Agronomy
 

(Moved from the happy me thread).

Just set up and looked through my telescope for the first time in several years. It's a Meade 25cm Schmidt-Newtonian and so it is just about portable. As it is close to local noon here, all I saw was the decrescent moon and the tops of a few trees. There was not much to see on the moon because of the low contrast and appalling seeing but at least Grimaldi was obvious.

Here's hoping the sky will remain clear tonight, even though it never gets dark at this time of the year up here in the sub-arctic.

Longer term aim is to hook up a web cam and take some images.

[QUOTE=xilman;302259]Here's hoping the sky will remain clear tonight, even though it never gets dark at this time of the year up here in the sub-arctic.

Longer term aim is to hook up a web cam and take some images.[/QUOTE]Eight-eighths here now, so no chance of observing and the scope has been put back indoors.

An old plastic pot with OD of 49mm is close enough to the 2" ID of the focusing assembly to serve as a mount for a cheap webcam. The pot now has a hole in the base and the entire interior surface painted mat black. The webcam has been suitably dismantled (primarily its lens and a protuberance on its front surface also taken off) ready to be glued onto the ad hoc adapter tomorrow when the paint will be dry.

With luck I'll be able to post some images next week when the moon is in a more favourable phase.

[url]http://www.space.com/16154-asteroid-2012-lz1-earth-flyby.html[/url]

[QUOTE=xilman;302275]An old plastic pot with OD of 49mm is close enough to the 2" ID of the focusing assembly to serve as a mount for a cheap webcam. The pot now has a hole in the base and the entire interior surface painted mat black. The webcam has been suitably dismantled (primarily its lens and a protuberance on its front surface also taken off) ready to be glued onto the ad hoc adapter tomorrow when the paint will be dry.

With luck I'll be able to post some images next week when the moon is in a more favourable phase.[/QUOTE]I'm amazed. Given my usual standards at DIY(*) I never expected the camera to work first time. The moon couldn't be seen --- too close to the sun and so too low contrast --- so the most distant object on which to practice was a tree about 100m away. Attached is a snapshot taken with the lash-up. With a 1016mm F/4 telephoto lens a remarkable amount of detail can be seen even at that range and with only 640x480 resolution and no post-processing at all.

Paul

(*) A commonly used abbreviation for "Damage It Yourself"

When we were little, Questar used to have ads in National Geographic magazine, and we always wanted to have one of their telescopes.

Of course, for what they want for one, you could buy a real awesome telescope, but even still we think the Questar is pretty cool.

[URL="http://www.bigbinoculars.com/nikko180.htm"]We also think this is real cool![/URL]

[QUOTE=Xyzzy;302356]When we were little, Questar used to have ads in National Geographic magazine,[/QUOTE]... not to mention [I]Sky & Telescope[/I] every month ...

[quote]and we always wanted to have one of their telescopes.[/quote]Ah ... yes ...

When I was in high school, I found out that our school system had a Questar that students could check out and take home for a weekend. So, I did. Wonderful.

[quote]Of course, for what they want for one, you could buy a real awesome telescope,[/quote](as true in the '60s, at $995, as it is now)

[quote]but even still we think the Questar is pretty cool.[/quote]Dreamy ...[URL="http://www.bigbinoculars.com/nikko180.htm"]
[/URL]

[QUOTE=cheesehead;306889]... not to mention [I]Sky & Telescope[/I] every month ...

Ah ... yes ...

When I was in high school, I found out that our school system had a Questar that students could check out and take home for a weekend. So, I did. Wonderful.

(as true in the '60s, at $995, as it is now)

Dreamy ...[URL="http://www.bigbinoculars.com/nikko180.htm"]
[/URL][/QUOTE]The El Camino College science club took a tour into Questar's Torrance facility that I attended. They were using red lasers to test collimation. I think they were using interferometry because they said something about half wave or quarter wave. They said something about them having a competitive advantage at the time because they found a way to get reliable precision more cheaply than competitors.

[QUOTE=only_human;307046]They were using red lasers to test collimation. I think they were using interferometry[/QUOTE]Collimation would use the straightness, rather than any interferometric property, of the laser beams.

[quote]because they said something about half wave or quarter wave.[/quote]Traditional mirror tests sometimes involve interference bands and can measure whether a mirror surface is within a quarter-wavelength of the desired shape, but do not need laser beams to do so.

One test of mirror shape, the knife-edge test, doesn't use interference.

Another mirror shape test, the fringe test ([URL]http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/stressedglass/fringetesting.html[/URL] or [URL]http://bobmay.astronomy.net/johnpierce/part8.htm[/URL]) does involve inspection of interference bands, but isn't really what is usually meant by "interferometry".

The fringe test is used for measurements of properties of an optical system, not measurements of the properties of distant objects.

Interferometry uses measurements by an optical system to deduce properties of a distant (outside the optical system, at least) object.

Interferometry can be (and is, nowadays, for expensive optics) used to test/measure optical systems, in ways differing from the classical fringe test. I don't know whether Questar was using it back then -- nothing in your description necessarily implies that it did.

[quote]They said something about them having a competitive advantage at the time because they found a way to get reliable precision more cheaply than competitors.[/quote]... which could have been through use of interferometry, or not.

They were looking for interference bands in laser light. There was splitting and recombining the laser light and observing things through an eyepiece that was part of the test rig. That is what my hazy and flawed memory thinks I was shown. I've never known what test was applied or term is appropriate for what I saw. I should have paid much closer attention. I would have liked to have seen some mirror grinding too but don't remember seeing any.

I have been inside the dome of a 4.1 m scope and been inside the largest solar scope. Also have been to a company that produced an ~1 m Dobsonian back in the day. Have looked through the telescope that holds the record as the most viewed through (more people have looked through it than any other).

[QUOTE=Uncwilly;307166]I have been inside the dome of a 4.1 m scope and been inside the largest solar scope. Also have been to a company that produced an ~1 m Dobsonian back in the day. Have looked through the telescope that holds the record as the most viewed through (more people have looked through it than any other).[/QUOTE]
I went about 6-8 times to a tall mountain which holds the biggest Thai astronomical observatory. The mountain is really nice, with many waterfalls, beautiful landscapes, and paved way to the very top (you can drive with a normal car there, is exhausting for the car, hehe, but really convenient for lazy guys like me), and the fucking observatory was closed for public visits EVERY time. The guards told us that it will be open "next month". Every time.

[QUOTE=only_human;307165]They were looking for interference bands in laser light. There was splitting and recombining the laser light and observing things through an eyepiece that was part of the test rig. That is what my hazy and flawed memory thinks I was shown. I've never known what test was applied or term is appropriate for what I saw. I should have paid much closer attention. I would have liked to have seen some mirror grinding too but don't remember seeing any.[/QUOTE]

My senior engineering project in college was the design, building and collimation of a beam splitter for a laser Doppler anemometry system to be used in fluids-turbulence research, so I have a little experience with applied laser interferometry. In my case, HeNe beam passed through a half-silvered 1cm^3 mirror (the cube silvering plane intersecting 2 opposing faces of the cube, via one diagonal of the respective faces), then we used several secondary mirrors to cause the 2 resulting beams to exit 10 cm apart (taking same-length optical paths in doing so) and reconverge several meters outside the beam splitter, in the place where the nanoparticle-seeded fluid chamber would later be. Placing an eyepiece at the convergence "point" (which due to nonlinear Gaussian optics that happens at near-wavelength scales is actually roughly in the shape of a 3-D ellipsoid) allowed us to project an enlarged image of the cross-section of the focal volume onto a nearby wall. Before final collimation, one could see two ~10cm-diameter red light splotches (brightness distribution following a radial Gaussian normal distribution) with the "edges" separated by several cm, with just a faint hint of interference fringes in the intervening gap. Once we got the collimation right by getting the two light splotches to merge into one, we got a beautiful circular set of fringes, each fringe several mm wide in magnified wall-projected terms.

In a mirror-collimation setting, perhaps one could test symmetry of the mirror in similar fashion: bounce 2 collimated beams off radially opposed points of the mirror, place an objective or electronic coherence checker at the reconvergence point, if the mirror is off by more than a quarter-wave, no fringes. It seems inefficient, but just saying, such interferometric collimation is indeed possible.

[QUOTE=ewmayer;307171]It seems inefficient, but just saying, such interferometric collimation is indeed possible.[/QUOTE]I regret using the word interferometry. I don't know what they were doing with those lasers.

[QUOTE=Uncwilly;307166]I have been inside the dome of a 4.1 m scope and been inside the largest solar scope. Also have been to a company that produced an ~1 m Dobsonian back in the day. Have looked through the telescope that holds the record as the most viewed through (more people have looked through it than any other).[/QUOTE]In January 89 we spent two weeks on La Palma --- our first visit to that island. An old friend of mine was chief scientist at the William Herschel telescope and his job was to get the thing commissioned. Jean and I were give a tour of the various domes (incidentally, the 2nd time I've seen the INT, the first being when it was still at Herstmonceaux) and I got to climb on the square frame of the WHT's Serrurier truss, from where I could look straight down to the 4.2m mirror. Somewhere I still have the photos.

I've looked through a 17th century telescope. It's part of the collection of the Museum of the History of Science in Oxford. The scope isa small refractor, perhaps 50mm aperture but it still works fine. All we could see was part of the roof of Blackwell's bookshop opposite the museum. One of William Herschel's Newtonian reflectors is in the museum. The roughly 20cm primary speculum is still in good condition but, unfortunately, the diagonal has been lost.


My Dob was much smaller --- only 46cm --- and was sold off about 20 years ago to a couple of people from the Rutherford Appleton Lab who wanted a half-metre class mirror to build a lidar for investigation of atmospheric haze.


Paul

My earlier post said Questar in error. I toured Celestron.

The Celestron founder, Thomas J. Johnson, died in March: [URL="http://www.astronomy.com/~/link.aspx?_id=9a67e349-362b-4bce-abfd-22cc532409b8"]Celestron founder dies at age 89[/URL].

This must be the innovation they were talking about when I visited:[QUOTE]Johnson’s biggest challenge with Celestron telescopes was to find a way to efficiently produce the Schmidt corrector plate used in the top-of-the-line catadioptric telescopes (hybrid of a reflector and a refractor). With his designers in 1970, the founder began making a telescope that took amateur astronomy by storm: the Celestron 8. This instrument revolutionized the hobby by bringing compact, affordable telescopes to the marketplace and led to more adaptations, making Johnson’s company a leader in the industry.[/QUOTE]As for what they were doing with the lasers during my tour, it's obvious that I don't have a clue. My guess is this: [URL="http://www.astronomics.com/main/category.asp/catalog_name/Astronomics/category_name/HXRPV4CNB5HB8GWJP2M5NKPW57/Page/1"]Classical Cassegrain Collimation[/URL][QUOTE] If you are using a single beam collimator with a Cassegrain that has a corrector plate, beam centering on the secondary must be judged by eye (viewed by reflection in the primary). This is not the best practice, but by moving your gaze in a circle around the secondary while checking centering, accuracy can be improved. With the holographic collimator you can see if the target pattern is centered on the secondary.

The next step is angular adjustment of the secondary so that the beam reflected from the center of the secondary is centered on the laser aperture on the face of the collimator. This sets the secondary square with the optical axis.

The holographic lens should be threaded into the collimator for the next step. The secondary will now reflect and project the holographic pattern upon the primary, and the primary should be centered within the pattern. The pattern is now reflected by the primary and projected in a collimated beam out the front of the telescope. The angular alignment of the primary is adjusted by projecting the pattern onto a surface or screen in front of the telescope and adjusting the primary to center the pattern on the shadow of the secondary. In the case of a corrector plate, if the pattern projected from the scope is undistorted, the corrector alignment is fine. If not, adjust the corrector to remove pattern distortion.[/QUOTE]In 2010, Celestron put together a 17.6 minute video" "In Celebration of its 50th anniversary, Celestron presents":
[URL="http://vimeo.com/10073192"]The Path Of Light (Episode 1) by Celestron Telescopes[/URL][QUOTE]"The Path Of Light" is a documentary celebrating astronomy, telescope making and human ingenuity.
Episode 1: “Generation of Dreamers” focuses on Celestron's founder, Tom Johnson, an electrical engineer, who developed the techniques for mass producing Schmidt-Cassegrain Telescopes, making these powerful astronomical instruments accessible to amateur astronomers.[/QUOTE]It is a bit grandiose at the start but has a lot of background of Celestron and their early years and briefly mentions their telescopes use at El Camino College.

[QUOTE=only_human;307335]My earlier post said Questar in error. I toured Celestron.[/quote]Ahh ... that explains a bit, when combined with:

[quote]Johnson’s biggest challenge with Celestron telescopes was to find a way to efficiently produce the Schmidt corrector plate used in the top-of-the-line catadioptric telescopes (hybrid of a reflector and a refractor).[/quote]Questars were also catadioptric, but never larger than 6-inch aperture in the 60s-70s IIRC. Once a Celestron 8 could compete on price with a Questar 4, there was a great boom in amateur telescopy.

A seemingly unrelated topic led me back to the subject of hand-grinding mirrors this afternoon. I previously discussed this elsewhere on the forum, but too lazy to dig out the thread - anyway it's irrelevant. Briefly: I have around a hundred packaged chips (non-working, these were from a defective test batch) from a defunct startup I worked for a few years back. These are packaged much like [url=http://pcper.com/images/reviews/634/cpu3.jpg]these Intel CPUs[/url] but have the silicon chip proper in the middle coated in a very hard and chemically resistant (I've tried fuming ntiric, sulfuric & hydrochloric acids to no avail) layer of black epoxy resin potting compound. I also have one of the same batch which was sent out to a specialty firm which precision ground off the potting goop and exposed the underlying chip, with the attendant iridescent diffractive effects. I would like to similarly remove the potting epoxy from the batch of chips I have and turn them into a piece of artwork, but such microgrinding is very expensive, so I need an inexpensive way of DIY removal.

Today it occurred to me that placing a bunch of the chips on a precision-flat metal surface and using a flat-surfaced mirror blank and some grinding compound might work - the multi-chip array would make it easy to grind the batch evenly, and the glass blank would allow me to see when I get down to the silicon, at which point I would switch to successively finer-grit abrasive. The only problem that occurs to me is that many (maybe most) blanks are pre-curved. Maybe just use a piece of plate glass? (It could even be rectangular here.)

Thoughts?

-----------------------

p.s.: Interesting page I found by a fellow who [url=http://www.mdpub.com/scopeworks/blanks/index.html]makes his own blanks out of scrap glass[/url].

Just took delivery of a pair of 12"-dia. (x 3/4" thick) mirror blanks I purchased from [url=http://www.telescopemirrorblanks.com/]this fellow[/url], for just $60 + $11 shipping. (They both fit neatly in the flat-format one of the two USPS medium flat-rate boxes). They both have some decent-size nicks around the edges, but each has at least one nice undamaged flat plate-glass-smooth surface.

Also bought a selection of four 1lb bags of various-grade grinding grits [url=http://www.ebay.com/itm/Rock-Grit-Kit-for-15lb-Tumblers-w-FREE-Polishing-instructions-Superior-Quality-/350586019603?pt=LH_DefaultDomain_0&hash=item51a08e1f13]on eBay[/url], cost $23.

Spent a couple hours this afternoon cleaning the glass surfaces and the metal backs of the chips I intend to grind the potting compound off of, spread a very thin layer of binary epoxy on one of the glass surfaces, and glued 32 of the chips (each ~1.75" square) down, in the pattern of a 6x6-tiled square with the 4 corner tiles missing. Once the epoxy cures, I can start grinding. Hopefully the epoxy will adhere to the smooth glass the way I intend. The chips are very uniformly manufactured, so the grit will hopefully remove the tiny raised-solder-dot I/O pins and the raised surface of the potting epoxy uniformly. I can track the progress through the translucent back of the glass grinding tool. Wish me luck!

When I'm done using them for the chip-related project, they will serve nicely as a blank/mirror pair for an eventual 12" Dobsonian, my "retirement scope".

How will you (or, will you) keep the grit from grinding a curve into the glass as well as grinding the epoxy?

[QUOTE=cheesehead;309340]How will you (or, will you) keep the grit from grinding a curve into the glass as well as grinding the epoxy?[/QUOTE]

a) The surface being ground is flat to begin with, except for the slightly raised epoxy rectangles and solder dots surrounding thrm, which are what will get ground off;

b) I will use a grinding stroke - perhaps a simple spinning will suffice - different that the telescope-mirror ones which are designed to impart curvature.

Stars are variably starry
 

[QUOTE=ewmayer;314167]Draco is one of my favorite constellations.[/QUOTE]
[aol]Me too !!!?!!!???!!![/aol].

Back in the good old days I used to observe AB Draconis as often as I could. An excessively faint (often invisible even in my 46cm Newtonian) eruptive variable of the U Gem type which would flare up very rapidly every now and again.

As Draco is circumpolar in these parts it can be observed essentially all year round.

[QUOTE=xilman;314177]Back in the good old days I used to observe AB Draconis as often as I could. An excessively faint (often invisible even in my 46cm Newtonian) eruptive variable of the U Gem type which would flare up very rapidly every now and again.

As Draco is circumpolar in these parts it can be observed essentially all year round.[/QUOTE]
My late father was a lifelong member of the AAVSO and huge fan of the eruptive variables, SS Cyg and U Gem types, mainly. He got me interested, as well, IIRC I had roughly ~2 years' of solid observing ending with August 1981, the last month before I went off to college, which ended my dabbling in that particular hobby. (My bent has always been to try understand the physics and mathematics behind things, not just collect observational data. Both are valuable, but were I to ever resume variable-star observing I would be doing it via the high-tech CCD/PC route, which is great because it eliminates both the tedium and much of the inaccuracy of the old-style eyeball observing, while also emabling a much greater data volume per scope.)

Anyway, the copy of my submitted monthly AAVSO observations from that month 8/81 is the only one I still have - tucked away in the back flap of my Norton's Star Atlas. Summary for the month:

Total Number Stars Observed: 175
Total Number Observations: 536

Let's see if any were in Draco: Yes, I see single data points for R, T, V, W, X, RT, SV, U and YZ Dra, but I don't see AB ... ah, here we go:
[code]
DESIGNATION VARIABLE JUL.D.&DEC. MAGN.
=========== ======== =========== =====
195377 AB Dra 2444,833.7 13.9
" " 834.6 14.0
" " 835.6 14.2
" " 836.7 (14
" " 837.6 (14
" " 842.6 (14
" " 847.6 14.3[/code]
For non-variable-star geeks, "(14" means "not visible; fainter than 14th magnitude".

[QUOTE=ewmayer;314192]Anyway, the copy of my submitted monthly AAVSO observations from that month 8/81 is the only one I still have - tucked away in the back flap of my Norton's Star Atlas. Summary for the month[/QUOTE]That was just before I started serious VS observations. In my case it was when working as a post-doc but before getting married. My observations were submitted to the BAA VSS (the British equivalent of the AAVSO) and to _The Astronomer_ magazine --- a rapid report publication for active observers. I'll have a rummage around to see whether I kept any records.

BTW, your coverage suggests that you lived in a much less cloudy area than I did at the time. Not difficult, I suppose, as the UK weather is globally notorious for such things.

[QUOTE=xilman;314177]Stars are variably starry [aol]Me too !!!?!!!???!!![/aol]...[/QUOTE]
[I]Starry[/I] and [I]horroshow[/I] are my favorite Burgess' words.

*sneak*
*backstab*
[URL="www.planethunter.org"]www.planethunter.org[/URL]
*poof*
*dissapear*

I was always interested in variable stars, but just couldn't participate regularly enough. During the late 80s and 90s, though, every night of observing (when it was possible, at least) included a check of T Pyxidis, a recurrent nova. Based on its roughly 22 year cycle, I kept watching for years for the huge outburst, but it finally came 20 years late, in 2011 (which I missed....)

Norm

Friend from Oz forwarded this, figured it a good way to revive the too-long-dormant Astormony (an anagram reflecting - pardon pun! - the kind of weather which might well lead to such dormancy ... or at least serve as an official excuse) thread:

[url=http://www.abc.net.au/news/2015-02-13/the-sky-is-no-limit-for-this-young-queensland-astronomer/6091754]Teenage astronomer aims for the stars - ABC News (Australian Broadcasting Corporation)[/url]

Spectacular photos! Kid's clearly got loads of talent and drive, hopefully a bright career in astronomy or some kindred field awaits.

My personal favorite is the one (right above the eclipsed moon) of the galactic disc tilting down toward the horizon - are those the 2 Magellanic clouds at left of the frame?

------------------------

p.s.: I merged the small "Stars are Variably Starry" thread in with this one, hopefully no one objects.

[QUOTE=ewmayer;395636]My personal favorite is the one (right above the eclipsed moon) of the galactic disc tilting down toward the horizon - are those the 2 Magellanic clouds at left of the frame?[/QUOTE]Mine is that of ω Cen. OK, it's a bright easy globular but it's still a superb picture.

[QUOTE=ewmayer;395636]My personal favorite is the one (right above the eclipsed moon) of the galactic disc tilting down toward the horizon - are those the 2 Magellanic clouds at left of the frame?[/QUOTE]

[QUOTE=xilman;395648]Mine is that of ω Cen. OK, it's a bright easy globular but it's still a superb picture.[/QUOTE]
I'm most taken with the "Carina nebula". Is that Eta Carinae by the way, or just some other nebula in the same part of the sky?

He's lucky to live in a part of the world with little light pollution as well as in the more interesting Southern Hemisphere.

Anyone been following the recent images from Dawn, Rosetta, and New Horizons? This year is going to be wonderful for minor body studies.

[QUOTE=Brian-E;395686]He's lucky to live in a part of the world with little light pollution as well as in the more interesting Southern Hemisphere.[/QUOTE]True for the first though I'd phrase the second as differently interesting. We don't get to see the LMC and SMC here but they don't get as good views of M33, M31 and its satellites and don't see M81/M82 at all. Variables, doubles and sundry other Messier / NGC objects are reasonably well distributed in both hemispheres. More of the latter are towards to the galactic centre but remember that Messier observed from France so it aint all bad.

[QUOTE=xilman;395692]True for the first though I'd phrase the second as differently interesting. We don't get to see the LMC and SMC here but they don't get as good views of M33, M31 and its satellites and don't see M81/M82 at all. Variables, doubles and sundry other Messier / NGC objects are reasonably well distributed in both hemispheres. More of the latter are towards to the galactic centre but remember that Messier observed from France so it aint all bad.[/QUOTE]
Okay, I guess I was suffering from grass-always-greener syndrome there. I remember our big spiral neighbour always being a clear naked-eye object 22+ years ago when I lived in the UK, even though I was in a large city at the time (Birmingham). The light pollution here (NL) and now is so bad that M31 is never visible with the naked eye.

I visited New Zealand and Australia a few years ago and took the opportunity to look at the Southern sky (naked eye only). I was disappointed never to manage to see our closest dwarf galaxies LMC and SMC, but I was pleased to be able to identify Alpha Centauri in our closest star system. (That's about my level, I'm afraid, but the night sky is gratifying to all of us.)

[url=http://earthsky.org/tonight/see-venusjupiter-conjunction-in-western-sky-after-sunset]Spectacular Venus-Jupiter conjunction[/url] | Tonight | EarthSky

Just went out to look for it, very nicely visible just above the high clouds above the W horizon (West coast frame of reference). Roughly 1 degree apart - that's about the same as the apparent diameter of the full-moon, which happens to be rising above the SE horizon in the opposite direction.

For the non-familiar-with-common-appearance-of-the-naked-eye-planets, Venus is the brighter one, leftmost of the pair.

[url=www.mercurynews.com/science/ci_28622338/how-watch-tomorrow-nights-big-meteor-shower]Meteor time! How to watch the big Perseid shower[/url] - San Jose Mercury News

[That 'tomorrow' refers to tonight]

Went out at 11pm for around 30 min - very difficult to find a reasonably dark area where I live. Only saw one bright meteor during that time, but 1 is better than 0.

My mom (who lives in Ohio) is in the process of preparing to sell the house she and my late father (d. 2002) shared for the last 15 years of his life, and move into a domicile better sized to a single elder person. That means disposing of the remainder of his possessions, some of which he willed to us kids. In my case, I inherit his home-built 10" Newtonian reflector. As I have limited real estate for storing such a beast, I am leaning toward telling Mom to ditch the large and heavy old equatorial mount he used for the 10", just send me the optical tube assembly, and I will build (or buy) a more-compact Dobsonian base. Since I plan to use the scope only for recreational 'targets of opportunity' observing rather than precision work (dad was a lifelong AAVSO member), I don't need the EZ-earth-rotation-tracking feature of the equatorial mount, and leaving it behind would surely save greatly on shipping costs.

Still, it would be nice to keep my future options open - been doing reading, seen various articles about 'equatorial wedge' add-ons for Dob. mounts, and also 'smart Dob. mounts' which use a laptop or smartphone to interface with the mount to rapidly go to any desired point in the sky. Some comments on such things and sources for good compact basic-mount designs from any active amateur stargazers here would be appreciated!

Hi Ernst,

I think this depends on you. I've bought an EQ mount for my Dob last year, while I costs a huge amount of money I still would do it again. Actually I can use my classic Dob mount and my EQ mount.
Dob: easy to use, less parts, less work before observing (but mirror still needs at least an hour to cool down...)
EQ: image doesn't move, you can leave the eyepiece and object will keep in view, photographs possible.
A goto-function is really nice.

Oliver

Thanks, Oliver.

On the compact-size and 'go-to function' fronts, astro-buffs may be interested in this Singapore start-up: [url]http://tinymos.com/[/url]