Starting new thread on this as previous hedaing is now very misleading. Although any advice will be happily received.
Current situation is that mirrors have arrived and so I am pushing hard to complete.
The Spider has been the focus of attention and came together well then I pulled it apart and isolated one pair of legs from the hub and the other pair so I can use them as the conductors for the internal dew heater of the diagonal. No wires, less diffraction. The mounting brackets for the spider to be fitted shortly. I am very pleased with my spider construction.
The mirror support diagonal is now being modified and setup for the heater and mirror backing plate. 2 or maybe 4 390 ohm resistors to be fed by low voltage (12V - 3 V)from a power pack will provide the watt or two that requires. Inside of the diag support will also get insulation to reduce unnecessary heat loss.
The UTA appears to be quite heavy so it's going to get some serious weight reduction. I'll cut big sections out of the side panels but I'll get some rigidity back by adding some short lengths of 10mm wide aluminium angle to the edge at critical points.
Basic setting circles have been added to the base and I'll add a red led light, spirit level and pointer for setting. The red led light is a cycle rear unit and also will give some illumination so I don't trip over the scope in the dark.
Last serious bit to build is the focusser. A 2" capable Crayford with reducer for the 1.25 eyepieces I currently have is the plan. Just working on that up in the design department now, you can hear the clanking and see the smoke coming from my skull as it whirs around.
Did an electrical isolation and heater operational test last night on the spider to confirm all was well then Silastic’d the diagonal mirror on.
Then attached the Mirror Cell mirror outside retainer ‘clips’ and sprayed everything flat black. Also got inside the cell LTA and sprayed all the exposed alum brackets, nuts, washers etc. Built a nylon suspended fan for below the mirror box, 4 screws, 1 small PC Fan, and about a meter of nylon fishing line.
Then finally made an internal mirror cover that slips down inside the cell for when it’s not in use. Used the Styrofoam mirror packing it came in because it fits over the special plastic cover that it comes with and because it is very light and won’t damage the mirror if I ever drop it in accidentally.
I’ll also make a hard cover for the top of the cell and the UTA and Diag.
Tonight ……. I’ll get real brave and load the mirror into the cell … scary lot of glass and silver. Rubber and cotton gloves time.
Still haven’t got a 2” focuser. There is a rack and pinion on Trademe for $125 Buy Now but at that price I would probably buy a new 2" Knife Edge Crayford for $199 although I am trying to build one at present. Just need time…
Pix of spider and mirror mount, can see the heater wiring, uses each pair of vanes as the conductors, no wires.
Pix of fan hanging in fully sprayed cell on nylon lines
Fan suspension system - nylon is nice and stretchy. Was easier to do than I thought. Ever untangled a fishing line mess ?
Looking really good, mate. Good reading about the progress being made.
Tangled fishing line? Mate, tried undoing a bird's nest in the dark? And then, in the middle of the cursing, you feel the bait being taken by something big...
Hi Alex, I've been a fisheman for ever it seems. I can untangle birds nests in the dark, under water, upside down and while fighting a good kawhai with the other hand. .
Normally got two or three rods working so I can multitask as well !!
Yep, pleased with progress so far.
Here's the az circle with red light and level with compass below. Line her up, level it and aim.
And the internals to the diag mirror with the resistor network on the copper plate used to spread the warm area.
Diag seems to have stuck well so made up a temporary focusser till I build/buy the Crayford. Dropped the spider & diag in place and did some simple alignment tests. Looking good.
So then I got real brave and put the primary onto it's base. Stuck it down on the Velcro and squirted three Silastic buttons around the perimeter against the limiter brackets. We're away for the weekend and the weather looks dud anyway so it can cure and I dont have to resist temptation to fiddle with it before it is cured properly. Covered on the bench.
Few more pix.
Temporary Focusser
Spider and Diag (Huge !!)
Mirror assembly showing the 6 point beams
Silastic 'button' squirted through hole in bracket.
Will be tonight. Got home from Wellington, weather was looking good so I fitted the mirror into the LTA, did some simple alignment tests and adjustments ( eyeballed it !! ) added a low power eyepiece and aimed it across at the Volcano about 3 miles away. And there it was !! A wee tweak on the mirror base and a bit of focal plane adjustment and the 12mm, the 20mm and the Barlow all work.
No, I know it is not properly finished as yet, lots of that to do and it's using a cruddy old 1.25 focusser which is probably vignetting the view to heck but it is now sitting up on the concrete pad in the garden waiting for darkness to come and to see it's first starlight. .
You'll hear the sounds of joy or dissappointment tomorrow but now I've got to find some targets for later. Damn this daylight saving !!
Awesome , I got lost up there, too many danged stars I didn't even know existed. Not a great night seeing wise but for all it's current limitations it worked amazingly well. Very hard to find things without a finder of some sort and the balance is close but not quite there so was difficult to hold position and switch up EP's. Found a few fuzzies that would be dim blurs in my 4.5" but were balls of bright jewels in the 10".
A Black plastic rubbish bag with the bottom cut out makes a great light shield btw. Bit of duct tape to keep it up and contrast can be restored easily. My red light idea is a failure, way too bright but we can fix that and I need that 2" Crayford and EP. A 25mm or 32 mm maybe. The 20 mm did well but Butterfly was bigger then the FOV.
I'll do a proper collimation with a Cheshire and shift the red laser finder over temporarily but a Telrad will have to join the fleet later.
I too remember first light in my 10". It too then had only a 1.25", but, boy, oh boy, wasn't Omega Centuri something else!
Don't be put of by giving the thing a real thrash with its 1.25" focuser. Really chase down the faint fuzzies. Push the bugger and make it earn its keep now. When the two inch focuser comes, even better.
Now it's looking finished, sort of. Took a bit more weight of the UTA, sprayed it matt black, resealed all the rocker box and base, made a light block for opposite the focusser. Attached a small finder scope and aligned it. Moved it outside and plastic bagged it. Then the clouds came across ......
But took a pic anyway. Current status. Still to build the focusser and fit the red led finder but it is starting to look the part.
Managed a quick look in between clouds later but wasn't worth the effort. Now just need to concentrate on the focusser and balancing.
I replaced the 1.25" helical focuser on my 10" for this one. This new unit is smoother in action, and with a greater range of travel too. Might be an idea to visit if you have the gear to machine with.
Cheers Alex, looks like a 'plumbing' job build. Pretty simple and 2" of travel. I have the guts for a helical but only with 20mm of thread travel and very fine so looking to extend that somehow or come up with something. A trip to the local big hardware place might be in order to see what turns up.
My 2" Crayford arrived from Aust on Monday ( Thanks Stacey ) and last night I got enthusiastic and decided to swap the old 1.25" out. A few extra holes and it was on. Dragged the scope outside the garage door and bingo, a perfect fit. All EP's working and mid ranged on the travel and the barlow still works.
So, feeling very enthusiastic I built a T connector for my DSLR from a spare body plug and 2" diameter alum tubing epoxied together. I think I will have enough intravel for this to work but if not I have another plan. My strut tubes just slide down behind the corner clamps and seat on the cell mount blocks. I can slide the struts up, place some 20-30 mm spacer blocks beneath, then reseat the tubes and I'll gain an extra 20-30 mm intravel. Yes, it was in the original planned functionality in case I got my calcs wrong.
Then feeling even more ambitious I attacked my 114mm f5 Newt, the instigator of my aperture fever. After viewing through the 10", the little 4.5" was showing it's faults. One of it's major faults was diffraction and poor acuity. The prime suspect looks to be the cheap cast aluminium front cap/spider/hub assembly. Although the diag mirrors minor axis is only 23 mm the hub is 40 mm and the 'vanes' are 5 mm wide !
Newt reveals it is failing on all vignetting points and obscuring 12% of the available photons + probably another 3% or so for the vanes, maybe more.
I have/had an old 4" newt I was given which has the same size tube as the 4.5". The spider and hub is a tiny little thing on three screw in rods of about 2.5mm diameter. The hub is about 18 mm across. I can attach the bigger mirror for the 4.5" to the hub with Silastic and replace the heap of scrap currently there I can fix all three vignetting factors and only obscure 3% of the available photons plus maybe 1-2% for the vanes. The vanes are currently chromed !! ...Flat black spray paint will fix that and I'll modify the outer ring of Alum so it stabilizes the OTA tube. I just gained about 10% more photons for free ! I may replace the vanes with 1mm alum like the 10" one day but for now I'm happy. Mirror still needs to be attached and aligned but I'll post the results when thats done.
I'll poke up a few pics of the Crayford install and if anyone is interested the mods to the little 4.5". I want to take this away as a grab and go for a 2 week travel trip next year so if I can improve it's performance, especially for nothing then it will have been well worth while. And if friends come round then I have another scope to share.
A few pix.
The 2" Crayford all mounted up and working well on the 10".
And the comparison of the spider assembly in the 114mm after I modded it. Hasn't seen starlight yet but the daytime alignment tests were incredibly improved. Cut the spider out of the front ring and refitted it to support the tube and look good. It just about lined itself up, very minimal tweaking required. 23 mm minimal diameter as opposed to 40 mm with 5 mm vanes. 10% improvement in photons.
Bought all the hardware to build the electrics for the 10" and I need to add a couple of big lead weights at the base to get the balance back
Now just need some clear skies.
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First Light soon ..!!
