Limitations

[Kevdan]

Hi all,

What ar ethe limits of my skywatcher 150p scope, at th emoment i have a 9mm and a 26mm plossl with a 2x barlow. It's just I have tried to find certain nebulas and come up empty, so for instance can I see M51 the Whirlpool Galaxy with my scope? or is it just my eyepieces are not up to it.

Also I have a 6x30 finderscope is it worth upgrading this to aid finding stuff.

Kev.

[WayBig]

A very good question, and I think the limiting factor is often your viewing conditions. So from a really dark site, you could see many faint fuzzier with a relatively small scope, from a light polluted site you will see less no matter what size of scope.

I've heard somewhere on here that if the surface brightness of the object is the same, or less than the surface brightness of your sky then you won't see the object no matter what size scope you use.

However if the surface brightness of the object is greater than that of your sky then the larger the aperture the brighter the object will appear...no easy answer I'm afraid

[Capricorn]

M51 is a 8th magnitude object, with decent skies you should see the central core, you will need something bigger to see the arms.

What is the light pollution like where you are?

I am guessing that much of the West Midlands is poor.

The skies could simply be much the same as the object so you see nothing.

Next what is the collimation like on the scope?

At f/5 it has to be kept collimated.

Also at f/5 you will need decent eyepieces to get the best.

Magnifing M51 will simply make a dim image of a dim object. You have only collected a small amount of light from M51 so spreading it out over a large image ain't going to help.

The standard eyepieces are never that good, a 7mm, 10mm of some quality should improve things, but they need to be able to give results on an f/5 scope.

Could you borrow an 8mm TV plossl ? Just to see what results it gives. Not sure what the planetary eyepieces are rated to. Ones like the 8mm WO SWAN is rated at f/6 and slower, which probably means f/7. I suspect that at f/6 it only manages to be just acceptable.

There so many questions about the 150P that I wonder why people buy the 150P, the 150PL will give more magnification, needs less critical collimation and will get along fine with less expensive eyepieces.

[Guest]

You should have good views of M51 with that scope - take it out into the countryside to get away from the lights. M51 is fascinating to view - the first time I viewed it through my C10n my jaw literally dropped :-) Aperture is king in observational astronomy so that is the first limitation in any set up. You can enhance things a bit with eyepieces of varying quality but its the photons you grab that dictate the view.

[tbird]

I have a 150p and found M51 for the first time last week. I have fairly dark skies at my location. With the supplied 25mm eyepiece it took a lot of searching to locate, and there was no discernable detail, only 2 grey smudges.

I'm hoping with some better eyepieces I'll get a better view.

[Kevdan]

Hi,

Thanks for the replies, Yes I am in west mids but quite High up in Upper Gornal near Sedgley so most of the Birmingham and surrunding area is below us to the East and the best views are to the south.

Im not expecting to be able to see Hubble quality views but just wondered what to aim for in quality with the scope I got.

Thanks,

Kev.