Yes the Ebony Star is OS. A bloke called Dean Sala has it precut. There is a link on the Stellafane website.
With the focuser board, that is an issue that I am still wrestling with. That is why I have made 4 upper rings out of cheaper ply wood to experiment with before the final build using marine ply.
My plan was to use dowells and glue and add a couple of metal 90 braces. But plans are always tentative until final build!! Or I discover I have no idea and start again.
I can get my hands on Ebony Star now from the Oz supplier. Ain't cheap, but now there's no other choice for textured laminate as Laminex no longer makes the textured "Dimensions" series.
Ebony Star (Wilsonart laminate 4552-90) is readily available, there is a place near me in Geelong that stocks it.
The Ebony Star that is traditionally used (and the stuff I have coming) is 4552-50. Kreiges book only mentioned the part number as 4552, so not sure how they all relate. I will give Deans stuff a go and if no good try the 4552-90.
I wanted to get precut as I have no laminate cutter and haven;t been able to source a router bit suitable for cutting it yet.
I've found kitchen manufacturers often keep offcuts of textured laminate as its so pricey they can't bear to throw it away,though ebony isn't the most popular colour .
I can get my hands on Ebony Star now from the Oz supplier. Ain't cheap, but now there's no other choice for textured laminate as Laminex no longer makes the textured "Dimensions" series.
Who/where is the Oz supplier? All I can find on Google are OS.
Finally some movement! My spider turned up today at last so I was able to progress. I have completed the first iteration of the OTA. All looks OK (it is rather late so I will wait until tomorrow to post pics) but I will need to get a first light on a star to check focusing then I may have to adjust the length of the struts to correct. I have a feeling I may have made the struts just a teeny bit short so have some spare tubing ready to go!
The focuser board worked OK, just made of 12mm marine ply and simply screwed and glued in place. It seems solid enough, but if it does flex with the Ethoi, I have a Bintel 68deg 15mm ep which is really light to use instead.
Once I have the OTA achieving focus I can work out where it balances then I can dimension my rocker box.
Hopefully, will have first light of completed scope by Sunday, weather permitting!
Pics of the OTA assemply are attached. I attached the spider by simply bolting some angle brackets to the ring and using those. Once assembled I have done a quick collimation (the system used on the primary works really wellm and with a short system it is pleasant looking in the cheshire while adjusting it!) and taken it outside to check if I can achieve focus. I suspect I am right that I have cut the struts too short by about a centimetre, so I will have to revisit my calculations. I think error was in guessing where the secondary would end up in relation to the ring and I guessed wrong! I will wait until I can do a formal star test before finalising the length.
Although it is only an OTA at this stage. I took it outside tonight to first light it. Simply rested on my observing table and pointed it roughly in the Sagittarius direction, managed to nab M8, M17 and M20!!
As I suspected I had cut the struts a little short so i simply put some wood block on the ends to temporarily lengthen to test focus and they need to be 2cm longer. Luckily I have plenty of tubing and made a spare set of inserts so easy to fix tomorrow and the I can set too building the rocker box and ground board over the long weekend.
Optically it appears ok. The f4 mirror makes focusing really finicky but even with the little 15mm Superview the field is really wide. Once I have a proper mounting I will be able to check coma etc.
Well I spent a couple of hours cutting out parts for the rocker box and ground board. Spent a hour or so working out dimensions and drawing it up then cutting with the jigsaw. I finally bought myself a decent jigsaw after borrowing friends in the past and makes a big difference, easy to get nice clean and straight cuts.
Pic attached shows the components laid out. I haven't cut holes in the rocker base yet as I am intending to glue the Ebony Star on first then make the weight saving cuts. I have also cut out the side rings as circle, but still have to do the inner cuts on them.
Lookin' good Malcolm. Did your secondary come with the spider? What size secondary did you end up with? I've gone with a 40mm for an f5 primary and a low profile Crayford helical focusser. I'll be making my own spider and secondary holder, but all is on hold for now as we're moving house in a couple of weeks.
Graeme
The spider and secondary holder are from Astrosystems. I thought about attempting to make them but decided that the woodwork was going to test my skills enough without throwing in metalwork!!
I went with a 50mm secondary. My calcs suggest this should be OK and from initial tests it seems to work alright.
I have knocked up the first iteration of the rocker box. needs some slight adjustments, as it is only screwed together atm, I have easily pull it apart and adjust.
OTA is now essentially complete. I may strengthenm the attachment fo the focuser board with Alex's suggestion but it is OK atm so I will see.
Only thing with the OTA is how I am attaching the red dot finder.
Attached photo show the OTA sitting in the rocker.
Jobs still to do
- Adjust the rocker box to give a teeny bit more clearence for the OTA as it moves.
- Put Ebony Star on botton of rocker and on the alt trunions
- complete the ground board. I have designed a little tripod arrangement that I think will work better (I hope!) than Gary Seroniks method, and will get scope off the ground a bit.
Had another test tonight. Collimation is still a bit dodgy, wasnt spending too much time on it as I am likely to be pulling it apart again tomorrow!
The alt action works fine even without Ebony Star on the trunions and as the ground board isn't ready the AZ action it the old "pick up and move" but at least I can get steady views!
The coma is really noticeable with f4 but stars in the centre are night and tight.
Or I discover I have no idea and start again.
