115 replies to this topic

[realflow100]

Naked eye limit 4.7 to 4.92 with extreme effort. even with the use of averted vision.

 

Andromeda is easy to find as well as orion nebula. but ive never ever spotted triangulum. theres just nothing there. I havent even been able to find the 4-star square around where triangulum is. made of some magnitude 8.1 to 9.25 stars

 

The dimmest deep sky object ive seen with my telescope is probably m32 or m81 with extreme effort in averted vision. and they are almost entirely invisible already. barely even detectable for brief moments.

The background sky is so bright I have to switch back and forth between each eye which causes a big dark area in my vision the same size as the eyepieces field of view temporarily when i look away from the eyepiece. Theres basically no dark adaptation at all.
 

I'm using a 70mm F6 refractor. with a 40mm plossl eyepiece. (Tried 20mm. it was no better and field of view is smaller so I stuck with the 40mm for wider field of view)

 

No chance of seeing it in binoculars. though andromeda is still easily spotted in binoculars as a dim glowy dot.

 

Is this within expectations for being unable to see m33 in b7?

Orion nebula is very dim and almost invisible. even with the aid of my UHC filter. its just a dim grey fuzzy glow with no features with a couple somewhat indistinct stars in the middle of the core.

[cookjaiii]

Same here, but with a 5" f/5 Newtonian.  I have to go to a darker site to see it.

[pyrasanth]

I image M33 from my Bortle 7 home site and even through the cameras continuous capture the subs are faint.

 

M33 whilst being bright on paper has that magnitude spread across a wide area- it will be faint.

[John Tucker]

It's not real bright.  You might have more luck with a faster scope like an F4 Newt, I don't think a lot of people do visual astronomy at F6.  

 

The other possibility to to do electronically assisted astronomy with a little camera and stack images.  Makes it a lot easier to distinguish the image from the light pollution.  I believe there is an EAA forum on CN. 

[lee14]

It's a very low surface brightness object. Under moderately light polluted skies I could only obtain it by star hopping. Undetectable in the finder, it was barely discernible in an 8 inch SCT. However, under the dark skies of the Sonoran Desert it was an easy naked eye object, and spectacular in 10 x 50 binoculars.

 

Lee

[MattT]

M33 is considered a test object for sky darkness. Sorry to say - your sky is failing the test!

 

It's a pretty high bar, tbh. Even from a site that I consider decently dark - limiting mag on a good night is 6.4 - if there's even a trace of haze in the air M33 can disappear, even though I've seen it many times and know right where to look.

 

A wider field 2" eyepiece helps with big faint targets like M33, to encompass enough sky so that you can see a ring of (very slightly) darker background sky around the object.

Edited by MattT, 12 December 2021 - 12:13 PM.

[DAG792]

M33 is almost impossible under those conditions. If your NELM is approaching 5 then it should be doable, but just barely, on nights of excellent transparency. It will still be very easy to miss, especially in that size of scope.

 

The best way to see it is to move to a darker sky. Under a truly dark sky, M33 is visible naked-eye and very easy in a telescope of ANY aperture. However, even a little light pollution greatly increases the difficulty of seeing it. 

[MarMax]

I can not see M33 either from my Bortle 7.5ish to 8 location (SQM-L 18.43) with my C11 visually. Even when doing EAA from home I don't get much.

 

Here is M33 EAA style from home. This is 32 minutes total with a Zenithstar 61mm refractor and QHY183C camera and there is still not much to see.

 

 

[LDW47]

Naked eye limit 4.7 to 4.92 with extreme effort. even with the use of averted vision.

 

Andromeda is easy to find as well as orion nebula. but ive never ever spotted triangulum. theres just nothing there. I havent even been able to find the 4-star square around where triangulum is. made of some magnitude 8.1 to 9.25 stars

 

The dimmest deep sky object ive seen with my telescope is probably m32 or m81 with extreme effort in averted vision. and they are almost entirely invisible already. barely even detectable for brief moments.

The background sky is so bright I have to switch back and forth between each eye which causes a big dark area in my vision the same size as the eyepieces field of view temporarily when i look away from the eyepiece. Theres basically no dark adaptation at all.
 

I'm using a 70mm F6 refractor. with a 40mm plossl eyepiece. (Tried 20mm. it was no better and field of view is smaller so I stuck with the 40mm for wider field of view)

 

No chance of seeing it in binoculars. though andromeda is still easily spotted in binoculars as a dim glowy dot.

 

Is this within expectations for being unable to see m33 in b7?

Orion nebula is very dim and almost invisible. even with the aid of my UHC filter. its just a dim grey fuzzy glow with no features with a couple somewhat indistinct stars in the middle of the core.

Don't worry I had a hard time in my Bortle 1 skies but maybe in my case it was the background stars. In my Bortle 4-5 backyard it is hopeless and don't let anyone tell you different, its another M101 only worse.

[Jon Isaacs]

Is this within expectations for being unable to see m33 in b7?

Orion nebula is very dim and almost invisible. even with the aid of my UHC filter. its just a dim grey fuzzy glow with no features with a couple somewhat indistinct stars in the middle of the core.

 

 

M33 has a visual brightness of magnitude 5.7.  That means it's total light output is equal to that of a magnitude 5.7 stars.  But M33 is very large, it covers more than three times the area of the moon.  It's very dim.. 

 

The intensity of the light from a deep sky object is measured by it's surface brightness, the amount of light per unit area.  The normal units are magnitudes per square arc-second (mpsas)

 

Under Bortle 7 skies, the sky glow is more than 4 magnitudes brighter than M33, that's 40 times brighter.  The eye is very good at seeing low contrast objects but that is too much.. 

 

This article by Tony Flanders explains all this (and more) very nicely including a discussion of M33.

 

https://tonyflanders...ace-brightness/

 

Jon

[LDW47]

M33 is almost impossible under those conditions. If your NELM is approaching 5 then it should be doable, but just barely, on nights of excellent transparency. It will still be very easy to miss, especially in that size of scope.

 

The best way to see it is to move to a darker sky. Under a truly dark sky, M33 is visible naked-eye and very easy in a telescope of ANY aperture. However, even a little light pollution greatly increases the difficulty of seeing it. 

My skies were Bortle 1, SQM-L 22.0 every clear nite at my remote camp but naked eye, I doubt it and I knew exactly where it was. And I spent years trying and only faint glances, with my f5 to f11.4 scopes and some pretty decent eps of various sizes, M101 was like the moon in comparison, lol.

Edited by LDW47, 12 December 2021 - 01:39 PM.

[payner]

I have observed M 33 with 5" and greater aperture from my Bortle 5 skies. It is difficult and requires good dark adaptation and truly transparent conditions. You'll also want to use a shorter focal length eyepiece to aid in maximizing contrast.

[sevenofnine]

I guess it was my lucky night  when I saw M33 with 15x70 binoculars under a Bortle 3-4 sky. It looked like a very large and faint smoke ring 

Edited by sevenofnine, 12 December 2021 - 02:36 PM.

[spereira]

Moving to DSO.

 

smp

[maroubra_boy]

As has been mentioned, M33 is low surface brightness. But what does this mean when its magnitude is listed as mag 5.7? Shouldn't it still be easy to see,?

Short answer, no.

Thing is the magnitude listing of a DSO is for all its light being in a single star-like spot. But DSO's have an area, so this star-like spot needs to be spread out. M33 is a large object, with more than twice the surface area of the full Moon. So that mag 5.7 light will be spread out VERY thin.

I've seen M33 naked eye from my Bortle 4 site. This doesn't happen often for me for two reasons:

1, it is never very high in the sky from my 34° South latitude;

2, Transparency needs to be very good.

If transparency is lacking it doesn't matter how dark your sky is, you will either struggle to see it or not see it at all.

M33 is one of the celestial landmarks I have by which I gauge the quality of transparency. If I can see M33 naked eye then transparency is excellent! Simple as that 👍. No ifs, no buts.

I have also not seen M33 from Bortle 2 skies, telling me transparency was not good.

Transparency will dictate your chances of seeing detail in galaxies. The transparency gauge doesn't stop at naked eye level. Here is the next level up which is telescopic - what details can you see? For me it is how easily or not can I see the spiral arms of certain galaxies. If I struggle to see the arms of these galaxies, then transparency at the micro level is short.

I have a whole bunch of celestial landmarks I use for this across the year. I then adapt my observing session to best suit conditions.

Site selection has a big part in this. Being able to identify the conditions that make one site better for astro than another will go a long way to having transparency routinely better than below par. If M33 is rarely a naked eye object from anything from Bortle 4 and better, then your site is not producing the goods you are expecting.

Alex.

[LDW47]

As has been mentioned, M33 is low surface brightness. But what does this mean when its magnitude is listed as mag 5.7? Shouldn't it still be easy to see,?

Short answer, no.

Thing is the magnitude listing of a DSO is for all its light being in a single star-like spot. But DSO's have an area, so this star-like spot needs to be spread out. M33 is a large object, with more than twice the surface area of the full Moon. So that mag 5.7 light will be spread out VERY thin.

I've seen M33 naked eye from my Bortle 4 site. This doesn't happen often for me for two reasons:

1, it is never very high in the sky from my 34° South latitude;

2, Transparency needs to be very good.

If transparency is lacking it doesn't matter how dark your sky is, you will either struggle to see it or not see it at all.

M33 is one of the celestial landmarks I have by which I gauge the quality of transparency. If I can see M33 naked eye then transparency is excellent! Simple as that . No ifs, no buts.

I have also not seen M33 from Bortle 2 skies, telling me transparency was not good.

Transparency will dictate your chances of seeing detail in galaxies. The transparency gauge doesn't stop at naked eye level. Here is the next level up which is telescopic - what details can you see? For me it is how easily or not can I see the spiral arms of certain galaxies. If I struggle to see the arms of these galaxies, then transparency at the micro level is short.

I have a whole bunch of celestial landmarks I use for this across the year. I then adapt my observing session to best suit conditions.

Site selection has a big part in this. Being able to identify the conditions that make one site better for astro than another will go a long way to having transparency routinely better than below par. If M33 is rarely a naked eye object from anything from Bortle 4 and better, then your site is not producing the goods you are expecting.

Alex.

Tell that to my SQM-L and my eyeballs.

[realflow100]

transparency is always very bad to poor across most of the year here.

Its maybe decent transparency 1 time out of the whole year if im lucky.

South carolina is just about the worst place for doing any observing! especially considering im right inside the edge of a big city.

 

I have a 4" reflector telescope and I see absolutely nothing new in it compared to my 70mm refractor. pretty much the same amount of stars too. Nothing fainter than I could see in the 70mm

if anything the view is much worse in the reflector because the glare is INSANE and very bad contrast.

my 70mm refractor gives me way better contrast due to the flocking i put in it and baffling. so the views actually cleaner.

No triangulum in either telescope.

I cant even star hop to find it at low power like 11x. 7mm exit pupil. Theres just nothing to star hop with. if I try to start from the "tip" of the triangulum constellation. and go up from there towards mirach. theres just nothing there. very occasional very faint dim almost invisible stars. Not enough to star hop with.

Edited by realflow100, 12 December 2021 - 06:48 PM.

[maroubra_boy]

Tell that to my SQM-L and my eyeballs.

Yep, I am.

What is it that you are questioning?

If transparency is good for you then you have the best situation. Where is the problem? I don't follow your quip.

[LDW47]

Yep, I am.

What is it that you are questioning?

If transparency is good for you then you have the best situation. Where is the problem? I don't follow your quip.

Its not a problem but I am under conditions, as per my post, that you would probably find it hard to get much better but as I mentioned it is very difficult to catch it in my variety of scopes other than very faint views, sometimes. This is a little different than what you are espousing but its no problem in the least, you are one lucky astronomer ! I never realized it was that easy to view.  And thus my statement. No problem in the least, I'm envious I guess especially seeing it naked eye.

Edited by LDW47, 12 December 2021 - 07:19 PM.

[weis14]

Like others have said, M33 is a very difficult target in light polluted skies.  I can't see it from my Bortle 7/8 back yard unless it is an exceptional night with no moon and extremely good transparency.  I've found that scope size matters less than you'd think.  At my dark site, there have been nights when it wasn't visible in my CFF160, but others where it was a naked eye object and magnificent in my Stowaway.

 

It is a very good EAA target though.  One of about 10 that I've ever done and you can get amazing detail if you are into that sort of thing (I found that I'm not much of a camera guy).

 

It's not real bright.  You might have more luck with a faster scope like an F4 Newt, I don't think a lot of people do visual astronomy at F6.  

 

The other possibility to to do electronically assisted astronomy with a little camera and stack images.  Makes it a lot easier to distinguish the image from the light pollution.  I believe there is an EAA forum on CN. 

Someone will probably chime in with a better scientific reason why, but faster scopes have no appreciable impact on views put up by a scope for visual astronomy, except that a given eyepiece will have a lower magnification and, therefore, a higher corresponding FOV than in a scope with a longer focal length.  A lot of visual purists actually want longer focal length scopes due to the depth of focus and the ability to get higher magnifications from longer focal length eyepieces. One of the most popular visual scopes of the last 50 years, the venerable 8" SCT, is a native f/10 instrument.  

 

Of course many people, including me, also prefer fast scopes because they are smaller and more portable than long focus refractors, but you can't gather light quicker with your eyes using a faster scope like you can with a camera.  Eyes don't work that way.

[Napp]

M33 is usually a better binocular object than telescope object.  I have observed it many times from a Bortle 3 site with binoculars.  On the best nights it is a faint naked eye fuzzy.  On those very good nights with M33 high in the sky I can see structure in the spiral arms with my 16 inch DOB.  But most nights it is hard to recognize you are seeing it in a scope due to its large size and low surface brightness.

[John Tucker]

Like others have said, M33 is a very difficult target in light polluted skies. I can't see it from my Bortle 7/8 back yard unless it is an exceptional night with no moon and extremely good transparency. I've found that scope size matters less than you'd think. At my dark site, there have been nights when it wasn't visible in my CFF160, but others where it was a naked eye object and magnificent in my Stowaway.

It is a very good EAA target though. One of about 10 that I've ever done and you can get amazing detail if you are into that sort of thing (I found that I'm not much of a camera guy).

Someone will probably chime in with a better scientific reason why, but faster scopes have no appreciable impact on views put up by a scope for visual astronomy, except that a given eyepiece will have a lower magnification and, therefore, a higher corresponding FOV than in a scope with a longer focal length. A lot of visual purists actually want longer focal length scopes due to the depth of focus and the ability to get higher magnifications from longer focal length eyepieces. One of the most popular visual scopes of the last 50 years, the venerable 8" SCT, is a native f/10 instrument.

Of course many people, including me, also prefer fast scopes because they are smaller and more portable than long focus refractors, but you can't gather light quicker with your eyes using a faster scope like you can with a camera. Eyes don't work that way.

Doesn’t fit my experience at all. Look up at night in a light polluted sky. How many stars do you see? Now do it again with a pair of binoculars and then with an F4 Newt.

Or for that matter, try reading faded print under dim light vs under bright light. The eye is better able to detect contrast when the signal is within the normal range of our visual capabilities.

[psy_zju]

M33 is considered a test object for sky darkness. Sorry to say - your sky is failing the test!

 

It's a pretty high bar, tbh. Even from a site that I consider decently dark - limiting mag on a good night is 6.4 - if there's even a trace of haze in the air M33 can disappear, even though I've seen it many times and know right where to look.

 

A wider field 2" eyepiece helps with big faint targets like M33, to encompass enough sky so that you can see a ring of (very slightly) darker background sky around the object.

I usually go to bortle 3 for viewing and had tried to find M33 by naked eyes. I am not sure if I see it or not, most likely not. What does it look like by naked eyes, a faint disc or a faint dot?

 

Thanks

[Napp]

I usually go to bortle 3 for viewing and had tried to find M33 by naked eyes. I am not sure if I see it or not, most likely not. What does it look like by naked eyes, a faint disc or a faint dot?

 

Thanks

I can see M33 naked eye at my Bortle 3 site only on nights with very good transparency with M33 high in the sky.  It looks like a small, faint fuzzy patch.

[maroubra_boy]

M33 is considered a test object for sky darkness. Sorry to say - your sky is failing the test!

 

Not as much as a test of transparency.

 

As I noted in my first post (No. 15) I have been able to see it naked eye from Bortle 4 skies, and also not seen it from Bortle 2 skies.  Transparency is the key, not necessarily how dark.  Dark is important by without transparency you ain't gonna see M33 either.

 

Alex.