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Practical Tracking Reflector for Visual (12" vs 14" vs 16")

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#1 MalVeauX

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Posted 09 October 2019 - 09:49 AM

Hey all,

 

So, I need some advice... practical and to avoid aperture fever to the point of impractical and inconvenience of use.

 

I'm getting very curious about a visual-only reflector. I have a 8" F6 quartz reflector that I use for visual right now. I use it manually on an alt-az mount with a refractor as its co-pilot. I have a C8 Edge HD that lives on my EQ mount in my observatory. I'm mainly thinking of getting a larger aperture for visual-only use for myself but also for others, my kids, and outreach with the local club. While I realize a 12" dob is inexpensive for the aperture, I really do get hung up on the idea of tracking. I don't even really care much about GoTo. I care more about tracking. The reason being, I use my scopes manually now and I definitely do not like slowly nudging, hand pushing, and constantly readjusting to be able to view something at more than low power. I am spoiled I guess by my C8 Edge on EQ mount where I can point it at a subject and it will stay on it and I can just observe instead of fiddling with adjustments. I live under a dark sky, so I already appreciate what I can see even with these modest apertures. So this has me thinking... a bigger visual instrument, but, I really want it to have tracking so that I can put it on a target and let it just sit there and spend more time observing, and others can observe, without having to chase things constantly so we can just observe.

 

So knowing the above context, there's a few things I'm curious about and considering.

 

Practical difference between a 12", 14" & 16".

 

I think I read the magnitude jumps and going from 8" to 12" is one, and then going to 16" is the next. So the 10" and 14" are the "in between" options that give a little more, but not quite a full magnitude step. So I'm curious what this translates to in real world with respect to visual. Primary subjects would be galaxies, clusters, a few nebula, planets. Namely, at what point under a dark sky can we really truly see the arms on a galaxy like M101, especially someone who is not a skilled observer at outreach, so they're seeing a galaxy and not just the idea of one might be there as a bright smudge. I realize the weight goes up significantly with the size of mirror here. I'm not especially fond of a huge complex heavy setup (which is why I have an observatory and permanent setup at home). So I'm leaning a lot more towards the 12" and 14" categories due to this. But, if 16" truly makes a difference in how much of a galaxy (the arms) one can see, this is still an option.

 

Tracking Platform

 

There are equatorial platforms to hold any dob. And there are computerized tracking dobs. And then there are Equatorial tracking mounts in general. I'm not sure where to go with this. I want it to be as simple and portable as possible for such a large size. I already have an EQ mount in my observatory on a pier. But I realize they are not ideal for visual with where the eyepiece can end up. Also, an EQ mount to handle a 12" or larger reflector is substantial even though the scope itself can be inexpensive, so that just seems less practical. So really maybe its between an Equatorial Platform and then just put a dob on it, or a computerized tracking dob itself. These are commercially available, but I have no experience with how good these motor systems are and if they will truly handle it and last enough years to be worth it. I know EQ Platforms also have a limited time of tracking then must be reset and start again, which is kind of not that attractive with outreach having to fiddle with something. But I'm not sure there, maybe someone can elaborate on that process more. So ultimately it seems more attractive to just look at a tracking computerized dob mount to begin with, the commercial stuff like from Skywatcher/Orion, etc.

 

I'm also especially interested in whether or not these various mount options like the tracking dob mounts can handle more than a 50mm RACI on the bigger scope. I really like the idea of putting a ST80 on there as the finder too. But this may not be an option I understand.

 

Portability and Setup

 

This is another big factor. I went towards observatory fast because I quickly tired of setup. Taking my EQ mount out, assembling, aligning, etc, then putting the scopes on, balancing, etc, was just annoying. Physically not a problem. But I'm a slave to convenience and it was just terribly inconvenient. So I'm very anxious about the idea of a complex or long "setup time" on whatever system I may get into here. If I can move the base. Plug in the controller or power. Seat the scope and it's good to go, I would be happy with that. I realize I'm going to have some setup time. But, this totally means I'm not at all interested in a scope that I have to assemble trusses or any other stuff like that. I would much rather move a 50lb tube and put it in a 50~75lb base. Then again, I would rather not move a 75lb base either. I think 50lbs is easy. But size matters. A small 50lb weight is easy, but something large with no grips is hard. So its relative. I'm curious what some experiences are with these larger scopes and their bases and how complicated it is to setup and move around. Due to this I have of course considered a SCT because I can get a big aperture there that is more portable, but visually I just am not fond of the narrow FOV and want to at least be able to get a 1 degree FOV out of this scope so that we can look at things at low power and not fuss too much with finding things. I realize some more portable systems use trusses or have collapsible tubes. This seems great, but I don't want to assemble in the field much. Also, opening the tube to the environment (humidity) is not good for me in Florida. I could always shroud it I suppose.

 

Binoviewing

 

I like to binoview with my Arcturus binos and 1.25" eyepieces. I use 2" eyepieces only for low power wide FOV. I definitely don't want to fool with a scope that cannot easily use binos or a focuser that cannot handle binos.

 

Environmental Considerations

 

I'm in Florida. Humidity is 99% from 10pm and on. Every. Night. I don't think an open tube will work here. Maybe I'm wrong? Right now, I have to heat all my optics. All of them. Even eyepieces. Or they dew over in minutes after 10pm no matter what. So this is something to consider as well. I would love to hear some experiences from others in high humidity climates (especially Florida or similar) with respect to this. Maybe I'm off my rocker about needing a solid tube to keep that mirror as covered as possible so it doesn't cool down below dew point.

++++++++++++++++++++

++++++++++++++++++++

 

So, considering maybe something like:

 

Skywatcher SynScan series GoTo with collapsible tube (use a shroud to seal it up).

http://skywatcher.co...dob-12-synscan/

http://skywatcher.co...dob-14-synscan/

http://skywatcher.co...dob-16-synscan/

 

$2k to $3500 or more. No time restriction.

 

Orion SkyQuest series (both solid & truss)

https://www.telescop...PriceDescending

https://www.telescop...PriceDescending

 

Or, an EQ Platform like one of these and put any big scope on it.

http://www.blandineq...lplatforms.com/

http://www.equatoria...platforms.shtml

 

$1250 + shipping on a Crossbow EQ platform. 60 minutes tracking time.

I can put a 12", 14" or 16" standard inexpensive Dob on there ($1k to 2k)

$2500 roughly for the whole thing potentially for a 12".

 

I'm sort of leaning away from EQ platform and more towards a Skywatcher SynScan as a more convenient option for visual and outreach use.

 

Thoughts?

 

+++++++++++++++++++

+++++++++++++++++++

 

Where we are coming from, visually:

 

200mm F6 Quartz reflector on Alt-Az. It handles great. The only drawback is that it's not easy to use after 150x magnification due to no tracking and keeping an object in the FOV. No slow motion control, but I found slow motion useless on a big instrument anyways because you cannot reach it and didn't want long wonky handles poking out to drop, lose, trip on, hang up, etc. So we kept it simple with a TW2 mount and we love it actually. Just not practical for bigger scopes and not good for high power visual with tracking obviously. We want that extra touch. And of course, more light grasp than our 8".

 

48609877387_03c74bc0e3_c.jpg

 

48696767587_8fd88bdd4c_c.jpg

 

Very best,


Edited by MalVeauX, 09 October 2019 - 09:54 AM.

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#2 zakry3323

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Posted 09 October 2019 - 10:14 AM

I've got nothing helpful for you, except that I can say that my pop's 16" Lightbridge is too much for me to set up by myself easily, and it's not motorized/computerized. 

 

Thanks for sharing the pics, they're great!


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#3 vtornado

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Posted 09 October 2019 - 10:25 AM

Hello Marty, I really respect your opinions here on the site.

 

Here are some general musings …

 

I had an 8 inch and 10 inch dob simultaneously and kept the 10. 

Even in light pollution, it showed more detail on what I could see.

My current quest is a 12 inch truss dob. My  thoughts are I like to view high power targets like

planets, globs, doubles at 1 mm exit pupil. My skies limit me to about 300x and that is the best of nights.

So I need a 300 mm mirror ergo 12 inches.  Faint deep sky will never happen for me as I am trapped

light dome where a 2 hour drive  is needed to get me out.  And the 12 inch is still f/5 and still does not

need a ladder so maybe I won't need a coma corrector either. 

 

I am leaning toward the truss because if I ever want to take it anywhere which does not look likely in the

near future, the truss will help.

 

I am only considering the used market because in the back of my mind I am thinking a 12 inch might be

to big to be convient although you do have an observatory.  I don't.  I don't want to take a $500 bath on

a scope that is too big.  And I'm not getting any younger either ...

 

The tracking dobs look sweet, but realize this usually ads a lot of weight and you now have a battery issue.

 

I have heard that trusses have problems at high power because heat from your body can drift into

the optical path.  I'm not sure if a shroud will keep it out??? Or maybe one can make a super shroud.

I was thinking of and insulator like reflectrix with a black cloth backing???  Also I am unsure

if moving the dob from high azimuth to low azimuth will require recollimation if high power views are

wanted.  Not the end of the world of course.  I notice my AWB scope shifts collimation, and it

is only 5 inches.

 

On final thought.  Two members have suggested that instead of going bigger I go better.  One can get

a cheap 8 or 10 inch dob, and have the mirror refigured. So maybe this brings a 8 or 10 inch scope

in the realm of a 12 or 14??? not in light gathering but in ability to push the power.

You can buy used, and save money because you are only going to refigure the mirror anyways.

And as far as tracking in general it is always going to be easier to have motors move an 8 or 10 inch

scope than a 12 or 14.  One member is doing this with a skywatcher 200 tracking dob.


Edited by vtornado, 09 October 2019 - 10:29 AM.

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#4 MalVeauX

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Posted 09 October 2019 - 10:25 AM

I've got nothing helpful for you, except that I can say that my pop's 16" Lightbridge is too much for me to set up by myself easily, and it's not motorized/computerized. 

 

Thanks for sharing the pics, they're great!

I truly think 16" is likely out of the question other than the ultra-light options out there which require assembly. I think in a permanently installation setup in my observatory it would be fine. But for moving it around, it's likely not fine. So this is really starting to lean back towards 12" to 14". Ultimately even the 14" is rather huge and I really do have doubts about the extra 2" being super meaningful at the expense of size and weight and convenience of use. The idea of a 40~50lb base and 40~50lb tube is fine. Manageable for one person, with the 12" options. If I ever get a 16" or larger, it likely will only be an option in an observatory setting as I will not want to move that thing ever I'm sure.

 

Namely, going from a 8" on alt-az without tracking to something with tracking that is significantly more aperture, and of course, 12.5" is the next big "stop" with magnitude reach and balance between weight and portability. But, I have to wonder... is 14" worth it?

 

Very best,


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#5 MalVeauX

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Posted 09 October 2019 - 10:32 AM

On final thought.  Two users have suggested that instead of going bigger I go better.  One can get

a cheap 8 or 10 inch dob, and have the mirror refigured. So maybe this brings a 8 or 10 inch scope

in the realm of a 12 or 14??? not in light gathering but in ability to push the power.

You can buy used, and save money because you are only going to refigure the mirror anyways.

And as far as tracking in general it is always going to be easier to have motors move an 8 or 10 inch

scope than a 12 or 14.

Thanks,

 

A good point about better mirrors. I have thought about that, but really, a better mirror isn't going to show limbs of a galaxy better in an 8" than a 12" or 14" I imagine from the simple aspect of light gathering? I totally get the idea of better optics for critical high power viewing of a planet or things like that. This really isn't going to be for critical observation, more casual, and commonly looked through by inexperienced observers, kids, etc. I will use it too, but ultimately I would likely be throwing money away on a better mirror when using this for outreach and with the kids. I have two good 8" mirrors as it is in the Quartz and Edge scopes I have. But this pathway is to get more light grasp for DSO mostly, especially with galaxies in mind and things like that and the tracking to be able to look at planets and other objects without chasing them around without tracking at low power which is annoying to me and not good for outreach and use with kids as its frustrating.

 

Also a good point about motors likely handling smaller instruments better.

 

Everything is pointing more and more towards 12" really and it's still affordable. I like the idea of the ones with encoders that allow you to move the scope and not mess up alignment.

 

Very best,



#6 havasman

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Posted 09 October 2019 - 11:45 AM

Hey all,

 

So, I need some advice... practical and to avoid aperture fever to the point of impractical and inconvenience of use.

 

Practical difference between a 12", 14" & 16".

 

So I'm curious what this translates to in real world with respect to visual.

It's pretty much huge.

Primary subjects would be galaxies, clusters, a few nebula, planets. Namely, at what point under a dark sky can we really truly see the arms on a galaxy like M101, especially someone who is not a skilled observer at outreach, so they're seeing a galaxy and not just the idea of one might be there as a bright smudge.

It's observing skill that lets us see the fine details. But I have shown M81/82, M31/32/110 and the Leo  Triplet to 1st-time observers with my XT10i very successfully.

I realize the weight goes up significantly with the size of mirror here. I'm not especially fond of a huge complex heavy setup (which is why I have an observatory and permanent setup at home).

The physical size of the tube becomes daunting pretty quickly >10" and >12" it's really long. That's where the value of the strut construction and collapsible structures becomes valuable.

So I'm leaning a lot more towards the 12" and 14" categories due to this. But, if 16" truly makes a difference in how much of a galaxy (the arms) one can see, this is still an option.

16" mass-market tracking Dobs I have seen used are REALLY massive. A 6'4" fit younger club member with one struggled with his and sold it. IMO the mass >12" enters the "burden" zone.

 

Tracking Platform

I'm also especially interested in whether or not these various mount options like the tracking dob mounts can handle more than a 50mm RACI on the bigger scope. I really like the idea of putting a ST80 on there as the finder too. But this may not be an option I understand.

ST80's going to be on the heavy side but Stellarvue offers some good large finder scopes. Resulting imbalance may require counterweights on the tube, easily implemented.

 

Portability and Setup

 

I realize some more portable systems use trusses or have collapsible tubes. This seems great, but I don't want to assemble in the field much. Also, opening the tube to the environment (humidity) is not good for me in Florida. I could always shroud it I suppose.

Understandable. Will discuss later.

 

Binoviewing

 

I like to binoview with my Arcturus binos and 1.25" eyepieces. I use 2" eyepieces only for low power wide FOV. I definitely don't want to fool with a scope that cannot easily use binos or a focuser that cannot handle binos.

You'll likely use an adapter. Focusers can be upgraded easily and ~cheaply via GSO, etc.

 

Environmental Considerations

 

I'm in Florida. Humidity is 99% from 10pm and on. Every. Night. I don't think an open tube will work here. Maybe I'm wrong? Right now, I have to heat all my optics. All of them. Even eyepieces. Or they dew over in minutes after 10pm no matter what. So this is something to consider as well. I would love to hear some experiences from others in high humidity climates (especially Florida or similar) with respect to this. Maybe I'm off my rocker about needing a solid tube to keep that mirror as covered as possible so it doesn't cool down below dew point.

Dew's a problem, but not so much for the primary as for everything else. Active dew control works great.

So, considering maybe something like:

 

Skywatcher SynScan series GoTo with collapsible tube (use a shroud to seal it up).

No experience with these. But I fully expect they work well.

 

Orion SkyQuest series (both solid & truss)

 

A past club pres has had an XX12g @ 5 years & I have used it. Good scope. Still works great. Tracks very well. Fine images. His has struts.

 

I'm sort of leaning away from EQ platform and more towards a Skywatcher SynScan as a more convenient option for visual and outreach use.

I tried a platform and didn't favor it; found it inconvenient but it did work OK.

If you want to max out your visual capability at reasonable cost, a mid-size mass market Dob is probably unbeatable. I have XT10i and 16" Starmaster. The 10" is very capable and the 16" is just more so, and by a lot. But it's heavier and is a strut Dob. If you're going to move the scope around, I think a 16" Dob not of strut construction is just too big. If you're going to transport the scope to another site and want to avoid struts then you may be well off with a collapsible if you want to go >10" because of vehicle sizes vs tube length.

Remember mass market Dobs are really starting points if the owner wants them to be. Dew control, primary fans, flocking, secondary mirror upgrades, focuser upgrades, finder upgrades and more are common mods that can significantly upgrade performance. They also work well as delivered.

​It's a bit difficult to respond to all the matters you raise. In general I think you're on the right track. I hope these comments are helpful. 


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#7 MalVeauX

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Posted 09 October 2019 - 11:58 AM

If you want to max out your visual capability at reasonable cost, a mid-size mass market Dob is probably unbeatable. I have XT10i and 16" Starmaster. The 10" is very capable and the 16" is just more so, and by a lot. But it's heavier and is a strut Dob. If you're going to move the scope around, I think a 16" Dob not of strut construction is just too big. If you're going to transport the scope to another site and want to avoid struts then you may be well off with a collapsible if you want to go >10" because of vehicle sizes vs tube length.

Remember mass market Dobs are really starting points if the owner wants them to be. Dew control, primary fans, flocking, secondary mirror upgrades, focuser upgrades, finder upgrades and more are common mods that can significantly upgrade performance. They also work well as delivered.

​It's a bit difficult to respond to all the matters you raise. In general I think you're on the right track. I hope these comments are helpful. 

Thanks,

 

The weight really does matter at the end of the day. I was just looking at the 12" and 14" bases on these things and it goes from 50lbs to 90lbs instantly. That alone is a big put off for me, with respect to being "portable" in terms of being a one-person-move job. The more I read and look at stuff, the reality of a 14" and 16" reflector is basically just not going to happen for a portable system. These tubes and bases are just too big, too heavy realistically. Any one component over 50lbs is just going to pose problems ultimately I'm sure, especially when tired and packing up.

 

Looking more and more like 12" is going to be the top size/weight category.

 

So next, it's figuring out what's ideal in that 12" range with tracking.

 

The SkyQuest series has good commentary and can be had in a solid tube or a truss system.

The Synscan series from SkyWatcher has a collapsible system to make it more portable.

Prices are quite similar. Don't care about accessories, I have eyepieces and all that.

I'm not seeing other options really looking at various vendors, seems this is likely the two options to consider.

 

Very best,


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#8 Chesterguy1

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Posted 09 October 2019 - 12:34 PM

Thanks,

 

The weight really does matter at the end of the day. I was just looking at the 12" and 14" bases on these things and it goes from 50lbs to 90lbs instantly. That alone is a big put off for me, with respect to being "portable" in terms of being a one-person-move job. The more I read and look at stuff, the reality of a 14" and 16" reflector is basically just not going to happen for a portable system. These tubes and bases are just too big, too heavy realistically. Any one component over 50lbs is just going to pose problems ultimately I'm sure, especially when tired and packing up.

 

 

My 15" mirror/rocker box weighs in around 60 pounds, but with the wheelbarrow handles what I lift is under 10 pounds. I think the entire scope weighs about 85 pounds. I never have a problem with that scope at home, even though I am 62 and no he-man. The problem is when one wants to maximize the capability of such a scope by traveling with it to a dark site. Although I have lifted it by myself into my hatchback, it's really a two-person job to protect your back. Of course you could make a ramp system to get it in the car/truck/SUV and make something that raises the interior cargo height so that it is level with the opening. I definitely do not want to be trying to do any of that by myself, especially in the middle of the night. My 8" is easily lifted, fits nicely on my two-wheel dolly and provides generally probably something like 65% of the capability of the 15". Even though it's a solid tube, the entire OTA/base weighs around 40 pounds and reaches ambient temperature quickly. I never even disassemble mine unless it's for travel.

 

Chesterguy


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#9 Starman1

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Posted 09 October 2019 - 01:03 PM

1 magnitude jumps: 8">>12.5">>20"

0.5 magnitude jumps: 8">>10">>12.5">>16">>20"

EQ platforms are the easiest way to provide tracking for a dob.

However, they preclude the use of slings to support the mirrors because then the mirrors swing laterally as the platform tips.

You are limited to 2-point or whiffle-tree supports.

The question is the need for tracking.

I moved from a computerized scope to a dob without tracking and I was sure I would miss the tracking.

15 years later, I still don't miss tracking.

I can track a planet or planetary as it crosses the field at 500x and still not feel the need for tracking.

You might be surprised at how little you would miss tracking.

 

What is key is:

--eyepieces with no astigmatism at the edge of the field

--eyepieces with very wide fields so very little nudging is necessary.

 

No one moves a complete scope in one piece if it's 12" or larger.

Yes, you can use wheelbarrow handles or even a hand-truck to move it complete, but why would you?

In practice, you set the rocker box down where you want the scope to be and assemble the scope right there for the night.

I don't think I've seen more than one or two people move a complete scope ever, and I've been to a lot of star parties.

 

Well-made scopes don't change collimation as they are moved up and down.

 

A tubed dob and a shrouded dob are pretty much equally resistant to dew.  If you have a high-dew area, you might end up using a dew heater on the secondary either way.

Stay away from scopes with particle board bases--these will fall apart in only a few years in high dampness environments.  Not to mention particle board bases are 

a lot heavier than plywood.

 

Ultimately, I chose to go high-end on the optics and stick with 12.5" rather than accept mediocre optics in a low-end package.

The complete scope is about 90 lbs, but no section is heavier than 54 lbs, which, at 68, I can still handle just fine.

The reason the mirror box is that heavy is 3 fans, 18 point cell, 2 complete mirror box baffles, top ring to mount poles onto, and heavy wooden trunnions of just under 20" diameter over 1" thick.

Built the same way, a 16" would be a heavy behemoth.

Ironically, my 8" SCT was almost the same weight and had one piece the same weight as my 12.5" mirror box.


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#10 MitchAlsup

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Posted 09 October 2019 - 08:13 PM

Listen to Don.

 

However, if you want visual tracking, get a scope with alt-az tracking built in.

 

Only If you want to experiment with astrophoto do you need EQ platform--but here, a rotating focuser will allow an alt-z mount to take astrophotos.


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#11 Jon Isaacs

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Posted 09 October 2019 - 11:19 PM

No one moves a complete scope in one piece if it's 12" or larger.

Yes, you can use wheelbarrow handles or even a hand-truck to move it complete, but why would you?

In practice, you set the rocker box down where you want the scope to be and assemble the scope right there for the night.

I don't think I've seen more than one or two people move a complete scope ever, and I've been to a lot of star parties.

 

In general, I agree with what Don has to say.  However, there are those of us who are only moving the scope from the garage to the observing pad and from the observing pad to the garage..  If you are putting the scope in a car or truck, that's a different story. 

 

Dobstuff Wheel Barrow Handles 1.jpg

 

6255551-Obsession lifting by handles CN.jpg

 

Tracking:  When all is said and done, the ease of manual tracking just might be the biggest difference between "commercial" and "premium" Dobs. If you haven't spent much time with a top notch Dob, it might be worthwhile giving it a try.

 

I have an equatorial platform, a Tom O Dual Axis Aluminum.  It tracks nicely but complicates setup.  With an after market tracking system, you buy the scope and then decide. 

 

Otherwise, it seems like you're not ready to make a decision, maybe you are not a Dob guy/gal.   A 12 inch or 14 inch SCT might be the right scope for you.  

 

Jon



#12 Starman1

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Posted 09 October 2019 - 11:30 PM

Jon,

I realize you have to clear the garage door with those scopes, but most people attach the wheelbarrow handles in the opposite direction so that, when they lift

the handles, the top of the scope doesn't dive toward the groundpoke.gif .  Just a note for people who might see your pix and think that's the normal way to

attach the handles.

 

Speaking of which, what does keep the top of those scopes from diving?



#13 Napp

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Posted 09 October 2019 - 11:58 PM

I’ve got a 16” Explore Scientific truss tube.  I’m 63 and not strong by any measure.  However, the 16” is the scope I take to dark sky sites.  I can easily lift the mirror box in/out of my SUV.  The mirror box has handhold cutouts.  I can assemble the scope all by myself, though it is easier with two to get the first fastener through the truss poles into the upper cage.  wink.gif   Setup and breakdown are fairly quick.  I made a few modifications to improve the scope to my liking.  The eyepiece at the zenith is actually a little lower than my eye level - I’m 6’2” - so my feet stay on the ground.  The scope is of course completely manual.  I got it after using goto autotracking scopes almost exclusively.  Hasn’t been a problem and I am enjoying it more than I expected.  I’m in Florida, too, so dew is always a concern.  The shroud is effective as is running the fans to prevent dew on the primary.  I don’t recommend the ES shroud.  It covers the trusses and the upper cage with slits for the finder and focuser.  I plan to encase the upper cage with plastic sheets.  I think that with the shroud only covering the trusses will work better.  I am also going to make a dew heater for the secondary.  Right now I just use a 12 volt hair dryer if dew forms on the secondary.  I don’t know when you plan to buy but ES usually attends the Winter Star Party.  I will be there, too.  Drop by and you can try out my scope.


Edited by Napp, 10 October 2019 - 12:04 AM.


#14 havasman

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Posted 10 October 2019 - 12:10 AM

Sure, nobody needs tracking. Or aperture. Or, in fact, telescopes either.

 

But legitimate reasonable choices can include choosing to have a telescope or even some telescopes. And to have aperture choices. And to even choose a tracking scope. Or to stick with binoculars. Or to build your own eyepieces and/or mounts. Particularly when an experienced amateur indicates thoughtfully derived preferences those can be used to frame the help offered. Sometimes.



#15 Jon Isaacs

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Posted 10 October 2019 - 12:53 AM

Jon,

I realize you have to clear the garage door with those scopes, but most people attach the wheelbarrow handles in the opposite direction so that, when they lift

the handles, the top of the scope doesn't dive toward the ground .  Just a note for people who might see your pix and think that's the normal way to

attach the handles.

 

Speaking of which, what does keep the top of those scopes from diving?

Don: 

 

The scope is still balanced about the center of rotation so it only rotates because I lift the handles. It doesn't "dive."  ubetcha.gif

 

If I remove the Paracorr and/finder, then I have to add some weight to keep it balanced so it doesn't drift up and hit the garage door. But basically, the scope doesn't drift while I am observing with it so it shouldn't drift when I am moving it unless I unbalance it.  In practice, if the ground is rough, the scope jiggles a bit and this can cause it to slowly drift, either up or down, depending on how the scope is balanced. 

 

If it drifts up, then the upper cage could potentially hit the garage door.  If it drifts down, then the mirror is basically resting on the sling and going over the garage sill can rattle the mirror support triangles.  These are minor worries....  

 

The real concern is lifting the handles too high and dumping the scope out of the mount.  This can happen with the handles mounted either way  This is not so fun.  I have done this a couple of times. At first I thought it had to to with the angle of the scope but that is not the case, it has to do with the angle of the rocker box and the positioning of the altitude bearing pads.  This is a statics problem and one can think of the scope as a concentrated weight at the center of balance.  

 

With my Starsplitter, I extended the handles so I can lift it to a comfortable position without risking lifting it too high.

 

Starsplitter 22 Lubing Azimuth bearing.jpg
 
(In this photo, I have removed the ground board to clean and soap the azimuth bearing)
 
Edit:
 
Thinking about it: 
 
If the handles are mounted behind the scope the way I do it, if the handles are raised too high, the scope slides forward and the front cross piece catches it and only the upper cage hits the ground.
 
If the handles are reversed and the handles are raised too high and the scope slides forward, there is nothing to stop the scope, the entire scope will slide forward with the mirror box hitting the ground and depending on it's orientation, and scope size, the upper cage could bonk the observer in the head, that could be serious.
 
Don said he has only seen a couple people move scopes in one piece.  I have done it hundreds of times. 
 
Jon


#16 25585

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Posted 10 October 2019 - 04:03 AM

Examples of solid tube 14" & 16" solid tube Dobsonians 

 

https://www.orionopt...VX/vxrange.html



#17 Starman1

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Posted 10 October 2019 - 08:54 AM

 

Don: 

 

The scope is still balanced about the center of rotation so it only rotates because I lift the handles. It doesn't "dive."  ubetcha.gif

 

If I remove the Paracorr and/finder, then I have to add some weight to keep it balanced so it doesn't drift up and hit the garage door. But basically, the scope doesn't drift while I am observing with it so it shouldn't drift when I am moving it unless I unbalance it.  In practice, if the ground is rough, the scope jiggles a bit and this can cause it to slowly drift, either up or down, depending on how the scope is balanced. 

 

If it drifts up, then the upper cage could potentially hit the garage door.  If it drifts down, then the mirror is basically resting on the sling and going over the garage sill can rattle the mirror support triangles.  These are minor worries....  

 

The real concern is lifting the handles too high and dumping the scope out of the mount.  This can happen with the handles mounted either way  This is not so fun.  I have done this a couple of times. At first I thought it had to to with the angle of the scope but that is not the case, it has to do with the angle of the rocker box and the positioning of the altitude bearing pads.  This is a statics problem and one can think of the scope as a concentrated weight at the center of balance.  

 

With my Starsplitter, I extended the handles so I can lift it to a comfortable position without risking lifting it too high.

 

 
 
(In this photo, I have removed the ground board to clean and soap the azimuth bearing)
 
Edit:
 
Thinking about it: 
 
If the handles are mounted behind the scope the way I do it, if the handles are raised too high and the scope slides forward and the front cross piece catches it and only the upper cage hits the ground.
 
If the handles are reversed and the handles are raised too high and the scope slides forward, there is nothing to stop the scope, the entire scope will slide forward with the mirror box hitting the ground and depending on it's orientation, and scope size, the upper cage could bonk the observer in the head, that could be serious.
 
Don said he has only seen a couple people move scopes in one piece.  I have done it hundreds of times. 
 
Jon

 

I don't think moving the scope in and out of a garage is rare, especially SCTs on Wheeley Bars.  Moving a scope once it's set up in an observing spot is.

 

I don't think many scope owners who have wheelbarrow handles think a lot about the length of them, though.

Having the mirror box slide out could be a serious problem.  Also, tipping the rocker box a fair amount lowers the UTA to the position where most have the UTA dive

toward the ground (most dobs I've seen and used will dive when below a certain angle).  You understand about dynamic balancing, but most scopes are not set up

that way.  Without a virtual counterweight, my Teeter will dive toward the ground when below a 30° altitude, though that is with an eyepiece and Paracorr.

 

My old Discovery had wheelbarrow handles, but the top dived for the ground if the handles were mounted like yours.

The instructions that came with the scope were explicit at mentioning they had to be put on the other way.


Edited by Starman1, 10 October 2019 - 08:56 AM.


#18 Eddgie

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Posted 10 October 2019 - 09:53 AM

First, if you have a place to store the scope that allows you to move it over mostly flat ground, it is pretty trivially easy to move a 12" Go2 dob using a hand truck.  My 12" lives under my covered patio, and using no special cradles or anything, I can move my dob out to the uncovered portion of my patio and be looking though the eyepiece in less than two minutes without lifting anything.  I just roll the hand truck under the dob base, grab the tube, tilt the whole thing back, roll it into position, tilt it down to the ground, roll the hand truck away, uncover it, put in my viewing device, and start observing.

 

Now, if you want tGO2, that means alignment, and that adds a couple of minutes depending on how exact the tracking needs to be.  In other words, if I just want to track a target like the moon, I can simply start the scope with the tube level and pointing north, turn it on, and go.  This will get me basic tracking without "Go2".  In other words, if I manually position the scope and let go of it, it starts tracking based on the sky map it built from the "home" position.   Now if my scope was not level and not pointed exactly north, then there will be some slight drift of course and the amount of drift depends on the amount of error, but for planetary observing, the drift is usually minor, and you can easily use the handset to recenter as necessary.  If you always set up level and have a good sight line to true north, you can get quite excellent tracking without any alignment

 

Many of the systems today are dual encoder meaning if you align, you can manually slew the scope and it will not loose the sky map. When you stop moving it, it continues to track normally.

 

Now the 12" is not easy to transport.  There are approximately  24 hand knobs that must be undone to break the scope down.  My base weighs 78 lbs and my tube weighs 50.   The base does break down "half way" with four hand knobs and this makes two parts, but the round base is still pretty heavy.

 

Again, I move this complete setup on a hand truck, and that includes a 7Ah battery that lives on the base of the scope.  I don't even take it off to charge it.  My charger has a cable with a 2.5mm socket on it and I just unplug the power cable form the battery to the mount and plug it into the cable from the charger.   This way, I can walk out the door, lift or carry nothing except my eyepiece/binoviewer, and be observing in less than 2 minutes.

 

Dob small - Copy.jpg

 

Binoviewers..   To reach focus, you are going to have to use a Denk/Earthwin power switch type system or some kind of amplifier.  The Denk/Earthwin will work as low as 1.2x, but 1.3x and even 1.4x is more typical.  The tube that goes into the focuser extends to raise the power of the amplifier enough to reach focus.  Alternately, you can fit a lower profile focuser and reach focus at 1.3x (1.2x for the Earthwin if you are lucky).  These systems are handy because you get three useful powers. 

 

The negative of these systems is that they are very heavy and can pretty quickly destroy the bearings in most Crayfords, and if the Crayford had an anodized focuser, in the process of failing, the bearings can scar up the focuser tube.  My best result with these heavy systems was the Feathertouch.  Expensive, but I could reach 1.3 in low power and I did not have to slip the BV out for high power (many focuser tubes will not allow you to reach focus in all three powers.  Usually, for low power you can reach focus, but for high power, you have to loosen the OCS extension tube from the focuser and slip the whole thing out).

 

Much lighter, but also limited to narrower fields and higher powers, is a T2 modified BV outfitted with a Televue 2x Bino Vue amplifier.  This makes the binoviewer parfocal with standard eyepieces, so it is a one size fits all solution.  This also is much lighter.  My inexpensive BV and TV 2x weighs less than a 31mm Nagler, but with heavy eyepieces (Baader zooms) it can still put a lot of stress on the focuser. 

 

So, if you have a place where you can roll the scope out, moving it with a hand truck is super easy no lifting, one trip solution. 

 

There is also image intensified astronomy. Now you can turn a 10" scope into a 20" scope and you can even use two eyes if you want.  I can see the Pillars of Creation using my 12" dob from white zone skies.. Not bad. Not bad at all.

 

PVS 7 in dob.jpg

 

(Now I showed the PVS-7 in the picture because that is a binoviewer like solution though without the negative of beam splitter loss, but in practice, I tend to use a monocular, but the PVS-7 works quite well for image intensified astronomy and we have several people on CN using them, though more use monoculars.)

 

Again, less than 2 minutes for me to be up and observing with my 12" dob and that is with tracking.  If I want Go2, it takes an extra 3 minutes.  I can move everything in one trip. I lift nothing.   Simply tilt the scope back on the dolly and away I go. 


Edited by Eddgie, 10 October 2019 - 11:10 AM.

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#19 Eddgie

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Posted 10 October 2019 - 09:58 AM

Here is my BV setup.  I had the Binotron, but since I moved to image intensifed astronomy, I only use the BV for planetary, lunar, or double star and since I was not using the Binotron anymore I sold it.   

 

BV with TV.jpg

 

This is showing the setup that I use for the Televue Bino Vue 2x amplifier.  The BV is converted to T2 with an RAF adapter.  The 2x simply screws on to the front.  Now the BV is parfocal with a standard eyepiece and will reach focus in just about any scope made with nothing else to buy.  2x Though. TV unit also corrects for spherochromatism.

 

Otherwise, the Denk or Earthwin can usually get you going at between 1.3x and 1.4x, and the Baader 1.7x Newt GPC and coma corrector gets you going at 1.7x. 

 

If you have a Televue 2x or 2.5x Powermate, you can use that too but it won't be quite parfocal, though likely close enough. Does not correct for spherochromatism either, but probably not a serious issue.


Edited by Eddgie, 10 October 2019 - 10:02 AM.


#20 InkDark

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Posted 10 October 2019 - 10:15 AM

Thanks,

 

The weight really does matter at the end of the day. I was just looking at the 12" and 14" bases on these things and it goes from 50lbs to 90lbs instantly. That alone is a big put off for me, with respect to being "portable" in terms of being a one-person-move job. The more I read and look at stuff, the reality of a 14" and 16" reflector is basically just not going to happen for a portable system. These tubes and bases are just too big, too heavy realistically. Any one component over 50lbs is just going to pose problems ultimately I'm sure, especially when tired and packing up.

 

 

Just my two cents: My friend built a 13 inch based mostly on the Obsession classic design. To make sure that the scope is solid, he made some components even thicker than the original plans from the book. However, the heaviest component, the miror box (with the mirror), has a very manageable weight. 

 

I'm sure a 14 inch Obsession style Dob is much more transportable, weight wise, than commercial truss/strut scopes.


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#21 Jon Isaacs

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Posted 10 October 2019 - 10:52 AM

Binoviewrs..   To reach focus, you are going to have to use a Denk/Earthwin power switch type system or some kind of amplifier.  The Denk/Earthwin will work as low as 1.2x, but 1.3x and even 1.4x is more typical.  The tube that goes into the focuser extends to raise the power of the amplifier enough to reach focus.  Alternately, you can fit a lower profile focuser and reach focus at 1.3x (1.2x for the Earthwin if you are lucky).  These systems are handy because you get three useful powers.

 

 

With a truss Dob like an Obsession, Starsplitter or most ATM scopes, a second set of truss tubes that are shorter is a viable option.  In San Diego, I can buy a set of eight 1.25 inch diameter, 72 inch long black anodized aluminum tubes for $80..

 

Jon



#22 Eddgie

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Posted 10 October 2019 - 11:26 AM

First, if you have a place to store the scope that allows you to move it over mostly flat ground, it is pretty trivially easy to move a 12" Go2 dob using a hand truck.  My 12" lives under my covered patio, and using no special cradles or anything, I can move my dob out to the uncovered portion of my patio and be looking though the eyepiece in less than two minutes without lifting anything.  I just roll the hand truck under the dob base, grab the tube, tilt the whole thing back, roll it into position, tilt it down to the ground, roll the hand truck away, uncover it, put in my viewing device, and start observing.

 

Now, if you want tGO2, that means alignment, and that adds a couple of minutes depending on how exact the tracking needs to be.  In other words, if I just want to track a target like the moon, I can simply start the scope with the tube level and pointing north, turn it on, and go.  This will get me basic tracking without "Go2".  In other words, if I manually position the scope and let go of it, it starts tracking based on the sky map it built from the "home" position.   Now if my scope was not level and not pointed exactly north, then there will be some slight drift of course and the amount of drift depends on the amount of error, but for planetary observing, the drift is usually minor, and you can easily use the handset to recenter as necessary.  If you always set up level and have a good sight line to true north, you can get quite excellent tracking without any alignment

 

Many of the systems today are dual encoder meaning if you align, you can manually slew the scope and it will not loose the sky map. When you stop moving it, it continues to track normally.

 

Now the 12" is not easy to transport.  There are approximately  24 hand knobs that must be undone to break the scope down.  My base weighs 78 lbs and my tube weighs 50.   The base does break down "half way" with four hand knobs and this makes two parts, but the round base is still pretty heavy.

 

Again, I move this complete setup on a hand truck, and that includes a 7Ah battery that lives on the base of the scope.  I don't even take it off to charge it.  My charger has a cable with a 2.5mm socket on it and I just unplug the power cable form the battery to the mount and plug it into the cable from the charger.   This way, I can walk out the door, lift or carry nothing except my eyepiece/binoviewer, and be observing in less than 2 minutes.

 

attachicon.gif Dob small - Copy.jpg

 

Binoviewers..   To reach focus, you are going to have to use a Denk/Earthwin power switch type system or some kind of amplifier.  The Denk/Earthwin will work as low as 1.2x, but 1.3x and even 1.4x is more typical.  The tube that goes into the focuser extends to raise the power of the amplifier enough to reach focus.  Alternately, you can fit a lower profile focuser and reach focus at 1.3x (1.2x for the Earthwin if you are lucky).  These systems are handy because you get three useful powers. 

 

The negative of these systems is that they are very heavy and can pretty quickly destroy the bearings in most Crayfords, and if the Crayford had an anodized focuser, in the process of failing, the bearings can scar up the focuser tube.  My best result with these heavy systems was the Feathertouch.  Expensive, but I could reach 1.3 in low power and I did not have to slip the BV out for high power (many focuser tubes will not allow you to reach focus in all three powers.  Usually, for low power you can reach focus, but for high power, you have to loosen the OCS extension tube from the focuser and slip the whole thing out).

 

Much lighter, but also limited to narrower fields and higher powers, is a T2 modified BV outfitted with a Televue 2x Bino Vue amplifier.  This makes the binoviewer parfocal with standard eyepieces, so it is a one size fits all solution.  This also is much lighter.  My inexpensive BV and TV 2x weighs less than a 31mm Nagler, but with heavy eyepieces (Baader zooms) it can still put a lot of stress on the focuser. 

 

So, if you have a place where you can roll the scope out, moving it with a hand truck is super easy no lifting, one trip solution. 

 

There is also image intensified astronomy. Now you can turn a 10" scope into a 20" scope and you can even use two eyes if you want.  I can see the Pillars of Creation using my 12" dob from white zone skies.. Not bad. Not bad at all.

 

attachicon.gif PVS 7 in dob.jpg

 

(Now I showed the PVS-7 in the picture because that is a binoviewer like solution though without the negative of beam splitter loss, but in practice, I tend to use a monocular, but the PVS-7 works quite well for image intensified astronomy and we have several people on CN using them, though more use monoculars.)

 

Again, less than 2 minutes for me to be up and observing with my 12" dob and that is with tracking.  If I want Go2, it takes an extra 3 minutes.  I can move everything in one trip. I lift nothing.   Simply tilt the scope back on the dolly and away I go. 

 

With a truss Dob like an Obsession, Starsplitter or most ATM scopes, a second set of truss tubes that are shorter is a viable option.  In San Diego, I can buy a set of eight 1.25 inch diameter, 72 inch long black anodized aluminum tubes for $80..

 

Jon

 

True, but it is usually necessary to oversize the secondary mirror to work at full aperture ad this only works for scopes slower than about f/4.5.

 

Assuming that the secondary provides a fully illuminated field of 10mm, shortening the poles will cost 1mm of illuminted field for every multiple of the focal ratio.

 

For example, if the scope has a 10mm fully illumined circle, and the scope is f/4.9, then cutting the poles past 49mm would reduce the image circle to zero, and anything shorter than this drives the scope into aperture reduction.

 

Then there is the aperture of the binoviewer.  Suppose the BV has a light path of 116mm and a clear aperture of 25mm.  If you divide 116 by 25, you get the fastest light cone the binoviewer can pass.  In this example, that would be f/4.65, so this would rule out most scopes bigger than 12" because most of these have f/4.5 mirrors these days.   It does not matter how big you make the secondary in this case because the binoviewer becomes the source of aperture loss.  The faster the scope, the more aperture is lost, so for a 16" f/4.2 scope it would be essentially working at f/4.64 and that would mean that the aperture was reduced to 14.88" and assuming a 20% secondary, the obstruction would grow correspondingly by the aperture decrease. 

 

Also, with wide field eyepieces, the illumination falloff is quite considerable (probably over 70%) but I know many people dismiss this kind of illumination falloff.

 

So, lets say the OP buys a 12" f/4.9 dob, and the OP has to cut the poles by 70mm to reach focus.  This means that is both decreasing the aperture (not much, but well, it is no no longer a 12" scope) and the secondary is now larger as a percentage of (remaining) aperture.  Not much, but now, rather than have a 25% obstruction (with secondary vanes) he might have a 27% obstruction. 

 

If none of that matters to the OP than yes, you can cut poles, but this really kind of limits the speed and size of the scope that can be used and still work at full aperture. 

 

You are absolutely right though. Poles are cheap, and if he is willing to loose a bit of aperture, he could indeed make the scope reach focus with binoviewers, but it would in most of the cases he is wanting, reduce the aperture and increase the central obstruction and make the usable field for planetary observing negative (which means that even 1mm off axis and the contrast is further lowered due to the loss of more off axis rays). 

 

Now in the OPs case, he has an Arcturus binoviewer.  These have a light path of about 96mm, but the front aperture is only about 21mm, so this means that his limiting light cone would be f/4.57.   No scope he uses these in at native focal length will be able to work at faster than this focal ratio.  He might be OK with this though but if he wanted to work at native focal length, the bigger and faster the scope, the higher the penalty on aperture loss and obstruction growth.

 

(Considering the dimming already imposed by the binoviewer, turning a 16" scope into a 14.88" scope, then further reducing the brightness to the level of a 10.5" scope seems like a lot of compromise, but if the goal is to binoview, the 30% dimming of extended objects is of course fixed regardless of aperture). 


Edited by Eddgie, 10 October 2019 - 11:52 AM.


#23 Starman1

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Posted 10 October 2019 - 12:43 PM

Just my two cents: My friend built a 13 inch based mostly on the Obsession classic design. To make sure that the scope is solid, he made some components even thicker than the original plans from the book. However, the heaviest component, the mirror box (with the mirror), has a very manageable weight. 

 

I'm sure a 14 inch Obsession style Dob is much more transportable, weight wise, than commercial truss/strut scopes.

I laughed when I saw this, since Obsession, New Moon, Teeter, Starstructure, SpicaEyes, Fullum, Astrosystems, et.al.

are commercial scopes.

I think you were referring to commercial Chinese scopes, which typically have heavy bases of particle board.



#24 Jon Isaacs

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Posted 10 October 2019 - 05:09 PM

I don't think moving the scope in and out of a garage is rare, especially SCTs on Wheeley Bars.  Moving a scope once it's set up in an observing spot is.

 

I don't think many scope owners who have wheelbarrow handles think a lot about the length of them, though.

Having the mirror box slide out could be a serious problem.  Also, tipping the rocker box a fair amount lowers the UTA to the position where most have the UTA dive

toward the ground (most dobs I've seen and used will dive when below a certain angle).  You understand about dynamic balancing, but most scopes are not set up

that way.  Without a virtual counterweight, my Teeter will dive toward the ground when below a 30° altitude, though that is with an eyepiece and Paracorr.

 

My old Discovery had wheelbarrow handles, but the top dived for the ground if the handles were mounted like yours.

The instructions that came with the scope were explicit at mentioning they had to be put on the other way.

Don:

 

I really don't know what other people do, I know what I have figured out.  I balance my scopes so they are balanced from the horizon to the zenith with any eyepiece I have, that means the scope will not drift with a 31mm Nagler nor will it drift without an eyepiece in the focuser.  This requires some fiddling, getting not only the top to bottom balance right but the front to back.  Omega Centauri culminates at 10 degrees and my view to the south is to the horizon so I enjoy it as well as a variety of other lower elevation objects in the southern sky.  My scopes do not dive. 

 

As I have discovered, one has to be careful not to "dump" the scope by lifting the handles too high, this will happen either way the handles are mounted.  Getting the 25 inch F/5 back on the rocker box was all I could do.. 

 

Anyway, moving a large scope that's assembled with wheel barrow handles requires some thought and understanding. The Starspitter manual states that the scope should not be moved fully assembled and would say unless one understands the various issues involved, that is good advice.  

 

This a topic but deserves attention but it really should have it's own thread and not here.

 

Jon



#25 25585

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Posted 11 October 2019 - 05:14 AM

 

 

Now the 12" is not easy to transport.  There are approximately  24 hand knobs that must be undone to break the scope down.  My base weighs 78 lbs and my tube weighs 50.   The base does break down "half way" with four hand knobs and this makes two parts, but the round base is still pretty heavy.

 

 

What makes the base weight so heavy?




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