fwm891

Sorting out the electrics today while waiting for the metal to arrive. I'll run this off a small 7Ah 12VDC battery - need a couple of push-to-break switches. There will also be an on/off switch and a (dim) red led. Not sure whether to put the led in the hand speed control or at the power entry...

Make some short legs to go under the baseboard to bring the eyepiece height up a bit. Then sort out a seat, then...

Set-up a temporary pivot and edges to simulate the drive and idle shafts so I can see the extent of the platform tilt in either direction. Initially I wanted a 45 min travel but I have enough for 60 mins plus. The level is set at ±8° the pencil marks show there is a cushion either side I can set switches on to cut power should it be left un attended. The aperture for the motor has been cut allowing some wiggle room. The holes to take the baseboard's feet have also been bored. Waiting on some metal rod now to make the two shafts and 2mm sheet to make the motor mounting plate.

TBC...

Tried the motor and PWM controller to confirm the speed range. On max it didn't quite get to the 2 rpm stated (though driving direct from the battery it did!) so I turned the controller back to it's mid point and made a few measurements. I now get at this setting 1 rev in 70 seconds. Given that I'm running through a 40:1 I can increase the drive shaft diameter to compensate for the slower revs. Drive shaft now 23.14mm OD which is good as it will allow better (shallower) contact between the drive shaft and the segment. Pleased I didn't assume the PWM controller would give me full speed.

My thoughts at the moment on the drive shaft and motor. Mounted it with the worm vertical so I can rotate the drive shaft around the worm shaft to fine tune the shaft contact with the curved segments. The motor come below the ground board so I will need a waterproof cover to protect the electrics (not shown)

Currently the segments are stuck to the top plate with double sided tape while I measure up heights, angles etc for the drive and idle shafts. I will also add a couple of safety blocks at the end of travel to prevent accidental overbalancing in either direction. These will probably incorporate cut-off switches to prevent the drive running but going nowhere (I have days like that!). I also need to disengage the drive shaft to re-set the platform - probably use a lift roller to accomplish that rather than a clutch... More thought required.

Equatorial Platform for my 10-inch GSO Dobsonian

Having recently purchased my dob (end October 2018). While waiting for it to arrive I decided amongst other things to build an EQ Platform for it to save some nudging at the eyepiece whether just me observing or at some observing event etc.

After searching the internet for a while and watching various videos of other people’s platforms I decided to build mine based around this web site:

http://www.reinervogel.net/index_e.html?/Plattform/plattform_VNS_e.html the vertical north sector (VNS) version in particular, as it formed a more compact unit at my 52° north latitude.

At this stage I hadn’t got a telescope to take physical measurements from so I relied on the details given on the TS website concerning sizes and weights, with a couple of emails to TS gave me other details not listed.

https://www.teleskop-express.de/shop/product_info.php/info/p1192_GSO-10-inch-f-5-Dobsonian-Telescope-Deluxe-Version.html

First. I needed to find a close approximation for the scopes centre of gravity. The only way I could do this was to take the physical sizes and weights for the base (rocker box) and the tube (OTA). These were given as 12.2 Kg and 15.5 Kg respectively. TS gave me 442mm as the spacing between the three feet under the ground-board.

The only way I could do this was to make some close approximations for the rocker box panel sizes, the circular ground-board and azimuth base were given as 540mm OD, the panel height at 640mm. Front panel I guessed at based on the size in the photo in the TS advert relative to the 305mm OTA diameter (having the actual scope to measure is so much easier!).

Armed with my known panel and base board sizes I calculated the surface area of the rocker box and given its assembled weight I found the weight per square cm (cm²) and multiplied this back to the individual components to give me their weights.

I used Excel to calculate a string of weight x distance sums, coarsely at first and then refining the distance steps until I found a balance between the rocker box and OTA distance/weights numbers and used that for my centre of gravity height.

This then allowed me to start using the information in the web site (above) to shape the vertical north segments for my 52° north latitude. The website gives templates for different latitudes around 50° north/south latitudes and a run time of about 1 hour. I was going for a run time of circa 45 mins to keep the segments shorter, so they didn’t stick outside the baseboard which in the dark I thought might be dangerous at ankle level. The segments are set at an angle (perpendicular to a line back to the pivot point).

My reading of the website calculations:

·         From the intersection of the CoG line and latitude lines find the length of the perpendicular side of the triangle.

·         Multiply this length by Cos (latitude + small angle below top plate) Total 65° in my case.

·         This gives the half height of the ellipse

·         The 1/Cos (angle formed by the roller supports) gives a modification to the ellipse shape to compensate for the angled segments

I used Photoshop to create a full-sized ellipse and the segments. I then printed off full scale, one of the segments on an A4 sheet and transferred that to the plywood.

I purchased some 18mm birch plywood (1 piece: 1220 x 610mm (4ft x 2ft)) which let me layout and cut the ground board and top plate plus the two north segments with lots left over to cut bearing mounting blocks, various supports for the VNS’s and the pivot block assembly.

After drawing out the components on the plywood I’ve used a jigsaw to cut out the main parts and glued the north segments together at a 25.2° angle so they form a single unit.

Next stage will be making up the ball race and motor mounting blocks…

Absolutely incredible -brilliant - call it what you will - bravo to the pair of you, magic

Wiki DSS link no longer working

Failed for me tonight - predicted clear at all levels from 11-02am but I got about 15 mins - try again another night - looks good though

You can certainly get away without a driven mount but a tripod is a must. I've shot Orion with a 50mm lens and a series of 4 second exposures (about 70 I think) then stacked those in DSS - just rotate the camera a little west after about 20 frames to compensate for earths rotation.

I've been playing with the iOptron Skytracker recently and have managed to image up to 600mm on it with resonable results - keeping exposures to about 1 min:

http://stargazerslounge.com/topic/215837-ioptron-skytracker-v2-600mm-sigma-mirror-lens-m51/

That is just incredible, true dedication to: capture, processing, research and annotation

....

I don't think so unfortunately. The microlens layer has a gel-like consistancy under the microscope and comes off very easily, but doesn't ever seem to come off it large chunks. The filter layer I would describe as almost crumbly - it doesn't seem like the coloured pixels in the layer itself are held together, only stuck to the layer beneath.

That said the idea of scraping it off with something very thin by getting underneath might work. But the trouble would be getting something to a sharp enough edge without it being made of metal or something that would scratch the glass. I'll happily experiment with my broken sensor.

...

OK I've only got to page 15 ATM but a wooden lolly stick cut from one side with a blade will give a 'soft' chisel edge - do not sand as abrasive grains will embed themselves in the wood.

If this has been covered later by someone - apologies

Francis

"The Abridged Debayering a DSLR" doesn't exist I'm afraid. TBH, I think it is worth reading through the thread as there are lots of projects followed through with detailed pics and lots of examples of pitfalls to avoid.

Only took me about 2 days to read!

I may have retired but...

I'm inclined to agree. There's a lot of information on what's worked and what hasn't, but it's quite haphazard. Until it's a successfully repeatable process I think it will probably remain that way. Just don't let your camera see the stuff that Gina has done to some of hers. It'll be running for the door before you have a chance to grab it

James

Having followed some of Gina's other projects I can well believe it!

Thanks both

Great thread - is there a 'short' version detailing the salient steps as I've only just started thinking about doing something with my 450D....

Cathy,

Try: http://www.motionco.co.uk/

Look under the MXL timing belts and pulleys. They will also do the rebores for if requested

You should be able to get similar in Aus - search for 'MXL timing belts'

Does NASA know about this.....

Great work

Great work Tony - I'd pull some cables or cable pulls through your pipes before the floor goes down just in case they snag at the 90º bends

....the loose blocks across the gaps are to stop the wifes tortoises going walkabout

Know the feeling re four legged friends (fast & slow ones).

Watching this Tony, looking good, great blockwork.

Do you still have your webcam link Gina so we can see the roof in action?

I also want to have a go with a test sensor(even an old webcam senor) with some form of paint stripper to see if it'll work without damaging the sensor. This would make it more easy and should give a cleaner finsh.

Anyway its a good thing i didn't listen to the internet and not give it a shot.

The micro lenses will be a moulded plastic so mind how you go with the paint stripper.

I'd also be worried about making the lenses 'frosted' with the dremmel - even using a soft tip?

I don't know really - it's a thought certainly, thanks Francis I'll see about that - of course, it would need long heavy duty cables (unless the battery is on the rolling part too).

It certainly wouldn't blow away again

This is my thought....

Blue outline obsy building, Black - RoR

Motor / pulley cab be at any height to clear building

Red cable/rope fixed to building at either end

Ropes should be self tightening in either direction.

Gina - you seem well on the way with this. Can you not mount the winch in the roof section so it travels with the roof and have fixed lines (at each end) with the winch taking-up and playing out rope as it goes back-n-forth...?

Just a thought

Thanks Steve, I guess 3.14159 will do fine for setting circles....

I know one guy who used a carpenters tape measure wrapped around the base of his dob. Then used a simple programmable hand calculator to work out what 'measurement' he needed to go to to find the next object. Did the same for the alt bearing making the dob a 'manual' goto...

I wonder what the current record is for the number of decimal places for solving pi....

As the outer edge of your base is black you could use one of the fine typing correction pens directly on the edge giving you white markings. I would suggest you over coat these when fully dry with a water based varnish/lacquer to seal and prevent chipping

Thinking about getting one of these while they're on offer - 5in1 Jumpstarter with Digital Air Compressor : InCar Battery Chargers and Compressors : Maplin

Maybe useful for people with dead powertanks

I bought one of these it wouldn't even charge properly from new - never more than the 'low charge' light showing (sadly I lost the receipt so they wouldn't change it )