Need help with light scatter in eyepieces

[Arty68]

EDIT:   Before going any further, please note that I have checked maps for smoke filled skies and that is, by far, the most likely culprit.  The thought of smoke from wild fires entered my mind, however I pushed that idea out of my head and blindly pushed forward.  The result was poor seeing without much of an answer to why, given my equipment and the good state that it is in.  If anything, hopefully this post will help the next person with poor views of the heavens, at least until the smoke clears.

 

Here is one map source, note that it changes, sometimes relatively fast:  https://fire.airnow.gov/

 

I recently got back into astronomy after decades of absence.  I live in town and visibility is usually poor to very poor.  Telescopes: a Sky-Watcher f/9 100mm ED refractor with outstanding collimation and a Meade LX65 8" f/10 ACF Catadioptric with GoTo mount, I can put both scopes on the same mount/head.  This evening I mounted both telescopes & rechecked the collimation on the 8".  Primarily I wanted to view Saturn.  It came out from behind some trees at about 10:00p.m. EDT.  By about 12:30a.m. this morning views of Saturn was about as good as it was going to get.  I could see the Cassini Division but barely and I could see Titan, Rhea, Dione and Tethys.  Enceladus was too close to Saturn and I couldn't see it for the glare/light scatter.  I could make out a little color in the clouds on Saturn.

Unfortunately the light scatter in the eyepieces was so bad that it nearly ruined the view.  If it were not for the light scatter everything I saw would have been much better, crisper more detailed.  I have a variety of eyepieces that I have picked up over the years, none top end but should get the job done, and every one of them had a great deal of light scatter with the University Optics 12.5mm Ortho giving the least amount of light scatter.

Eyepieces are:  5.5mm 62 degree & 14mm 82 degree Explore Scientific, 6mm & 12.5mm UO Orthos, 7.5mm Orion Epic ED-2, 9mm Fujiyama Ortho, 32mm Meade Plossl, & a very old Celestron Ultima SV series 2x Barlow [the good one, model 93506].  All are 1 1/4" [don't have the money for good 2" eyepieces].  I have a series 4000 f/6.3 field flattener for the Meade telescope but I didn't use it last night on planets.

Does looking at a light filled sky in town have an impact?  Should I try to paint the interior of the eyepieces?

Edited August 4, 2021 by Arty68
Smoke is a serious problem for amateur astronomers in many areas

[John]

The lowest levels of light scatter that I have experienced with eyepieces have come from HD orthos such as Baader Genuine Orthos, University Optics HD orthos and Fujiyama orthos and also the TMB Supermonocentric.

The more complex designs (including the premium ones) do seem to introduce a little additional light scatter in return for their wider fields and longer eye relief. The Pentax XW range seem to control this well for a more complex design though. I believe the Tele Vue Delites are very good as well.

Of course keeping your scope optics free of dust / condensation and well cooled and collimated helps minimise scatter as well.

The low altitude of Jupiter and Saturn (at least where I am in the UK) does not help with the visiblity of these finer details either. Instability of the image can vary hugely moment to moment so patience and time at the eyepiece is required more then ever to catch those short golden moments of clarity.

This reviewer has attempted to quantify the effects of light scatter with a number of planetary eyepieces:

http://www.wlcastleman.com/equip/reviews/5mm_EP/5mm_ep.html

 

Edited August 4, 2021 by John

[vlaiv]

Does scatter change as you move your eye around? If so then you might need to clean your eyepieces.

I often have such issues with my eyepieces because of long eye lashes - it is very easy to grease up eye lens of the eyepiece and that creates distinct light scatter.

Another thing that creates scatter is dust / smoke / humidity in the air. These present more like halo around objects (both planets and stars) - that does not move / change as you move scope and you eye around.

If there are forest fires near by or you have large body of water like a lake, swamp or river and temperature is high - you could be having issues from the atmosphere.

[jetstream]

2 hours ago, Arty68 said:

Does looking at a light filled sky in town have an impact?

Right now forest fire have the sky here filled with haze, really bad viewing conditions, including scatter. I use really low scatter equipment, but it doesn't matter at the moment.  Particles in the air scatter light, made worse by planets low elevation. The 82ES ep's have more scatter than your (vg) orthos. A 12.5mm Circle T is a mainstay in my TSA120, for some reason I really like this eyepiece.

To minimize effects use your great 100mm f9 with orthos- one thing what diagonal do you use? I had an expensive poor one that cause massive scatter in a 90mm APO years ago. The SW mirror diag I have is vg- but maybe check "straight" through?

[Louis D]

Don't forget the effect all those optical elements in you SCT can have on scatter as well.  There's also the possibility of poorly controlled stray light seeping around the baffles.  Were the views equivalent between the frac and the SCT as far as stray light?

Try removing your diagonal and then view straight through to eliminate the possibility that it is adding scatter.  Dielectric diagonals tend to scatter more than silver or prism diagonals.

Make sure your field lenses on your eyepieces are clean.  Being closer to the field stop, any grime there has an outsized impact on light scatter.  Use a super bright tactical flashlight to look for any greasy film buildup on them.

Move Saturn around the field of the eyepiece and look for changes in the view.  This can help you pinpoint where the actual problem lies.

[Arty68]

4 hours ago, vlaiv said:

Does scatter change as you move your eye around? If so then you might need to clean your eyepieces.

I often have such issues with my eyepieces because of long eye lashes - it is very easy to grease up eye lens of the eyepiece and that creates distinct light scatter.

Another thing that creates scatter is dust / smoke / humidity in the air. These present more like halo around objects (both planets and stars) - that does not move / change as you move scope and you eye around.

If there are forest fires near by or you have large body of water like a lake, swamp or river and temperature is high - you could be having issues from the atmosphere.

Light scatter does not move when I move my eye around the eyepiece.  Thank you for your help, I appreciate your experience.

 

[Arty68]

2 hours ago, jetstream said:

Right now forest fire have the sky here filled with haze, really bad viewing conditions, including scatter. I use really low scatter equipment, but it doesn't matter at the moment.  Particles in the air scatter light, made worse by planets low elevation. The 82ES ep's have more scatter than your (vg) orthos. A 12.5mm Circle T is a mainstay in my TSA120, for some reason I really like this eyepiece.

To minimize effects use your great 100mm f9 with orthos- one thing what diagonal do you use? I had an expensive poor one that cause massive scatter in a 90mm APO years ago. The SW mirror diag I have is vg- but maybe check "straight" through?

I never thought about smoke from wild fires.  I looked the information up and - there is a lot of smoke in the atmosphere and it is most likely the problem.  Thank you for your help.

My diagonals, both were supplied by the manufacturer, 1 1/4 for the Meade and 2" for the Sky-Watcher.

[Arty68]

2 hours ago, Louis D said:

Don't forget the effect all those optical elements in you SCT can have on scatter as well.  There's also the possibility of poorly controlled stray light seeping around the baffles.  Were the views equivalent between the frac and the SCT as far as stray light?

Try removing your diagonal and then view straight through to eliminate the possibility that it is adding scatter.  Dielectric diagonals tend to scatter more than silver or prism diagonals.

Make sure your field lenses on your eyepieces are clean.  Being closer to the field stop, any grime there has an outsized impact on light scatter.  Use a super bright tactical flashlight to look for any greasy film buildup on them.

Move Saturn around the field of the eyepiece and look for changes in the view.  This can help you pinpoint where the actual problem lies.

Light scatter does not change when I move my eye around the eyepiece.  Both diagonals are silver.  The lenses are relatively clean, only a very slight amount of dust particles, I keep they covers on them when not in use.  You present some good ideas.   It looks as though the problem is smoke from wild fires, something I did not take into consideration.

[Arty68]

5 hours ago, John said:

The lowest levels of light scatter that I have experienced with eyepieces have come from HD orthos such as Baader Genuine Orthos, University Optics HD orthos and Fujiyama orthos and also the TMB Supermonocentric.

The more complex designs (including the premium ones) do seem to introduce a little additional light scatter in return for their wider fields and longer eye relief. The Pentax XW range seem to control this well for a more complex design though. I believe the Tele Vue Delites are very good as well.

Of course keeping your scope optics free of dust / condensation and well cooled and collimated helps minimise scatter as well.

The low altitude of Jupiter and Saturn (at least where I am in the UK) does not help with the visiblity of these finer details either. Instability of the image can vary hugely moment to moment so patience and time at the eyepiece is required more then ever to catch those short golden moments of clarity.

This reviewer has attempted to quantify the effects of light scatter with a number of planetary eyepieces:

http://www.wlcastleman.com/equip/reviews/5mm_EP/5mm_ep.html

 

It looks like the most likely culprit is wild fires.

[jetstream]

1 hour ago, Arty68 said:

I never thought about smoke from wild fires.  I looked the information up and - there is a lot of smoke in the atmosphere and it is most likely the problem.  Thank you for your help.

Your welcome, I'm north of you up in north west Ontario where we have over 100 forest fires burning, not including the ones in eastern Manitoba. Right now as I look across the lake a thick haze is present and there is an air quality warning. T storms tomorrow and I hope no more are started from the lightning.

[Louis D]

I was just up in Michigan and Indiana a few weeks ago, and the skies were eerily hazy despite there not being a single cloud in the sky.  The moon was red when the haze thinned out.  Once a front blew through, it massively cleared up the sky.  The weathermen up there were ascribing the haze to western forest fire smoke.

Try again after another northern front blows through and see if the scatter issue improves.

Down here in Texas, we get haze from Saharan dust and Central American farm fires in the spring before planting season.  Luckily, the western forest fire smoke is staying north of us for now.

[John]

Interesting to hear that forest fires can cause this sort of issue.

It's not something I've come across here in the UK so my mind went to other possible causes.

Sounds like it may well be behind your light scatter problem though.

 

Edited August 4, 2021 by John

[Voyager 3]

11 hours ago, Louis D said:

I was just up in Michigan and Indiana a few weeks ago, and the skies were eerily hazy despite there not being a single cloud in the sky.  The moon was red when the haze thinned out.  Once a front blew through, it massively cleared up the sky.  The weathermen up there were ascribing the haze to western forest fire smoke.

Try again after another northern front blows through and see if the scatter issue improves.

Down here in Texas, we get haze from Saharan dust and Central American farm fires in the spring before planting season.  Luckily, the western forest fire smoke is staying north of us for now.

Are you kidding me ? Sahara desert's dust in USA ?! That's more than 6000km ! I've heard these dusty particles move and cause problems for the southern European countries . I have also heard Gobi and Taklamakan deserts' dust in India and Pakistan but these are wimpy compared to this .. 

Edited August 5, 2021 by Voyager 3

[Ags]

I am surprised too. I would have that that hot and dry part of the USA could be self-sufficient in dust and wouldn't need to import any from Africa!

[Louis D]

7 hours ago, Voyager 3 said:

Are you kidding me ? Sahara desert's dust in USA ?! That's more than 6000km ! I've heard these dusty particles move and cause problems for the southern European countries . I have also heard Gobi and Taklamakan deserts' dust in India and Pakistan but these are wimpy compared to this .. 

Yes, surprisingly large amounts of Saharan dust travels across the Atlantic and ends up over the southern US.   Western Africa also sends us their low pressure systems that develop into hurricanes.

4 hours ago, Ags said:

I am surprised too. I would have that that hot and dry part of the USA could be self-sufficient in dust and wouldn't need to import any from Africa!

The eastern part of the state is swamp-like while the western part is close to being a desert.  In between where I live is more temperate in rainfall (about 32 inches a year), but still hot and humid.  Because the ground is covered in some sort of growth just about everywhere in the deserts of the Southwest, we don't get much dust from them.  The most dust comes not from the undisturbed desert but from the Panhandle (northern Texas) and nearby surroundings because they plow up the high plains and irrigate them with groundwater.  When winter fronts blow in from the northwest, we sometimes get agricultural dust from there between growing seasons.

[jetstream]

8 hours ago, Voyager 3 said:

Sahara desert's dust in USA ?

Thats what the fertile soil of the Brazilian rainforest is built on ...IMHO

It can definitely hit the USA.

[Don Pensack]

North America smoke map:

https://fire.airnow.gov/?lat=34.0778841&lng=-118.491626&zoom=10

[jetstream]

Yeah, fires are all over the place. Got 9 within 40 miles of me, in Quetico.

https://www.lioapplications.lrc.gov.on.ca/ForestFireInformationMap/index.html?viewer=FFIM.FFIM

[Louis D]

41 minutes ago, Don Pensack said:

North America smoke map:

https://fire.airnow.gov/?lat=34.0778841&lng=-118.491626&zoom=10

Yep, smoke is finally supposed to be making it's way south to Texas.  I haven't noticed any strong effects from it on the sky, though.