Views of DSOs from my 10" Dob

[andrewk_82 (Andrew)]

I received a 10" GSO Dob for my birthday a couple of days ago. Last night I took it out for a look. I've seen pictures of NGC 1365 in Fornax before and was quite keen to see it through my new scope. I eventually found it, but it really wasn't what I was expecting. It just appeared as a fuzzy patch with not really much detail. With averted vision I could just make out the spiral arms. The astronomy book I have says that it is around magnitude 9, so I figured that given the apparent 14+ magnitude capability of my scope, it should stand out like dogs balls.The sky was fairly dark as I live in a rural area (I can clearly see the milky way, and andromeda galaxy with naked eye), although I do live in town with a street light across the road and the neighbours kitchen lights on.

My questions are, am I expecting too much from my scope, or should my scope be able to see much more? The EP I was using was the 25mm GSO SP that came with the scope. Would a better EP enable me to see galaxies more clearly?
I think the scope is reasonably well collimated, as when I do a star test the star forms a perfect circle when defocused, but stars do seem to have a slight tail (look like mini comets) when properly focused. Is this from the EP or something else?
I did leave the scope out for 2 hrs to cool down before I used it. Focus was quite good to start with, but after an hr or so stars would not focus properly. I did notice though that the temp did drop quite quickly before this happened, could this be the cause of the poor focus?
Sorry to ask so many questions but I'm new to this and any help would be grealty appreciated.
Cheers

[Starkler (Geoff)]

Originally Posted by andrewk_82

I've seen pictures of NGC 1365 in Fornax before and was quite keen to see it through my new scope. I eventually found it, but it really wasn't what I was expecting. It just appeared as a fuzzy patch with not really much detail. With averted vision I could just make out the spiral arms. The astronomy book I have says that it is around magnitude 9, so I figured that given the apparent 14+ magnitude capability of my scope, it should stand out like dogs

If you are seeing the spiral arms you're doing ok. The quoted magnitude is a figure describing the total light output from the galaxy. Being rather large in apparent size, this light is spread out over a wide area. Galaxies of the same magnitude but smaller will appear brighter due to the light being concentrated in a smaller area. The figure more descriptive of visibility is "surface brightness".
Are you expecting too much? If you expect galaxies to appear in the eyepiece the same way as they appear on long exposure photographs, then yes you are.

The EP I was using was the 25mm GSO SP that came with the scope. Would a better EP enable me to see galaxies more clearly?

The 25 makes a good finder eyepiece, but you can often see more detail by bumping up the magnification a bit. If the seeing is good, try a 10 or 12mm.

I think the scope is reasonably well collimated, as when I do a star test the star forms a perfect circle when defocused,

The thing to look for is the little bright dot you see in the centre of the rings when defocused just enough to show a few rings. This should be bang in the centre when centred in the eyepiece. The 25mm probably doesn't give you enough magnification to see this.

but stars do seem to have a slight tail (look like mini comets) when properly focused. Is this from the EP or something else?

Nope not from the eyepiece. It could be poor collimation, astigmatism in your optics, or in your eye. Does the orientation of the tail flip 90 degrees as you rack to the other side of focus? If so your secondary mirror might be bound too tightly in its holder.

I did leave the scope out for 2 hrs to cool down before I used it. Focus was quite good to start with, but after an hr or so stars would not focus properly. I did notice though that the temp did drop quite quickly before this happened, could this be the cause of the poor focus?

Most definitely! This is why cooling fans are important to help keep the mirror close to ambient temperature.

P.S. I'm jealous of your viewing conditions if you can see 1365s spiral arms from home

[rmcpb (Rob)]

Brilliant first view. Fancy seeing the arms! Enjoy

[Satchmo]

Andrew

You'll find a 10 or 12mm ( about 2mm exit pupil) about ideal for fainter galaxies. The arms will stand out much better with the higher power.

There are brighter galaxies around which you should turn to like M83 and NGC 253.

It is certainly hard when you are starting out to re adjust your expectations when you are use to looking at photograghs. All I can suggest is to practise marveling at what you _can_ see, rather than what you can't .

I firmly believe that a long and happy life as an astronomer comes from the ability to see things in the 'mind's eye' with a little prompting from the telescope. A large aperture isn't really that important; a dark sky and an imagination to see what is really there is much more so

[Blue Skies (Jacquie)]

If you could just see the spiral arms then it sounds like everything is ok. That's what it should look like. NGC 1365 is one of my favourite galaxies and in my 8" I just get the hint of the arms with averted vision, but I still get a thrill out of that! Starkler has already talked about sruface brightness - its a pretty big galaxy as we see it so the mag 9 is spread out over quite a distance.

[andrewk_82 (Andrew)]

Thanks for the advice, it is much appreciated. I think my expectations were a bit high for my new scope.
I've read another thread about seeing whether my scope has astigmatism, but unfortunately its just my eyes, so I guess a trip to the optometrist is in order. Also tomorrow I will have a go at improving the collimation.
The cooling down of my scope is also a bit of a problem, as it didn't come with a fan. Does anyone know were to get a fan from and how much it would be?
I had a bit of a look at the helix nebula tonight. It was a nice round disk, and with averted vision I could see the dark spot in the middle.
I'm looking at buying a nebula filter, what would be better to buy a UHC or an O111? Also would a broadband filter help bring out detail in the galaxies?
Cheers

[Satchmo]

Originally Posted by andrewk_82

I'm looking at buying a nebula filter, what would be better to buy a UHC or an O111? Also would a broadband filter help bring out detail in the galaxies?
Cheers

Andrew, A UHC filter is much more useful for general purpose than an O111, as it still lets a fair amount of star light through and gives a much more natural view. Filters don't really work well for galaxies I'm afraid.

[Paddy (Patrick)]

Originally Posted by andrewk_82

The cooling down of my scope is also a bit of a problem, as it didn't come with a fan. Does anyone know were to get a fan from and how much it would be?
I had a bit of a look at the helix nebula tonight. It was a nice round disk, and with averted vision I could see the dark spot in the middle.
I'm looking at buying a nebula filter, what would be better to buy a UHC or an O111? Also would a broadband filter help bring out detail in the galaxies?
Cheers

Hi Andrew,

Have a look at Scott Tannehill's article on IIS about modifying your scope to cool the front of the primary. This is a very easy modification (and it will tell you where to get a fan). My scope came with a fan, but this mod made a huge difference to the scope's performance.

Also I have a UHC filter which does bring out more detail on nebulae, but I don't think you'll be blown away by its effects on galaxies. Even with nebulae, Is till often prefer an unfiltered view. I have found the biggest boost to my capacity to see detail in galaxies is practice in observation. I would suggest that you don't rush into spending on things, just keep looking (using averted vision) and you will see more and more, especially with the dark skies I would expect you have. You will be amazed at what you find over time.

[GrahamL]

Tandy ,,dick smith sell fans and such

these guys are good to deal with I found if you can't find exactly what your after locally

http://www.coolpc.com.au/catalog/index.php?cPath=127_5

I'd try and get out of town a bit .. I can clearly see from my backyard all what you mention.. but its certainly not a dark sky... I have chanced a view down on the town I live in from about 900 ft above sea level and 19kms away.. the light pollution is pretty bad .. yet most of the clusters in fornax were still an easy shot from home in my old 10 ".. you must have some really dark sky nearby out your way ..enjoy
cheers