Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Observing >> Deep Sky Observing

Pages: 1 | 2 | 3 | (show all)
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
12" versus 16" for galaxy structure
      #5664102 - 02/05/13 06:17 PM

I'm in the middle of choosing between a 12" or 16" reflector. I love dust lanes in galaxies and such but the 16" is twice the cost of the 12". I've looked through both but for galaxies would u guys strongly recommend the 16 or is it a shrug? 20" is huge but simply out of my budget.

Thanks in advance. My sky's are generally 6.2-6.5v where I'd use it.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
Achernar
Postmaster
*****

Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: 12" versus 16" for galaxy structure new [Re: azure1961p]
      #5664194 - 02/05/13 07:15 PM

A 16-inch will always show more than a 12-inch from the same site, but a 12-inch will also show a lot on galaxies from a good dark site. Are you looking for a mass-produced or a premium Dob? If you can afford a 16-inch without breaking the bank, I would take that route if you are looking for a telescope that will be more than enough aperture for observing galaxies. A 16-inch takes in about 80 percent more light than a 12-inch, a signifcant difference that will show through the eyepiece.

Taras


Post Extras: Print Post   Remind Me!   Notify Moderator  
Dave MitskyModerator
Postmaster
*****

Reged: 04/08/02

Loc: PA, USA, Planet Earth
Re: 12" versus 16" for galaxy structure new [Re: Achernar]
      #5664236 - 02/05/13 07:47 PM

I recommend getting the 16-inch for galaxy and other DSO observing.

Dave Mitsky


Post Extras: Print Post   Remind Me!   Notify Moderator  
IVM
scholastic sledgehammer


Reged: 01/07/08

Loc: Western New York
Re: 12" versus 16" for galaxy structure new [Re: azure1961p]
      #5664357 - 02/05/13 09:37 PM

Galaxy structure is probably my primary observing interest. Although I never did a side-by-side comparison, it seems that my 12" driven SCT is roughly equal to my undriven 16" "Dob" in how much they reveal in practice, and my undriven 12" "Dob" is not very far behind. When the magnification used with a 12" is 3/4 of the magnification used with a 16", the surface brightness in the two scopes is the same. This theoretical relationship fits with my impressions. I use the 16" most of the time only partly because of its aperture (due to its design it happens to be the most portable of my 3 large scopes).

Post Extras: Print Post   Remind Me!   Notify Moderator  
JayinUT
I'm not Sleepy
*****

Reged: 09/19/08

Loc: Utah
Re: 12" versus 16" for galaxy structure new [Re: IVM]
      #5664493 - 02/05/13 11:32 PM

Aperture wins, always. Having said that I have a 14 inch I use and am content on that. The 16 will show you more. Weight is a concern.

Post Extras: Print Post   Remind Me!   Notify Moderator  
HellsKitchen
Pooh-Bah


Reged: 09/05/08

Loc: Melbourne Australia
Re: 12" versus 16" for galaxy structure new [Re: JayinUT]
      #5664669 - 02/06/13 05:49 AM

My 12" can show galaxies as faint as visual magnitude 14 from my outer suburban location. A good 12" is a very nice thing to have, but for faint fuzzies, aperture is king.

If weight, size, portability and transport are not an issue, get a 16". The mass produced asian ones (e.g GSO, Lightbridge) have large and heavy bases which may be an problem for handling it, but are quite affordable and you really do get a lot for your money (especially compared to even a decade ago). Alternatively there are several flavours of premium models that may be lighter and incorporate a variety of features that facilitate portability and are often customizable to your needs. But you'll be paying at least triple the price of a mass produced model.

Edited by HellsKitchen (02/06/13 05:50 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Feidb
Pooh-Bah


Reged: 10/09/09

Loc: Nevada
Re: 12" versus 16" for galaxy structure new [Re: HellsKitchen]
      #5664904 - 02/06/13 10:04 AM

I'd recommend the 16-inch also. I've been using one exclusively for 25+ years. First one I made, a 16-inch f/6.4 but it just got too cumbersome to lug around. I now use a 16-inch f/4.5 commercially made and you just can't beat the aperture for not only catching the faint fuzzies, but for structure. I've compared my commerical one side by side with 12 inchers from standard to premium optics and there is still a noticeable difference.

Post Extras: Print Post   Remind Me!   Notify Moderator  
coutleef
Post Laureate
*****

Reged: 02/21/08

Loc: Saint-Donat, Québec, Canada
Re: 12" versus 16" for galaxy structure new [Re: HellsKitchen]
      #5664910 - 02/06/13 10:11 AM

i would say get the biggest aperture you can transport to a dark site. looking through briefly a 16 inch i had the impression that the jump from 12 to 16 was similar to the jump from 8 to 12. so quite worthwhile. galaxies or details you could see with averted vision on the 12 were seen with direct vision on the 16.

it will be significant especially on galaxies. but the 16 was just too big a scope for me to handle.

Edited by coutleef (02/06/13 10:11 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Madratter
Post Laureate


Reged: 01/14/13

Re: 12" versus 16" for galaxy structure new [Re: Feidb]
      #5664917 - 02/06/13 10:12 AM

As others have said, bigger is better. But even with a 20" f/5 (my scope) you can only see so much in terms of structure.

The bigger reason I like the larger scope is I really enjoy groups of galaxies. And the more light you can pull in, the better.

If you are interested in galaxies, get the biggest scope you will use on a regular basis. Big scopes are MUCH heavier.


Post Extras: Print Post   Remind Me!   Notify Moderator  
GlennLeDrew
Postmaster
*****

Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: 12" versus 16" for galaxy structure new [Re: Madratter]
      #5665057 - 02/06/13 11:43 AM

It's not so much that the bigger aperture collects more light, but that extra light collected supports the 33% larger image scale at given exit pupil. For the observation of object structure, image scale is the primary consideration, and the larger aperture provides higher surface brightness at any particular magnification.

Unlike bright object observation, the dim fuzzies have your eye working at rather low resolving power. You need the extra light to afford every advantage in eaking out those subtle details you strive to see.


Post Extras: Print Post   Remind Me!   Notify Moderator  
killdabuddha
Pooh-Bah
*****

Reged: 08/26/11

Re: 12" versus 16" for galaxy structure new [Re: GlennLeDrew]
      #5665070 - 02/06/13 11:49 AM


Wow Glenn, you do have a way. Thanks for stating it so succinctly.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tony Flanders
Postmaster
*****

Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: 12" versus 16" for galaxy structure new [Re: azure1961p]
      #5665119 - 02/06/13 12:17 PM

Quote:

I'm in the middle of choosing between a 12" or 16" reflector. I love dust lanes in galaxies and such but the 16" is twice the cost of the 12".




I must admit that I've never compared a 12-inch and a 16-inch side by side. But it seems to me that galaxies really start to open up in the 16- to 18-inch aperture class.

There are certainly plenty of galaxies that show a great deal of structure through a 12-inch scope. But the number of such galaxies really blossoms when you hit the next aperture bracket up.

It's sort of like globular clusters. An 8-inch resolves many of them, but also fails to resolve many. With a 12-inch, it's always a bit of a surprise when you find a globular cluster that doesn't show some degree of resolution.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Ed D
Carpal Tunnel
*****

Reged: 04/30/10

Loc: Sunny South Florida
Re: 12" versus 16" for galaxy structure new [Re: Tony Flanders]
      #5666059 - 02/06/13 09:32 PM

Pete, for what you want to do the more aperture the better. So, it boils down to getting what you can afford, what you can lift and handle, and what fits in your vehicle. Also, keep in mind that you will probably want a good quality laser collimator, adding to the expenses if you don't already have one.

Also, Glenn hit the nail on the head about thinking in terms of exit pupil and image scale. An observing friend and I both find a 3mm exit pupil to hit the sweet spot for observing galaxies, if that helps.

Ed D


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: 12" versus 16" for galaxy structure new [Re: Ed D]
      #5666151 - 02/06/13 10:21 PM

Thanks guys - a lot of wisdom there and its appreciated. I love long focus but I can't entertain even medium f/6 in 16" . I'm going to build the thing out of carbon fiber cloth and epoxy with some wood laminate.

Ill go with Agenas 16" .

Again, gratis.

Pete
Ps: short term goal is having spectrum put 98% reflectivity on my 8" for spring galaxies and such.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jgraham
Postmaster
*****

Reged: 12/02/04

Loc: Miami Valley Astronomical Soci...
Re: 12" versus 16" for galaxy structure new [Re: azure1961p]
      #5667065 - 02/07/13 01:11 PM

I have two biggo scopes; a homebuilt 16.5" f/6.5 and a Lightbridge 16 which is f/4.5. While I dearly love my homebuilt monster, the shorter, lighter Lightbridge is a joy to use. I made the jump from a homebuilt 10" f/6.7 to my homebuilt 16.5" and when you get up into the 16" range the sky just starts to open up. Having said that, there's no substitute for dark, transparent skies. To this day the best galaxy observing that I've ever done was with a homebuilt 6" f/4.5 from a very, very dark site (35 years ago from Cades Cove in the Great Smoky Mountains National Park). Alas, these days I do all of my observing from my red zone back yard. A bonus for me with the larger scopes is that they give you enough light that filters start to become effective.

Post Extras: Print Post   Remind Me!   Notify Moderator  
k9yr
super member
*****

Reged: 05/21/08

Loc: Far North suburbs of Chicago
Re: 12" versus 16" for galaxy structure new [Re: jgraham]
      #5668059 - 02/07/13 11:03 PM

I have a 13" and built a 16" 2 years ago. The best thing I can say is the 16" has wow factor on basically everything. I took the 16" to dark skies in MN last year and M51 spooked me out. Go with a 16" and a gym membership

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: 12" versus 16" for galaxy structure new [Re: GlennLeDrew]
      #5668137 - 02/07/13 11:49 PM

Quote:

It's not so much that the bigger aperture collects more light, but that extra light collected supports the 33% larger image scale at given exit pupil. For the observation of object structure, image scale is the primary consideration, and the larger aperture provides higher surface brightness at any particular magnification.

Unlike bright object observation, the dim fuzzies have your eye working at rather low resolving power. You need the extra light to afford every advantage in eaking out those subtle details you strive to see.




Yep, my reasoning in moving from a 12.5" to a 16".

With the 12.5 I felt that most galaxies didn't have much to offer, I was just checking off items from a list. Of course given the vast number of faint galaxies, that might be nearly as true with the 16!

Another big improvement for me in moving up in aperture is the addition of tracking. Based on past experience I suspect this will be as big a jump in performance as the added aperture.


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: 12" versus 16" for galaxy structure new [Re: Jeff Morgan]
      #5668608 - 02/08/13 09:44 AM

Thanks for the input.

I'm going with the 16. I've got a lot of fiberglass/composite experience so Ill make the whole thing out of carbon fiber with aluminum or steel where needed. I m looking at Kriegs ultralight dobs as the way to go. I want the lines as clean and low profile as possible for ease of transport and storage. It's going to have a minimilast thing about it. I was going to buy the optics first THEN build it but ill probably do it the other way around

Has anyone got dob parts suppliers for truss tubes, mirror cell, etc. I'm going with Novak for the diagonal.

Jgraham, ill bet that longer focus 16 is a beaut but alas the size of it all. I'm 51 and back in the day when I was 30 or younger I had distant dreams of a 16" reflector at f/7 and the glorious climb up the ladder to contrasts views bare none. That was then lol. Now even the short step ladder for my 8" f/9 is about all I want to bother with. I've gotta believe though the big 16 turns out some spectacular sights given great seeing.

Normally I'm skittish about an f/4 or f/5 system as I never liked my ten, but here's no other way for me to comfortably use 16" in anything longer and it'd be a custom pricey order so the overwhelming light gathering advantage is swamping my resistance on several points.

It'd be great to see eyes in the owl, dust lane on 891, even some obscure galaxies coughing up do e goodies now and again.


I question how good a figure Agena can turn out on a 16" glass. That's a chin rubbing factor I'm not settled on.

Probably start building at the end of feb.

Pete

Edited by azure1961p (02/08/13 09:45 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doug Culbertson
Post Laureate
*****

Reged: 01/06/05

Re: 12" versus 16" for galaxy structure new [Re: GlennLeDrew]
      #5668835 - 02/08/13 11:54 AM

Quote:

It's not so much that the bigger aperture collects more light, but that extra light collected supports the 33% larger image scale at given exit pupil. For the observation of object structure, image scale is the primary consideration, and the larger aperture provides higher surface brightness at any particular magnification.

Unlike bright object observation, the dim fuzzies have your eye working at rather low resolving power. You need the extra light to afford every advantage in eaking out those subtle details you strive to see.




I just thought that this needed saying again. Thanks for putting it in such a succinct manner.


Post Extras: Print Post   Remind Me!   Notify Moderator  
deepskydarrell
member


Reged: 03/09/08

Loc: Abbotsford, BC Canada
Re: 12" versus 16" for galaxy structure new [Re: azure1961p]
      #5668901 - 02/08/13 12:23 PM

Quote:



Jgraham, ill bet that longer focus 16 is a beaut but alas the size of it all. I'm 51 and back in the day when I was 30 or younger I had distant dreams of a 16" reflector at f/7 and the glorious climb up the ladder to contrasts views bare none. That was then lol. Now even the short step ladder for my 8" f/9 is about all I want to bother with. I've gotta believe though the big 16 turns out some spectacular sights given great seeing.

Pete




Consider one thing before you write off a longer 16" -- An orchard ladder. I use a six foot, three legged, aluminum with a flared base. It grabs onto any uneven terrain and is the most solid, stable thing I've ever climbed. It cost under $100, is excedingly light but very solid and if it didn't fit in my vehicle it rode the bike rack on the back.

I'm 58 and can understand the age concern, but I hope I'm climbing those two or three wide steps for many years to come.

And the 2.6 inch secondary gives excellent contrast.

All the best on your building endeavour.

DSD.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | (show all)


Extra information
3 registered and 7 anonymous users are browsing this forum.

Moderator:  Dave Mitsky, Phillip Creed, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 2661

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics