1. Aug 29, 2006

vincentm

Hello Everyone,

I currently own a small dobsonian telescope and with recent trips out to E. Washington state, i've been curious about upgrading to a more powerful scope.

This is the one i currently own:

Bushnell voyager dobsonian

And the one i'm currently looking at:

Meade 4.5" Telestar Telescope with AutoStar

My question is. Will i notice a more significant difference in using this one? Or should i spend a bit more for a more powerful model, i want to eventually get into some astrophotograhpy and probably have one that will allow me to do so. I've been doing my stargazing near the LIGO area, It's a great site and soon i will shedule a tour of this fascinating observatory itself.

2. Aug 29, 2006

franznietzsche

Depending on your budget, I would recommend going up to either the orion or meade 6-8 inch dob models. If you're good (I have seen people who have done this) you can equip those mounts with motors or build your own motorized dobsonian mount (or even upgrade later to an equatorial mount and keeping the dob tube, I've seen people do that as well). For extra-solar system astrophotography, you really need aperture (or ridiculous exposure times).

3. Sep 6, 2006

Apart from having the stability of a tripod (if you're sling-observing with the bushnell), you won't notice much difference. Both are 4.5" in diameter, so deep-sky objects won't be noticably brighter, and for double-stars your diffraction-limited resolution won't change either. Telescope choice really depends on what you want to look at, but either way you should be willing to spend $500 for a _real_ improvement over what you currently own. For planetary observing, you can find a decent refractor with a long focal length (since you already own a wide-field scope), or you can upgrade to a standard 6" dob from Orion. Light gathering power goes as radius squared, so a 6" scope will have a little less than 2x the light gathering power than your 4.5" scope. 4. Sep 6, 2006 chroot Staff Emeritus The optical and mechanical quality of a Meade scope is certainly going to beat that of a Bushnell scope. However, as others have pointed out, it's the same aperture and won't be fundamentally any different from what you currently have. Of course, youu may enjoy the computer control. If you're interested in astrophotography -- and you want to be able to take the kind of pictures you see in Sky & Telescope magazine -- you're almost assuredly going to end up using a high-end apochromatic refractor (commonly referred to as 'apos'). Telescopes like the TeleVue TV-76 and NP-101, or the Orion ED-80 offer extremely high optical quality, little or no optical element flexure, short focus, wide field of view, large-format optical backs to reduce vignetting -- all crucial features for photography. If you couple an apo with a capable computerized equatorial mount, you will have yourself an excellent platform for astrophotography. Just to make things extraordinarily clear: a "good" astrophotography platform is going to cost, at minimum, around$5k, and there's a steep learning curve in the use of such equipment: polar alignment, guiding, image processing, all the rest.

If you're interested in less-ambitious astrophotography, like afocal coupling with a consumer-grade camera or webcam planetary photography, your needs are much less demanding, and you can get by with an altazimuth mount and a mid-grade Newtonian telescope. Imaging with modest equipment can still be an extremely rewarding hobby, but the resulting images won't be all that impressive to your friends, who are used to Hubble images by now.

Note that the 4.5" Telestar scope you linked is not appropriate for most kinds of astrophotography, because it is only offered with a pillar-and-claw altazimuth mount.

- Warren

5. Sep 6, 2006

turbo

For $40 less, you can get an Orion 6" Dobsonian with no bells and whistles. If you're willing to go to$360, you can get an 8" Orion dob that will blow the doors off the 4.5" in light-gathering.

6. Sep 7, 2006

Chronos

As Turbo noted, size does matter when it comes to aperature. Even a borderline average quality 8" primary will blow the stockings off a sublimely perfect 4" rig every time. If astrophotography is the goal, a rock solid equatorial mount, IMO, makes the most sense. It's cheaper than a computer aided tracking system, which means more money for aperature and/or a nice CCD camera. You can also impress women with your rough and resourceful ability to find stuff using the ancient setting circles method.

7. Sep 7, 2006

chroot

Staff Emeritus
This is absolutely false. If your goal is astrophotography, a short-focus, essentially flawless apochromatic refractor is a better tool than an 8" light bucket, even if the 8" has visually acceptable coma and spherical abberation. You want pictures with pinpoint stars and flat fields, and that's very, very, very hard to achieve with a Newtonian.

Visual observation and good photography demand very, very different hardware.

I'm sorry, but this is also false. Unfortunately, even the most "rock solid" equatorial mount will suffer from both periodic drive error, and your human limitations in accurate polar alignment. Any decent astrophotograph must be guided. You can guide either with an off-axis guider -- an incredibly dull process involving looking through the crosshairs of an eyepiece for hours -- or you can use a CCD camera with a guide imager, which is automatic and very precise. Of course, to use an autoguider, you need a computerized mount, or, at a minimum, a mount with a decent two-axis electronic drive.

The best images tend to come from astronomers using excellent mounts (like the Paramount) coupled to modest-aperature short-focus apos, or, if larger aperature is desired, specially-designed RC telescopes or astrographs.

A run of the mill 8" Newt mounted to a plain, one-axis equatorial mount will, frankly, produce awful pictures.

- Warren

Last edited: Sep 7, 2006
8. Sep 7, 2006

turbo

chroot has given you good advice. My advice was simplistic, since a low-cost upgrade to a decent 8" dob from a ball-mount newtonian is a no-brainer. To go further requires a lot more money, and the most bang for the buck at the level you mentioned involves buying aperture. I have owned newts (Meade, Coulter), SCs (Dynamax, Celestron, JSO), a mak (Questar), and a couple of APOs (currently own both, along with a Celestron Comet-Catcher for quick looks on the deck). I have an 80 mm f:5.6 Vernonscope APO and a 6" f:8 Astro-Physics APO on a great mount. Either of these instruments will take great astophotos, but I must warn you that you will spend a whole lot more money than you are anticipating to get even a decent 80mm APO OTA, and then you still don't have a mount and drive controller - and you do have to guide every astophoto for best results, because there is no mechanical drive that is free of periodic error.

If you're used to scanning the skies with that ball-mount scope, take the next step to a larger dob. Even if you later decide that you want to get a 'scope capable of astrophotography, you probably won't get rid of the dob because it will let you see "faint fuzzies" visually. If I buy another scope (after I build my roll-off roof observatory), it will be a 12" or larger dob for visual observing. I love finding faint stuff visually and identifying it with Uranometria or another good set of charts (there are good tools on-line, too).

If you can attend a star party put on by your local astronomy club, you will get a chance to look through a variety of instruments and gain some insight into what direction you want to take.

Last edited: Sep 8, 2006
9. Sep 7, 2006

chroot

Staff Emeritus
Yup. Again, the distinction has to be made between "basic" astrophotography (using a consumer digital camera held up to an eyepiece, etc.) and good astrophotography, which produces the sort of images you're used to seeing in magazines.

Nearly any telescope can be used to take pictures of the "basic" variety, but a significant amount of money and effort has to be expended to get the "good" variety.

I think I just drooled all over my desk. That baby must've cost you a pretty penny. $15k? AP refractors are practically the gold standard for astrophotography, and the waiting list for a 6" is usually several years long. What kind of mount do you use it with? - Warren 10. Sep 8, 2006 turbo It wasn't bad. I ordered one shortly after reading a rave review of that scope in Astronomy over 20 years ago. If I recall, the OTA, mount, and tripod set me back less than$3000, and since Roland's fame hadn't spread too far at the time, the scope was delivered only about 10 months after the order. The mount is a 706, and it rests on a very heavy oak-legged oak tripod. I customised the laminated oak center brace by drilling holes to hold eyepieces, and added window latches to capture the rods in the legs (extra security). I usally photograph through the AP and use the Vernonscope APO as the guider-finder. I haven't done astrophotography for a while now because I don't want to hassle with the long exposure times required by film. I'm going to have to spring for a SBIG camera and filters, or similar, and that will probably cost 3x what the scope did. Sometime in the next couple of years, I'm going to build a roll-off roof observatory for it, with a steel pier for the mount, so I can leave it set up and go out and use it on short notice. We moved to this dark-sky location just last year, so I've still got a lot of projects ahead of me.

11. Sep 8, 2006

vincentm

Thanks for the replies everyone, very useful information this is why i love this site. I'm thinking about going with turbo-1's advice and getting a larger Dob for the time being, given my budget. There is some awesome stargazing to do out near the LIGO site, The size of most larger Dobsonians won't be an issue as i will be having this shipped to my fiance's parent's house in Tri-cities (transporting that thing in a Plymouth Neon from Seattle 3 hours east won't be easy) And will just keep it there for when we visit.

right now i have it boiled down to two decisions

Orion® SkyView™ Pro 8 EQ Reflector

And

SkyQuest XT8 Classic Dob Plus 3 Free Accessories

Last edited: Sep 8, 2006
12. Sep 8, 2006

franznietzsche

Both excellent choices. I still have my first Meade 8" Dob (my first real 'scope, though I had a tiny Tasco refractor when I was 7 or 8). Wonderful quality scope.

13. Sep 8, 2006

Labguy

Go with the DOB at the lower price. Being "commercial grade" scopes (Chinese), the ~f/5 of the EQ model vs. the ~f/6 of the dob can often make a very big difference though it doesn't sound like much. The longer focal ratios will almost always have a more accurate figure than the short f/ratios, Chinese or not. It is easier to make accuracy on any longer f/ratio mirror (and lenses too). At about f/10 on a mirror, it doesn't even need to be parabolic unless particularly large aperture.

Plus, the Dob is ~50% of the EQ . Plus, sell the eyepieces and upgrade at least a bit to two good 55 degree+ Plossls and one decent Barlow lens. $70 each can get you good quality, don't buy into the "Gotta Have a Televue" hype. Last edited: Sep 8, 2006 14. Sep 8, 2006 franznietzsche I would also recommend getting a helical focuser to replace the rack and pinion, and a Telrad finder scope(or at least an 8x50), rather than the default 6x30 one. That will help a lot with deep-sky objects. 15. Sep 8, 2006 turbo If I may make a suggestion: the SkyView Pro 8 is on a mount that looks marginal for the scope. An equatorial mount and the tripod on which it rests must be solid and massive or you will be fighting vibrations, especially at higher magnifications and especially on breezy nights. The basic non-intelliscope Newtonial that you linked is$600. For only \$530, you can get their XT10 dobsonian. Remember that light-gathering capabilities scale as a square of the mirror size. For rough numbers, you can square the aperture of the 8" scope and the 10" scope and get 64 and 100 respectively. The 10" gives you 72% more light-gathering ability than the 8", and the dobsonian mount will be far more stable and vibration-free than the equatorially-mounted 8" Newt that you linked. Now would be a good time to attend a star party and get an idea what scopes like these can do - then set your goals and your budget. Good luck!

Last edited: Sep 8, 2006
16. Sep 8, 2006

Labguy

Agree 100% on the Telrad. Most helical focusers are shorter than the standard (very high) R&P focusers, and if it is too low for the prime focus you have to:

(1) Get a short extension tube, or:
(2) Move the primary mirror back a bit (not hard to do).

17. Sep 9, 2006

vincentm

Heading out to tri-cities in a few, just joined the tri-cities astronomy club thank you for all your help turbo-1 i really appreciate it

18. Sep 9, 2006

turbo

Good for you! Joining a good club is the best way to get good practical advice and some hands-on before you jump in and buy a scope. Be sure to let the other members know that you are in the market for a scope. Some of them may want to sell one to finance an upgrade or some other new equipment, and you may be able to get a really good deal that way. Plus, you get to try out the scope first, and if the scope needed some accessories like a cooling fan, tel-rad finder, etc, the previous owner may have already fitted those. Good luck!

19. Sep 10, 2006

Chronos

Thanks for correcting my misperceptions. Your wisdom has not gone unnoticed.

Last edited: Sep 10, 2006
20. Sep 16, 2006

Chronos

I'm a sucker for aperature. It's not the cure for all your astrophoto needs, but it covers many sins. I haven't taken any pics for . . . about 20 years . . . so chroot's criticism is probably correct and my experience is probably hopelessly outdated. I lived and died by a 6" Newtonian f7 that came with a heavy equatorial mount and chintzy clock drive. It worked well for me. I vice gripped a 35 mm camera, prime focus, and snapped away. Yea, I never did get the thing lined up just right. Anything over a 20 minute exposure was living on the edge, but, I had great fun with that tube and learned how to use star charts. In 1970, I went to an AAVSO meeting in Memphis TN. One of the guest speakers invited us to his observatory on the edge of town. Me and this other kid from Detroit showed up. He had a 24 inch Cass. Wow, the Andromeda galaxy flickered to life like I never dreamt it could be. That's what sold me on light buckets. I never got around to upgrading my scope, but, I never forgot how breathtaking that views was . . . can we cut to a commercial now? Long and the short is . . . I agree with Chroot's advice. He has more recent experience and all you guys and gals interested in astrophotography will benefit more from his advice than anything I have to offer. Heck, I used to have a lab to develope my own photos - I was exposed to toxic chemicals and girls who danced with poles.