Peter Drew

I've always found the standard SW 50mm RACI finder perfectly adequate for telescopes up to 200mm aperture. On my large telescopes I use SW ST80's with a diagonal and a SW150 on a 16" SCT.

Stu is correct re the light being refracted from the 45 degree angled face.

A video of the action would be good!

I no longer use PTFE blocks to support the weight of Dobsonians over 16" aperture. It seems better to use stainless steel ballrace bearings and stainless steel strips on the side bearings and a stainless steel disc running on bearings for the azimuth axis. Damping of the bearings is applied by adjustable PTFE "brake pads" which allows the movement effort to be set as preferred.

My Watec 120n shows in 10 seconds DSO images better than can ever be seen visually through the same telescope and in the same monochrome colour. That's what I call near real time.

I have a Shywatcher Skyliner 8" and the similar Orion XT8, this is the first time I've seen the Bresser 8". I wouldn't expect there to be much difference in performance but the Bresser does seem to have some design advantages, the value of these will depend on your plans for the future use, ultimately they may be beneficial from a resale point of view. The eyepieces in each case are entry level so an extra eyepiece is no big deal. I prefer an optical finder over a red dot, the SW unit is excellent, but many users differ. I'm sure the Bresser is good value.

Shaun. Gordon Ewen from Moggerhanger near Bedford has a Lunt152, (see Solarchat), probably the nearest to you.

I've just been trying out a type1 Paracorr on a 20" F3.5 Dob, used in conjunction with a 19mm Luminos eyepiece which just permitted a full lunar image, the craters were in sharp focus from edge to edge. Impressed!.

I have a couple of larger Dobs and can confirm that large objects like M31 can be disappointing initially due to the small field of view even with exotic eyepieces, the dust lanes require moving the image off centre to see them at their best. Smaller spiral galaxies might be rewarding. Regarding the secondary mirror issue, the three adjusting screws impart considerable pressure on the central screw, you really need to back these off a fraction before trying to unscrew it. I'm sure it will all come together in due course and that you have a lot to look forward to.

Hello Paul, welcome to SGL and come up and see us at the Astronomy Centre near Todmorden.

Don't blame you Shane, it looks like an assasins kit, security would have a field day.

The prisms in the 45 degree erecting diagonal are quite small, they might vignet the field of wide angle long focus eyepieces. Worth checking.

Dave. My recommendation was based on experience. I have 80mm, 102mm and 150mm ST refractors and 90mm, 102mm, 125mm, 180mm and 203mm Maksutovs. I have used these extensively for astro and terrestrial use. IMO for high power observation there is no contest between them, the Maksutovs win hands down. The short focus refractors are exceptional value for wide angle low power use, a combination of a 80mm ST and a 10mm-150mm would cover all bases.

I think a 4" or 5" Maksutov would give a better land or nightsky performance than the ST120 if you are interested in high power views.

I've used multistage electrically driven commercial extending piers for rise and fall camera obscura tables up to 100cms overall lift when the budget allowed as they are expensive. For smaller budgets I've made my own. They do call for engineering facilities but are straightforward in construction. You need two large section square tubes, the smaller having around 10mm clearance when slid into the larger. Two sets of four ballraces are then mounted in brackets such that bearings will protrude through slots cut in the outer tube and bear on the face of the inner tube. Placed in two groups of four this effectively makes a linear bearing. The bearings can be slightly loaded to eliminate any side play and the square section removes any rotation. The inner tube base can have a plate tapped to accept a threaded lifting screwed rod powered by hand or an electric motor. Not the full details but I hope the principle is clear.

To this I would add that a black cloth over the head to obscure stray light will give a significant boost to the detail seen, a binoviewer also adds an extra dimension.

The design lives on, I've just made a similar roll off housing on wheels to cover an outside Fullerscopes Mk4 mount.

Well said Scorpius, no ripples in the "Pond".

Of the many domes I've made between 10ft and 30ft diameter I've found the sideways opening doors, usually opposing pairs, to be the least trouble and easiest to operate.

"And now for something completely different", I'm using a 60mm F700mm fitted with a SM60 Coronado Ha etalon and BF15 for grab and go solar observation. Excellent images with a zoom eyepiece.

Hurrah! At last someone else giving the hollow concrete "Tod" pier a go, I've been banging on about these for ages on the grounds of their simplicity and cost effectiveness. I just bolt through using M10 studding, preferably stainless, same for the mount. You can grind one block face against its mating one to get a good flat surface and the final build can be clad for appearance sake. I now have 5 units on site.

My Mk4 already has a AWR Technology stepper drive system, it just needs the worm brackets upgrading. I have started from scratch with the OTA, it is now a truss tube assembly with primary mirror focusing. I will eventually have the choice between the Mk4 or a fork mount that I originally made for a 12" Maksutov. I have a keen interest in telescope performance and have been looking forward to comparing it to my long focus 12" Newtonian and 12" LX200.

I'm currently rebuilding one from an optical set I purchased a few years ago. It is a F5-F20 set by David Hinds, the alternative set that he made was F4-F16. Have a look at the back of the mirror, if it has a number followed by an A or just an A then I doubt anyone would refigure it to a better standard. I also have a Mk4 mount which carries either a 8" f8.5 Newtonian or 11.75" F8.5 Newtonian, hard to find a beefier mount at low cost.

Things I've found out through experience. 1) Always buy good quality keys. 2) The ball ends are not as strong as the plain end. 3) Avoid sets packed in flimsy plastic holders, the keys never go back in unless you are either a Swiss watchmaker or a bomb disposal expert.

Human hair is a good source of crosshair material. I have a bald patch as proof! :smiley: