65 replies to this topic

[davidgmd]

Here's a thing, sometimes a DSO can be too bright. If it has bright areas, that can spoil your sensitivity to fainter areas, similar to a bright star beside a fainter object.

 

With globulars a bright centre can interfere with seeing fainter stars as you move outwards. For M13 in particular, I can see stars at the centre, dark lanes as well as outer detail in my 12". While I am very happy with that, I am curious how much brighter and more detail a 14" or 16" would show. M13 is my test DSO and overall favourite, I have recently added another 12" F5 to my Dobs flock.

  
But with a smaller aperture all the stars will dim, which I suspect would offset (some of/all of/more than?) the gain in dark adaptation. No free lunch?

[CrazyPanda]

Here's a thing, sometimes a DSO can be too bright. If it has bright areas, that can spoil your sensitivity to fainter areas, similar to a bright star beside a fainter object.

 

I have that problem with M42 in my 14.7" when comparing eyepieces and looking for the faintest areas.

 

I tried comparing my older 35 Pan to a new 35 MOP and newer 34mm Svbony 72 degree eyepiece.

 

In doing so, I realized it was kind of a pointless exercise because the nebula was bright enough to affect my dark adapted vision. Every time I switched eyepieces, the view would look brighter than the previous eyepiece.

 

Simply looking away from the eyepiece for 15 seconds to fetch a new one would affect continuity of my dark adaptation.

[BGazing]

I have that problem with M42 in my 14.7" when comparing eyepieces and looking for the faintest areas.

 

I tried comparing my older 35 Pan to a new 35 MOP and newer 34mm Svbony 72 degree eyepiece.

 

In doing so, I realized it was kind of a pointless exercise because the nebula was bright enough to affect my dark adapted vision. Every time I switched eyepieces, the view would look brighter than the previous eyepiece.

 

Simply looking away from the eyepiece for 15 seconds to fetch a new one would affect continuity of my dark adaptation.

M42 is for the end of a session, it pretty much does away with one's night vision. M8 is fairly close...

[25585]

I find M31 can be too bright when looking for M101. M13 has a smaller globular nearby, which is challenging as well.

 

Of course the big bright star near the Horsehead nebula must be a nuisance (apart from as a guide star).

[CHASLX200]

M42 is for the end of a session, it pretty much does away with one's night vision. M8 is fairly close...

Never hurt my eyes.

[Starman1]

Never hurt my eyes.

Try looking at the center of the Orion Nebula and then looking up at the sky.  You'll have a dark area in the center of your vision, indicating a loss of night vision.

It's one of very few objects that can affect your night vision.

[Starman1]

I find M31 can be too bright when looking for M101. M13 has a smaller globular nearby, which is challenging as well.

 

Of course the big bright star near the Horsehead nebula must be a nuisance (apart from as a guide star).

I think you mean "M13 has a small galaxy nearby", because the nearest globular to M13 is M92, and it is quite bright.

[TayM57]

Try looking at the center of the Orion Nebula and then looking up at the sky.  You'll have a dark area in the center of your vision, indicating a loss of night vision.

It's one of very few objects that can affect your night vision.

Chas pretty much only observes planets so I would think being dark adapted is low on his list of considerations, if it is even on there to begin with.

[RichA]

Here is an interesting question.

 

My most frequently used magnifications fall between 150x and 200x with my 12.5" scope, though an all-night range will be larger.

This is because:

•  

Hopefully, out of this people will draw one key conclusion:  That larger scopes are BETTER in bad skies because at least you can SEE something.  So many dummies have said "no point in getting a big scope under bad skies."  

Edited by RichA, 17 May 2025 - 01:36 PM.

[CHASLX200]

Hopefully, out of this people will draw one key conclusion:  That larger scopes are BETTER in bad skies because at least you can SEE something.  Some many dummies have said "no point in getting a big scope under bad skies."  

Deep sky looks bad in any scope in my yard.  18" looks bland on globs vs a 8" in dark skies. Like looking at a TV with bad black levels. No snap and pop with a lack of contrast. But i got the dream seeing for planets at over 1000x in a 18" for planets.  A 18 to 20" F/6 Dob would be perfect if i had a bigger house.

[azure1961p]

Try looking at the center of the Orion Nebula and then looking up at the sky.  You'll have a dark area in the center of your vision, indicating a loss of night vision.

It's one of very few objects that can affect your night vision.

True with my 8.  Oh it's dazzling to see that beautiful green wedge but yes, it's infringing on scotopic vision for the view. No free lunch!

 

Pete

[azure1961p]

I think you mean "M13 has a small galaxy nearby", because the nearest globular to M13 is M92, and it is quite bright.

And it's a cool little galaxy, star involved! It's feels like a bonus for the effort to locate and view the Great Glob.  Once I learned of it it became standard fare when in the neighborhood.  With the 8 anyway, never bothered with the C6 and certainly not with the frac lol

 

 

Pete

 

Pete

[Starman1]

And it's a cool little galaxy, star involved! It's feels like a bonus for the effort to locate and view the Great Glob.  Once I learned of it it became standard fare when in the neighborhood.  With the 8 anyway, never bothered with the C6 and certainly not with the frac lol

 

 

Pete

 

Pete

You're referring to NGC6207, a nice little galaxy visible in small apertures.

 

With 12" or larger, there is a small galaxy actually in the outskirts of M13: IC4617.

It's a little off the line from M13 to NGC6207 and about halfway from the center of M13 to 6207

1.2' x 0.4', so it's tiny.

Here is a pic:

https://theskylive.c...y/ic4617-object

[Procyon]

You're referring to NGC6207, a nice little galaxy visible in small apertures.

 

With 12" or larger, there is a small galaxy actually in the outskirts of M13: IC4617.

It's a little off the line from M13 to NGC6207 and about halfway from the center of M13 to 6207

1.2' x 0.4', so it's tiny.

Here is a pic:

https://theskylive.c...y/ic4617-object

IC 4617  Will look for both in the 11". I wonder if I'll find 25585's hidden little globular somewhere around there. 

 

https://en.wikipedia.org/wiki/IC_4617

 

Edited by Procyon, 17 May 2025 - 01:40 PM.

[RichA]

Deep sky looks bad in any scope in my yard.  18" looks bland on globs vs a 8" in dark skies. Like looking at a TV with bad black levels. No snap and pop with a lack of contrast. But i got the dream seeing for planets at over 1000x in a 18" for planets.  A 18 to 20" F/6 Dob would be perfect if i had a bigger house.

I'd rate major urban skies to country skies as an 11" scope being on par maybe with a 4-5," that is the price people pay for living in big cities.  But, if you observe deepsky, a big scope gives you something, especially with narrow band nebula filters.

[Procyon]

I'd rate major urban skies to country skies as an 11" scope being on par maybe with a 4-5," that is the price people pay for living in big cities.  But, if you observe deepsky, a big scope gives you something, especially with narrow band nebula filters.

I can see 11 mag Galaxies and 12-13 mag PN's, especially the fast blinking types, with an 11" SCT from my backyard, say in an 8.5 bortle zone, probably closer to 8 because the backyard is connected to a small forest nearby. With the 8 Edge I had though, no, that's tough. I'd say an 8" would make a better comparison.

 

PS> I observe towards and near zenith 90% of the time.

Edited by Procyon, 17 May 2025 - 02:21 PM.