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Setting Circles and other mods to my Lightbridge


Dellis
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I've had the Lightbridge for several months now and am happy that a dob is the scope for me ultimately I'm aiming for a custom made example but for now I'm happy with the Lightbridge with a few small mods and accessories, none of them are ground breaking or unique but I thought I'd catalogue the changes so far.

So here goes and starting with collimation I added a set of Bob's Knobs secondary collimation thumbscrews to eliminate the risk of dropping something on the primary, they are inexpensive and make collimating the secondary a breeze. Second part of the collimation improvements were to the primary springs which I've replaced with a set from Bob's Knobs which are considerably stronger than the originals and have meant that collimation holds for much longer. Next on the list was a light shroud and I went for the Astro Engineering semi rigid version the reasons being two fold firstly to cut down on stray light and secondly as some additional protection for the primary. Next on the list was an upgrade in the finder department and I really went for it here and have added both a Telrad and a 10 x 50 straight through finder, the Telrad gets me pretty much there and to be honest the optical finder is a largely unnecessary. All this lot has added a bit of weight and sent the scope way out of balance so a set of counterweights have been added, nothing spectacular just four car roof magnets fitted with weights turned from mild steel and lacquered to prevent them going rusty, they work a treat and are easily moved to achieve good balance. The last thing was to add a Wixey and an altazimuth circle to the base, initially I marked the circle by hand but once I proved to myself that it worked has a vinyl degree circle made up. I like hunting for objects but now if I'm struggling to find my target and can fall back onto Stellarium and 'push to' whatever it is I'm looking for.

With a few simple changes the scope is much easier to use and I'm sure will give me many happy observing hours before I can afford my custom made dob.

Dave

Setting Circle

EE6E5AD1-0E77-45E0-B081-104346660EB5-2598-000002044BE47F18.jpg

My Scope

32B27EDF-BE33-4F1D-878F-5D16F048B429-2598-000002044BDE8318.jpg

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  • 1 month later...

Very nice mods! And I like that shroud.

Is the setting circle pointer adjustable? I assume it is.

George

The pointer doesn't need to be adjustable you just plonk the base down pointing roughly north with 0 deg at the pointer then rotate the base to fine tune. However I have discovered a problem, the base needs to be level for the setting circle to remain accurate for the full 360 deg rotation. This is well known but I didn't realise how critical it is so I'm now in the process of making a levelling platform which I'll share when it's completed - should be next weekend.

Dave

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hi there, nice job, i want to do that as well but struggling to find a decent enough large image of some setting circles to get printed, could you possibly post the file you used, i`m sure many on here would find it very helpfull, i`m personnaly thinking of making a leveling base and putting the setting circle on the base rather than the dob to save cutting the base and then just having a movable pointer on the dob.

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The setting circle mod on a dob is the best one I've done but aside from the levelling platform the thing I've found most useful is when you first use it on a nnights session is to align your scope to Polaris or Vega or Jupiter for example and make sure the coords on your phone or laptop match exactly the wixey or setting circle Mark by resetting the wixey and moving your sc marker .it only has to be done once each time but can save a lot of frustration later on

Sent from my GT-I9300 using Tapatalk 2

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hi there, nice job, i want to do that as well but struggling to find a decent enough large image of some setting circles to get printed, could you possibly post the file you used, i`m sure many on here would find it very helpfull, i`m personnaly thinking of making a leveling base and putting the setting circle on the base rather than the dob to save cutting the base and then just having a movable pointer on the dob.

Hi FFJay I have one which is a perfect fit for a 200p Dob if its any use- the format is svg so you would need an autocad package to open it I'm afraid - if its any use if you want to pm me your email address I'll willingly send it on. I think the thing after that though is getting it printed as their way too big to do on a normal household printer so you may have to take the file to somewhere like staples to get it printed off.

good luck anyway - its well worth perservering with.

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I'll dig the file out and attach it. I had it made by a vehicle livery company in Burton who did and excellent job and, as with any other printers, will be able to scale the circle to whatever size you want.

Dave

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The setting circle mod on a dob is the best one I've done but aside from the levelling platform the thing I've found most useful is when you first use it on a nnights session is to align your scope to Polaris or Vega or Jupiter for example and make sure the coords on your phone or laptop match exactly the wixey or setting circle Mark by resetting the wixey and moving your sc marker .it only has to be done once each time but can save a lot of frustration later on

Sent from my GT-I9300 using Tapatalk 2

That's pretty much the method I use but my pointer is fixed so I rotate the base which is easy enough to do.

Dave

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Attached is the file I used. It's clockwise so needs to be attached to the ground base with the numbers the correct orientation to be viewed from the left side of the scope as per Meade focuser location. It is marked in half degree increments and printed in the centre is a 90 deg scale for altitude if you decide not to use a wixey. As I said earlier this can be scaled to any size.

Dave

Az Circle Clockwise.pdf

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Here's a shot of this mornings efforts, the large holes are to allow the feet of the standard base to locate in and the smaller holes will have 'T' nuts and bolts fitted to allow the base to be levelled. The paint was still wet when I snapped the photo.

Edit - the small holes are not easily seen but are to the outside of the large holes.

file-127.jpg

and here's a shot of the setting circle on the base board.

file-129.jpg

Dave

Edited by Dellis
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The pointer doesn't need to be adjustable you just plonk the base down pointing roughly north with 0 deg at the pointer then rotate the base to fine tune. However I have discovered a problem, the base needs to be level for the setting circle to remain accurate for the full 360 deg rotation. This is well known but I didn't realise how critical it is so I'm now in the process of making a levelling platform which I'll share when it's completed - should be next weekend.

Dave

The reason I asked is because having an adjustable pointer makes a huge difference in ease of fine tuning the alignment. Instead of moving the entire base for final alignment you simply move the pointer.

Here's my Lightbridge setting circle with adjustable pointer:

post-23888-0-40542800-1357244704_thumb.j

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Thanks Knobby.

And Dave, as you indicated, leveling the base is critical for the accuracy of the scope to point to its targets. I installed a simple bullseye level at the rear of the base. Plus, it only takes seconds to level the base with the adjustable leveling feet.

post-23888-0-65464900-1357319351_thumb.j

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I like the work you've done with your base and I suppose it would be easier if I made an adjustable pointer, there's no point in making anything any more difficult than it needs to be! Is the bullseye level good enough to get decent accuracy with the setting circle?

Dave

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The bullseye level or a cheap cross level will get you close enough, as good as any precision cross level for this particular application. These dob bases are almost never 100% orthogonal so they will always be slightly off level at any given azimuth position.

Also, an adjustable pointer is more practical as you do not have to re-level the base each time you make slight changes in alignment. I sometimes find myself making very slight alignment adjustments with the pointer during the observing session depending on which part of the sky I'm at.

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Well I got to work this afternoon and finished the job off. The wing nuts are there to lock off the bolts when the base is levelled thus reducing any movement due to the tolerance in the threads. If the clouds ever clear I'll test it out and report back. I took Carbon's advice and fabricated a moveable pointer to make alignment fine tuning easier - sorry fella but it's a direct rip off of your idea.

Dave

file-130.jpg

file-131.jpg

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