the MAS Announcements and Discussion section of our forums you can find a post made on Sunday, October 4, 2020 at 9:18. The post provides a link to a filter expert who spoke to our club during the October meeting. It was very informative.
FYI,
Brandon