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

General Astronomy >> Beginners Forum

Pages: 1 | 2 | 3 | (show all)
Atl
professor emeritus
*****

Reged: 04/13/12

Re: What advantages do Dobson Telescopes have? new [Re: panhard]
      #5544590 - 11/28/12 09:31 PM Attachment (16 downloads)

If you just want to play you can certainly photo the moon and planets. Here is an image from my dob at 100x with no tracking...not exactly art...but very cool.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Atl
professor emeritus
*****

Reged: 04/13/12

Re: What advantages do Dobson Telescopes have? new [Re: Atl]
      #5544608 - 11/28/12 09:42 PM Attachment (119072 downloads)

And another...also no tracking. So dobs are not a lost cause for photography. Is it ideal? No, but we are not all out to be Damien Peach...lol...and it gives great views!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike4242
Pooh-Bah


Reged: 11/02/11

Loc: Memphis, TN
Re: What advantages do Dobson Telescopes have? new [Re: Atl]
      #5544680 - 11/28/12 10:14 PM

Great shots!

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

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: What advantages do Dobson Telescopes have? new [Re: panhard]
      #5544684 - 11/28/12 10:16 PM

Nothing impresses at an outreach like a good-size dob. To the general public, even a 6" dob looks huge. My 10" and 12" are well received by the unwashed masses.

Post Extras: Print Post   Remind Me!   Notify Moderator  
GOLGO13
Carpal Tunnel


Reged: 11/05/05

Loc: St. Louis area
Re: What advantages do Dobson Telescopes have? new [Re: kfiscus]
      #5544699 - 11/28/12 10:24 PM

Kfiscus,

It's funny you say that about the size of the dobs being impressive. When I got my 10 inch dob I thought...holy moley this is big. Then I went to a site with a 30 inch dob, and my friend has a 16 inch dob. Now I look at my 10 inch and think, it's kinda medium to small sized.


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


Reged: 08/05/12

Loc: N of Cedar City Light Dome
Re: What advantages do Dobson Telescopes have? new [Re: Atl]
      #5544714 - 11/28/12 10:31 PM

Quote:

And another...also no tracking. So dobs are not a lost cause for photography. Is it ideal? No, but we are not all out to be Damien Peach...lol...and it gives great views!



Took my first prime focus moon photo with my dob the other night using my still camera as a video recorder, followed by Registax. Nothing I'd want to show here. Would you care to mention what you used, and what your settings were? Also, is this a single frame, or stitched?


Post Extras: Print Post   Remind Me!   Notify Moderator  
omahaastro
sage


Reged: 08/30/06

Loc: Omaha, NE
Re: What advantages do Dobson Telescopes have? new [Re: Seldom]
      #5544734 - 11/28/12 10:41 PM

Quote:

Above 10-inches or so with a solid tube, and 16-inches with a truss tube, they are heavy and bulky and require a larger vehicle to transport.




I actually consider this an advantage... how many folks do you see moving around 10+" refractors or 16+" SCT's ?? Dobsonians at least make it feasible to transport (after being able to afford it financially) such a large aperture.


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


Reged: 05/17/11

Loc: East Texas
Re: What advantages do Dobson Telescopes have? new [Re: Seldom]
      #5544740 - 11/28/12 10:46 PM

I don't believe all GoTo Dobs have auto-tracking as well. The Orion "g" series does, but they're expensive.

Field rotation will spoil astrophotos with exposure times of longer than a few minutes, but I've heard that people have taken some very good astrophotos using Dobs with auto-tracking and exposure times of only a few minutes.


Post Extras: Print Post   Remind Me!   Notify Moderator  
jerwin
scholastic sledgehammer
*****

Reged: 05/17/12

Loc: Romeoville IL
Re: What advantages do Dobson Telescopes have? new [Re: panhard]
      #5544759 - 11/28/12 10:54 PM

I have a 10 inch dob and an 11 inch SCT. If I could only keep one I'd keep my SCT, but I do like the speed in which I can observe with my dob.

You’re not going to get more than shots of the moon and Jupiter and Saturn with a dob, but I'd also suggest you read the post at the top of the beginners forum called, why of why AP for beginners. I've spent a LOT of money on AP. It's way more complicated than hooking up your camera and snapping a picture for DSO's.

If I could do any one thing different I wouldn't have tried AP. However trying to get my SCT to do AP was the reason I bought the dob so I had something to look at while my rig was photographing the sky.

So bitter sweet I guess.

But a few things on a dob, most don't track. So if you take a break or take your eye off the eyepiece your object is going to drift out of your FOV.

On planets I get pretty substantial diffraction spikes, so basically a big bright + through the planet. there is ways around this but it will cost some $$. Jupiter is smaller in my dob than in my SCT but with pretty good contrast.

goto dobs are more expensive, there is the intelliscope that will help you find objects in the sky, but I think typical dob owners are locating DSO's by star hopping or simply knowing where stuff is. If your new this can be frustrating trying to find something cool to look at.

A good used\cheap dob is a good investment for visual use. AP can get expensive no matter if you are using a newt, SCT or refractor.

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
Atl
professor emeritus
*****

Reged: 04/13/12

Re: What advantages do Dobson Telescopes have? new [Re: Seldom]
      #5544765 - 11/28/12 10:56 PM

I used a web cam at 800x600 for both shots. I let the image drift across the eyepiece, then exported my best frame as a reference frame. Then I stacked the frames in registax. On the planet I told registax to stretch the histogram for fine gamma control. Then I played with the wavelets until all was nice. Jupiter was 1000 frames and the moon 30. I feel like I will do much better next time I try as you start developing a feel for this.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Atl
professor emeritus
*****

Reged: 04/13/12

Re: What advantages do Dobson Telescopes have? new [Re: jerwin]
      #5544771 - 11/28/12 11:01 PM

Quote:

I have a 10 inch dob and an 11 inch SCT. If I could only keep one I'd keep my SCT, but I do like the speed in which I can observe with my dob.

You’re not going to get more than shots of the moon and Jupiter and Saturn with a dob, but I'd also suggest you read the post at the top of the beginners forum called, why of why AP for beginners. I've spent a LOT of money on AP. It's way more complicated than hooking up your camera and snapping a picture for DSO's.

If I could do any one thing different I wouldn't have tried AP. However trying to get my SCT to do AP was the reason I bought the dob so I had something to look at while my rig was photographing the sky.

So bitter sweet I guess.

But a few things on a dob, most don't track. So if you take a break or take your eye off the eyepiece your object is going to drift out of your FOV.

On planets I get pretty substantial diffraction spikes, so basically a big bright + through the planet. there is ways around this but it will cost some $$. Jupiter is smaller in my dob than in my SCT but with pretty good contrast.

goto dobs are more expensive, there is the intelliscope that will help you find objects in the sky, but I think typical dob owners are locating DSO's by star hopping or simply knowing where stuff is. If your new this can be frustrating trying to find something cool to look at.

A good used\cheap dob is a good investment for visual use. AP can get expensive no matter if you are using a newt, SCT or refractor.

Jim




I agree. To me learning the sky is a pre requisite for any other astronomical activity...astrophotography included so a dobsonian is a good first choice.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: What advantages do Dobson Telescopes have? new [Re: jerwin]
      #5544793 - 11/28/12 11:14 PM

Quote:


On planets I get pretty substantial diffraction spikes, so basically a big bright + through the planet. there is ways around this but it will cost some $$. Jupiter is smaller in my dob than in my SCT but with pretty good contrast.




The straight spider vanes of a Newtonian produce diffraction spikes. However the effect of these on the image is small because the represent a very small area. In terms of the effect on the contrast of the planets, the relatively large central obstruction of the SCT is more damaging than the comparatively small CO of the Newtonian.

Jon


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


Reged: 11/20/12

Loc: Iowa, USA
Re: What advantages do Dobson Telescopes have? new [Re: Atl]
      #5544817 - 11/28/12 11:28 PM

These photos are great (at least from my point of view). As a new beginner, I'm thinking I want to be able to track and stay on target for the photos I need long time exposures. No doubt it is going to take a while before I get to that level but having a cooperative telescope is going to be a big plus. I know many of you make things look easy no matter what you use.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: What advantages do Dobson Telescopes have? new [Re: wdretired]
      #5544991 - 11/29/12 05:38 AM

Quote:

These photos are great (at least from my point of view). As a new beginner, I'm thinking I want to be able to track and stay on target for the photos I need long time exposures. No doubt it is going to take a while before I get to that level but having a cooperative telescope is going to be a big plus. I know many of you make things look easy no matter what you use.




If you really want to get into astrophotography, you do want a scope with an motorized equatorial mount of some sort. The Dobsonian is designed for visual observation and Dobsonians are very effective for that. But when doing astrophotography, the mount is the most important factor, a great scope on a poor mount results in poor photos. Equatorial platforms make astrophotography possible but the good ones are expensive and the bulk and length of a Dob make it all a difficult task.

GOTO Dobsonians face the same problems as other ALT-AZ mounts, field rotation. As an alt-az mount tracks across the sky, the outer stars rotate about the center so only short exposures are possible. As much as I love my Dobs, if Astrophotography is definitely on the menu then it is best to look elsewhere.

I suggest looking at the Cloudy Nights Imaging forums, they are about half way down the page to get an idea of what is possible.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: What advantages do Dobson Telescopes have? new [Re: Seldom]
      #5545078 - 11/29/12 08:20 AM

Quote:

Quote:


Astrophotography is almost out of the question unless you want one mounted on a heavy eq platform with a modified low profile focuser.



How long an exposure can you expect from a dob on an equatorial platform?




Till a butterfly beats its wings anwhere within a 1000 mile radius. Problem with big newts (8" and larger) is that they're wind socks. Without an observatory with a pier mount stuck into the ground, don't go that route. Talk about setup time, better arrive the day before. It's also very, very, very, did I say very expensive. A nice CG5 (minimum) or a Losmundy and you could mount a decent sized APO or triplet for some really nice AP. You probably, technically, use a Losmundy G11 with an 8-10" Newt, but it would still be a windsock.


Post Extras: Print Post   Remind Me!   Notify Moderator  
csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: What advantages do Dobson Telescopes have? new [Re: Tony Flanders]
      #5545086 - 11/29/12 08:26 AM

Quote:

Quote:

Is there an advantage to having a goto Dob? I noticed they were a bit more expensive but except for mounting the camera, you wouldn't have to worry about keeping up with the target.




Go To Dobs have two advantages: They track the sky and (of course) they find the objects for you, rather than requiring you to star-hop.

However, they are not suitable for long-exposure astrophotography. For that, you need an equatorial mount to avoid field rotation.

Quote:

Are you actually looking over the top of the telescope into the eye piece or are they moveable to the side?




Big Dobs -- ones where you often need a ladder -- usually have the eyepiece mounted horizontally. Small and medium-sized Dobs usually have it mounted so that it points up at 45 degrees when the tube is horizontal.

Few Dobs allow you to rotate the eyepiece to different positions.




You know, I've never seen a Dob with ring mounts that could allow you to rotate the scope. It's seems it would be pretty easy technically to do, would probably make the mount a little bigger and the additional weight of the rings, but definitely feasible. I wonder why no one's marketed something like that. It would be a boon to Astronomy club public viewing scopes.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mark Costello
Post Laureate
*****

Reged: 03/08/05

Loc: Matthews, NC, USA
Re: What advantages do Dobson Telescopes have? new [Re: jerwin]
      #5545128 - 11/29/12 09:03 AM

"goto dobs are more expensive, there is the intelliscope that will help you find objects in the sky, but I think typical dob owners are locating DSO's by star hopping or simply knowing where stuff is. If your new this can be frustrating trying to find something cool to look at."


Hello everyone. I'd thought I'd just point out that goto Dobs, at least the ones rolled out by Orion, are in the ballpark of half the price of goto SCTs from Celestron and Meade at the same aperture. I'm still inclined to get a SCT or MCT as a complement to my achro refractor but this little tidbit is one consideration that keeps the Dob in the running, another being the somewhat superior images of a Newtonian compared to a Cassegrain type reflector (includes SCT or MCT) of the same aperture and build quality. If I got a goto Dob, I'd locate objects in the "Intelliscope" or "push-to" mode then turn on the tracking.....


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: What advantages do Dobson Telescopes have? new [Re: csrlice12]
      #5545261 - 11/29/12 10:31 AM Attachment (7 downloads)

Quote:

You know, I've never seen a Dob with ring mounts that could allow you to rotate the scope. It's seems it would be pretty easy technically to do, would probably make the mount a little bigger and the additional weight of the rings, but definitely feasible. I wonder why no one's marketed something like that. It would be a boon to Astronomy club public viewing scopes.





The original Dobsonians did not attach the altitude bearings directly to the tube but rather had a box and the tube could often be rotated. This makes for a heavy and bulky scope. In the photo below, you can see the 13.1 inch Blue Tube Coulter and how large and bulky that design was. In my experience, rotating the tube is not much of an advantage, with smaller scopes where one is viewing seated, the eyepiece is ideally between 30-45 degrees from "horizontal", it's really only with very large scopes that require a ladder where the "straight out the side" is best.

One time I used some standard tube rings to mount the altitude bearings on a 8 inch F/5 Newtonian. The advantage there was not so much being able to rotate the tube, rather it allowed me to balance the scope. The downside was that the added clearance necessary meant the 8 inch scope fit a 10 inch mount.

Jon

Edited by Jon Isaacs (11/29/12 10:33 AM)


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

Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: What advantages do Dobson Telescopes have? new [Re: csrlice12]
      #5545425 - 11/29/12 12:05 PM

Quote:

You know, I've never seen a Dob with ring mounts that could allow you to rotate the scope.




My 7-inch Dob, the Starmaster Oak Classic, holds the tube by friction inside a square box that pivots on the altitude bearings. That makes it fairly easy both to rebalance and to rotate the tube.

It's debatable whether the StarBlast and its tabletop cousins count as Dobs, due to the fact that they're mounted on a single arms rather than a box. But these mostly come with tube rings -- a very nice feature.

The ultimate in rotatability are the Astroscan and Portaball. These make superb star-party scopes for that reason. But it's reaslly a stretch to call them Dobs.


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


Reged: 08/05/12

Loc: N of Cedar City Light Dome
Re: What advantages do Dobson Telescopes have? new [Re: Jon Isaacs]
      #5545549 - 11/29/12 01:29 PM

Quote:

GOTO Dobsonians face the same problems as other ALT-AZ mounts, field rotation.




Does Registax compensate for field rotation if video files are used?


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


Extra information
17 registered and 30 anonymous users are browsing this forum.

Moderator:  WOBentley, kkokkolis, Chuck Hards 

Print Thread

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


Thread views: 1428

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics