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Filters for Galaxies

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#26 GGK

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Posted 15 April 2021 - 03:48 PM

For finding galaxies with my C8 SCT in Bortle 4 skies, the best filter I have is a dark hood covering my head and eyepiece. 

 

My normal lightweight hood that allows a small amount of ambient light through the fabric is fine for clusters and brighter objects. But for the small faint galaxies, I see a stepped improvement when changing to a very opaque hood that blocks all ambient light around my eyes.  I also wear an eyepatch over my other eye when using the dark hood.  I also have to remember to breath fully because if I start taking shallower breaths or hold my breath, I tend to have more difficulty seeing the faint objects.  

 

Gary


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#27 vtornado

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Posted 15 April 2021 - 10:12 PM

I live in Bortle 7 and can view Bode's galaxy with difficulty in an 100mm scope.

 

I have tried the orion sky-glow filter.  It does not enhance the view.

On paper I was thinking this filter would remove more light pollution, (sodium, mercury vapor)

than galaxy light (full spectrum).  But in reality I did not notice a difference.



#28 brentknight

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Posted 15 April 2021 - 11:03 PM

I think it really depends on what type of light is in your light pollution. To the south in my backyard, the lights are all yellow/orange. Filters seem to help somewhat with contrast. To the north in my front yard it's more full spectrum and I doubt I'd see much improvement (no improvement now since I can't afford the rainy cloud filter)...

#29 radiofm74

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Posted 19 April 2021 - 09:33 AM

Original post:

Posted 10 April 2021 - 11:34 PM
Hi all, I'm relatively new to astronomy and I have been using my new Orion Goto Star Seeker IV 150mm (f/5) reflector since this past Christmas to view the stars,  the Orion Nebula, Mars, the Moon and M31, M81, and M82 galaxies. I would like to see the galaxies better and wondering if there are any filters that could help. I was looking at the Lumicon UHC and the Orion Ultrablock filters, trying to keep the cost under $100. I'm using a 25mm plossl and the Orion 7.2-21 zoom. Thanks in advance for any suggestions.

 

 

Update: (April 14, 2021)

I went out last night in our light polluted skies in my backyard. With fairly accurate goto tracking I honed in on M-81 (Bode's Galaxy) and used some of the tips I received from the forum. I let my eyes adjust to the dark, I used little to no red light to set up, also tried to block all peripheral light, and used averted vision. I was surprised how well those simple techniques worked. I was able to see so much more of the galaxy and definitely saw the brighter center with the averted vision thing. I have a New York State Park Star Gazing Permit that allows me access to certain state parks on Long Island after they close at dusk. One spot I will soon get to is Hither Hills in Montauk. I have heard from many that it offers some of the darkest skies on the island for viewing. I have been to Montauk so many times and know how dark the skies are out there but I only brought my surfboard not my telescope (this time I'll bring both).

Congrats for your close encounter with Bode's Galaxy!

 

You got your answer re:filters but along the lines of what Tony Flanders and others did, I'd like to suggest two "light-pollution-resistant" galaxies for observation from your backyard: M94 (in CVn, the "Cat's Eye" or "Croc's Eye") and the awesome M104 ("Sombrero Galaxy").

 

Possible from the city for a newbie like us, but definitely harder: M51 (Whirlpool, wonderful), M63 (Sunflower), M64 (Black-eye), M65 and M66 (part of Leo's trio). 

 

To find them, and for your edification on Messier objects, may I suggest Tony's awesome guide: https://tonyflanders...essier-project/

 

These suggestions are the result of a one-month struggle with galaxy-hunting in urban settings (in the center of Milano, I'm around Bortle 7). I feel your pain and am a bit jealous of your getaway opportunity ;D But note this: while the Moon is up it will be much much harder to see dim objects like most galaxies are, even under a darker sky. I'll resume the quest from April 29, and meanwhile enjoy colorful doubles, the last visible bright clusters from Winter season, and the Moon itself.

 

Happy quest and clear skies!


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#30 Asbytec

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Posted 14 May 2021 - 09:17 AM

Here's what David Knisely had to say about the DGM Optics Galaxy Contrast Enhancement (GCE) filter:

The DGM Optics GCE filter is at least somewhat effective on a number of galaxies when viewed under dark sky conditions, and in many cases, is a bit more effective than the Lumicon Deep-sky filter. The improvement is often subtle, requiring low power and some study to see. However, under even mild skyglow conditions, a standard LPR filter like the Lumicon Deep-sky may be somewhat more effective than the GCE, although again, any improvement in the view will be slight at best.

https://www.cloudyni...ce-filter-r1595


I agree with Tony and others, there is no substitute for dark skies. I agree with Tony, specifically, about getting a lot of experience (practice) and eyepeice time to better see galaxies. You'll need all that experience, anyway, just to see the slight improvement a wide band filter might make. Like David Knisely, I do notice a very slight improvement with an Orion SkyGlow filter under slightly light polluted rural suburban skies. No idea if it will be the same in brighter urban skies.

#31 Angeles

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Posted 14 May 2021 - 09:41 AM

the only issue i have the made up term "GAS FILTER" is its not really real just a made up term, not many people know there is  something called a gas filter in a car most people only know the oil filter.

 

also more important this assumes everyone own a car or drives, when i got into hobby for many years i didnt drive nor own a car, everything was made from lp zones. So just saying we shouldn't assume they drive either.

 

I have also heard a stat where i live over a million people take transit a day, so there has to be a whole lot % of people that dont drive.

 

as per the question no filter really helps, if you cant get away or have a car your next choice is to get bigger min 8 to 12 inches that will help look at the dso. It will only go so far its better then nothing.


Edited by Angeles, 14 May 2021 - 09:42 AM.

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#32 Jon Isaacs

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Posted 14 May 2021 - 10:57 AM

I don't know that I quite agree with this - and everyone is different of course.  With my 14" in B5 skies (SQM-L 19.59), I'm well on my way to 60 H400's in Coma/Virgo - most between 11m to 12m.

 

Another thing required is to know exactly where they are - no scanning around the field.

 

LP is definitely a problem here, but I can clearly see these galaxies - although they don't look like much...

 

In my mind, a big issue in threads like this is understanding just what level of light pollution the OP and others are dealing with. Goodtostargaze.com tells me my skies in San Diego are "Bortle" 7.0.  What that means. I have no real idea.. Bortle ratings are an individual's evaluation and not a computer generated number.

 

I measure them as Brent has done at 18.6 mpsas on a good night at the zenith.  What "Bortle 6" in Dayton Ohio means, Midwest transparency, urban light pollution.. it could be worse than my urban backyard.

 

Jon



#33 Wouter1981

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Posted 14 May 2021 - 12:27 PM

I haven't read all the replies, so I probably just repeat things, but filters are as good as useless for galaxies and will sometimes actually do more harm by blocking useful light. A darker observing site is the best way to see more galaxies, a bigger telescope is the second best option. If both are not possible, find the darkest place at your current observation site and try to shield yourself as much as possible form local light sources. I sometimes use a sunshade on wheels to give me more shadow. Wear a hoody or even put a towel over your head and search for the galaxy. If you are pretty sure you are looking at the right spot keep looking there for several minutes, if needed 15 minutes or longer with the hood or the towel over your head to give your eye as much time as possible to get dark adapted. Galaxies in a light polluted sky are often really hard or impossible to see. I've only see M31 and although I've searched for hours, other galaxies are invisible due to my small telescope (100mm) and my huge levels of lightpollution.
Try to memorize maps to find galaxies. Looking away from the eyepiece at your smartphone or a map to check the location destroys your night vision quickly, even if you use redlights.



#34 brentknight

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Posted 14 May 2021 - 02:17 PM

I haven't read all the replies, so I probably just repeat things, but filters are as good as useless for galaxies and will sometimes actually do more harm by blocking useful light. A darker observing site is the best way to see more galaxies, a bigger telescope is the second best option. If both are not possible, find the darkest place at your current observation site and try to shield yourself as much as possible form local light sources. I sometimes use a sunshade on wheels to give me more shadow. Wear a hoody or even put a towel over your head and search for the galaxy. If you are pretty sure you are looking at the right spot keep looking there for several minutes, if needed 15 minutes or longer with the hood or the towel over your head to give your eye as much time as possible to get dark adapted. Galaxies in a light polluted sky are often really hard or impossible to see. I've only see M31 and although I've searched for hours, other galaxies are invisible due to my small telescope (100mm) and my huge levels of lightpollution.
Try to memorize maps to find galaxies. Looking away from the eyepiece at your smartphone or a map to check the location destroys your night vision quickly, even if you use redlights.

I agree with most of what you say and it's great advice.

 

I don't agree with your "filters are as good as useless..." comment though.  Now I might not recommend spending a whole lot of cash on filters to test them out, but if you have good quality wideband filters and you have limited LP, they do make a difference.  The conditions I am describing are decent suburban skies (maybe somewhere around SQM-L 19.0 or better) and LP that is restricted to the orange/yellow frequencies.  With filters (I use a Baader UHC-S) in these conditions, you can see noticeably darker sky backgrounds and galaxies stand out a bit better as they are dimmed less than the general background.

 

Also, it's important to preserve dark adaptation, but it's also important to know exactly where the target galaxy is in the eyepiece field.  Scanning usually won't show low-contrast objects and I personally find it very difficult to memorize star locations, angles and distances.  As long as steps are taken to keep screens reasonably dark, glancing at them to verify star patterns won't ruin night vision - especially when the sky itself is fairly bright.  Just give your eye a chance to readjust.


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