rfdesigner

I assume you mean it needs re-aluminising. I had my 12" "re-aluminised" as it too was in a bit of a state, that was about 10 years ago and it's still pretty good now (but then my scope's got a window so that helps) I used Telescope House.. although things might well have changed since then. They weren't the only ones offering a re-aluminising service, have a phone around. I seem to remember it cost me ~£100 for the 12" and about £60 for my 5.5", It might cost you ~£200 for a 16" in todays money (wild guess) Good luck, dark clear skys! Derek

I hope everything settles down soon so you can take another look at Saturn. Good luck. Your recount of your fantastic opportunity with the clark telescope reminds me of a Holiday I took taking in LA. There's a 16" refractor there (right next to the Hollywood sign) benefitting from the stable air currents comming off the pacific. When I visited it was pointed at Jupiter.... You know all those fantastic planetary pictures we see taken with high speed cameras where the best 0.001% of images are selected and then sharpened... well the view was like that finnished product, but at the eyepiece, just a bit of shimmer. I only wish I'd seen Saturn with that scope. Good luck Derek

Hi If you take the spider out and put it back in on the origional bolt holes it won't be far out. You ought to recollimate but that's a skill you should aquire anyway. A home made cheshire collimator is all you need, and is only £25 if you buy one. I fitted out my old TAL1M with tube baffles which has a similar effect.. all but eliminating the glow from bright objects.. well worth doing. good luck. Derek

Nothing much technical to report from Saturdays imaging session.. alignment is going to have to get better, but that's all. Lots of imaging: M42, M1, something as yet to be identified which was supposed to be M81 but wasn't , M82, M51. However with the counterweight all black it's not terribly visable.... Not terribly visable as in: bang ouch! :mad:, cut knee through jeans... why do voices carry so much at night? What was perhaps more impressive was that the scope never lost track!..:D 1 streaky frame and then everything was back to normal. I suppose that's what you get for the scope+mount being heavier than me.. it wins! Oh and my M82 image has just gone into the deep sky imaging section under the novel title of M82.

M42/trapesium is now on the imaging deepsky section.

Well I finally managed to get back outside after what seems like a month of bad weather, poor sleep due to my youngest teething, car problems and colds & bugs. The drive system has been adapted with a new shaft coupler.. I'm very pleased with this... all much tighter better algned etc. Testing: So of course it was a full moon. very very thin cloud and all planets too low, too dim or just not visible.. so where to point.. ah yes M42. Well after a bit of aligning I stopped the stars drifting north or south and I got a chance to image with the lodestar. a 240 second pic (one full rotation of the worm) produced star trails ~25 arc second long.. pretty goood, certainly much much better than with the old shaft coupler. Tried taking lots (450) of 1 second images of the trapesium. Used IRIS to select the best 100 images and the deconvolved out a bit of the remaining noise got down to ~2 arc second FWHM.. not so great. Prboably due to living on a North-South road so I end up with my south view being churned up by the heating systems of the entire road. Next: Hand controller communication then second axis then autoguider port.

Well I finally managed to get back outside after what seems like a month of bad weather, poor sleep due to my youngest teething, car problems and colds & bugs. The drive system has been adapted with a new shaft coupler.. I'm very pleased with this... all much tighter better algned etc. Testing: So of course it was a full moon. very very thin cloud and all planets too low, too dim or just not visible.. so where to point.. ah yes M42. Well after a bit of aligning I stopped the stars drifting north or south and I got a chance to image with the lodestar. a 240 second pic (one full rotation of the worm) produced star trails ~25 arc second long.. pretty goood, certainly much much better than with the old shaft coupler. Tried taking lots (450) of 0.2, 1 & 10 second images of the trapesium. Used IRIS to select the best 100 images and the deconvolved out a bit of the remaining noise got down to ~2 arc second FWHM.. not so great. Prboably due to living on a North-South road so I end up with my south view being churned up by the heating systems of the entire road. Next: Hand controller communication then second axis then autoguider port.

Got the tracking correct, finally. What was it?.. a miscalculation.. no. mis-specced/counted motor/worm.. no. straight lack of understanding.. no. pure and simple foul up.. that'll be it. The software has a sin lookup table for generating the microstepping, it used to use a 128 sample 1/4 sine ramp to generate it, but I found that a 150 sample 1/4 sine ramp improved theoretical performance. I had changed the lookup table without error, then forgot to change the software that turns that 1/4 wave ramp into sine and cosine waves:BangHead: end result was a 'choppy sinewave' running 150/128 too fast. At least it was a simple fix. So tried some pics and got Jupiter, M1 and the trapesium. Tracking still dragging in fits and spurts, found the worm was slipping against the shaft coupler, so need a new and better one... but at least the images are starting to work.

This is more of a note to myself The focusser was in the origional position (far too close to the primary mirror) so I cut a new hole for the focusser 55mm closer to the top of the tube. After collimating images are quite a bit better. No more vingetting at 0.001 degrees off axis. Seeing was only ~2 arc seconds, Trapesium stars looked about 1:4 size to seperation.. but at low altitude. Straight up was ok still need to get collimation bang on, not 100% happy right now, although a focoult measurment showed the optics generally were still on the nose. Next: electronics boxes!

A quick potted history is probably due. The scope is a Fullerscope MKIV mount with a 12" newt on it. I bought it about 11 years ago knowing it need pulling apart and rebuilding, but the price was low, the mount solid and the optics were good.. The bits that were rubbish I could change. The Newt has now been modified with a window so I no longer have diffraction spikes and tube currents are better suppressed. It does however make it rather heavy... I can just about lift it, portable is not the word. The mount was refurbished with the paint being stripped off and was then powder coated in white. It has a drive system under development which has to date been through 3 itterations. The whole project was started before I took my break from astronomy and so by the time I came back to the hobby a few months ago was mostly obscelete. It was a stepper motor system driven off a PC.. not the excellent Mel Bartels system, but one of my own as I like to challenge myself to new things. These days you don't need a PC, a PIC will do the thinking quite adequately and is easy to programme. The driver chips available now also mean microstepping is a doddle. As it stands the Drive is silky smooth despite the stepper motor direct driving the worm. The 150x microstepping is quite sufficient to stop vibrations, and the lack of a gearbox means I have fewer errors to correct. (driver chip : allegro A3972) What I now need to do is change the PIC I'm using. A 16F690 is fine for basic timing but no use for anything involving "sin x", tried it and a 32 bit "sin" takes over half the memory for that one instruction. So will be migrating to a dsPIC... but not until I've got the rest of the system good enough to warrant it. Which means my home brew hand controller also needs to do the business... at the moment it's not mechanically up to it. So I need some boxes around the electronics otherwise they get wet and stop working. Hopefully this Blog will trace the continued development of the hardware and software. Derek