Mr H in Yorkshire

17 hours ago, fwm891 said:

I like to tinker

I like to tinker too. My current project, which will take about a year, is a binochair incorporating the design principles already developed (see Motorised Binochair design for 100mm binoculars here on SGL), except that this one will have a 6" f/5 BT and the whole caboodle will be trailer mounted. So far I've bought an old trailer (had to dig it out of a field almost) and cut it to a 'chariot' form and I'm working on the azimuth drive base at present. I want a two speed drive this time, as the drive rate of the Mk1 is about 180 seconds per full revolution. This is a compromise which is tolerable for slews but a bit fast for centring and following targets in the binos. I have all the optical parts for the BT, got a pair of Jaegers a decade back. When I have solved the two speed base issue I will start a proper thread for the project.

With the level of precision of adjustment in alt az this will give, what are you going to do about levelling on a pier or tripod?

Can't guarantee the weather but overall I can say 'enjoy' without fear of failure. Nidderdale is a contrast from London, lived here since '88, half my life, not had a bad day.

I keep a shortcut to this on my laptop.  https://www.sciencedaily.com/

6 hours ago, PeterStudz said:

I haven’t heard of that product

By chance I was in my local agricultural merchants today - they sell everything, including I now know 'trailer board'. it's 18mm ply coated with black phenolic resin and on one side a mesh surface for grip. Not much more than ordinary ply. Based on that finding I'm sure the stuff must be available elsewhere should you need it. Just checked google - it's also known a s Buffalo board.

1 hour ago, paulastro said:

Yes, it does.  It's a problem for people new to the hobby, as they won't know who's view is the correct one, or most useful.

I've researched (lurked) for years on the internet on various astro topics and I have to hand it to this forum for character and humility. In my experience an alternative and popular forum seems to have a number of souls who are sensitive to the worth of their opinions!

8 hours ago, paulastro said:

When reading anything on an an astronomical forum or blog, don't just assume it is true.

Does that explain the plethora of responses to even a simple question, with an evenly matched number of totally contradictory opinions?

9 hours ago, Moonshed said:

I see! We will say no more about it, but just so you know I am not angry, just very disappointed!

I feel your pain but try not to dwell on it. I've never had a top class refractor but I do own a Meade SCT.😒

2 hours ago, skybadger said:

I use a 15% or so thinned varnish

Some years ago I did a DIY floor sanding job and bought some lacquer that you mixed with sawdust to seal the gaps. Been using the lacquer ever since as a first coat - it has very low viscosity and is very fast drying being thinners based. Very useful properties.

4 minutes ago, mikeDnight said:

Thick or what

It is depressingly easy to jump to conclusions!

2 hours ago, mikeDnight said:

I doubt anyone would be interested

I am, what was it that you'd done or not, to see such a bad star image in a perfect scope?

It is said curiosity killed the cat.

As a ten year old my parents bought me a telescope, a terrestrial job but nonetheless I was absolutely awed by the sight of the moon, jupiter, a comet (forget the name) and other stuff. I mean ABSOLUTELY awed. However being always curious, I dismantled the scope, a lot of tiny lenses positioned with springs shot out of the eyepiece end and I never managed to reassemble it. I was very upset, nearly as much as my parents - money was very tight and the scope had been a big spend. Many years intervened before I could earn and buy another real telescope, but the first sights of the heavens had never left me. I'm proud to say that pursuing the interest also led my son into catching the bug. the head teacher told me in amazement how he once asked him a question and was given an hour long lecture about astronomy, by an 8 year old. Bright lad is my son.

Re. curiosity killing the cat, as a youngster I opened the back of a television and stuck my hand in. I must have contacted the HT around the tube because I was catapulted across the room (luckily, rather than stuck to it) somewhat tearful and stunned. I have actually had a charmed life because that is far from the only such event.

11 minutes ago, paulastro said:

Well Mike, we've really had some laughs together

Just read this thread. You seem to figure significantly in MikeDnight's series of errors. Is there something you're not telling him?

Do you have much woodworking experience? I ask because for a good circular finish to a base, assuming you want it circular, you'll want a plunging router - £100 or so but much better than a jig saw. Freehand will be awful and even attached to a radius piece, because the blade tends to flex out of the vertical and create a wonky edge, it will not be good. For a project I'm working on (will post some stuff soon) I just did that - cut some 18mm ply with a jig saw, rubbish warped edge, recut with a router, perfect finish but now smaller diameter than originally planned. Then routed the inner edge of an aluminium bike wheel rim coated with a thin layer of high performance wood filler. The router easily dealt with all these materials, even though my whole workshop is now coated in a layer of white dust and microscopic aluminium shards and that's despite attaching a garage vacuum to the router. As they say, it's a dirty job...

If you must have birch ply, although more expensive per unit area, you don't need a whole sheet for a base. Alternatively you even get melamine faced MDF, or as has been proven successful, kitchen worktop offcuts. Just pay careful attention to sealing all cuts and for one sided finishes, glue on a balancer sheet.  Another possibility is to buy a thinner sheet and glue a number of layers together, to get them flat put spare pieces on top, and park your car wheel on the pile. It's been done.

19 hours ago, Ratlet said:

It's quite nice panning about with the Dob

That's one reason, taken to a another level, that I generally go binocular roaming, 25 x 100 field of view is great, things like the Plieades and the bigger globular clusters are just wonderful.

You might find this of interest https://www.blocklayer.com/protractor-printeng

and possibly this, if you have the time

https://www.cloudynights.com/topic/63081-degree-circles/page-2

That really is a handsome result for your efforts.

Good solutions, I like magnets and yes, a vernier is the item you need, but do you really need 1/10ths? In practice a half degree mark would probably do and you could 'eyeball' it for smaller amounts, it's surprising how accurately one can estimate visually - you'll need a light too don't forget.

How are you to read the azimuth angle, an arm with pointer, attached to the stationary base? If I understand correctly, if you do that you'll need to align the ground base to North. To get decimal accuracy you'll need decimal degree initial alignment. Am I just a pain?

Edit. Thinking about this, does the dob base have a flat outer edge? If so you could determine the circumference and mark/print a strip with the degrees marked off, probably enough resolution to mark part degrees if not actual decimal parts. I have no doubt this is not an original idea. Attach the pointer to the ground base.

All very interesting but the gizmo has gears and where there are gears there will be backlash. If I follow your reasoning above, you won't reverse but merely change relative rotational speed, as a change occurs is that not where the backlash will appear, as the pressure on the gears changes even if in the same overall direction?

11 hours ago, Ouroboros said:

there is a sort of ‘look’ to amateur astronomers

The last time I went to such a meeting with my son (then 38), he leaned to me and whispered 'it's like being in a Breugel painting'. Could have been worse, Hieronymous Bosch!

If you accurately level your base then glue a few of these on in the desired orientation you will have a calibrated level. A. couple of quid on ebay.

2 hours ago, Ratlet said:

I did consider the fully digital option

On a motorised binochair (described here on SGL) I have used encoders, part of the DobsonDream equipment designed especially for dobs, I didn't need to the attachment hardware. They work well with Skysafari on an Android tablet (app shows an arrow for the direction to move towards target) or on a PC tablet with Stellarium and David Ek's encoder driver which paints a big red box with numbers on screen. You reduce the numbers to zero to find the target.

Obviously a much more expensive option, but if you ever consider it I can vouch for the kit and the helpfulness of Alexander the company head - AstroGadgets.

Hi Ratlet, I think I can withdraw that comment I made. A tiny bit of reading indicates that the repeatability of these is pretty good - 0.1 degrees. So once you have calibrated against your known altitude target the device should continue to read +/- 0.1 of that value. That has to be good enough for a dobsonian because pushing to a tenth of a degree is not that easy. So it's all a question of 'digital' (your hands) input versus digital output!