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Not been in this section for a quite while but I now have a project in hand. I've ordered a mirror set from John Nichol (16" f5) 411 OD x 44(ish)mm thick with a focal length of 2032mm. Nothing to challenging in the design it's for visual use on an EQ platform, possibly some iamging but that's not the main intention. Mirror support cell will be an 18 point structure, the optical layout and support has been worked through with "Newt for the Web" and Plop respectively. Mirror box etc have been designed around these constraints. The drawing as it stands shows the layout (horizontally) across the top half with plan views of the mirror box and rocker box bellow. The upper cage is still a work in progress but show the intended angle of the output cone (45°). The focuser is a Baader Diamond SteelTrack NT (I have this already) this will be mounted on a plywood panel between the upper cage rings. I intend this to be a "floating" arrangement with enough movement to allow the final focal plane's position to be optimised. The secondary support will also be adjustable axially to enable it to sit directly under the focuser. Mirror support main frame will be made from aluminium (HE30) box section 1.5" x 1" with 16swg wall thickness (1.6mm) with inserts where box sections meet to allow parts to be bolted together with gusset plates for ridgidity. Brass bushing will be used for any pivot points. The whole cell will be adjustable for collimation from the front. The mirror box arrangement can be seen in drawing 2. The mirror edge support will be a pair of pivoted arms with pads. That's where I am at the moment. I'll order the aluminium so I can make a start on the mirror support construction. Marine grade Birch plywood will be used for all the 'timber' parts. I intend to use 8 poles in the usual triangles at each side. TBC

Fit your new focuser and tilt unit first. Keep the tilt unit as close to the focuser as you can. Then follow your intended route

Not used Gimp but I think it's like Photoshop without ($$$$$) sign. It should have a saturation adjustment. Try small adjustments and gradually build up colour, also levels, make levels adjustment in small increments but avoid using the sliders right at the blank and white adjustment ends as that will result in clipping these areas. Adjust saturation and levels switching between them . Once you've had more practice you'll get more confidence in bigger adjustments but I still prefer keeping changes small. With a Ctrl+Z after the check on differences...

Hi Grant - I've had a play with your image file. I've processed it in PI, theres a great deal of information in your image. There's a patch of blue in the lower right of the image I haven't tried to remove. Can I ask if you covered the camera eyepiece during exposures as that can cause awkward patches of light on images. My try...

Earth shine ?

Very nice imaging with a Dob

Great report Alan and thanks for your thoughts in the PM. I've now ordered a 16 inch f5 from John Nichol which should arrive in a couple of months. Now working on the base and truss tube ready for the mirrors. I like the look of your mount and can see me 'borrowing' a few pointers. Like others with my 10 inch dob I used an RDF rather than a finder scope plus a low power eyepiece. Thanks Francis

I use https://www.12dstring.me.uk/fovcalc.php Whether visual or imaging by entering the scope / camera / eyepiece combinations you can then enter a target and get an impression of what you'll get either on the camera or in the eyepiece. For imaging I usually save the image and print it so I have a reference sheet. If I'm wanting to have a visual clue as to what various objects look like in a particular area of sky then I'll enter ngc refs for the objects from a chart first and print off my own ref sheet for that area - ticking themoff as I record or view them.

This is a single 300s sub processed in PI. The sky got just too bright to continue with,, I'll have to try shooting this first before M20 nextr time...

Worth the wait - you bet. This for me is one of the best objects in the night sky (for us northerners). After 2 this morning before it slide out from behind tree cover managed to get a few 300 (4) and 2x 600 second subs before the sky began to get brighter and brighter. TS RC8 with 0.67x reducer, ASi533 MC Pro at -12°C, Baader UV/IR cut filter on an iOptron CEM60 mount. All processing in PI Hope you like (need some breakfast now)...

I don't see any Baader boxes....

Thanks Steve, Just finished making and fitting a pair of tilt rings so I can reverse the tilt of the focuser when altering the primary. I have no problem with back focus now - probably too much...

The colli quest continues. I did find one unexpected problem though. One of the adjustment machine scrrew for primary tilt wasn't engaged with the mirror. I had to tilt the scope vertically and rotate the said screw anticlockwise till I heard the thread click then re tighten the screw. I was then able to do a visual basic adjustment with a peep/cap sight (Cheshire)? after unscrewing the baffle tube exension. Star test was reasonable so a few more minor adjustments and try out on M 27. diffraction spikes are still not as clean as I'd like them to be. Must make up the tilt rings! Image 12x 300s processed in PI and PS Cheers Francis

Sadly been there got the tee shirt...

Finally getting near with the collimation pispite having to find stars in the bright evening skies and patchy cloud cover to do it. After making a few final tiny tweaks to the main mirror tilt I've done a test on M13. The integrated image has 4x 3=120s and 3x 300s. Processed in both PI and PS. Colour is off and stars at the edges are still slightly elliptical. Stars still have soft edges and my back focus seem short so mirror separation may be another factor here. Comments welcome.

Thanks very much for all your help Martin. I've been retired ten and a bit years now - enjoy it, it goes quickly.

I have to admit that I usually find myself watching the recordings as Sun eve is usually set aside for other things...

That is incredible Peter. The colours, composition, processing.... Magic!

That is superb Peter. Not seen that before. Great imaging, great processing.

Incredable Goran. Superb imaging.

Stacked all the subs as one stack in APP, colour has gone but stars are now more even elliptical shape... Pixel scale on this is: 0.47571 sec/pixel and the scopes current focal length works out at 1630.3 mm, about 6mm longer than the 1624 mm in it's specs. Playtime continues

Hi Olly, The image above is a combination of the two stacks (pre and post flip). I tried for a long time last night to find the best focus: manually and via electronic means. Defocused stars were showing off centred dough nuts so collimation is a definite issue here at the moment. I'm just about to have another play with the two stacks using different software and see where that takes things...

As a base to start from here is my 1st light image of M51 (no adjustments fromm delivery). Total of 14x 300s subs, processed in PI and scaled in PS. PI had great problems stacking these subs as it was shot in two sessions each side of a meridian flip and the initial stacks failed to rotate the images post flip anf gave me two non rotated images in the same frame - very artistic but not what the doctor ordered. So I ended up stackingg the two sets separately, rotating one set and combining the two. Lots of errors but the potential is there...

Well after trawling through many varying RC collimation techniques on the web I found this one: https://www.dropbox.com/sh/1349fp34gqpbalm/AADPeMNonKZNk-1AkKUZ1dL4a?dl=0&preview=RC8+Collimating+Frustration+revision+1.4.pdf Inital reading was a little daunting but definitely the most thorough how-to I've found.

Well true to tradition - new scope and clouds. In fact it was clear until 5 mins before dpd delivered the TS 8 inch RC then it rained with hail... Anyway I digress. I set the scope up on a ridgid tripod and pointed it at a light blank wall to check out the collimation with just the focuser fitted, racked right in with a peep sight in the focuser. Quite pleased just a minor tweak on the secondary adjust bought the reflections into alignment. But then the problem. All the collimation reviews I've read, and what I've done with other RC's I've owned is to then adjust the primary to leave a thin ring of daylight around the secondary housing - concentric with the tube baffles. BUT no ring of light. I had to take out the peep sight and place my eye further in the focuser before I could see anything around the secondary housing. I found this odd but then I didn't know if TS had changed the design/layout of the scope making it impossible to see a ring. Perhaps they intend their customers to buy a laser collimator? So I turn the scope around on the tripod to view a distant tree to establish I could at least get an image. I needed all 3 of the supplied extension tubes, plus a further 35mm extension tube and the focuser with another 30mm extension to get an image of the tree (well top branches) with my asi533 attached. I've never had that much extension behind the back plate before so I thought I'd check the secondary to see if I could ease it up the tube a little to bring the focus in further, getting rid of some of the extension from what is a back heavy scope anyway. The secondary mirror was right up against it's support so no outward movement was possible. There was one thing I noticed (probably wrong) but the spider vanes are a shallow non symmetric triangle and I'm thinking that perhaps the vanes have been reversed taking the secondary mounting 2-3mm further into the tube. That would certainly push the focus further back requiring the extra extension. Forecast says clear tomorrow so I'll try it as-is first with the long extension. i will get a small inward shift when viewing stars as the tree whilst a good distance isn't at infinity. But to me I think I'm about 50-60mm further back that I should be. A plate solve should tell me what the native focal length is, it should be 1624mm... I'll add some photos tomorrow to show what I'm thinking may be an issue. TBC