Stub Mandrel

Thanks John. I've just stripped the focuser and cleaned out the gunk and readjusted it. It's nothing exceptional;, but is now quite smooth.

Probably best if you start a new thread - this one isn't for detailed discussion of image processing, but in GIMP try colours, auto, stretch contrast and make sure 'preserve colours' isn't checked.

First light! Only half an hour at twilight. The base isn't very smooth, probably the battered old pads. I will replace with the teflon glider pads when they arrive. Finding targets with no finder is 'interesting' so I had to use low power 32 and 40mm plossl most of the time. Jupiter looked great at about 55x with the moons as sharp points in a blue sky, although so bright I could see no detail. cloud came in so I found Vega and tried to get the double double. Lots of faint stars almost everywhere I looked even in blue sky. The focuser has tight spots and although I found a pair of stars I couldn't split them again in the 10mm EP, but simulating the view in Stellarium they were much to close together to be the double double. Saturn then appeared as it was getting darkish and looked tiny but perfect, even though far from properly dark Titan stood out really clearly! Saturn hid behind a roof before I could focus the 10mm ep on it. The ability to drag the scope around the garden to keep a low planet visible contrasts with the GEQ - but when aimed so low down it's tough finding planets above roofs! I tried the 18mm ortho EP that came with the scope on the stars left behind by saturn. I didn't find eye relief an issue even with my glasses on. I'm no expert but my impression was like looking at stars through a hole or window, they seemed tiny but dead sharp. Then it just got too cloudy before it was even properly dark. Main impressions: Focuser is rough as a badger's bottom at the moment, not helped by rack being loose! If I can get AZ as smooth as ALT it will be very easy to point. I need an EP rack hung on the base! A mirror can look absolutely shot and still deliver good views. I suspect it's going to be ace when recoated. Decent finder is essential. I'm printing a new finder bracket now!

Hi Foetawn, do you have an auto adjust function in your imaging program? Your picture responds very well to the one in Photopaint.

I got a pair of Vixen rings for £13 off Ebay (including postage!) to fit the little scope. I've stocked up on distilled water so all I need to do is cast some lead electrodes and dive in!

Result! My steplad just got in. he used to fit kitchens and he's found me a door with super smooth and flat laminate on both sides. Cut to size and soon to replace the base of the upper unit ?

I ordered some teflon furniture sliders just in case, but they are OK, its the sheet of formica they slide on I broke ? Battling with my VAT return or I would head out to B&Q...

The temporary repair to the mirror cell has gone well. It refitted it using the new holes with just a little persuasion as the tube had taken a minor set out of round. A peep down the end showed the mirror with an even gap all round instead of slightly offset ? The focuser is fitted with a washer for packing. I suspect this may not bee needed with the mirror in the right place, but I won't fiddle with its alignment until I have the recoated mirror assembled into a new cell, especially as I may build a new focuser or at the least do a hefty tuning of the existing one as it is a bit worn. Collimation was way off, but took hardly any time at all to sort with my home made laser collimator. The three brass hex screws on the secondary moved easily, and it appears to be sprung which made adjustment straightforward, although as I can see no point in putting a centre spot on the mirror in its present state I had to estimate the centre. It's not far off now compared to about 2" off before. Adjusting the primary literally took 30 seconds to get the beam straight back up the pipe from not even hitting the secondary. If I can sort the az bearing I will hopefully get some clear sky tonight for a tryout before I remove the mirror from the cell ready for recoating.

"I'm just a Gummi Bear, with orange underwear..."

Rats, a clear night but I can't try the scope out. The Lens cell is made of MDF and has split where each of the three screws go in. As a temporary fix I have filled the deep cracks with most excellent "Super 'Phatic" glue which is watery soaks in and is very strong and sticky, then clamped the cracks closed. This should restore the strength enough to take firm (and slightly longer) screws. It will dry overnight. I've also taken the opportunity to drill two new mounting holes so they are now evenly spaced at 33.1mm. This should better centralise the mirror in the tube. The base wouldn't rotate smoothly. the MDF of the bottom of the upper part of the base (if that makes sense) has swollen with water absorption over the years making it convex by enough to rub and stop more than two teflon pads working at a time. I tried to peel off the formica on this surface, went well until right at centre, when it split ? I will need to remove the base and fit a square of ply instead, or maybe just a 1/4" thick ring of something hard to replace the formica. I've measured up the holes for the finder mount, I should be able to 3D print a nice dovetail socket to fit neatly in the same place that will take one of my guidescope finders.

20mm UV pass filter that dropped straight into a cheap 'Datyson' 1.25" filter cell. Revelation Astro x3 ED Barlow ?

http://www.scientificmirrors.co.uk/Aluminising.html

I think it will be easy to modify my lens cell to match that just by adding clips. They look like car valve springs!

Great, thanks Bruce. The link I gave earlier says they can recoat your primary for £54 plus postage.

Interesting! Thanks for going to the effort of posting all that, it's fascinating. This one is definitely not less than 64" focal length and probably a bit more 60" would barely get the focal point out of the main tube. Together with the lack of mirror clips and choice of metallic blue hammerite, I wonder if it is an early prototype, or if it's just natural variation in hand-made mirrors. The 10x50 finder looks like the one in the photo, it appears heavily vignetted by the tube, they must have bought in a big job lot of cheap binoculars to 'repurpose'! I love the marketing speak which makes just about every aspect of the scope a 'feature' ? It makes you realise what a massive impact the arrival of mass produced scopes must have made.

Good news, the mirror is held on by four blobs of silicon. The holes are in the wrong place, the elderly tube sprang back into round when I had removed two of three screws. Also, most of the mirror is still reasonable, the dark patches are missing silvering (about 10%) and there is one large patch of blooming about 30mm across and a few small ones. I've washed it off gently under and dried carefully to avoid scratching. Even dirty it cast a clear image of a window onto a wall. I will a go of it under the stars before I send the mirror to recoating, I can't miss a chance to see exactly what I've got first! The finder scope is two bits of binoculars fitted to a tube. I'll swap in a 50mm finder I have made already. I have a 0.925" 20mm huygens EP that I have fitted crosshairs to that will do for the finder for now. The focuser is 'serviceable' and of decent metal construction. It may reward gentle reworking. The secondary is tiny, probably about 40mm! Mostly in OK condition, but will get a recoat at the same time as main mirror. I don't imagine it's worth upgrading to a 2" focuser unless I get both a bigger secondary and some 2" EPs. Basic assessment - after cleaning the mirror and fitting a better finder, all I need to do is sort out the pads on the base to get it working well enough to try out. In the longer term with recoated optics, I think this can be smartened up into a really nice scope. Question is, do I keep the blue hammerite or go for another colour? It has adhered perfectly to the tube so I'm not going to risk stripping it, the texture will have to stay. Perhaps white would be nice? But on the other hand the original Dark Star finish has weathered time OK.

The heart of it is a 1/8 wave David Hinds mirror set. This appears to be 'a very good thing' ?

Mirror seems to be 'close bonded' to the backing piece. Next 'issue' - the mirror cell isn't central, a quick check shows the three attachment points aren't evenly spaced around the tube, so the tube is distorted. That, at least, will be an easy fix. Looks like focal length is about 1.7m At least one teflon pad is missing from the base, which has a few minor issues. The alt movement is very smooth. The devilish words 'barn door tracker' are already forming in the back of my mind...

I did wonder about using a router to thin it down to a couple of MM then prising what's left off with hand tools.

I found a PDF about an almost identical scope that appears to be by the chair of my astro club! My main worry is that, unlike others, the primary appears to be glued to a plywood triangle instead of held with clips! I can make a mirror cell, but how to get it off for recoating????

Amazing to have such a scope virtually given away less than half an hour from where I live. It was meant to be!

Some pictures. It's big. Bigger than full-size a labrador: Every screw in this picture is loose! But apparently this 'volcano top' circle-T eyepiece is not to be sneezed at: This looks to have been made using binocular objective and eyepiece, joined with a plain tube, but will surely do the job: Looks like I may need to send this off to be redone! Black staining suggests it may be silvered rather than aluminium? The maker's details. the mirror appears to be glues to a wooden triangle. Three bolts through this second triangle adjust collimation:

Thanks to a tip-off in another thread, I've just gone and bought a Dob. Oops! Quite a story really, the seller's aunty had it made specially, and looking through it at the planets led the seller to do an astrophysics degree. He went on into teaching, became a head of physics, but now he's sold his house and in a few days is off to teach in South Korea. Although the scope is in need of much TLC he put off parting with it but was glad to see it go to an appreciative new home. It's a Darkstar scope with a 10" mirror of what appears to be about 1800mm focal length. It feels very 'hand made' and certainly needs every single screw adjusting, if not replacing! The mirror is stained, not just dirty, and will need recoating, and probably the secondary will as well. It has very thin vanes and relatively small obstruction. The 1.25" focuser is basic and needs tuning. A hefty 2" straight-through finder looks like its made from half a pair of binoculars with the prism taken out. The eyepiece is an 18mm circle-T marked 'Or.' Presumably this means 'orthoscopic' and would fit with the scope being intended partly as a planet-killer. The wooden dob base isn't too bad in alt, but the az is very stiff and probably needs new teflon pads. It's probably a bit big to try and mount on my HEQ5 pro ? Can anyone tell me a bit about Darkstar scopes? My assumption is that this is a decent scope well worth a bit of investment in time and beer tokens that will reward me with amazing views and the opportunity to do some pretty hefty planetary imaging, if I can get the knack of keeping it on target! Other than not ruining the mirror trying to clean it, what sort of things should I watch out for on the assumption it needs a full strip down and rebuild? I may even look at making a new truss-tube OTA in the long run, but first things first.

These are the Custom functions on my 1000D, I copied the ones of my 450D so I'm pretty sure they are the same, all for use with an interval timer: Exposure level increments - doesn't matter Flash sync - doesn't matter Long exposure noise reduction - off High ISO speed noise reduction - off Auto lighting optimiser - disable AF assist beam firing - off AF during live view shooting - off Mirror lock up - disable shutter/AE lock buttonm - AF/AE lock SET button when shooting - LCD monitor on off LCD display when power on - Display Add original decision data - off Also: Set mode to 'M' and exposure length to 'BULB' Best ISO is probably 800 Menu 1: Quality RAW (when shooting RAW things like exposure compensation, white balance etc. have no effect whatever) Red eye off Beep off Shoot w/o card - personal preference Review time -- your choice, I go for 4 sec Menu 2 - none of these matter, but don't set dust delete data, you use flats for this. Menu 3 - don't matter, except choose RGB or White for histogram to suit preference Menu 4 - don't have auto power off too short LCD off/on - I have this on shutter/disp as if shutter you can take pictures by accident! Hope that helps.

130P-DS Camp mat - rolled into a tube, stuck with superglue, ringed with gaffer tape, and lined with flock. 150PL never seems to need one. C90 Mak - 3D printed tube, lined with flock.