markse68

Hi Stu, that looks really great- are those dob mounts aluminium plate then? I’ve been working in Munich all week- on my way back home now and it looks like it might be clear in London so if not too late and not too knackered I might get proper first light on my new old slow 8.5”- exciting! 😃

Thanks Paul, judging by the number of extra holes in the tube I think this one has had a few lives and this may not have been the original mirror or secondary mount. I’ve not read anything but good things about Jim Hysom and his mirrors- I think he was a very respected maker http://www.europa.com/~telscope/tsenglnd20C.txt I did get a very brief first light on Sunday but only a glimpse of the moon before it disappeared behind clouds, and the gas giants never showed, but the moon was wonderfully contrasty and richly coloured- a definite step up from the 4” Tal I’ve been using, so I have high hopes for this one 😊 Would be interesting to find out how the likes of his and David Hinds etc mirrors stack up against modern high quality mirrors 🤔 Mark

Hi Stu, yes it was the one on eBay. Advertised as 9” f8 but it’s actually 8.5” (I centre spotted it so measured it) and by my measurements actually f7.5 but that’s fine- it should be excellent on Jupiter and Saturn if only it weren’t raining grrr! Off for a week- so will have to delay first light- can’t wait 😊

This beauty 😍 Well ok it wasn’t the postman- had to drive to Cambridge to pick it up. And yea ok it’s not really beautiful- pretty damned ugly really 😉 But beneath its ugly exterior lies a Jim Hysom 8.5” f8 mirror in immaculate condition- it’s a beast! And this surprised me in a really nice way- a really nice clever easy to adjust secondary mount and the crusty old focuser has a fine focus (geared) knob! And is really nice to use with no sloppiness. Anyone know if the focuser and secondary mount are Fullerscope parts? The finder is. Of course it had to be cloudy today... oh and it’s got a little door so you can get in there with a feather duster to remove cobwebs!

Thanks Ricochet. It wasn’t as much a bright cross like the diffraction spikes from bright stars but more like a hazy smear but yes maybe that’s what it was. Tbh I was on the way home and pretty tired and it was late so I didn’t hang around long- the scope surely hadn’t temp equalised. But it was worth it for Saturn 😊

Last night I took my trusty Tal-1 to a new viewing site- the common right near my home in Plumstead with a much better view of the horizon and a bit further away from direct street lighting- and what a difference it made! Saturn which up till now had been the boring cousin of magnificent Jupiter suddenly revealed its beauty- Cassini division, shadow of rings and even hints of banding! Up till now it had been just a homogenous blob with ears 😉 BUT Jupiter really disappointed. I tried a few eyepieces but I was getting terrible flare in a broad hazy cross centred on its disk. It wasn’t enjoyable to view at all. I worried my scope had gone out of collimation but then why Saturn so clear? I think I may have reached the limits of my primary in its original poor condition. Could this (bacterial/mould?) damage be causing the flare I’m seeing and is it time for resilvering?

And yes- one mullered bearing. Found an SKF on eBay - it’s size 62 x 40 x 12mm or type 61908 or 6908. The lower bearing seems fine so can stay A6272C85-13AF-4A84-8B04-951BEE124D3E.MOV

Now the upper bearing housing unscrewed with ease

Then it clicked- the threads weren’t galling up at all. In fact I probably didn’t need the special spanner at all though nice to have. You have to remove the lower threaded cap as it locks the shaft and the upper bearing into the housing 🤦‍♂️ A little heat and it came off easily

I know this isn’t very interesting to most but I couldn’t find this info anywhere so maybe it’ll be of use to someone down the line. Made progress today- I made a spanner for the upper bearing housing using the heads of 2 m4 Allen screws to engage the notches in the housing. Alas I still couldn’t unscrew it...

I like the spring balance assist- haven’t seen that before and was thinking of using springs on my 12” design to enable use of smaller rockers and have some adjustability for heavy eps etc. Is that something unique to that dob? I haven’t come across it before. Didn’t see you mention it (sorry if you did) but do you know who made it?

At the other end- the counterbalance weight end, there are more threads locked with grub screws 🤦‍♂️ It looks like the part the weight bar screws into is in turn only a short cap threaded onto the main shaft and locking the shaft to the inner race of the lower bearing and preventing its removal. I failed to loosen this part but in the process loosened the OTA mounting plate 👍😉 I think I’ll tackle this part next time with a bit of heat from a blow torch, gripping the other end in the vice. I don’t want to damage the threads though...

I made a bit of progress- the OTA mounting plate does screw onto the shaft after all and came loose while I was attacking the other end. Under it is a threaded collar that I assume holds the top bearing in place. Whilst the machining and design of this mount seem very robust they had an unfortunate habit of using pointed grub screws to lock threads- distorting the threads in the process and making dismantling for service a bit of a pain! I gave up unscrewing that collar after only managing about one turn before it felt like it was galling up. I had to grip it in a vice which is making a bit of a mess and will require paint touch up and re-forming of the steel notches. I tried drilling out the messed up threads where the grub screws bit and WD40, but no luck- I’ve given up for now. I think I’ll have to fabricate a special tool capable of a lot of torque to get this free.

Hi, I bought a Tal-2m recently 🤦‍♂️ But I think it has some issues with its equatorial mount- particularly the dec axis which seems very rough in motion like it has ball bearings that have suffered a shock and dented their races. So I’d like to open it up and have a look to maybe replacing them if they are standard bearings I found Astro Baby’s excellent detailed tear down of the Tal-1 mount but the 2 seems a different beast even though it looks very similar. I read of someone on here in the past replacing the RA bearings. Wondering if anyone ever came across information or ever took the DEC apart before? There are 2 grub screws that appear to lock the OTA mounting plate to the DEC shaft but I’ve undone those and it doesn’t want to budge and I don’t want to damage it anymore. It’s hard to say if that plate is threaded onto the shaft or just a press fit but it’s solid. Any experienced help much appreciated BTW the RA bearings feel ok though there is a definite detent when the DEC shaft is moved to be in line with the pier mount- wondering if it’s intentional to aid in putting the mount into its box or perhaps also damage 🤔 Mark

Thanks Steve and Mick. I quite like the look of the old transformer as it goes 😉 but it’s not very portable- and that old clock drive was very noisy and shaky. I had to slacken off the worm a bit as it had a tight spot and I’ve limited the winding current to 200mA on the stepper to get it really silent, and it was stalling, but now it seems to be working excellently. I was using it last night for 3hrs(!) on the first clear night in what seems like ages with all the rain. Best nights viewing since I bought the scope- Jupiter, Saturn, Moon- so crisp and clear and the drive makes it so enjoyable 😊 Tried to split Antares and failed lol- think I might need more than 4” for that- though it did look different from other stars. Dont know if it’s because they were all fairly low but they did drift a little- I can probably tweak the speed a little but it’s so much more stable an image than with it switched off I probably won’t bother. Yes Mick- it’s meant to be a USB charger that you clip on your battery packs but makes a great little interface to other things with a simple drilled hole and soldered wires- I should fuse it really. They’re 10.8v (3cell ) packs so 12.6 fully charged and the stepper runs down to 8 or 9V I think. Mark

Thanks all Carole I'm in N Greenwich area most of the time- hoping to catch the Flamsteed Society at their next viewing meetup on Blackheath but they don't seem to have had one since April. Demonperformer yes for its size it was meant to be a good performer and certainly impressed my naive eyes with the moon- beautiful! And yes "once completed"- that is the stumbling block at the moment- designing something is the easy bit Mark

It does look like the tube is distorted into peaks where the screws attached the old focuser- maybe from overtightening or an accident? Could you use larger washers to spread the screw pressure further from the holes and pull the peaks flat again against the Moonlite mount while tightening the screws? The tube looks quite thin so should reform quite easily? Trying to decide myself what colour Moonlite to order - think it will be red like yours 😍

Hi, sorry I forgot my netiquette and already posted elsewhere 😬 I’m Mark from SE London where the skies are bright and you can occasionally see a constellation or 2 40+ years ago my grandad showed me Saturn through his huge to me then telescope. It was such a strange sight I was convinced he was kidding me and had drawn it on the eyepiece! That was my only viewing through his scope unfortunately. Back in the 90’s something ignited an interest in the universe and I bought a little Tal Alcor 65mm newt from Telescope House in London. It was a fantastic little thing and the views of the moon, Jupiter and Saturn were awe inspiring but life happened and I didn’t stick to the hobby for long. Still have that little scope though I think it must have been the images of the black hole that re-ignited interest and I was soon owner of an old first version blue 4” Tal-1m - the motorised equatorial mount appealed after the manual alt-az mount of the little Tal, and the views have been a real step up! Now I’ve gone and bought a huge 12” mirror 🤦‍♂️ and am designing a dobsonian mount for it- dreaming of immersing myself in deep sky objects- those amazing galaxies and nebulae I keep seeing in beautiful photographs that I dream of seeing with my own eyes. Can’t wait (I know they’re not going to look like the photos - maybe that’s a future development of the hobby for me 🤷‍♂️ Baby steps at first) I’ve already learnt so much browsing this and other forums - thank you all 🙏 Trying unsuccessfully to avoid spending too much on eyepieces and other paraphernalia .... Mark

Just measured my Tal-1 and it's 850mm (~33.5") . I think the Tal 120 was designed to be shorter so I think you must have a Tal-1 Mark

Thanks for all the replies! Nigel and Craig there's definitely a family resemblance there so it's looking almost certainly to be a David Hinds mirror- which is great I think and likely from a Fullerscope- did they have model names like R12, R3 etc? I'll do some more digging and contact the David Hinds webpage. I did find another picture on here of a Fullerscope D.Hinds mirror- looks to be similar layout though a different hand. Mine lacks a grading letter but I chose to be optimistic and as 6" is the largest scope I've ever looked through I'm really excited and inspired to build something with this and have my mind blown Mark

So I've caught the astronomy bug quite badly after the Tal-1m... I saw this mirror on ebay and rather recklessly took a punt on it. It's a 12" mirror - the seller didn't have any information about it but it looked like a telescope primary- it had it's focal length written on the back anyway I think it's a fair few years old and would love to know more about it if anyone recognises the style of inscription- if it's from a known maker? It has inscribed on the back "R12/49" and I was wondering if that had any meaning- perhaps in relation to the figuring or a test result? The plan is to build a dobsonian with it and get even better views of the moon and Jupiter Mark

Hi, I just recently bought a Tal-1m on ebay after a strange urge to look at the moon and Jupiter again took hold of me- something I haven't done for years... My previous experience had been with a Tal 65mm newt I bought brand new back in the day from, I think, Telescope House- lovely little thing but this Tal-1 is something else! I wanted a motorised equatorial mount as that was the thing that was a bit of a pain with the 65's alt-az mount and when I looked it was there waiting for me on ebay- and I love it The plan is to stick it in the boot of the car and drive off somewhere with a bit better seeing than SE London so I wanted to convert it to battery power. Plus the synchronous motor drive was very noisy...and shaky- you had to turn it off if you wanted a clear sharp image I opted for a stepper as I knew about these Trinamic drives with built in controllers and opted for one with "Stealthchop" which gives very smooth motion at low speeds. Bit pricey for a stepper but worked out quite neat and simple. You can programme in the speed you want it to run at and it will just start up and run at that speed as soon as it's powered. It runs off a Makita battery pack through the original connector, draws about 250mA so should last for hours, and is very very quiet. I got my measurements a bit wrong I think when I was drawing up the 30:1 reduction gears so I have to mount it slightly off line to avoid the big worm gear clutch screws clipping the new brass gears but it works fine and tracks the moon well. Mark IMG_2974.MOV