EQ Platform HELP!!

[spaceboy]

Hi all

Due to following Moonshanes EQP thread http://stargazerslounge.com/diy-astronomer/127311-equatorial-platform-dobsonian-telescopes.html it has now got me hooked on the idea of being able to use high power EP's. I plan on going down a slightly different route of a VNS EQP after finding this website http://www.reinervogel.net/index_e.html?/Plattform/Plattform_e.html.

I was never a wiz at maths so I could do with a little help on the VNS calculations. As you will see from Reiner's site there is an explanation for calculating the cos angle to change from a CS EQP to a VNS EQP. My calculations (probably incorrect) are attached but I now require the cos a & 1/ cos beta measurements which are over my head.

My plan is to construct a platform similar to the aluminum version on this site Equatorial Platforms: About Our Platforms but in mild steel. (just because I have some spare)

Any help would be humbly appreciated

SPACEBOY

[Moonshane]

you can do it by trig but you can also do a scale drawing which would be more than accurate enough for visual.

[spaceboy]

I did try trig but came up with cos 0.727 which means nothing to me ?? Dose the scale drawing work by setting the height you want the platform ?

[Moonshane]

I'll send a drawing later when I have a bit more time.

it will explain what to do.

[spaceboy]

Cheers Shane! My hearts in it but my brain isn't Frustrating as once I have all the angles and measurements figured out it will only take a day or so to get the steel cut and welded. Will be a case of waiting longer for the electronics from China.

[Moonshane]

you are quite right about timing. I'd wait until mine works with DC motors and you can then go ahead with more confidence. have a butcher's at SGL6 (I am only there Thursday night and Friday to pm).

also, I am writing the process I followed with pics etc in a single pdf. should have this done soon.

[spaceboy]

You saying about motors, I also found this in my search Gallery - equatorial-platforms-uk it appears they use a Variable power Celestron Astromaster EQ drive to power theirs. These run off a 9v battery for approx 40hrs but I would imagine it is easy enough to power it from a power tank or gel battery with a little wiring. The advantage here is the motor and PCB are already contained in a nice neat case and have a flexible connection for attaching to the drive gear. Bit pricey at around £44 and I doubt they come up 2nd hand too often, but as they are already used for astronomy you know they will work and even if they didn't someone with an Astromaster mount would take it off ones hands. I see you want more to the setup than just a motor so I doubt it would have suited you but it obviously is a proven method for a straight forward solution.

[Moonshane]

too true matey. there's many more ways to skin a cat than one

[spaceboy]

Just had a thought. These platforms are no good for objects coming up off the horizon are they? Is it just for objects already up in the southern skies? Not that this is a bad thing.

[Moonshane]

I may be wrong but I thought you just point it at anything and it tracks. in effect it turns to alt-az mount into an EQ mount which of course is not restricted as you say.

http://www.tomhole.com/images/WPerers%20Platfor%20A&B.pdf gives a great explanation and design and you could use this especially fig 5 to measure your own sectors. bear in mind that if you are using a pivit rather than a south sector then you need to 'move' the boards to the far right of the angle and this will reduce the radius of your north sector. in fig 5 J would then be in the apex of the latitude angle.

[spaceboy]

I think your right. My head just isn't with it today. Think it's a lack of sleep from a late nights observing on stellarium . More Like my brain cells are on over load trying to figure out all these sums.

It will won't it. It just means you have to adjust the height of the objective every time you reset the EQP.

[Jgw]

Hi Spaceboy,

Just in case you are wondering about your Fig:

If b=641... and a=37,9 Deg,

Then c= 393,75..

Just can,t make out you writting, let me know if you need help with the drawing..

Cheers John..

[spaceboy]

Hi John

I wondered how long it would be before someone noticed. It's me causing confusion there. Half asleep when doing the calculations. a = 52.1' for northern hemisphere 37.9' should be the Adjacent / Hypotenuse angle and I'm assuming the angle at which the CS radius would be. It here where I am struggling as I need this angle to be erected to 90' while compensating with cos calculations for the change in radius to the pivot point. It's times like these why I tell my kids they need to pay attention in school. LOL I can remember saying to my friends what it the point? when will we ever need to know things like this in life ? 20 years later and I'm now finding out

[Jgw]

Hi Spaceboy,

Wait until you reach 60!!.

As I say, Age is a matter of mind, if you don,t mind is dosen,t matter....

Here are some calculations.. a=52,10 / b=37,90= Hyp=641/A=393,75/ B=505,80

Bye 4 now John

[spaceboy]

Thanks John

[spaceboy]

Slowly but surly the ball has begun to roll on this project. A big thank you goes out to Reiner at Telescopes and Deep Skyfor helping me out and updating his site with VNS segment details. http://www.reinervogel.net/Plattform/images/Vorlage%20Plattform%20neu.pdf

I managed to pick up the same EQ drive that Gallery - equatorial-platforms-uk appear to use successfully with a 12" truss dob Konus 1706 R.A. motor drive EQ2 for 1749 on eBay (end time 14-Mar-11 19:01:03 GMT) and now only need to draw up a template ready for the steel work and source some bearings for the VNS segments to ride on. An idea that came to mind was using some skate board / roller skate wheels. These come in a variety of materials (thinking something abrasive to avoid any slipping but soft enough not to cause vibrations), they are hard wearing and have self contained HD bearings and the hope is that one of my friends and family have their kids old skateboard they plan to chuck out.

I will update on my progress for anyone interested but don't hold your breath as I'm not the most motivated person in the world

SPACEBOY

[spaceboy]

Made a start on the EQP yesterday and have got the top section all done. The VNS segments are made of aluminum as it was suggested it offers for better friction across the drive bearings and are removable should I ever need to change them. The main body is made of 30mm box section as I had some spare from an old roof rack. I plan on having it zinc plated so some drain holes were required but as it happens this worked to an advantage as a previous mod on my dob seen me put adjustable feet to the rocker box base for leveling http://stargazerslounge.com/equipment-discussion/118335-dobsonian-leveling-sorted.html. When the feet are removed 3 x M10 studs are exposed and these will sit nicely in the drain holes to help avoid any dob slippage. The feet from the rocker box will then be used on the EQP base to aid leveling in the same way. I'm waiting on bearings for the VNS to run on before I start the base as it will give me a better idea of dimensions. As you can imagine it's already a bit of a heavy weight but this should work out OK as a 10" solid tube dob is going to sit on it where as the the original plans for the platform were drawn up for a 12" truss dob which would be significantly lighter.

[Moonshane]

superb job so far Nick!

I may well make one like this myself - may father in law is a decent welder.

[spaceboy]

JOB DONE!

Got the base of the EQP finished in no time but figuring out how to run the VNS was a different matter and took me 2 days of trial and error to get it right. Finally got it all buttoned up for today and as luck would have it the sky's are playing ball and staying clear. 1st light test run proved a total success. I was able to keep Saturn in view at 400x. Conditions didn't allow for any visual at this magnification but it was purely to see if the image wondered off. There was some slight adjustments required from time to time so either my COG is a tad off, it was not correctly level or my efforts to pointing true north failed which I'm more inclined to believe it was the later. Either way a 50' FOV and 400x magnification had Saturn sat in view for a good 10 minutes before a slight ALT adjustment was necessary. I am amazed at the fact I am now able to track using my 10" dob for a fraction of the cost it would have been for me to have the same setup on an EQ mount. I had originally had my doubts about the motor being up to the job but due to the way the VNS system works next to no torque is required as gravity dose all the work and the motor controls the rate of decent. I also had my concerns due to weight. This again is reasonably light given that it was constructed from mild steel. I will be having the steel coated to protect it against the elements so it should offer me both strength and durability. Anyone with a dob and some DIY skills should give it a go as it is a surreal experience to be able to track with what is actually a manual dob.

SPACEBOY

[Moonshane]

stunning job mate!

I had a go with Saturn too last night and mine works a treat also.

easily maintained in view at 250x which is more than adequate and like you with a slight adjustment every now and again.

great to be able to walk into the house to get another eyepiece and put it in with the target still in view eh?

the best thing is no 'settling' due to constant nudging, just observing.

[spaceboy]

Cheers Shane I have always had tracking mounts since I started the hobby so talk of an alternative to nudging got me interested. It was so weird being able to use my dob and not having to nudge. I now have the aperture and the ability to push it to the max. Glad to see yours is all sorted. As we both have to make similar adjustments I can only assume it is the alignment to north. It's no big deal as I usually move on to the next object after 20 minutes anyway. Popping to the platers tomorrow to see how much it is to hot dip but as funds are tight I may just hammerite it. I'm itching to get out under dark skies now to give it a go on some globulars. I had M13 in my sights last night at 250x and it was amazing how much detail the 10" brought out even under less than ideal skies.

[spaceboy]

Got the frame back from the powder coaters today. Decided on powder coating to keep costs down plus it meant I didn't have to mess waiting around for paint to dry. I'm happy with the overall finish of the EQP considering it was thrown together. I'm now itching to get out under dark skies and really put some magnification in to those globulars

Again I'd want to say a massive thank you to Reiner at Telescopes and Deep Sky, Moonshane for his inspiration and JGW for helping with the math.

[spaceboy]

fig:

[lquinlan]

Hi Spaceboy,

Thanks for the tip on the EQ2 motor drive the other day. I've made some good progress on my platform over the past couple of weeks. Only a day or so away from a proper test run with my scope now. Very exciting !

I had a thought on the south bearing/pivot. Do you happen to know if it is important in these VNS designs to have the actual pivot point (ie. the point at which the bolt touches the shoe) at the same height as the top of the north rollers ?

My gut feeling is that it would, but I can't think why ! lol

[Jgw]

Hi Spaceboy,

looks good. well done. hope it works out Ok.

Cu John