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Filters that work for galaxies

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#26 Illinois

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Posted 14 February 2015 - 07:44 AM

Interesting posts! I always thought that filter is not good for galaxies. One time I tried Orion Skyglow to look at M31 in Chicago and it don't get better. M8 Lagoon nebula is little better on filter.

 

Dark Sky and large scope is best for galaxies! About 10 years ago that  I cant see M97 in my Orion 10 inch dobsonian and I can see it clearly at farm field about 100 miles away from Chicago!



#27 Bill Steen

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Posted 14 February 2015 - 02:33 PM

Just to give an update, I have ordered a "Planetarium" filter on eBay from a business in China, that has a very good satisfaction rating.  The price is a little over $38 delivered to my home.  It has no markings on it, but there is a very good explanation about what light it will filter out and says it is "similar" to the Baader Planetarium Moon and Sky Glow Filter.  The only drawback is its 2 to 4 week delivery time.  This in not a delay on the part of the shipper, since it was shipped the day after I ordered it.  (Must be coming on that proverbial slow boat!)

 

As a bit of explanation for those advising to go to a dark site, for health, stamina, and work reasons that I will not go into, I have a total astronomical activity limit normally of about 90 minutes, with an absolute limit of 120 minutes.  If I went to my astronomy club's site, I would drive for an hour turn around and drive back home.  If I went to another site, which is often used by drug people, I could drive there, set up my scope, allow it to cool for 30 minutes, pack it up, and drive back home.  By back yard is the only place where can I truly enjoy astronomy,until I can retire from work.

 

From my back yard, most of the close (within a half mile) light pollution is either from yard lights, or low temperature sodium street lights.  The modifications I have made to the scope, privacy fencing, a hood over my head, seem to obliterate stray light from yard lights.  My back yard neighbor can now turn on his four sealed beam flood lights and I see absolutely no affect in the view.  If the filter can do anything with low sodium light, then I should be able to locate a significant number of additional galaxies....at least I hope so.

 

Increasing magnification does help contrast, which helps see nebulous things better, but anything greater than about 100X with this 130mm scope starts look surrealistic to me in a dark field and is not enjoyable.  This condition may change after I have cataract surgery.  Additionally, reducing the field of view to maybe two-thirds of a degree is unacceptable for searching purposes, in my opinion.  That small of a field might be fine with a computerized scope, but not with a manual one.  I consider an attempt to selectively reduce the level of unwanted colors of light and do the best I can at keeping the light with information and a wide field of view is the logical and most reasonable attempt that I can make to see these objects.

 

For me, I am thinking a 1.25 inch eyepiece in the 14 to 25 mm focal length, with as wide an AFOV as I have available to me, with this 130 mm f/5 scope, using a selective reducing filter is the most reasonable option to try from my back yard.  Why the 130 mm scope?  It is the largest truly introductory scope that I own and I think it stands a better chance of seeing galaxies and other dim things in my light pollution that any of the smaller ones.

 

I will let you know how successful I am when I get the filter.

 

Thank you for all of your thoughts and opinions.

 

Bill Steen



#28 Starman1

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Posted 14 February 2015 - 03:13 PM

Bill,

If you wear glasses, look for a 20mm eye relief and 68-72 degree field.

If you do not, look for 10mm or more of eye relief and 82 degree field.

Here is a list of available eyepieces to see what's available in 1.25" eyepieces (the most-recent download list is on post #46):

http://www.cloudynig...e-to-eyepieces/



#29 Bill Steen

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Posted 14 February 2015 - 04:23 PM

Thanks, Don!

 

I have downloaded the spreadsheet and will go over it and see if there is something that catches my eye.  If you can think of any that you would consider good candidates, I would appreciate your enlightenment.  I do not, however, consider Televue or Pentax within my window of opportunity right now.

 

I think I have some pretty good ones for this purpose as things stand, with the Meade 5000 series UWAs, Meade 5000 series Plossls, an HD 60 25 mm, and the three ES 68 1.25 inch eyepieces.  So far, the HD 60 25mm seems to have the best over-all characteristics for this particular finding task, even though it does not have the best characteristics in every way...a little less field of view, which is offset by a little better light transmission than the ES 6824 eyepiece, etc.  Once I get the filter, I will be checking out all sorts of eyepieces with it.

 

Best Regards,

 

Bill Steen


Edited by Bill Steen, 14 February 2015 - 05:01 PM.


#30 Achernar

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Posted 14 February 2015 - 04:53 PM

Just to give an update, I have ordered a "Planetarium" filter on eBay from a business in China, that has a very good satisfaction rating.  The price is a little over $38 delivered to my home.  It has no markings on it, but there is a very good explanation about what light it will filter out and says it is "similar" to the Baader Planetarium Moon and Sky Glow Filter.  The only drawback is its 2 to 4 week delivery time.  This in not a delay on the part of the shipper, since it was shipped the day after I ordered it.  (Must be coming on that proverbial slow boat!)

 

As a bit of explanation for those advising to go to a dark site, for health, stamina, and work reasons that I will not go into, I have a total astronomical activity limit normally of about 90 minutes, with an absolute limit of 120 minutes.  If I went to my astronomy club's site, I would drive for an hour turn around and drive back home.  If I went to another site, which is often used by drug people, I could drive there, set up my scope, allow it to cool for 30 minutes, pack it up, and drive back home.  By back yard is the only place where can I truly enjoy astronomy,until I can retire from work.

 

From my back yard, most of the close (within a half mile) light pollution is either from yard lights, or low temperature sodium street lights.  The modifications I have made to the scope, privacy fencing, a hood over my head, seem to obliterate stray light from yard lights.  My back yard neighbor can now turn on his four sealed beam flood lights and I see absolutely no affect in the view.  If the filter can do anything with low sodium light, then I should be able to locate a significant number of additional galaxies....at least I hope so.

 

Increasing magnification does help contrast, which helps see nebulous things better, but anything greater than about 100X with this 130mm scope starts look surrealistic to me in a dark field and is not enjoyable.  This condition may change after I have cataract surgery.  Additionally, reducing the field of view to maybe two-thirds of a degree is unacceptable for searching purposes, in my opinion.  That small of a field might be fine with a computerized scope, but not with a manual one.  I consider an attempt to selectively reduce the level of unwanted colors of light and do the best I can at keeping the light with information and a wide field of view is the logical and most reasonable attempt that I can make to see these objects.

 

For me, I am thinking a 1.25 inch eyepiece in the 14 to 25 mm focal length, with as wide an AFOV as I have available to me, with this 130 mm f/5 scope, using a selective reducing filter is the most reasonable option to try from my back yard.  Why the 130 mm scope?  It is the largest truly introductory scope that I own and I think it stands a better chance of seeing galaxies and other dim things in my light pollution that any of the smaller ones.

 

I will let you know how successful I am when I get the filter.

 

Thank you for all of your thoughts and opinions.

 

Bill Steen

What will also help are light screens to block out nearby lights. You do not need to spend lots of money to make them, and there's lots of ways you can make them. That does make a significant difference in my experience. I quite understand why driving to dark sites is usually not an option for you. Believe it or not, most of my observing I do right from the driveway, despite the light pollution.

 

Taras


Edited by Achernar, 14 February 2015 - 04:54 PM.


#31 Bill Steen

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Posted 14 February 2015 - 08:32 PM

Thanks, Taras!

 

I have been thinking about something like that, but for probably a little different reason than one might think.  I am well protected for my neighbor's flood lights themselves.  But, they shine over the top of the fence and reflect off of my bedroom windows.  This can often catch me by surprise and can be quite blinding.  I have been thinking about something to put over the windows when I go out to catch that reflection.

 

Just FYI, my neighbor really pays attention and is really courteous.  He has a dog that needs to go in the back yard and do his business every now and then.  The flood lights come on then, the dog comes out for a while, then is called in, the lights are turned off.  If the neighbor hears me in the back yard, the time the dog is out is kept to an absolute minimum.  I really cannot ask for me than that from the neighbor, in my opinion.

 

Other than this one reflection situation, I am pretty well protected.

 

Eventually, I will be building a 10 by 16 foot shop that will block all light from the west (the city of Tulsa and one permanent back yard light) and then a 10 by 16 foot astronomy patio with a six foot fence around it with the top two feet being very solid.  The bottom four feet will be lattice with vines to allow some ventilation.  HOA Covenants only allow 10 by 16 foot maximum out buildings and at this point only allow one, unless I do something like take them to court.  Therefore, the astronomy item is a patio.  If the situation changes, the astronomy patio will get a roll off roof.

 

Thanks for the input!

 

Bill Steen



#32 Scanning4Comets

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Posted 14 February 2015 - 08:56 PM

Galaxies, (except for bright ones), get hurt by light pollution in the city.....best to drive even 20 min away....which really helps a lot. I gave up on city observing when it comes to galaxies.....I mainly do the bright stuff in the city, but even that is rare because it just kills a LOT of things to see.

 

20 min away does wonders.....as long as there isn't another big city right where you are if you drive 20 min away.

 

:grin:



#33 penguinx64

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Posted 15 February 2015 - 11:29 AM

Wow, what a great discussion.  It got me curious, so tonight I'll do my own filter challenge on the Andromeda galaxy. I plan to view Andromeda with and without 6 different filters 1 by 1, and rank them ++ + 0 - -- depending on how well they work.  If I can see the Triangulum galaxy tonight, maybe I'll repeat the test on it too.



#34 russell23

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Posted 15 February 2015 - 11:33 AM

Wow, what a great discussion.  It got me curious, so tonight I'll do my own filter challenge on the Andromeda galaxy. I plan to view Andromeda with and without 6 different filters 1 by 1, and rank them ++ + 0 - -- depending on how well they work.  If I can see the Triangulum galaxy tonight, maybe I'll repeat the test on it too.

Awesome!  I can't wait to hear what you find. 

 

Dave



#35 faackanders2

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Posted 15 February 2015 - 12:27 PM

Only filter that works on galaxies is DGM GCE, providing galaxy is bright enough to shine through filter.



#36 David Knisely

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Posted 15 February 2015 - 02:12 PM

Only filter that works on galaxies is DGM GCE, providing galaxy is bright enough to shine through filter.

 

Actually, any decent broad-band filter can help some of the larger and more diffuse galaxies.  The GCE helps on some galaxies, but may not be quite as effective on others, as is the case with many other broadbands.  In fact, with any additional light pollution, some of the more "standardized" LPR filters may provide slightly superior performance to the GCE, which does not have quite as much of the fine "notching" that other LPR filters may.  Take a look at the following review of the GCE which should answer most of the questions about it:

 

http://www.cloudynig...ce-filter-r1595

 

Clear skies to you.


Edited by David Knisely, 15 February 2015 - 02:13 PM.


#37 penguinx64

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Posted 15 February 2015 - 02:16 PM

Ok, here are the results of the Andromeda Filter Challenge.  Andromeda was about 45 degrees abouve the horizon.  I used a 17mm TV Plossl eyepiece at 26x with a 1.9 degree TFOV and a 4.4mm exit pupil.  It was about an hour after sunset when I started with the usual moderate light pollution, 85% humidity, 10% cloud cover and it was 4 degrees C.  I tried each filter several times, but all I could see was Andromeda's core with or without filters.  It should have filled the whole eyepiece.  After an hour or so, I gave up because it was getting too cold.

 

25% ND filter:  Couldn't see much of anything with this filter.  It was just too dark. No surprise here;

Ranking: -2

 

Orion Skyglow Broadband filter:  This filter darkened the sky background some, but darkened everything else too.  Not much of an improvement at all.

Ranking: 0

 

Zhumell Crystalview Moon filter:  This filter darkened the stars a a little, but made Andromeda's core almost invisible.  Strange.

Ranking: -1

 

Ostara Moon & Skyglow filter:  This filter darked the sky background some, but not as much as the Orion filter.  It seemed to improve contrast very slightly.  This filter looks identical to the Zhumell filter, but didn't make Andromeda harder to see.

Ranking: 0+

 

Meade #8 light yellow filter:  This one was a surprise.  It didn't darken the sky but it made the stars and core look brighter.  The core was still a fuzz ball, but it looked slightly larger. 

Ranking: +1

 

Celestron #80A blue filter:  As I suspected, this filter was very dark.  Not quite as dark as the 25% ND filter.  I could still see the core, but not very well.  An #82A light blue filter might work better, but I didn't have one to try.

Ranking: -1


Edited by penguinx64, 15 February 2015 - 02:17 PM.


#38 Bill Steen

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Posted 15 February 2015 - 04:16 PM

PenguinX64,

Thanks for posting! You definitely got some interesting results. I will have to try the light yellow filter just to see what it looks like through my scope. I would not have thought it would have that result. However, remembering my old black and white photography days, a yellow or orange filter could be used to darken blue skies to make clouds show up better. Since we basically see in black and white, maybe it is working about the same way. Human perception is a strange thing.

Best Regards,

Bill Steen

#39 penguinx64

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Posted 15 February 2015 - 05:22 PM

My scope only has 4.5 inches of aperture.  The darker filters may have worked better with a larger scope.  I had high hopes for the Orion Skyglow Broadband filter.  It works great for the Orion nebula, but not so great for galaxies.  I wasn't sure if the eyepiece made a difference in these tests.  I also planned to try a 15mm RKE and a 12.5mm Ortho to compare, but it was just too darn cold out there.



#40 Bill Steen

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Posted 15 February 2015 - 05:55 PM

I understand the issues with small scopes. That is what I use mostly. The only filters that I have been able to successfully use with a small scope are light ones....82A, 11, etc. That is what attracts me to something like the Baader Planetarium Moon and Sky Glow, which appears to have a very light general cast.

#41 Brian Carter

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Posted 16 February 2015 - 08:58 AM

With smaller scopes, in my experience, the best filter is none at all. Regardless of the filter type, it is going nowhere to block out light and there's a scarse supply of light in small scopes.

That's just my experience though.

#42 REC

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Posted 16 February 2015 - 09:44 AM

Just to give an update, I have ordered a "Planetarium" filter on eBay from a business in China, that has a very good satisfaction rating.  The price is a little over $38 delivered to my home.  It has no markings on it, but there is a very good explanation about what light it will filter out and says it is "similar" to the Baader Planetarium Moon and Sky Glow Filter.  The only drawback is its 2 to 4 week delivery time.  This in not a delay on the part of the shipper, since it was shipped the day after I ordered it.  (Must be coming on that proverbial slow boat!)

 

As a bit of explanation for those advising to go to a dark site, for health, stamina, and work reasons that I will not go into, I have a total astronomical activity limit normally of about 90 minutes, with an absolute limit of 120 minutes.  If I went to my astronomy club's site, I would drive for an hour turn around and drive back home.  If I went to another site, which is often used by drug people, I could drive there, set up my scope, allow it to cool for 30 minutes, pack it up, and drive back home.  By back yard is the only place where can I truly enjoy astronomy,until I can retire from work.

 

From my back yard, most of the close (within a half mile) light pollution is either from yard lights, or low temperature sodium street lights.  The modifications I have made to the scope, privacy fencing, a hood over my head, seem to obliterate stray light from yard lights.  My back yard neighbor can now turn on his four sealed beam flood lights and I see absolutely no affect in the view.  If the filter can do anything with low sodium light, then I should be able to locate a significant number of additional galaxies....at least I hope so.

 

Increasing magnification does help contrast, which helps see nebulous things better, but anything greater than about 100X with this 130mm scope starts look surrealistic to me in a dark field and is not enjoyable.  This condition may change after I have cataract surgery.  Additionally, reducing the field of view to maybe two-thirds of a degree is unacceptable for searching purposes, in my opinion.  That small of a field might be fine with a computerized scope, but not with a manual one.  I consider an attempt to selectively reduce the level of unwanted colors of light and do the best I can at keeping the light with information and a wide field of view is the logical and most reasonable attempt that I can make to see these objects.

 

For me, I am thinking a 1.25 inch eyepiece in the 14 to 25 mm focal length, with as wide an AFOV as I have available to me, with this 130 mm f/5 scope, using a selective reducing filter is the most reasonable option to try from my back yard.  Why the 130 mm scope?  It is the largest truly introductory scope that I own and I think it stands a better chance of seeing galaxies and other dim things in my light pollution that any of the smaller ones.

 

I will let you know how successful I am when I get the filter.

 

Thank you for all of your thoughts and opinions.

 

Bill Steen

Are you going to use the LS8 as well?  I have one and use the Baader M&S with my Meade 24mm SWA for some galaxies from my red zone back yard and it helps a little with the contrast when I look east to where there is a light dome.  Like now with the Big Dipper rising in the NE there are a lot of them in that direction.



#43 penguinx64

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Posted 16 February 2015 - 10:08 AM

I'd like to try more, but I only have the 6 filters mentioned previously.  None of these filters did much.  So far, it seems like the best filter is no filter. 



#44 faackanders2

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Posted 16 February 2015 - 07:47 PM

 

Only filter that works on galaxies is DGM GCE, providing galaxy is bright enough to shine through filter.

 

Actually, any decent broad-band filter can help some of the larger and more diffuse galaxies.  The GCE helps on some galaxies, but may not be quite as effective on others, as is the case with many other broadbands.  In fact, with any additional light pollution, some of the more "standardized" LPR filters may provide slightly superior performance to the GCE, which does not have quite as much of the fine "notching" that other LPR filters may.  Take a look at the following review of the GCE which should answer most of the questions about it:

 

http://www.cloudynig...ce-filter-r1595

 

Clear skies to you.

 

The only LPR filter I have is Orion Skyglow and this does not improve galaxies (but works good with differnt/multiple objects like Owl nebula & M108 in same view).  The DGM GCE is the only filter that I have used (and others will confirm) that improves the noticable motling of galaxies.

 

clear skies to you also

 

Ken



#45 penguinx64

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Posted 17 February 2015 - 01:06 AM

I found this review of the DGM GCE filter:

 

http://www.cloudynig...gm-optics-r2765

 

The transmission curve is a notch, blocking wavelengths 510-610 nm.  I compared this to the transmission curve for the #8 light yellow filter:

 

http://motion.kodak....ilters/w2-8.pdf

 

The light yellow filter appears to be similar to the lower half of the DGM GCE filter transmission curve. 



#46 Bill Steen

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Posted 17 February 2015 - 06:54 AM

Thanks, penguin! That is really good information! I will definitely try mine.

#47 David Knisely

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Posted 17 February 2015 - 07:54 PM

I found this review of the DGM GCE filter:

 

http://www.cloudynig...gm-optics-r2765

 

The transmission curve is a notch, blocking wavelengths 510-610 nm.  I compared this to the transmission curve for the #8 light yellow filter:

 

http://motion.kodak....ilters/w2-8.pdf

 

The light yellow filter appears to be similar to the lower half of the DGM GCE filter transmission curve. 

 

The Astronomik CLS has a simliar-sized and located primary "notch" to the GCE filter but that Astronomik CLS notch has somewhat steeper sides and nearly zero transmission in the main notch.  The CLS has a slightly narrower primary passband, but it also will exclude the nasty blue-violet 4358 "triplet" line of Mercury Vapor, which the GCE lets through at nearly full strength.  The IDAS LP-1 filter also will kill the Mercury vapor line and has multiple passbands with a series of notches, although those additional narrow secondary passbands in the yellow part of the spectrum will get contaminated by the broad HP-sodium emission band (a.k.a. "The High Pressure Sodium Monster").  Again, none of these broad-band filters (including the GCE) will provide an extreme boost in contrast on galaxies, but on at least some of the larger and more diffuse ones, they may at times pep up the contrast just a hair.  Clear skies to you.



#48 Dave Mitsky

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Posted 17 February 2015 - 08:50 PM

There's more on the DGM CGE filters at http://uncle-rods.bl...q=galaxy filter and http://www.npbfilters.com/about.html

 

Dave Mitsky



#49 penguinx64

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Posted 19 February 2015 - 03:51 PM

It appears that the Orion Mars Observation has a similar filter curve as the DGM GCE filter:

 

http://www.telescope...lter/p/5599.uts

 

Would the Orion filter work as a 'poor mans' galaxy filter?  It's cheaper and seems like it does almost the same thing.



#50 Bill Steen

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Posted 19 February 2015 - 09:01 PM

It appears that the Orion Mars Observation has a similar filter curve as the DGM GCE filter:
 
http://www.telescope...lter/p/5599.uts
 
Would the Orion filter work as a 'poor mans' galaxy filter?  It's cheaper and seems like it does almost the same thing.


Looks like it would work, and better than the #8 filter. It seems to cut out more light, in a wider swathe than the DGO GCE or Orion's Moon and Sky Glow Filter. On the other hand, the DGO GCE might make a really good Mars filter. It might be worth saving a few more nickels and buying the better filter.


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