Tips on Nebulae and Galaxys - larger scope or filters

[Jazzmatazz]

Hi to you all!!!!

I've been gazing since august on a AStromaster 130-650 newt using a Meade 5000 24mm for DSO (I only own 2 other EPs, wich are very, very dark can barely see M31(!!!!))!

Anyway, when it comes to clusters, it's been no problem to see, but I always struggle with Nebulae and Galaxys, M31 is no problem, but, the triangle galaxy, still cant see it, and im sure about its location, since my search method and my guide software on ipad (skySafary Pro) have worked in the past!

I've reduced light pollution near me and been observing towards the zenith as to reduce the influence of heat coming out of other houses and observing over street lamps. 

I should add that allthough im not experienced with a lot of EPs, I find the Meade 5000 24mm really brigh. 

So i'm thinking either i need to go for a new larger scope, or its somewhat a contrast problem? does that make sense?

so my question is, is it worth it to buy some filters for a rather weak scope? or with a larger aperture and no filter would my life be easier with DSO??

Thank you guys!

[jetstream]

M33 is not that easy, eventhough dark skies make it a great sight. I would try M81, M82 as they show well, finding them in your 24mm and then switching to a 10mm-12mm eyepiece should help. NGC 7331 may also be worth a try.

As many will say, dark skies are needed to see a lot of DSO's well, regardless of aperture.

[cotterless45]

Ensure that your eyes are dark adapted. This may take up to 20 minutes. Use an eyepatch and a dull red torch if you have to look at charts etc. Under reasonable skies 130mm will show you the brightest dso's as Gerry has indicated above.

You could try a x2 Barlow or a 10mm ep . This will boost your magnification to x50-x65, sufficient to enjoy galaxies and give more contrast to the background. This'll make targets easier . If you can get to a dark sky, then M33 is a wonderful sight.

This free monthly download gives a simple idea of what's up,

http://www.skymaps.com

Nick.

[SteveB72]

M33 is tricky, it is quite indistinct from my back garden due to light pollution even in my 16" scope.

The Orion nebulae will be clearly visible in your scope.

You can also try this downloadable object list for ideas, you should be able to see most of them in your scope:-

http://www.skyandtelescope.com/observing/111-deep-sky-wonders-for-light-polluted-skies/

[Special K]

A UHC filter for nebula could be handy for you and certainly works on some objects in my 130mm which is identical to yours. While you can go for a bigger scope to improve your viewing, researching EPs and filters will yield excellent results and this knowledge is useful for any telescope you'll use.

M81 and M82 mentioned by Gerry will blow you away!

[ollypenrice]

I don't find aperture has much to do with M33. I can see it easily in 8x42 binoculars. The absolutely key thing is the darkness of the sky. It is diabolical to see with any LP.

Olly

[Jazzmatazz]

Thank you for your feedback Guys!!!!!

As said by Cotterless45 do you recomend a Barlow 2x to increase contrast? 

[acey]

It is, as you say, a contrast problem, due to the sky being too bright. Filters do nothing for galaxies and aperture doesn't improve contrast, so really the answer is to find a darker site or stick to targets with higher surface brightness. If you can't see the Milky Way with naked eye then most galaxies will be difficult with any aperture.

[greglloyd]

When you have a decent sky, aperture does matter. All things being equal sky quality wise - simply put, the bigger the scope the brighter the object will look and the more resolution you will get. I have quite dark skies where I live and M33 stands out fairly well in everything from 8x50 binoculars to my 12" dob.

The most important thing to have is a dark sky. Period. Galaxies are faint - especially ones like M33 which has a very low surface brightness. The smallest amount of glow in the sky is simply going to wash it out completely. And in that case it doesn't matter what size of scope you use because there is simply no contrast between the colour of the sky and the galaxy. It will be hidden within the glow.

For reference, at my location M31 is visible to the naked eye with direct vision. The double cluster in perseus is easy with direct vision. And on the best nights of transparency, I can just about see M33 with the naked eye because I know exactly where to look and the size, surface brightness, and orientation of the galaxy.

Other factors to consider are:

1. Ensuring there is no moon in the sky

2. No high clouds (even the slightest bit of high altitude haze that you cannot even really see with your eyes will harm the views greatly.

3. Relative Humidity (lower is better).

4. Dark adaptation (you must let your eyes adjust to the dark for at least 30 minutes if you want the best views)

5. Quality eyepieces.

Better quality eyepieces give better contrast. Also, selecting an eyepiece that gives an exit pupil size of around 2mm to 3mm gives good results providing a good power and good contrast with a dark sky background to get the most details.

A lot of people say "use the lowest magnification you can with M33" but I find that although that might help with finding the object (the theory being that most people fail to find it because it is so large at higher powers), that is not the best approach for seeing details in it. You want a moderate power in the range of 80x to 120x for a better chance of seeing the spiral arms and NGC's within it. In fact, I don't even bother with a low power most times. I can find it easily enough in the Delos 17.3mm (87x) or 14mm (107x), as I know what size to expect in the first place. A lower power in the 12" of say 54x is good for an overall view with the galaxy in context with it's surrounding and showing a bright halo, but spiral arms and NGC's are more difficult to see at this power.

Often, the best nights for viewing galaxies are on moonless nights after a cold front has come through. The air is usually very clear. 

As has been mentioned before, the galaxies with the highest surface brightness - and therefore the best chance of seeing in brighter skies are the likes of M81, 82, 31. But again, these will look more impressive from a dark sky. 

I've owned a number of different sizes and types of scope over the years and for comparison from my same location the views of M33 have been :-

5" (130mm) reflector: A very faint, large smudge. No detail at all detectable. View much the same as if you viewed it through binoculars because the increased magnification from the scope dims the view to be equivalent to the brightness seen in binoculars.

6" SCT: A very faint, large smudge. No detail seen. Slightly brighter than with the 5" but not by much. View very similar overall.

8" reflector: A faint, large smudge. Generally no detail to be seen, but with some averted vision you should notice that the central core looks brighter than the rest of the halo. NGC604 (the brightest emission nebula in M33) may be seen to the north. It may appear fairly dim. At low magnification NGC604 will be very small like a defocused star, but bumping the magnification up to around 100x will make it large enough to see it's nebular characteristics.

10" reflector: Much the same as the 8"

12" reflector: M33 is seen easily. At first glance it's a very large smudge that can been seen easily with direct vision. Within a few seconds of study you will see the two main spiral arms going north and south of the core. Various knots and brighter features can be traced along the lengths of these two spiral arms. The core is obviously brighter than the surrounding halo - but M33 has a fairly weak core as far as galaxies go. NGC 604 becomes a very bright object of decent size at 107x and some detail to it's shape. It's very clearly visible with direct vision. Two other NGC objects can be seen fairly easily (NGC 592, NGC 595). With averted vision, a third spiral arm can be seen coming out the eastern side of the galaxy. Averted vision also allows you to see further out regions of the brighter spiral arms.

The 12" also allows you to get away with seeing the galaxy in less than ideal conditions much more than the smaller scopes do (i.e. when skies are not very transparent, or with a moon present), but then the views become more like what a 6" scope provides. It just becomes a smudge again.

So, in summary:

1. Dark Skies that are transparent

2. Aperture

3. Dark adaptation

As you can see, given dark skies aperture does matter with detail in M33 as an example becoming much easier to see in a 12" scope.

Clear Skies

[Moonshane]

No doubt a dark sky is the key factor with extended objects but I differ slightly in my view of aperture increases at light polluted sites. I feel at any site more aperture provides more pleasing views. The views of extended objects at my light polluted garden site are better in my 12" than my 6" scope and better again in my 16" scope. Not as good as at a dark site but better than in smaller aperture.

Some objects e.g. The Veil are always better with an oiii filter but more so from light polluted sites. My answer to your question is both but not necessarily for the same objects.

Dont sell your 130 though as a decent wide field scope is always useful.

[greglloyd]

Agree. Larger aperture will always provide better views than smaller scope - even under poor skies, though the performance increases will be even greater under darker skies. But it's always worth having the largest scope you can regardless of your skies. 

[Moonshane]

Dont forget that larger aperture=more resolution=more detail on planets/moon and closer splits on doubles.

[Jazzmatazz]

Thank you a lot guys! 

That was a MASTERCLASS!!!!

Thank You! Thank You! Thank You!!!!!!!!!!! 

[DeepSkyBagger]

One final point. The remarks about dark adaptation are critical. I notice that you are using an ipad. Do you have it covered with a quality red filter such as Rubylith, or are you looking at it unfiltered? If you look at it unfiltered (even with 'night colours' set) you will destroy any night vision you have instantly.

If you look on ebay and search for Rubylith, you will find that you can buy it by the sheet (it's not expensive). Cut this to size and tape or Velcro it onto your ipad. Your eyes will thank you.

Cheers,

Patrick

[AndyWB]

I cover my iphone with rubylith, and last week I think I proved that even then it damages adaption. My phone ran flat, so I finished the session using charts - and I'm sure I started to see dimmer DSOs

[ollypenrice]

Agree. Larger aperture will always provide better views than smaller scope - even under poor skies, though the performance increases will be even greater under darker skies. But it's always worth having the largest scope you can regardless of your skies. 

...but this makes two assumptions. The first is that all things are equal, which they may not be. We may be able to afford true optical finesse in smaller apertures but not in larger. This certainly describes me.  My 20 inch doesn't have the optical quality of my 5.5 inch. It could have - but it doesn't! It also assumes that the target will fit in the field of viw, which a long focal lengths it may not.

Olly

[Jazzmatazz]

By optical quality you meen detail on the DSO? Can you expand your point??

[greglloyd]

...but this makes two assumptions. The first is that all things are equal, which they may not be. We may be able to afford true optical finesse in smaller apertures but not in larger. This certainly describes me. My 20 inch doesn't have the optical quality of my 5.5 inch. It could have - but it doesn't! It also assumes that the target will fit in the field of viw, which a long focal lengths it may not.

Olly

I get what you are saying. At the end of the day there is no "one ideal scope" for everything. But for galaxies and nebulae (what this particular thread is about) I have always found that larger apertures for the most part improve views (under my relatively dark skies).

Greater aperture equals bigger image scale to more easily see details in DSO's and fours times brighter an image at a given magnification each time you double the diameter of the primary aperture.

The field of view point you make is definitely a valid one for large DSO's as scopes with larger apertures (which typically come with longer focal lengths) will inherently have higher magnifications and smaller true field of view at a given eyepiece focal length.

[jetstream]

By optical quality you meen detail on the DSO? Can you expand your point??

Hi Jazz, some telescopes and eyepieces give great contrast on DSO and I'm not really sure why. If you ever get a telescope that gives great high power views and delivers high contrast DSO views....keep it! There are most likely lots of technical reasons why, but the real test is under stable, dark skies IMHO.

[greglloyd]

Part of the reason for greater contrast in some eyepieces is that generally with greater power, you in turn get a darker background sky colour. My understanding is that this is because of the smaller exit pupil.

Low power eyepieces with large exit pupils tend to increase the sky background colour. So although the DSO itself will be brighter because of the larger exit pupil, so will the sky colour. 

Higher power eyepieces will dim the DSO somewhat, but will also dim the sky a lot. Also, the larger image of the DSO hitting your retina helps your eye detect it better as it activates more rods in your eye. This can cause the contrast boost.

[ollypenrice]

By optical quality you meen detail on the DSO? Can you expand your point??

Sure. All optics have defects. They cannot be made to perform perfectly. You can calculate the theoretical resolution (the Dawes limit) for a given aperture and the resolution does go up with aperture on the laws of physics.

But other factors include colour correction, edge of field distortions like coma, contrast (which is reduced by internal reflection and any central obstruction) etc. Refelctors are perfectly corrected for colour till you put glass in the system, as you have to. In our 20 inch I get a big strong image but the stars are quite large and the contrast is decent but not outstanding. In the small but top class refractor the image is not so bold but is more subtle with tiny stars and very high contrasts. 'Better of worse' isn't the point. They are just diffrent - and a 20 inch with a Zambuto mirror would be different again. The big one shows things not seen in the small one, but the quality of the view in the small one is finer - to my eye.

Olly

[Jazzmatazz]

Thats a great point!

[jetstream]

Part of the reason for greater contrast in some eyepieces is that generally with greater power, you in turn get a darker background sky colour. My understanding is that this is because of the smaller exit pupil.

Low power eyepieces with large exit pupils tend to increase the sky background colour. So although the DSO itself will be brighter because of the larger exit pupil, so will the sky colour. 

Higher power eyepieces will dim the DSO somewhat, but will also dim the sky a lot. Also, the larger image of the DSO hitting your retina helps your eye detect it better as it activates more rods in your eye. This can cause the contrast boost.

Yes extended objects and the sky dim equally with increased magnification, the object will be seen easier because it gets bigger, up to about a 2mm exit pupil. This assumes the object needs to get bigger, to see easier, they all do not ie NA neb which I obs @ 6mm exit pupil in my 1200mm fl dob. This is just my opinion however.

[greglloyd]

Agree with the above. Best view of NA I've had before was in low power bino's in fact.

What power do you use in your scope for the NA? Do you use any filters? What AFOV?

[John]

Part of the reason for greater contrast in some eyepieces is that generally with greater power, you in turn get a darker background sky colour. My understanding is that this is because of the smaller exit pupil.

Low power eyepieces with large exit pupils tend to increase the sky background colour. So although the DSO itself will be brighter because of the larger exit pupil, so will the sky colour. 

Higher power eyepieces will dim the DSO somewhat, but will also dim the sky a lot. Also, the larger image of the DSO hitting your retina helps your eye detect it better as it activates more rods in your eye. This can cause the contrast boost.

Very true and it's worth applying a little more magnification sometimes to get that darker background.

It's also one reason that ultra and hyper wide eyepieces are popular with some - you can see the same width of sky but at a higher magnification and with a more efficient exit pupil.