78 replies to this topic

[Deep13]

10" is a good size. Nice size without being too hard to move around.

[JoeBlow]

I concur with most people here, 10" is indeed a great size!

 

I consider 10" as the "compromise size" in dobs, being the perfect compromise of portability and aperture. If you go much smaller you too often feel the limits of your light gathering/resolution power (usually on DSOs), but if you go bigger transport/potability/setup start to become significant considerations. 10" is the happy medium.

[25585]

I have a 12 F5, but use a 10 F6 or F5. The F6 suits my height better when vertical. Its also less critical on collimation and is great general purpose.

 

My 10 F5 is more car transportable, 10 inches less in length makes a difference.

 

But they are both good. Not quite so bright as my 12, but easier to manhandle. 

Edited by 25585, 16 November 2018 - 03:22 PM.

[Magnetic Field]

I have a 12 F5, but use a 10 F6 or F5. The F6 suits my height better when vertical. Its also less critical on collimation and is great general purpose.

 

My 10 F5 is more car transportable, 10 inches less in length makes a difference.

 

But they are both good. Not quite so bright as my 12, but easier to manhandle. 

 

The OP wants a telescope for planets, so I would like to ask:

 

Realistically how easy is it to track say Mars at 200x with a Dobsonian?

 

Are there many people here who are able to use a Dob for planets while making planetary drawings?

 

I find it very hard to make sketches of planets with my alt-az mount (Vixen Mini Porta) and slow motion controls. I would even find it harder with a Dob.**

 

 

**Never looked through one though.

Edited by Magnetic Field, 16 November 2018 - 03:36 PM.

[niallk]

It depends on the Dob! With my 15" Obsession, hand tracking is feasible at 560x (the highest mag I've had it up to on Jupiter - I live under the jetstream!). 330x is no prob at all - a common mag I use on decent seeing nights. My 10" 250px doesn't move anywhere near as sweet, tbh, and I used lower mag typically in that scope.

[Deep13]

I have an 8" f/6 Discovery DHQ from 2000. I've made some adjustmens to aid azimuth tracking, reducing the need to break friction when moving a little. I used to routinely observe planets with a 12.5mm UO ortho (43 deg. AFOV) and a 2.2x Barlow. I managed it pretty well, but the shortcomings are that I could not really go any higher in magnification and still be able to keep up. Also, the need to move the scope every 20 seconds or so meant I could not just stare at the planet as it sat motionless in the center. I still use that scope for planets, but I use Pentax XW EPs with 70 degree AFOV.

[25585]

Depends on the smoothness and easy progressive motion. 

[stargazer193857]

I agree the Obsession is very worth it if you want high power. But I would not go above 200-300, so I do ok with cheaper scopes, which mostly just need a Teflon upgrade. Good luck changing the eyepiece fast enough to not lose the planet.

[spencerj]

You get a real feel for tracking with a dob over time. If the mechanics of the scope are smooth it is really not that big a deal. And for any alt-as scope, wide-field eyepieces really make the whole experience a lot more enjoyable.

[OleCuss]

You can nudge a Dob along at 200x just fine while observing.  The problem will be the periods when you are not observing and are instead sketching.

 

If you want to be sketching I'd urge you to go with a GoTo system to make the tracking problem largely go away.  It'll make the experience much more pleasant.

[Asbytec]

Even with an undirven GEM, I have to recenter an object while observing it for a sketch. Yea, it will move out of the FOV when you are making notes or sketching it. That's normal. It's just a matter of re-centering it. We almost have to do that, anyway. And you can get a feel for tracking a Dob at most magnifications, and yes, smooth movement does help quite a bit. Bottom line is, in descent seeing, a 10" may show you more than you can sketch before the planet rotates significantly and you lose the sketch because of the rotation. IMO, the race to sketch in a 10" is limited by the planet's rotation more so than the Dob movement. Smooth movement can save some time, though. So, is a 10" enough? Sure it is. Try sketching Jupiter. 

[Jon Isaacs]

Realistically how easy is it to track say Mars at 200x with a Dobsonian?

 

Are there many people here who are able to use a Dob for planets while making planetary drawings?

 

I find it very hard to make sketches of planets with my alt-az mount (Vixen Mini Porta) and slow motion controls. I would even find it harder with a Dob.**

 

 

It depends on the scope as well as the operator.  I have no trouble tracking Mars at 400x manually with my GSO 10 inch Dob.  

 

On the other hand, if Mars were the on the table in front me, I couldn't make a sketch of it.  

 

Jon

[aatt]

Hi guys
I have been offered by my daddy that as a gift I can either buy some eyepieces or filters or I can wait for 2 years and get a 10 inch dobsonian. I am that kind of person-opted for the 10 inch. I already own a 5 inch scope. So would a 10 inch scope with 1250mm focal length be good enough for DSO and planetary observing.
Clear skies

Get the 10"! It is a good aperture for all objects and is at the limit for reasonable portability.Under dark skies, it will reveal quite a bit. Prior to the dobsonian revolution a 10" was considered a monster fantasy scope by most enthusiasts. It will not disappoint-that is until you get the strange affliction called aperture fever. That being said, a 10" will serve you well even if you go bigger in the future and if you dodge the fever, it will provide a lifetime of satisfying viewing.I know I still use my 6" even with a larger scope on hand.

[Asbytec]

On the other hand, if Mars were the on the table in front me, I couldn't make a sketch of it.  

 

Jon

Yea, probably not in our lifetime. Way too much detail.  

[tmichaelbanks]

FWIW, I concur with others in this thread that tracking Mars with a Dob at 200x is feasible.  I did it this past summer with an 8-inch Dob and a 6mm Delos, and you get about 20-30 seconds before slight adjustments are needed.  Although even with good seeing I couldn't see much more than a white dot for the polar cap and darker surface markings in the southern hemisphere, so any sketches might show more clarity than was really there...   

[GeneT]

A 10 incher is a great size for a telescope. Reasonably portable, very good on planets, pretty good on deep sky if you get out to a dark sky site, excellent on double stars, pretty good on globular clusters, and ok on galaxies and nebula.

[Wildetelescope]

Hi guys
I have been offered by my daddy that as a gift I can either buy some eyepieces or filters or I can wait for 2 years and get a 10 inch dobsonian. I am that kind of person-opted for the 10 inch. I already own a 5 inch scope. So would a 10 inch scope with 1250mm focal length be good enough for DSO and planetary observing.
Clear skies

In reading through this thread, it is very clear that you have thought deeply about this purchase and are asking very good questions.  I think you will really enjoy the dob when you get it.  The commercial Chinese dobs are by and large quite a good value, and if you keep it collimated, it will reveal the universe at a level that very few smaller scopes(of any price) can approach.  The dob in my signature was my first scope, and it never ceases to take my breath away.  As you grow in the hobby, you will probably get other scopes, but the 10 inch can stay with you for a lifetime.  Your patience will be rewarded, and your adventure is just beginning!  Have fun!

 

jmd

[Asbytec]

It's important to realize, as well, not only is a 10" good enough, but let's not forget the role of the observer employing his skill and experience to ensure it is good enough. A 10", any aperture really, can show one thing to a novice or inexperienced observer, and quite a bit more for a skilled observer who is also good enough.

I find most apertures are good enough within their ability to resolve and gather light. Especially when the observer can employ any aperture to the best of his or her ability. Observing is not a passive pursuit, it's a very active one that brings a very personal reward.

I never rely on a scope to show me anything. Instead, I have learned to take responsibility for what I can make of what is trying to show me. In the end, it can often be less a question of whether a scope is good enough. Rather, are we?

Edited by Asbytec, 28 November 2018 - 11:07 AM.

[BlueTrane2028]

Brass tax regarding planets, the GRS on Jupiter is kinda brown in my 6”, noticeably red in 8” or larger.

I don’t know how people swear by planetary viewing on small bore scopes. I mean, if it makes you smile, great, I just want to see as much as I can whenever possible.

OP, I’d personally go for a 12”. I have no desire to go bigger.

[vsteblina]

At 14 years of age?
Anyway, I prefer my refractors for planetary viewing. The dobs work best for DSO.


Tapatalk on SGS7

Hey, I ground and made two telescopes when I was fourteen.

 

Really, haven't accomplished much since that time. I believe the expression is one year of experience for sixty years.

 

Vladimir

[charotarguy]

Absolutely....

[havasman]

It's important to realize, as well, not only is a 10" good enough, but let's not forget the role of the observer employing his skill and experience to ensure it is good enough. A 10", any aperture really, can show one thing to a novice or inexperienced observer, and quite a bit more for a skilled observer who is also good enough.

I find most apertures are good enough within their ability to resolve and gather light. Especially when the observer can employ any aperture to the best of his or her ability. Observing is not a passive pursuit, it's a very active one that brings a very personal reward.

I never rely on a scope to show me anything. Instead, I have learned to take responsibility for what I can make of what is trying to show me. In the end, it can often be less a question of whether a scope is good enough. Rather, are we?

 

 

Well said. I wish I could observe all that my 10" can show.

 

And as Jon said earlier, I think I can observe fairly well but I can't sketch for squadoosh. In the field I make little doodles of threshold DSO positions to check against WikiSky.org the next day to see if I saw what I thought I saw but as far as getting representational, nah it ain't happenin' for me. But I admire the skill of those who can do it.

Edited by havasman, 28 November 2018 - 02:51 PM.

[Wildetelescope]

It's important to realize, as well, not only is a 10" good enough, but let's not forget the role of the observer employing his skill and experience to ensure it is good enough. A 10", any aperture really, can show one thing to a novice or inexperienced observer, and quite a bit more for a skilled observer who is also good enough.

I find most apertures are good enough within their ability to resolve and gather light. Especially when the observer can employ any aperture to the best of his or her ability. Observing is not a passive pursuit, it's a very active one that brings a very personal reward.

I never rely on a scope to show me anything. Instead, I have learned to take responsibility for what I can make of what is trying to show me. In the end, it can often be less a question of whether a scope is good enough. Rather, are we?

For sure, I agree completely.  From the conversation, it is pretty clear that this young man has caught  "the Bug", and spends quite a bit of time with his 5 inch scope already.   The fact that he is willing to delay gratification and wait more than a year for the Dob shows great patience at that age.  I strongly suspect the larger scope will be put to good use further developing the skills you are discussing;-)  I will wager he is out observing while we continue to comment on the thread he started, LoL:-)

 

JMD

[Asbytec]

I wish I could observe all that my 10" can show.

 

Yea, that's an interesting statement. I am not sure what a 10" actually is showing us, what does the image actually look like? A digital image? I guess we can only perceive what we have learned to perceive of some amount of light and resolution the aperture is delivering. There is probably more to be seen than the best we can make of the image. If so, it's up to us to go after the (afocal) image present the best we can. Can we see all that is there to be seen? Maybe not, but we can certainly work toward doing so.

 

...it is pretty clear that this young man has caught  "the Bug", and spends quite a bit of time with his 5 inch scope already.

 

Yes, no doubt. Sometimes I think "the bug" is merely, and maybe certainly it is, an intense desire to see more. After tepidly stepping down in aperture one thing became very apparent. I was afraid of losing deep sky, until I finally learned to observe because I had to. In the past, I was always chasing aperture to see more, and it probably worked. I've seen some amazing things. What was literally eyeopening, though, was learning to see more in a smaller aperture, too.

 

The image presented to us through a smaller aperture is a bit harder to observe than the same object in a larger aperture. Larger aperture offers more light, more resolution, and a larger image conducive to the eye. So, we are gonna see more in a larger aperture under a given set of conditions. But, I was awed by the additional detail we can see in a smaller aperture - every aperture really - by improving our own abilities and techniques. And conditions, etc. 

 

I still cannot see what a 10" can offer, but I believe I can see much of what a 6" can offer. That has made all the difference because it is very often rewarding just to see anything other than a featureless faint fuzzy or two belts across Jupiter. I prep my scope, have nice observing conditions, and give it the old college try. I've had a blast pushing man, machine, and conditions observing through a 6". So, I tend to agree, a 10" is certainly enough. Enough to show you whatever you can make of it's image. And that's no small amount of detail waiting for the OP when he goes after it. 

[rnc39560]

Just checked in after a long absence from CN, and observing in general. I can tell you this, from my back yard on the MS coast, I have seen the shadow of one of Jupiter's moons cross the surface of the planet in my older Orion xt8, conditions were very good that night, but it took me totally by surprise witnessing it.