What aperture to see spiral arms in galaxies?

[paulastro]

On 03/08/2023 at 08:54, Carbon Brush said:

@Zermelo has raised an important point.
As we age our ability to discern detail at low light level declines considerably.
I was told by an optician that by age 60 we have 1/3 the night vision of age 20.
So aperture will brighten an object to help compensate for old eyes.

 

I'm even more pleased I've bought a Seestar having read this 😅.

[mikeDnight]

On 29/03/2024 at 20:04, paulastro said:

I'm even more pleased I've bought a Seestar having read this 😅.

The Seestar is obviously giving you a lot of enjoyment Paul, and it's nice to see the images it produces,  but it's not the same as seeing something for yourself through an eyepiece.  

 I first saw the spiral structure in M51 visually back in 2001 when using a 6" Helios F8 achromat. I was out of town and at a dark site and so was well dark adapted, but it struck me that if I could see the spiral and the bridge, why did it not get discovered sooner as it wasn't difficult, but neither was it immediately obvious.

 

Edited March 31 by mikeDnight

[John]

1 hour ago, mikeDnight said:

The Seestar is obviously giving you a lot of enjoyment Paul, and it's nice to see the images it produces,  but it's not the same as seeing something for yourself through an eyepiece.  

 I first saw the spiral structure in M51 visually back in 2001 when using a 6" Helion F8 achromat. I was out of town and at a dark site and so was well dark adapted, but it struck me that if I could see the spiral and the bridge, why did it not get discovered sooner as it wasn't difficult, but neither was it immediately obvious.

 

My 1st experience of seeing, with my eye at an eyepiece, spiral galaxy structure was M51 with a Skywatcher 12 inch dob at my first SGL star party which must have been around 13 years ago now. Saw my 1st supernova with that scope as well. Magical memories 🙂

A couple of years later the same target with a 20 inch David Lukehust dob gave such an "in my face" view of the spiral structure that it's still engraved on my memory.

 

 

[paulastro]

2 hours ago, mikeDnight said:

The Seestar is obviously giving you a lot of enjoyment Paul, and it's nice to see the images it produces,  but it's not the same as seeing something for yourself through an eyepiece.  

 I first saw the spiral structure in M51 visually back in 2001 when using a 6" Helion F8 achromat. I was out of town and at a dark site and so was well dark adapted, but it struck me that if I could see the spiral and the bridge, why did it not get discovered sooner as it wasn't difficult, but neither was it immediately obvious.

 

Mike, I do know an image is not the same as looking at the same thing through an eyepiece!  Indeed I saw the spiral structure of M51 well before you did in 2001!   I'm surprised you felt the need to point this out to me, or what purpose it served?

In case you are not aware, images are not just only about eliciting enjoyment, but they can be used to learn about the subject and monitor changes and developments in objects which you cannot see through any available telescope you may have.  

[mikeDnight]

10 hours ago, paulastro said:

Mike, I do know an image is not the same as looking at the same thing through an eyepiece!  Indeed I saw the spiral structure of M51 well before you did in 2001!   I'm surprised you felt the need to point this out to me, or what purpose it served?

In case you are not aware, images are not just only about eliciting enjoyment, but they can be used to learn about the subject and monitor changes and developments in objects which you cannot see through any available telescope you may have.  

 I commented simply because the OP asked the question "What aperture to see spiral arms in galaxies? Then M51 began to play a major part in the following posts. I mentioned my first observation of the spiral structure in 2001 because I was using a smallish aperture and felt it was of interest as it took a significantly larger telescope to make the initial discovery, which could lead some to believe only large apertures will reveal the arms and bridge. Sharing my experience with a 6" shows that smaller aperture scopes can reveal this detail, and that may be encouraging to some here on SGL!  What aperture did you first see the spiral arms in Paul?   I'm not at all surprised that you saw it before me, as you are much older than I am and you have been involved in the hobby much longer. I have a Box Brownie photo of you stood alongside an old 2.25" refractor in the 1960's to prove this. I was still in infant school at that time!   Astronomy was on my mind though, and after seeing a first quarter Moon from my bedroom window, I set off on my very first astronomical adventure. I put on my coat and walked along street after street after street in my attempt to get underneath that 1st quarter Moon. My suspicion was that if I could get beneath the Moon at 1st quarter,  it would look like a dairylea cheese triangle. I'm still not convinced it doesn't!  (Cheese - Moon - Dairylea, it all makes perfect sense to a six year old!)  Anyhow, I ran out of streets and the Moon had got no closer, then I realised I was a long way from home and set off back disheartened. It would be another twelve years before the astro bug bit!

  Back to the original OP's question; Visually, M81, M33, and M31 are others under dark transparent skies have revealed spiral structure to me, even in apertures as small as 4" (3.9" in the case of my FC100DC & DZ). I even feel that a 4" would begin to reveal the spiral structure of M51 under the right sky conditions. I haven't bothered to check, but I'd imagine Walter Scott Houston, Steve Omeara, and other observers using 4" refractors may very well have seen such detail.

[paulastro]

1 hour ago, mikeDnight said:

 I commented simply because the OP asked the question "What aperture to see spiral arms in galaxies? Then M51 began to play a major part in the following posts. I mentioned my first observation of the spiral structure in 2001 because I was using a smallish aperture and felt it was of interest as it took a significantly larger telescope to make the initial discovery, which could lead some to believe only large apertures will reveal the arms and bridge. Sharing my experience with a 6" shows that smaller aperture scopes can reveal this detail, and that may be encouraging to some here on SGL!  What aperture did you first see the spiral arms in Paul?   I'm not at all surprised that you saw it before me, as you are much older than I am and you have been involved in the hobby much longer. I have a Box Brownie photo of you stood alongside an old 2.25" refractor in the 1960's to prove this. I was still in infant school at that time!   Astronomy was on my mind though, and after seeing a first quarter Moon from my bedroom window, I set off on my very first astronomical adventure. I put on my coat and walked along street after street after street in my attempt to get underneath that 1st quarter Moon. My suspicion was that if I could get beneath the Moon at 1st quarter,  it would look like a dairylea cheese triangle. I'm still not convinced it doesn't!  (Cheese - Moon - Dairylea, it all makes perfect sense to a six year old!)  Anyhow, I ran out of streets and the Moon had got no closer, then I realised I was a long way from home and set off back disheartened. It would be another twelve years before the astro bug bit!

  Back to the original OP's question; Visually, M81, M33, and M31 are others under dark transparent skies have revealed spiral structure to me, even in apertures as small as 4" (3.9" in the case of my FC100DC & DZ). I even feel that a 4" would begin to reveal the spiral structure of M51 under the right sky conditions. I haven't bothered to check, but I'd imagine Walter Scott Houston, Steve Omeara, and other observers using 4" refractors may very well have seen such detail.

Mike, you still didn't answer my question in my first paragraph as to why you thought I needed to be told the difference between an image and a visual observation - which has nothing to do with the question asked about what aperture it needs to see spiral structures in galaxies.   I thought it was patronising and unecessary.

 

[Stu]

1 hour ago, paulastro said:

Mike, you still didn't answer my question in my first paragraph as to why you thought I needed to be told the difference between an image and a visual observation - which has nothing to do with the question asked about what aperture it needs to see spiral structures in galaxies.   I thought it was patronising and unecessary.

 

Gentlemen, you are supposed to be friends, can you please behave like it!

Thank you.

Stu

[michael.h.f.wilkinson]

I have readily seen the spiral structure in M51 from a very dark site (Bortle 1) with my 8" SCT, but it is very hard from my Bortle 4-5 garden. A 16" RC at work can readily pick up the spiral arms from the outskirts of the city of Groningen (Bortle 6-7 I would guess). I should add that the view from the dark site in Southern France with an 8"was more impressive than what the 16" could do from the city. Aperture is apparently less important than sky background. With M101 things are curiously different. Due to the low surface brightness I could not really see the arms  from a fairly dark site (Bortle 2-3) with my C8, but as my eye moved over the FOV, I got the impression of rotating motion, which is a common illusion when looking at spiral patterns. Using Olly Penrice's 20" Dob (Sir Isaac) from his beautifully dark site made the spiral arms stand out very clearly indeed.