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double checking area for dob placement...

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#1 bujin9


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Posted 15 August 2022 - 06:37 AM

Hi all....regarding an upcoming purchase of a 22UC dob, just crossed my mind and wanted to check with you guys if this is or isn't going to be a possible issue....

My driveway does have a small grade. At the top of the driveway where the scope would be (behind the cars), it's relatively flat, but not without a grade. Usually, when doing AP, I have to level my mount before anything. I've noticed that pretty much all of you have darn near flat surfaces you put these big dobs on. So I'm wondering if my slight grade will be a potential issue. I've attached pics of the area I'd be using it (basically rolling it out of my garage to the driveway)



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Edited by bujin9, 15 August 2022 - 06:38 AM.

#2 briansalomon1



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Posted 15 August 2022 - 07:42 AM

My 15" dob is used in remote areas, so I always have to level off a place for it. If it were me, I'd want it on grass but either way, you'll end up wanting it fairly level.


You might experiment with some plywood or wood stock of 1/2" or so thickness to "shim" the groundboard to fairly level. If you're tracking by hand it doesn't need to be precise, but a small bubble level might be useful and they're inexpensive.



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Posted 15 August 2022 - 08:16 AM

There's also this consideration >>>    Tom

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#4 bbasiaga



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Posted 15 August 2022 - 08:35 AM

Shouldn't be a huge issue.  The more level it is, the better your DSCs will work, but for manual tracking you're probably OK.  In the longer term you could level off an area of the grass an put a few paver stones down to have a level platform for it.  Shouldn't cost much and probably just take a weekend day or so to knock out. 



#5 Jon Isaacs

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Posted 15 August 2022 - 10:09 AM

My two cents:
I've observed a few times from my front driveway with my 22 inch F/4.4 Starsplitter. It's a 2.6 degrees and It wasn't a problem.  
Starsplitter 22-3 CN.jpg
With a 22 inch UC, you will need a ladder of some sort, that's more of a concern than scope.. Observing on grass is generally preferred but with a ladder, a solid surface is preferred.

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#6 ButterFly



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Posted 15 August 2022 - 01:42 PM

Leveling usually makes no difference for a well balanced dob.  When everything is balanced, the difference is that the slight tipping can change the level of friction as some bearing surfaces take the brunt of the weight.  For example, for a dob pointed along an isocline, the alt bearing on the downward side is getting more weight due to the slight tipping.  The downward side of the az bearing is getting the brunt of the weight in any direction, as is the upward side at the pivot.


For DSCs, that can be modeled out with a few stars.  Using a local align is just easier.


Mirror support is the biggest challenge as the mountain gets more prominent.  Your mirror can swing back and forth with a cable sling.  The cell support points change as the mirror moves.  A slight stickiness to the pads can hold that off for a while.  For fixed edge support, only one may be doing its job.  The thinner the mirror, the bigger the problem.


At the level of a driveway at the top of a hill, it's fine and nothing to worry about.  If that's what gets you out observing, GOOD!

#7 ButterFly



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Posted 15 August 2022 - 01:45 PM

There's also this consideration >>>    Tom

I don't see any streaks from where it tipped over, so that's just the fast way to get it out of the garage.

#8 Napp



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Posted 15 August 2022 - 02:09 PM

My driveway has no level section though the slope is very gentle just before entering the garage.  I set up either of my DOB's there with no problems.  Both are manual.  I would much prefer to set up in the grass but then I can't hide behind my pickup from two unshielded LED streetlights.

#9 Bill Weir

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Posted 15 August 2022 - 03:03 PM

I have a couple of short sections of 2x4 that I place under 2 of of the legs of my 20” when I setup in my slightly sloped gravel drive. What you need to take into account is whether the base will make contact with the uphill side of the slope in azimuth movement.



#10 Keith Rivich

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Posted 15 August 2022 - 10:30 PM

Flat places to set down my 25"? Ha Ha! Only in my dreams...



Will the scope have go-to and tracking? Supposedly my servo-cat / argo-navis is not supposed to care about level, if the two star alignment is done correctly the software will compensate for the unlevelness. In reality I find the system works better if the scope is level so I cut a handful of 4" square 1/8" thick pieces of wood to use as leveling pads. They work just fine. 

#11 kfiscus


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Posted 15 August 2022 - 10:46 PM

I have a flat driveway that you can use.  wink.gif

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#12 CowTipton



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Posted 16 August 2022 - 11:56 AM

My driveway is also sloped.


I typically place my dob with one of the three feet facing downhill and shim that one to get it leveled.

I use a circular bubble level like this.  It's never perfectly leveled but I get it pretty close with just a scrap piece of wood.




That typically gets my GOTO quite accurate.  Everything ends up in the FOV of my 12.5mm eyepiece which gives a 1/2° FOV.

Before I had GOTO I would use the same procedure with my manual dob and it would help keep my taped-on azimuth circle readings accurate to about 1.5°.  Along with a digital inclinometer it was generally pretty easy to find objects.


Don't let the sloped driveway stop you from enjoying that dob.  It's a very minor obstacle to overcome.

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