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10'' or 12'' Dobsonian as first telescope?

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#76 stargazer193857

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Posted 21 June 2019 - 03:30 PM

Someone who is serious about astronomy could buy a 20" as their first scope. It might not be a bad purchase; it just is not a good first scope. Many objects won't fit in the view or will be hard to find, and many nights won't be worth taking the scope out. It certainly is a nice extra for someone who already has smaller scopes.
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#77 areyoukiddingme

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Posted 21 June 2019 - 05:31 PM

My take is quite different.  This is a first scope.  If all goes well, there may be others.  A first scope needs to be easy to use, capable enough to show the major classes of objects in good detail.  It should not be overwhelming or physically challenging so that it just sits in the corner.  In terms of Dobs, that comes down to the 8 inch versus the 10 inch.  

 

Both are capable, both are good scopes.  The 8 inch is significantly lighter and easier to manage, it's easier on eyepieces, collimation is less critical. The 10 inch is more capable.

 

As far as: "I could have seen 99.9% of what I have with a 10" dob and three decent eyepieces", that is not true for me.  Three eyepieces is not enough to see a fair amount of what I have seen with my 10 inch and I have seen many objects that are beyond the reach of a 10 inch.  But I have been doing this more than 25 years and spend a good amount of time under dark skies with relatively large scopes.

 

There is time for that. 

 

Jon

It is a first scope, and the decision between 8 and 10 should be thought about carefully if you are the kind of person who is likely to have issues handling the 10. But if relatively young, the differences in lugability are far from insurmountable. Most people, I would guess, are about equally likely to let an 8 or 10 sit in the corner. Reasons other than scope size are likely at play--time constraints, other hobbies, cold weather, thoughts of hairy-toothy-beasts in the undergrowth. . . 

 

And bear in mind that you are far from representative of this hobby. My biggest scope is a 16", and the vast majority of time observing time has been with 12.5" and 11" scopes. The differences among these and a 10" are small to modest.

 

As for the eyepieces, make it two--one a zoom with a barlow, the other a low-power wide-field. 

 

In my 12.5", my zoom gives me ~100-200x native, and ~200-400 with a barlow. Then it's a 31mm for 59x and wide field. That's all the coverage I need. Beyond that is luxury, like 100 degree fields. The same can be easily achieved with a 10" F5.

 

Again, that covers double stars, planetary nebulae, galaxies, planets, many open clusters, nebulae . . . what you are missing is the fainter galaxies, and on the rare best night, the finest planetary details. The real limits are the skies and the observer's experience.

 

For the small percentage of people who have access to a 22" (and formerly a 25"), then sure, my statement doesn't apply. But I suspect my statement does apply to a majority of observers, more or less.


Edited by areyoukiddingme, 21 June 2019 - 05:31 PM.

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#78 Jon Isaacs

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Posted 21 June 2019 - 10:07 PM

And bear in mind that you are far from representative of this hobby. My biggest scope is a 16", and the vast majority of time observing time has been with 12.5" and 11" scopes. The differences among these and a 10" are small to modest.

 

As for the eyepieces, make it two--one a zoom with a barlow, the other a low-power wide-field.

 

In my 12.5", my zoom gives me ~100-200x native, and ~200-400 with a barlow. Then it's a 31mm for 59x and wide field. That's all the coverage I need. Beyond that is luxury, like 100 degree fields. The same can be easily achieved with a 10" F5.

 

Again, that covers double stars, planetary nebulae, galaxies, planets, many open clusters, nebulae . . . what you are missing is the fainter galaxies, and on the rare best night, the finest planetary details. The real limits are the skies and the observer's experience.

 

I realize that I am not necessarily your median/typical observer.  But with a 10 inch, the range of useful magnifications is from about 32x to about 800x and even with a zoom, that just doesn't get covered adequately.  And while you were thinking of large apertures, much of what doesn't get seen with a 10 inch is stuff that one sees in a small scope.

 

But this is neither here nor there.  The 8 inch - 10 inch dilemma is pretty much a win-win, both are good scopes.  One does have to keep in mind the size of a 10 inch, that is easy to forget if one is used to manhandling larger scopes.  A while ago, I was going to loan my 10 inch Dob to a friend who was about 50.  It never occurred to me that he would not be able to manage the OTA, it was just too big and too heavy.

 

Jon


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#79 Z10junky

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Posted 22 June 2019 - 11:54 AM

10 inch solid tube dob is the money scope. you can throw it in the back of a car, it reveals tons of deep space objects, holds collimation very well, and they are generally very durable. throw on a telrad and get some inexpensive explore scientific eyepieces, and you will be rocking and rolling. good times. 


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#80 cuzimthedad

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Posted 22 June 2019 - 08:49 PM

10 inch solid tube dob is the money scope. you can throw it in the back of a car, it reveals tons of deep space objects, holds collimation very well, and they are generally very durable. throw on a telrad and get some inexpensive explore scientific eyepieces, and you will be rocking and rolling. good times. 

I like your attitude Z10junky



#81 turtle86

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Posted 22 June 2019 - 09:54 PM

I like your attitude Z10junky

Me too.



#82 turtle86

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Posted 22 June 2019 - 10:14 PM

10 inch solid tube dob is the money scope. you can throw it in the back of a car, it reveals tons of deep space objects, holds collimation very well, and they are generally very durable. throw on a telrad and get some inexpensive explore scientific eyepieces, and you will be rocking and rolling. good times. 

 

+1

 

10” definitely hits the sweet spot in a solid tube.  Easy to set up, portable, and enough aperture to go deep.  Its portability and easy set up really encourages you to take it out and use, whether in your backyard or at a dark site.  

 

Even though I already had 12.5 and 18” truss Dobs, I decided to get a 10” solid tube Dob because it’s so much easier and faster to set up, a huge consideration for me for quick peeks during the week when I’m tired from work.  


Edited by turtle86, 23 June 2019 - 10:40 AM.

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#83 areyoukiddingme

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Posted 23 June 2019 - 02:41 PM

+1

 

10” definitely hits the sweet spot in a solid tube.  Easy to set up, portable, and enough aperture to go deep.  Its portability and easy set up really encourages you to take it out and use, whether in your backyard or at a dark site.  

 

Even though I already had 12.5 and 18” truss Dobs, I decided to get a 10” solid tube Dob because it’s so much easier and faster to set up, a huge consideration for me for quick peeks during the week when I’m tired from work.  

Interesting. Rather than take out the AP 130, you go for the 10" Orion in this situation? Or do you pair them up?

 

(I'm halfway tempted to get a 120/130mm apo, despite having a really good 8" F7)



#84 cuzimthedad

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Posted 23 June 2019 - 05:42 PM

Interesting. Rather than take out the AP 130, you go for the 10" Orion in this situation? Or do you pair them up?

 

(I'm halfway tempted to get a 120/130mm apo, despite having a really good 8" F7)

I'm not speaking for Rob, but a 10" xti can be up and running in minutes compared to having to set up a heavy eq mount and scope with all the accoutrements that go with it. I'm thinking about doing the same thing for doing spur of the moment observing from my back yard. A 10" dob would be a great home grab n go from the garage to the back yard.


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#85 GoFish

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Posted 23 June 2019 - 05:50 PM

I built a little wheeled dolly for my XT10 and it lives in my garage, covered. In 10 minutes I can be observing from the driveway.

 

Granted, some, shall we say, customization of the street light at the end of the driveway was needed. So far only one neighbor has noticed the odd lighting pattern, and he approves. 


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#86 turtle86

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Posted 23 June 2019 - 06:12 PM

I'm not speaking for Rob, but a 10" xti can be up and running in minutes compared to having to set up a heavy eq mount and scope with all the accoutrements that go with it. I'm thinking about doing the same thing for doing spur of the moment observing from my back yard. A 10" dob would be a great home grab n go from the garage to the back yard.

 

Dan, that’s exactly it.  The 10” XTi really can be up and running in minutes, a huge plus for me on week nights when I’m tired from work and have to get up early the next day.  As much as I like my AP 130 GT it’s not as easy to set up with my GM8 mount.  I plan on getting a DM6 to make observing with my AP 130 GT easier and simpler, but that’s a different topic. 


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#87 turtle86

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Posted 23 June 2019 - 06:16 PM

Interesting. Rather than take out the AP 130, you go for the 10" Orion in this situation? Or do you pair them up?

 

(I'm halfway tempted to get a 120/130mm apo, despite having a really good 8" F7)

 

I’ve had the 12.5 Starmaster and AP 130 GT out together a few times, but only on weekends and holidays.  The two complement each other very well.  But on work nights, the 10” XTi is great for a quick fix.


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#88 areyoukiddingme

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Posted 23 June 2019 - 08:11 PM

Thanks both for the perspective . . . 

 

I might look into getting/making a dob base for my 8" F7 (right now it rides on a Skytee 2 and CG5 tripod).

 

A really nice ~5" apo is very, very tempting however.

 

Getting a DM6, or possibly a Stellarview MC2 would make that set up go really nice and quickly.


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#89 stargazer193857

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Posted 24 June 2019 - 02:56 AM

I really like mine in my 8" F5.9 and 12" F5. I would put this on Par with the ES 82 series.


What is better with the ES series?

#90 Jon Isaacs

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Posted 24 June 2019 - 05:28 AM

Dan, that’s exactly it.  The 10” XTi really can be up and running in minutes, a huge plus for me on week nights when I’m tired from work and have to get up early the next day.  As much as I like my AP 130 GT it’s not as easy to set up with my GM8 mount.  I plan on getting a DM6 to make observing with my AP 130 GT easier and simpler, but that’s a different topic. 

 

The advantage of the refractor is thermal stability.  Still, I had an Orion 120mm Eon on StellarVue MG-2 ALT-AZ mount.  The scope weighed 15 pounds with a 2 inch diagonal, the mount weighed 19 pounds, it was a one trip out the door to the backyard scope.  And it was a nice scope.  But I found I just wasn't using it.  My 10 inch Dob took more effort to setup and it definitely took much longer to cool, even in San Diego's mild climate with fans running.  But the views were enough better in the Dob to make it the choice.  

 

Of course, having a very good 4 inch F/5.4 TeleVue helped tip the scales as it's a better deepsky companion to a large Dob.  

 

Jon


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#91 turtle86

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Posted 24 June 2019 - 06:58 AM

The advantage of the refractor is thermal stability.  Still, I had an Orion 120mm Eon on StellarVue MG-2 ALT-AZ mount.  The scope weighed 15 pounds with a 2 inch diagonal, the mount weighed 19 pounds, it was a one trip out the door to the backyard scope.  And it was a nice scope.  But I found I just wasn't using it.  My 10 inch Dob took more effort to setup and it definitely took much longer to cool, even in San Diego's mild climate with fans running.  But the views were enough better in the Dob to make it the choice.  
 
Of course, having a very good 4 inch F/5.4 TeleVue helped tip the scales as it's a better deepsky companion to a large Dob.  
 
Jon


I think the 120mm Eon is an f/7.5. I agree that a faster apo like the NP 101 would be a better companion to a large Dob.
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#92 25585

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Posted 28 June 2019 - 07:44 AM

I realize that I am not necessarily your median/typical observer.  But with a 10 inch, the range of useful magnifications is from about 32x to about 800x and even with a zoom, that just doesn't get covered adequately.  And while you were thinking of large apertures, much of what doesn't get seen with a 10 inch is stuff that one sees in a small scope.

 

But this is neither here nor there.  The 8 inch - 10 inch dilemma is pretty much a win-win, both are good scopes.  One does have to keep in mind the size of a 10 inch, that is easy to forget if one is used to manhandling larger scopes.  A while ago, I was going to loan my 10 inch Dob to a friend who was about 50.  It never occurred to me that he would not be able to manage the OTA, it was just too big and too heavy.

 

Jon

30 years older from when I started, I was shocked to find how heavy a solid tube 12" F5 is now. 10" in 2 pieces, OTA & mount, I can carry, but the 12" needs a sack truck journey for each part. Any larger and a motorised solution would be needed.

 

The difference physically between 10" and 12" is more than the extra 2" aperture suggests. In fact its larger between than that of an 8" and 10" when transport and handling are concerned. Tube width of a 12" is 14", but its only 12" for a 10". Primary mirror weight, its cel weight,  will both be more. Then the stand will be a larger area, heavier and ideally more robust, having a heavier load to bear. That extra 2" in aperture can add 20lbs in weight for the whole kaboodle.


Edited by 25585, 28 June 2019 - 07:47 AM.

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