Should I be able to resolve stars on M3 with a 10" dob

[Wurzil]

Hi all - quick question

Should i be able to see stars on M3 with a 10" dob - i had a go the other night and the blob was definitlely brighter than with my 120mm refractor but i couldnt resolve any individual stars. Will I be able to resolve stars on globs with this scope under moderarte LP or do i need to take the thing out to a dark site.

The whirlpool galaxy was also the faintest of splodges with the dob (it was completely undetectable with the refractor!). Again, do i need to take the beast out into the sticks to see these things?

Oh - while im comparing the omni to the dob i may as well waffle for a bit:):-

I still prefer, by far, the views of mars with the refractor compared to the dob. Mars is very white in the reflector and probably needs coloured filters which i havent got.

Saturn looks nice and crisp in both scopes - possibly the dob wins here as i can push the mag up really high, whereas the omni maxes out at about 200x.

Sweeping around stars and open clusters the refractor is the more satisfying of the two (i can now understand what people say when they say that refractors are more contrasty).Maybe under darker skies the dob will resolve more stars in the open clusters?

I pushed the mag up really high on the moon with the dob and it was very impressive (like being at a lunar landing) - it wins over the refractor on that one due to the extra mag and lack of any CA.

I much prefer using EQ mount as it has the slow mo tracking knobs which saves me nudging things in (and WAY out) of view. I guess Ill get used to being gentle with the dob in time. The EQ mount is better for looking at things lower in the sky, the dob is better for looking up at zenith.

I suppose I should have some sort of useful conclusion to my comaprisons now....but I havent. The scopes both excel at different things (but the omni looks way cooler in my living room:)).

Warren

[John]

I've not tried M3 but I could certainly resolve M13 with my 10" newtonian when I looked at it the other night. I could see resolved stars right across but with an unresolved core sort of hiding within the resolved stars in the centre of the cluster - aperture is really good for globular clusters.

M51 appears as two spots of nebulosity with fainter but detectable outer regions on the brighter one. I've not been able to see spiral structure from my back garden so far but I reckon I'd be in with a shout if I can get the scope to a darker site. I did see the spiral structure wonderfully with a 12" dob at the SGL star party last April.

My back garden has a bit too much light pollution to be good for galaxy spotting TMH.

I enjoy having both a newtonian and refractors because, as you say, they are good at different things

[Chris H]

I can resolve individual stars in my 10" dob but I have to use my Ethos 8mm to do so. At x150 I can see many resolved stars but the core is unresolved.

[barkis]

A well aligned optical train of a 10" Newt. should resolve the stars in M3, although it might take a 12" to resolve the stars in the clusters core, which is quite densely populated.

As long as you have good seeing conditions, you should be able to resolve a good proportion of this very fine globular.

Ron.

[Wurzil]

Thanks guys - I was using a skywatcher 10mm, 25mm and a ts hr 5mm - which probably arent that great for globs.

I was thinking about getting a 9mm ortho (as i cant really afford televue stuff) maybe this will help??

Ill give M13 a go as well.

W

[russ]

Hi Warren,

M3 is a great target and all three scopes (8" dob, your 10" dob and the SCT) resolved the outer stars no probs. I was having a look at M3 last week and my best view came with the W70 19mm and a 2x barlow, giving 126x. A nice sprinkling of stars around the outer region and a few more using averted vision. Fortunately M3 rises in the best part of my sky (mag +5 on a good night) and this helps a lot. On a poor night (last night for instance) M3 is just a blob.

I've never had any luck with M51 from the backgarden. It's just two faint fuzzy patches and that was even with a 12.5" dob. In the 8" it is barely detectable.

With Mars you could try an Orange #21 filter but may not be worth it now as it's shrinking fast.

Saturn and the Moon were indeed very good with the 10".

Other objects where i found the 10 beat the 8 noticeably were:

M81/M82/NGC3077 - 3077 was easier to spot with the 10 and the other two slightly brighter

M108/M97 - definitely easier to spot M108 with the 10, a real challenge with the 8 unless a very good night

Leo triplet - again a real struggle in the 8 to get the third galaxy but a tad easier in the 10.

I think a dark site will allow the 10 to stretch it's legs a bit and put some distance between itself and the XLT120.

Regards

Russ

[DarkerSky]

A 9mm Ortho would be a good purchase for sure, although I'd go for a Plossl over an Ortho. A bit more expensive, but worth it.

I have resolved stars in the outer halo of M3 with a 6" newt at Mag x180 from a dark sky site. With the right eyepiece and good collimation you should have no problems getting a really grand view

[Wurzil]

Hi Russ!

Ill check out the owl nebula next time its clear - ive not tried to find it before - i didnt realise it was right on ursa major(just check stellarium). Ill have a go at some of those galaxies too.

Im definitely planning on driving the dob out somewhere soon, now that its not so blumming cold.

BTW - To work out the magnitude of my sky here, do i need to look at what faint stars i can only just see with the naked eye, and then check on stellarium for their magnitude?? Is that how its done?

Thanks

Warren

[mdstuart]

I find that the stars are more visible with high power in my 10 inch dob. So at 9mm they start to apprear, at 6mm they are pretty good and at 4mm I want to watch it pass through the view over and over again..

M51 is two cores in my scope with a faint halo around M51 and a field star embeded in M51 which I thought was a Nova for a few minutes...

Mark

[mdstuart]

Yes to work out your sky try to work out the faintest star you can see high up. I can manage mag 5.5 and in the 10 inch dob I can get to about mag 14.5 which is Pluto level! The ability to see faint objects falls off as you go towards the horizon significantly!

Mark

[Chris H]

A good way is to use Ursa Minor see this web page ASP: Light Pollution