What aperture to see spiral arms in galaxies?

[Mandy D]

24 minutes ago, bosun21 said:

Why would the 300PDS be lighter? It’s 300mm longer  and 50mm wider 🤔.

300 mm longer and 50 mm wider than what? What are we comparing? I'm lost.

[Jim Smith]

Thanks for all of the suggestions and offers of help. I will probably keep it in a garden storage box about 12 feet from where I will set it up so there shouldn't be too much of a struggle. However I've decided to go for 10" instead of 12" to be on the safe side. I can probably forget those spiral arms unless I get some unusually good conditions.

[bosun21]

11 minutes ago, Mandy D said:

300 mm longer and 50 mm wider than what? What are we comparing? I'm lost.

Than your 250PX

[Mandy D]

1 minute ago, bosun21 said:

Than your 250PX

Oh, I see the confusion, now. No, I was comparing it with my 300PDS.

[bosun21]

Just now, Mandy D said:

Oh, I see the confusion, now. No, I was comparing it with my 300PDS.

Now I'm confused. You said you thought that the 300PDS would be lighter than the 250PX. I asked why when the 300PDS is 300mm longer and 50mm wider 

[Mandy D]

Just now, bosun21 said:

Now I'm confused. You said you thought that the 300PDS would be lighter than the 250PX. I asked why when the 300PDS is 300mm longer and 50mm wider 

Perhaps I phrased it badly. You should probably read my earlier comment where I was comparing the 300PDS with a longer focal length 12 inch newt that was mentioned by someone else. I was surprised that it was 17 kg compared with the 26 kg of my 300PDS. Then, later, I noted that I can comforatbly lift and carry the 250PX, which was intended as a separate comment.

[bosun21]

Ok I understand now. A 12" Newtonian sure is a large scope. I bought straps with carry handles to move mine around easier.

[John]

2 hours ago, Mandy D said:

I was, honestly, very surprised at the weight of the 300PDS. I'm used to being able to pick up any of my existing OTAs with one hand, even the 250PX, but this one is a whole new ball game. The 300PDS is f/4.9, so ought to be lighter!

20% more glass and maybe slightly thicker as well as the additional tube size ?

 

[Nik271]

All things being equal the weight increases proportionaly to the cube of the linear increase, so 20% extra in aperture gives (1.2)^3=1.728 so about 73% heavier. 

[Guest]

14 hours ago, Jim Smith said:

Thanks for all of the suggestions and offers of help. I will probably keep it in a garden storage box about 12 feet from where I will set it up so there shouldn't be too much of a struggle. However I've decided to go for 10" instead of 12" to be on the safe side. I can probably forget those spiral arms unless I get some unusually good conditions.

Be sure about this.  I do love my ten inch, its a great scope, but to this day I wish i had bought a 12 inch to start with.   Since you are keeping it in a storage box out side any way, a dolly will make it easy to move, or you can easily make a cart with pneumatic wheels to move it. You had an offer on here someplace to go look at one, i would HIGHLY recommend taking up the offer before deciding. 

[JuergenB]

For anything bigger than 8", I would go for a truss type Dobsonian any time, but don't forget a shroud for increasing contrast if your skies are worse than Bortle 2. Although the weight of a solid tube 10" or 12" might be still acceptable, handling of a large telescope is very cumbersome. You shouldn't be afraid of collimating it though.

Juergen

 

[John]

Truss tubes don't always equate to weight savings. The Skywatcher flextube dobs actually weigh a little more than the solid tube versions. They are more compact to store and move around though.

 

 

[Jim Smith]

I took delivery of my StellaLyra 10" Dobsonian. I've added two handles to the base and Farpoint handles/straps on the tube. It seems quite manageable over short distances. I think the 12" would have been too heavy and awkward for me. There wasn't enough room for a Telrad between the focusser and the finderscope but a Rigel QuikFinder fits in well.

First light was last night with just enough time to see encouraging views of Mizar, M13 and Saturn before the clouds rolled in from the East.

So...in my quest to see galaxy spiral arms through an eyepiece, not a camera...which galaxy is the best one to try?

[Zermelo]

Try for M51.

[bosun21]

As already recommended M51 is a good start, but also consider M33 and M81. Good luck and happy hunting.

[JuergenB]

I hadn't the mass market truss type Dobsonians in mind, but the lightweight "Travel Dobsonians", like the Martini (Germany) 12" f/5.3 Dobsonian I once had. Storage, transportation and set-up were very easy.

 

[Jim Smith]

OK. M33, M51 and M81 it is.

I've thought of another question! Is there a best focal length of eyepiece to use to spot subtle features? Is a higher magnification better?

[Barry-W-Fenner]

On 05/08/2023 at 17:51, John said:

Truss tubes don't always equate to weight savings. The Skywatcher flextube dobs actually weigh a little more than the solid tube versions. They are more compact to store and move around though.

 

 

Very true, I own a 300p flex - lovely scope, But heavy, I have had lower back problems for the last year which has prevented me from bringing the scope out. I sometimes wish i had kept the 200p as it was light and compact enought to lift complete with base attached.

In the ideal world I need the 300p set up perminent in a dome, Under very dark skies, Oh and in rural Devon!! 🙂

 

 

[mikeDnight]

M51 and M81 reveal subtle detail related to spiral structure, and M31 shows a very obvious arm all in a 4" refractor on a transparent night. And a "relatively bright" region of M33 is also observable and related to the spiral structure, again visible in a 4" from bortle 5, with good dark adaption with no filters, and a transparent sky. With a 6" things start to become considerably easier to see, and an 8" really begins to open up M31 and its dark dust lanes.

Edited August 18, 2023 by mikeDnight

[John]

Even if you don't see the spiral structure in M33, it is worth looking out for a small smudge of light close to a foreground star a little away from the core of the galaxy. That is NGC 604 which is an immense star forming nebula within the galaxy M33. It is quite something to be able to see a deep sky object that is in another galaxy 🙂

This Sky & Telescope article covers how to see this one plus a couple of others in M33. 

I have seen NGC 604 with my 100mm refractor so your 10 inch should be able to spot it relatively easily 👍

Low magnification and a wide field of view for this one.

Edited August 18, 2023 by John

[Deadlake]

All this talk of 12” dobs, I find my C11 (with a glass EP, but better with an intensifier) works well and using an AltZ mount makes the scope very mobile plus push to is easy to add.

It’s around two trips to assemble in the garden and a lot easier to store then a dob.

Very mobile in a car, when I need to find more altitude for more stable air.

Only downside is the use of a dew shield however that’s a minor issue and if you are used to a APO the stars colour and sharp ness is not the same.

Edited August 18, 2023 by Deadlake

[Jim Smith]

It was clear last night, so I had my first attempt at galaxy spiral arm spotting with my new 10" Dobsonian under my Bortle 4 sky. I did a collimation in the afternoon. From my garden M51 was not obscured by trees so that was my target. I set up at 22:00 but waited until 23:00 for the moon to set, the mirror to cool and my eyes to adapt to darkness. I put my dark hood over my head, popped in a 25mm eyepiece and found M51 pretty easily...two distinct fuzzy blobs in a less obvious ovalish, fuzzy patch. Over the next half an hour I continued observing also trying 18mm and 12mm eyepieces.

I have to report that I did not see any spiral pattern of any sort. However, I noticed that the eyepiece field stop was clearly visible with the sky background appearing quite light. Sunlight reflected off particles in the atmosphere perhaps?  I think I may have more luck when M51 is higher in the sky and/or the Sun and Moon are further below the horizon.

[Jim Smith]

I gave in and bought a Seestar S50.  Now I can see spiral structure easily! The attached image is 7 minutes stacked in camera but spiral arms are visible even on one 10 second exposure.

[Louis D]

Or, rather going for a bigger scope, invest in an image intensifying system.  They're also really handy for observing diffuse nebula in real-time.  The only problem is you generally have to adapt non-astro systems to astro use, which can result in a lot of trial and error.

[Louis D]

6 hours ago, Jim Smith said:

I gave in and bought a Seestar S50.  Now I can see spiral structure easily! The attached image is 7 minutes stacked in camera but spiral arms are visible even on one 10 second exposure.

Out of curiosity, I edited and upsampled your image in Photoshop Elements and Noiseware to see what it would look like, and I was surprised at how good it came out below:

Those little Seestar S50 camera-scopes sure are nice.