Glenore Grove Observatory progress

mch62 (Mark) · #1 18-05-2005, 10:58 AM

Just an update on my Observatory and EQ friction drive fork mount.
Some statistics for people interested in Friction Roller drives.

The drive system uses 2 servo motors with encoders running on large smooth drive discs.
No worm gears here just the frictional force of a drive roller against a disc as used in a lot of large observatory set ups.
The advantage is little or no PE and back lash and a lot cheaper than 12" plus low PE worm wheel gears sets.
The disadvantage , possible slippage and loss of positional orientation.

There is some PE and back lash due to reduction gearboxes but if there chosen carefully low PE is the result and also due to the primary reduction any gear box PE is reduced by that amount.

In a worm wheel set up you have the PE of the gear box as well as the worm wheel.

The over reduction for RA and DEC is 2212.5 : 1 with an encoder resolution of 4531200 .
This winds up about 3.5 ticks per arc sec resolution at a maximum slew speed of about 6 degrees /sec.

The primary roller reduction is 15:1 with a 660mm diameter SS rimmed steel disc for the RA and a SS rimmed ply disc for the DEC .
The DEC drive will be using a timing gear and belt on a ply disc and not a roller friction drive.
This set up is lighter on the fork for balance and the PE error of this is not as important for the DEC drive.

To ensure positional orientation if slippage occurs or the scope is moved manually as in drag and track mode , 2 extra shaft encoders are used to compare the motor encoders to the shafts.

The controller is Mel Bartels Servo drive system and can be adapted to just about any scope mount EQ design including ALT/Az and Dobs.

http://www.bbastrodesigns.com/NewPro...ouncement.html
http://www.bbastrodesigns.com/#servoitemsforsale

I still have the fun part to do yet which is the mounting of the motors and there reducers and setting up all the parameters , but hope to be up and running within a month.

The observatory is self explanatory from the pics.
A simple roll off roof.

Question welcomed

Mark

mch62 (Mark) · #2 18-05-2005, 10:58 AM

fork

mch62 (Mark) · #3 18-05-2005, 10:59 AM

observatory

mch62 (Mark) · #4 18-05-2005, 11:05 AM

P.S. so far the set up is very stable and even takes my 115kg weight.
I sat on the end of the fork and checked for droop and vibrations and got a nice 360deg ride

slice of heaven · #5 18-05-2005, 11:12 AM

You have been busy.
Looks good Mark

astro_south (Andrew) · #6 18-05-2005, 01:03 PM

Looks great mate - be out in a few weeks to check it out.

h0ughy (David) · #7 18-05-2005, 02:03 PM

Mate size matters, I am more than impressed!

atalas · #8 18-05-2005, 03:57 PM

Looks great Mark! your hard work is paying off.

Louie

Orion · #9 18-05-2005, 04:08 PM

I was going to ask you how it was going. It looks great Mark can't wait to see the finnished result.

Jonathan · #10 18-05-2005, 08:20 PM

Great stuff Mark. I'm impressed

Astroman (Andrew Wall) · #11 18-05-2005, 09:23 PM

That is amazing stuff there, you should get a ATM medalion for that piece of art.

Keep up the great work.

PS looks like my mini fork I made a long time ago.

gaa_ian (Ian) · #12 18-05-2005, 09:53 PM

Hi from the Top End Mark !
Its looking great !
All you have to do now is register as a research observatory, & get the council change the streetlights to full cutoff fittings

Seriously, I did read somewhere it is possible to register an observitory & get action on light intrusion !
I believe it is in the Australian Standard on
"Controlling the obtrusive effects of outdoor lighting"
I will check it out & post any details I find !
There I go ...on my soapbox again

[1ponders] (Paul) · #13 18-05-2005, 10:03 PM

Excellent Mark. Whens the Grand opening and official First light?

mch62 (Mark) · #14 19-05-2005, 06:41 AM

When it's finished

I have a few things that need changing on the mount and I still have to mount the servos and there drive rollers.
But the ,lets say , interesting part will be getting the things to work correctly and communicating with a charting program ect.
I am hoping for a month or there abouts but hope to have the OTA on sooner than that and at least be able to push it.

Mark

iceman (Mike) · #15 19-05-2005, 07:58 AM

Looks awesome Mark, that's some piece of work. It's going to be a monster when it's done.

Striker (Tony) · #16 19-05-2005, 05:48 PM

Great stuff Mark......hurry up and finish will you...I need you at my place......

Starkler (Geoff) · #17 19-05-2005, 11:04 PM

The fork looks great !
Are you going to construct some sort of rotating cage for the newt? I can imagine some very awkward eyepiece viewing positions occuring.

mch62 (Mark) · #18 20-05-2005, 09:12 AM

Actually the whole OTA will rotate within the fork.
But just to get started I will just temporarily fit the OTA in with out the rotation set up.
It's been so long since I have looked through my Newtonian I just want to get it on and start viewing.

How I will do the rotating tube is to fit 2 sets of four rollers around the center box assemble .
This will then run inside 4 rings of ply and aluminium sheet made up into like a bearing assemble --sort of.
The OTA can then be adjusted to be parallel to the RA axis by moving the rollers along the box section.
Even thou I will be primarily imaging with the f6 Newtonian , it will be nice for visitors to be able to have a looky with out bending over backwards.

Mark

dhumpie · #19 20-05-2005, 02:54 PM

Hey Mark,

That is looking good. Can't wait to see the difference between your mirror and Andrew's (astro_south). Wonder if there will be a big difference. So where is the EQ6 and the Celestron 80ED going to go now

Darren

mch62 (Mark) · #20 20-05-2005, 03:15 PM

The Celestron is going to be a finder ,guide scope and wide field imager piggy backed on the Newtonian.

The Eq6 is my grab and go mount , just have to have a think about what to put on it for that purpose.

I could wait and see if a certain C11 comes on the market

Know what I mean .

Mark