Large scopes and bad skies

[glennbech]

I've recently felt the urge to "see" more of the things I image. I already have an 8" newtonian but have never used it under real dark skies. (Shame on me!).

My experience so far is that sky-contrast is king, aperture comes second. At least for nebulae and faint galaxies. Am I right?

I really don't see myself "open cluster" hopping with a 16". I have the 3.5" APO for visual use now and it gives amazing views of open clusters. If I go to that Size I'll probably try to hunt down galaxies and Planetary nebula and maybe finally get to use the 2" OIII filter that I have no idea why I bought last year.

I now want to put and end to the "aperture fever" and just want you guys to telle me that I will have no good use of an 16" Lighrbridge under medium skies? M31 Will not show it's arms, and M33 & M101 will still be impossibly elusive right?

[Ben Ritchie]

I now want to put and end to the "aperture fever" and just want you guys to telle me that I will have no good use of an 16" Lighrbridge under medium skies? M31 Will not show it's arms, and M33 & M101 will still be impossibly elusive right?

It's true that dark skies are king, under really dark conditions you get people like O'Meara doing the whole Messier catalogue with something like a 3" refractor which is impossible under any sort of light pollution.

But ...

Aperture matters too. You'll never see as much under moderate light pollution as you would with a similar 'scope elsewhere, but for me - under Bortle Yellow sky - moving from an 8" f/4 to a 12" f/5 newt certainly has dragged a lot of things into view (or from averted vision to direct vision). So i'd say it's well worth it. Much easier to go up in aperture than to move somewhere dark...

[glennbech]

It's true that dark skies are king, under really dark conditions you get people like O'Meara doing the whole Messier catalogue with something like a 3" refractor which is impossible under any sort of light pollution.

He has made a sketch in his book of M31 with all the spiral arms... All at the EP of the 3" That is amazing. If he didn't have the rep. he has I would have said he cheated Crazy stuff.

So I guess it boils down to

1) Take more trips with my 3.5" to dark sites (I can get away with 2-4 hours of driving for near perfect skies)

2) Spend Cash to see the same things from my back yard with a 12".... (Is this considered a "brute force" attack on the problem?!)

[GazOC]

Options 1 and 2 don't need to be mutually exclusive....

[russ]

Options 1 and 2 don't need to be mutually exclusive....

Exactly, get the 16, use it at home most nights for an immediate improvement and then really knock yourself out with the 16 at a dark site.

As Ben says, the larger aperture brings in objects that were once elusive or makes others easier. You may still struggle to see the dustlanes in M31 or the spiral arms of M81 but overall the improvement is easy to see.

My i own personal surprise is how easy M97 and M108 are now. I struggled big time with the 8 to see those two. With the 12.5 i couldn't miss them.

[SteveL]

....and then really knock yourself out with the 16 at a dark site.

Dont take that literally, OK?

[Ben Ritchie]

Exactly, get the 16, use it at home most nights for an immediate improvement and then really knock yourself out with the 16 at a dark site

Being slightly facetious, there's an argument for not doing that ... because it's a right bummer to get back home again and discover how much light pollution sucks. I got to use a big 18" Obsession dob under Arizona desert skies at one point (transparent, still and dark, 300 nights a year), and visual Astronomy in the UK really sucked after that. Sometimes it's better not to know

[russ]

Indeed, myself and Ant found that out the hard way too. One really good night at Kelling, stunning skies etc. Then got home and couldn't go out for 4 months.

[Ant]

Yeah I remember that!

But that was back when even Kelling was much better than it is now.

That was a great weekend!

Ant

[MartinB]

The other good thing about aperture is that you can afford the light hit caused by LP filters. Using a CLS filter with my ED120 really doesn't help bringing out detail in faint galaxies since they all but disappear whereas it really does enhance things with my 12" skyliner

[PhilM]

Don't give up on the OIII with the 3.5" - I regularly use an OIII with my 3.5". It's complete rubbish when people say they are no good for smaller scopes. Yes, stars become a lot fainter but it gives me lovely views of the Veil, and I see a lot more of M27, M76 and M42 with it, let alone blinking it in and out to spot small planetaries.

As for aperture fever - there is no cure

You can't make a bad sky better but you can see more through a big scope...

[kniclander]

The other good thing about aperture is that you can afford the light hit caused by LP filters. Using a CLS filter with my ED120 really doesn't help bringing out detail in faint galaxies since they all but disappear whereas it really does enhance things with my 12" skyliner

what is a CLS filter? i've seen lot's of references to it but can't work out what it is (I fear I am being really thick) :scratch:

thanks

Dan

[MartinB]

It's just Astronomics LP fliter.

[kniclander]

thanks