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Questions About First M31 Viewing

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#1 andstuff

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Posted 22 October 2019 - 11:09 PM

Total beginner here. For background, I bought a department store grade telescope at a garage sale about a month or two ago and have been pointing it at the moon and planets. Decided a couple weeks ago it was interesting enough to upgrade and just got a Celestron Omni 102 XLT with CG-4 mount on sale this past week along with an 18mm and 9mm EP.

 

Tonight I decided to try and find something a bit more challenging than I had been, so I went for M31. I should mention I own "Turn Left at Orion" and am using the free version of SkySafari. With those two resources I was able to locate it after about 40 minutes of searching (well gotta start somewhere...).

 

So, couple of things about this...

 

It was really faint! According to the "Clear Outside" app I'm in Bortle Class 6 skies / darksitefinder.com "Red" zone. I see Turn Left at Orion marks it as "Dark sky". I get that light pollution is a big factor, however would it be higher contrast or not as faint if I was using a telescope with a larger aperture which pulls in more light or would it still be faint because of the ambient light? Should I bother picking up a filter to help with this?

 

It was really hard to focus on. I was surprised about this the most, I couldn't really tell if I was in focus or not. I just started using the nearby stars to set focus, but due to the faintness it just seemed fuzzy and it was hard to tell really if I was seeing anything clearly. Is that a function of the state of the atmosphere as well? The Celestron doesn't have a fine focus so I also was wondering if I was just being a bit too heavy handed on the focus wheel or not...

 

What does "Low power" mean in the Turn Left at Orion book? I was able to actually see M31 in the stock 6x30 finder (surprised at that!). I had the 18mm on the scope to start with (55x) and swapped it out for the 9mm (111x) once I got it centered. Is that a good power to be viewing at? I'm not sure what range "low power" in the book is trying to convey.

 

Thanks.


Edited by andstuff, 22 October 2019 - 11:11 PM.


#2 RyanSem

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Posted 22 October 2019 - 11:31 PM

40 minutes isn't so bad! I have a few buddies who started off with GoTo telescopes and even though they knew they were pointed at M31 they called me over to double check. Because you're right, it is much fainter than you're led on to believe. 

 

In terms of your focus, as long as the stars are pinpoints of light, you're about as good as you're going to get. Before swinging over to M31 next time, focus in on a relatively bright star and make sure it's a perfect tiny dot. This is the same focus you'll use on Andromeda. 

 

Low power can be kind of confusing at first because it seems counter intuitive. When I first heard "low power" I immediately picked up my 10mm EP because it was the EP I had with the lowest number. But in the case of Turn Left at Orion and astronomy in general, when they say "low power" they mean to use an eyepiece that will give you less magnification. Andromeda is very very big, so you want to use an EP that will get the most of it in frame as you can. 

 

50x magnification is a pretty good guideline for hitting that low power sweet spot. It should frame Andromeda pretty well. I use a 40mm in my scope when I look at Andromeda, and since mine has approximately double your focal length that's roughly on par with the views you're getting. 



#3 Traveler

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Posted 22 October 2019 - 11:49 PM

 "It was really hard to focus on"

 

Yes i understand M31 is not the most polite object to adjust focus. My strategy is focus on a bright star first (Polaris for example), tighten the focusscrew (!) and only after that, go find Nebula objects. If erverything is ok, M31 will show in focus...

 

Now you found M31, M33 is the next step. Have fun!



#4 Traveler

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Posted 22 October 2019 - 11:50 PM

BTW good to read "Turn left at Orion" is still in use.



#5 Jeffmar

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Posted 22 October 2019 - 11:50 PM

A larger telescope can make up for light pollution to a point. In my light polluted neighborhood even my C8 gets mostly a fairly large fuzzy area with m31 and very little detail. I don't even try for galaxies anymore in my backyard, even with my C14. I avoided traveling to dark sites for years but lately I have been getting away from the city and it is totally worth it. If you can find a place away from city lights you should go for it. You will be surprised what you can see in your 4 inch scope at a dark site. If you are observing in your neighborhood try looking for Messier objects that have brightness of 6 or better like the star clusters m13 and m11. You might get a decent look at m57, the ring nebula. The Orion Nebula, m42, will be a good target in a few months. 

 

Low power would be 55x or lower. You might want to get a 25mm eyepiece which would give you about 40x. Most things look brighter and tighter at low power. If the atmosphere (seeing) is good then you can switch to a higher power. If your image is moving around then stick with the lower power. I have eyepieces that can get a lot of magnification with my telescopes. I rarely use them because even though they are fairly large scopes, turbulence in the atmosphere will make low power a much better way to view things. 


Edited by Jeffmar, 23 October 2019 - 12:06 PM.

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#6 GoFish

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Posted 23 October 2019 - 12:07 AM

Congrats on the new scope and your early success. If you have already found M31 by star hopping in Bortle 6 skies, then I think you have a future in this business!

 

Your scope has 1,000mm focal length. So the magnification for a given eyepiece will be 1,000 divided by the eyepiece focal length. Your lowest power eyepiece, at 18mm, will yield 55X magnification.

 

More important, though, is that this eyepiece in your scope will give only around 0.8 degrees field of view (FOV).  According to SkySafari, M31 covers an area of sky equal to 3 degrees by 1 degree. So your 18mm plossl (I assume) eyepiece will not show much of M31. 

 

To see more of M31, a 40mm plossl would show you 1.8 degrees FOV, a big improvement for wide objects like M31. For more money, you can buy an eyepiece that has AFOV wider than the 45 degrees typically provided by a plossl design. 

 

But for $35, I think this 40mm GSO Super Plossl eyepiece would serve you well:  https://agenaastro.c...l-eyepiece.html

 

 

 



#7 sg6

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Posted 23 October 2019 - 04:19 AM

It was really faint! According to the "Clear Outside" app I'm in Bortle Class 6 skies / darksitefinder.com "Red" zone. I see Turn Left at Orion marks it as "Dark sky". I get that light pollution is a big factor, however would it be higher contrast or not as faint if I was using a telescope with a larger aperture which pulls in more light or would it still be faint because of the ambient light? Should I bother picking up a filter to help with this?

 

It was really hard to focus on. I was surprised about this the most, I couldn't really tell if I was in focus or not. I just started using the nearby stars to set focus, but due to the faintness it just seemed fuzzy and it was hard to tell really if I was seeing anything clearly. Is that a function of the state of the atmosphere as well? The Celestron doesn't have a fine focus so I also was wondering if I was just being a bit too heavy handed on the focus wheel or not...

 

What does "Low power" mean in the Turn Left at Orion book? I was able to actually see M31 in the stock 6x30 finder (surprised at that!). I had the 18mm on the scope to start with (55x) and swapped it out for the 9mm (111x) once I got it centered. Is that a good power to be viewing at? I'm not sure what range "low power" in the book is trying to convey.

 

Yes it is faint, that is owing to how "magnitude" is determined. Magnitude is the total amount of light coming off an object. So a dim but large object can have a good viewable sounding magnitude. M31 falls into this.

 

Focusing on it will be "difficult". You are seeing the central bulge and that is a bit of a fuzzy indistinct ball of stars and so difficult to obtain a sharp focus.

 

Low Power means Low Magnification. Owing to the Mag = ScopeFL/EyepieceFL then the longer focal length eyepieces are the low power ones.

 

Problem is that M331 is too big to fit in a scope of 1000mm focal length.

What you see in terms of field is Eyepiece field / Magnification.

 

If you had a 32mm plossl wit a 50 degree field that is a mag of 30x and so a fiels of 1.66 degrees. M31 is twice that in size. You cannot see all of it. That is likely why it took 40 minutes to find it.

 

M31 is easier in binoculars. Or oddly a small often inexpensive scope. With a Plossl and 3 degrees view required you need a mag of 16x, with a 30mm EP that is a scope focal length of 500mm. Scopes like the ETX 70 80 are good as is a 72ED at 420mm and the ST80's. M31 is a "problem" to many.


Edited by sg6, 23 October 2019 - 04:31 AM.

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#8 epee

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Posted 23 October 2019 - 07:04 AM

Light pollution does horrible things to defuse objects and aperture can only half solve that problem. A 102mm will give a very nice view of both M31 and M33 in dark skies.


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#9 JoeInMN

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Posted 23 October 2019 - 10:10 AM

Also among the most important bits of "equipment" for a beginner are accurate expectations of what things actually look like. Even a huge and relatively bright object like M31 will look nothing like the pictures we've seen of it, which are long-exposure photographs; this, coupled with the fact that seeing details in faint objects is a skill that develops with practice, leads a lot of beginners to think that they haven't found the object they're looking for, when they're actually looking right at it.


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#10 leroybrown

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Posted 23 October 2019 - 10:33 AM

I have similar skies to yours - maybe closer to B7 than B6 - and was actually looking at M31 last night. I have just bought a 2" 32mm eyepiece for my TAL (having noticed it had a 2 inch focuser after owning it for about 8 years - d'oh) so seemed a good target for a test. At roughly 23x it was just a dusky blob which was not enhanced by any greater magnification. Theoretically the galaxy should fill my entire eyepiece but the pollution just doesn't allow it to be seen - guess a darker sky is what is needed. 

 

On the other hand the Pleiades cluster looked amazing - give that a go next!!


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#11 rhetfield

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Posted 23 October 2019 - 11:10 AM

Total beginner here. For background, I bought a department store grade telescope at a garage sale about a month or two ago and have been pointing it at the moon and planets. Decided a couple weeks ago it was interesting enough to upgrade and just got a Celestron Omni 102 XLT with CG-4 mount on sale this past week along with an 18mm and 9mm EP.

 

Tonight I decided to try and find something a bit more challenging than I had been, so I went for M31. I should mention I own "Turn Left at Orion" and am using the free version of SkySafari. With those two resources I was able to locate it after about 40 minutes of searching (well gotta start somewhere...).

 

So, couple of things about this...

 

It was really faint! According to the "Clear Outside" app I'm in Bortle Class 6 skies / darksitefinder.com "Red" zone. I see Turn Left at Orion marks it as "Dark sky". I get that light pollution is a big factor, however would it be higher contrast or not as faint if I was using a telescope with a larger aperture which pulls in more light or would it still be faint because of the ambient light? Should I bother picking up a filter to help with this?

 

It was really hard to focus on. I was surprised about this the most, I couldn't really tell if I was in focus or not. I just started using the nearby stars to set focus, but due to the faintness it just seemed fuzzy and it was hard to tell really if I was seeing anything clearly. Is that a function of the state of the atmosphere as well? The Celestron doesn't have a fine focus so I also was wondering if I was just being a bit too heavy handed on the focus wheel or not...

 

What does "Low power" mean in the Turn Left at Orion book? I was able to actually see M31 in the stock 6x30 finder (surprised at that!). I had the 18mm on the scope to start with (55x) and swapped it out for the 9mm (111x) once I got it centered. Is that a good power to be viewing at? I'm not sure what range "low power" in the book is trying to convey.

 

Thanks.

The galaxies and nebulas are faint.  In light polluted skies, you will not see much more than the center of the galaxy.  It will look like a faint ball of fuzz even under perfect focus.  In dark skies, you will see the surrounding disk.  They will also be fuzzy.  They are not discrete objects.  They are diffuse collections of gas, dust, and stars.

 

As others have pointed out, your scope/eyepiece combination is geared towards planet killer and you won't be able to see the entire thing all at one time until you get a wide angle eyepiece.  Bigger scopes will pull in more light and give a brighter and more detailed view.  It takes astrophotography to make it look like the pictures. 

 

Filters will help with nebulas, but not much with galaxies.  The emission nebulas emit specific frequencies of light and they pop when a filter designed for them blocks out the other frequencies of light pollution.  Galaxies emit all frequencies and get dimmer when filtered.  The UHC filters work well with nebulas.  Light pollution filters get mixed results at best in the era of LED lighting.

 

"Low magnification" is somewhere around 4-10x the diameter of your aperture in inches.  Maybe around 25-30x in your scope.



#12 havasman

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Posted 23 October 2019 - 11:37 AM

Hi andstuff and welcome to the forums!

 

I looked up M31 and its very close neighbors a week or so ago in my brand new 4" refractor from home under the Dallas light dome white zone and was quite pleased to see a prominent extended fuzzy patch with a much smaller non-stellar fuzzball that was M32. I have seen the objects from here and from other sites many times via 4.5, 5, 10 and 16"" aperture refractors and Dobs and they are very familiar to me.

 

Last night I took that same scope to our club's SE Oklahoma dark site and looked the big galaxy up again for the scope's 1st light object from a good dark spot. I saw a great bright very elongated galaxy that extended almost across the entire 4.7 degree field at 17x. The core was bright and extended and dark lanes could be traced far along the halo. NGC206, the giant star cloud in M31 was detected in the SW extension of M31. M32 was clear, small, tightly compact and placed right along the edge of the big galaxy. M110 showed brightly as the large but poorly concentrated extended object that it is. A goal of the observation was detection of one of the several giant globular clusters that are a part of the M31 system and can be clearly seen via larger aperture but, without any disappointment, that remains a goal for future opportunities.

 

Other galaxies that were observed included M33, NGC253, M77, M81/82, NGC7331 and NGC891 (by far the toughest of the lot.)

 

The point here is the contribution dark sky conditions make. Either of my 4 or 4.5" scopes will drastically outperform either my 10 or 16" scope when the small scopes are used from the good (but not world class) dark site if the larger scopes are restricted to observing from the city. I never even bother to set up the 16" here at home; inadequate payback for the effort involved.

 

The best accessory for any scope is more time spent observing from under dark skies and that is true for both our new, powerful 4" refractors. I don't know where you are but encourage you to experience the shocking difference good conditions WILL make in your observing. Find and utilize a dark observing site.


Edited by havasman, 23 October 2019 - 12:08 PM.

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#13 Diana N

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Posted 23 October 2019 - 11:52 AM

Light pollution does horrible things to defuse objects and aperture can only half solve that problem. A 102mm will give a very nice view of both M31 and M33 in dark skies.

The sad thing is that under excellent skies M31 is actually an easy naked-eye object.  It's NOT faint, not at all!  (Neither is the Milky Way.)



#14 havasman

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Posted 23 October 2019 - 11:58 AM

The sad glorious thing is that under excellent skies M31 is actually an easy naked-eye object.  It's NOT faint, not at all!  (Neither is the Milky Way.)

The sad part is how rare are excellent skies. But your point is certainly well made and I agree. 



#15 andstuff

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Posted 23 October 2019 - 02:11 PM

Wow, thanks all for the super positive response.  I was aware of how to calculate magnification, but clearly need to understand quite a bit more about how field of view works. I should have mentioned, the eyepieces I picked up were both Celestron X-CEL XL which according to the specs have a 60 deg field of view. Seems like my next step is to read some more about how that works field of view works and why it matters.



#16 Tony Flanders

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Posted 24 October 2019 - 07:43 AM

Total beginner here. ... I just got a Celestron Omni 102 XLT ...
 
Tonight I decided to try and find something a bit more challenging than I had been, so I went for M31. ...
 
So, couple of things about this...
 
It was really faint!


So say most newbies. Come back in a year, after you have viewed some objects that are genuinely faint, and M31 will seem overwhelmingly bright through exactly the same telescope under exactly the same skies. If you can see M31 through your finderscope, I can pretty much guarantee that.

Incidentally, did you look for it naked-eye? I can see M31 very easily naked-eye from Bortle 6 skies. But then, I know what to look for.

Alas, however, you're not going to see significant detail within M31 under Bortle 6 skies, even with the world's biggest and best telescope. That's not a function of overall brightness but rather the galaxy's structure and the angle from which we see it. Overwhelmingly bright though it be, M31 is a tough nut to crack. Many much fainter galaxies yield their details much more easily.

All this assumes that you don't have bright lights shining in your face. No matter how dark the sky overall, you can't see much of anything at all if you're sitting under a streetlight -- even if it's the only streetlight for 100 miles around.


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#17 cupton

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Posted 24 October 2019 - 11:19 AM

This screenshot is from SkySafri set for my scope and eyepiece. This is pretty accurate as to what I saw the other night when looking at M31 with my 5” MAK and a 32mm Plossl eyepiece. Basically a dim giant cotton ball. Might be able to get a little more detail by going to a darker site but the FOV is about maxed out more my little MAK. I make up for it by looking at the moon.

Not sure what my skies are on the Bortle scale but being 20 minutes north of Pittsburgh I would imagine I’m at a 5 or so.

c03b89bfdbd617f5c7865b33a4297f3d.jpg

#18 geofizzy

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Posted 24 October 2019 - 12:09 PM

In Turn Left at Orion, the circles in low-power drawings are scaled to 80 arc-minutes (60'=1°, so 80' = one and a third degree): in medium and high power drawings the circles are 40' (2/3 of a degree) and 20' (1/3 of a degree), respectively.

As you say, with your 1000mm telescope focal length your 18mm eyepiece gives about 55x (1000/55).  Since your true field of view will depend on your eyepiece's apparent field of view as well as the magnification, if the apparent field of view is 55° (fairly typical of inexpensive eyepieces) then the true field (the patch of sky in the eyepiece) is 55°/55=1°.  A more expensive wide-field 18mm eyepiece (with, say, an 82° apparent field) would give you the same 55x magnification, but a true field of 82°/55, or about 1.5° (90').

Either way, for a really big object like M31 I much prefer the view at low power.  That way you can see M32 and maybe even M110 in the same field, as well as getting a better perspective on the shape of the object, even under moderately light-polluted skies.  That's why we have the M31 drawing as 'low power', with an 80' circle.




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