Yeah, I got started in astronomy when I was a teenager back in the 70s. Back then, you aspired to build a 6" scope. Then, when I got some money in the 80s,...
20281
Robert Houdart
rhoudart
Jul 1, 2012 2:07 pm
Very exciting times, we're approaching first light for the 1100 mm telescope. The telescope is now nearly finished, everything has been adapted to the new ...
20282
dobson 2005
pierredesvaux
Jul 1, 2012 5:15 pm
Congratulation Robert! It has been a long way, but the waiting was worth! The whole scope looks really nice! If you happen to go south, I would be very pleased...
20283
Robert Houdart
rhoudart
Jul 2, 2012 7:45 pm
Hello Pierre, thank you, I do pass in Bourgogne sometimes (mostly when I'm driving towards the Provence), so maybe one day we can arrange a meeting. It would...
20284
celestial_lion_leo
celestial_li...
Jul 7, 2012 6:30 pm
Hello, If it is possible, turn the mirror upside down. Be careful not to scratch it. Lay the box on top of it. Then, turn the mirror over. Another method would...
20285
celestial_lion_leo
celestial_li...
Jul 7, 2012 6:30 pm
I have a "big" Dob. A Hardin 10 inch. I got the whim to go into amature astronomy last year on my 66th b/d, this month. I haven't had this scope out yet. It is...
20286
ctastronomer
Jul 27, 2012 3:53 am
Hope you won't consider this too off-topic. I have a new 24" and am looking for a used Sky Commander XP4 & encoders if you are looking to change your setup. ...
20287
John Mahony
jmmahony
Jul 27, 2012 4:14 am
You should (also) post this on the Sky Commander yahoogroup. -John...
20288
Fabio Falchi CieloBuio
fabio_falchi
Aug 4, 2012 4:31 pm
Dear all, I'm building a 706 mm f/3.1 newtonian. I prepared a facebook's page to describe it. It is in Italian, but the photographs are multilanguage ;-) Here...
20289
howieglatter
Aug 5, 2012 2:40 pm
Very nice ! Did you make the upper cage rings by rolling straight aluminum extrusion? If so, did you fill the extrusion with something like sand before...
20290
szasa0
Aug 21, 2012 12:18 pm
Hi to the Group, I am from Hungary so I am sorry for my bad English. We build a 24" Dobsonian with a friend. We already have a home built 16" and 20" and want...
20291
jacques
savardjacque...
Aug 21, 2012 1:31 pm
what stickness have you 1 inch 2 inch or 2 cm or 4 cm for mine I go to my dental place and asking him to make a grove unther whit it instrument like...
20292
Jan van Gastel
janvangastel
Aug 21, 2012 1:43 pm
Sandor, I have glued my 500 gramm secondary to aluminum with only three dots of silicone. That will be enough for yours as well. The dots I use are about 1 cm...
20293
Raphaël Guinamard
rguinamard
Sep 1, 2012 1:15 pm
Sandor, I also glued my 130 mm secondary (20 mm thick) with the silicon transparent type (for aquarium if I remember weel). To avoid any differential...
20294
Robert Houdart
rhoudart
Sep 10, 2012 6:10 pm
It's been a long journey, but finally the 1100 mm telescope with Lockwood optics has seen its first star light. An update with pictures is given on our web...
20295
tc3642
Sep 17, 2012 1:45 pm
Robert, Congratulations on FINALLY getting your scope finished. I have felt bad for you for the last five years while you were waiting… Anyway, now it is...
20296
hustonfamily@...
omahaastro
Oct 2, 2012 7:33 pm
Hi, relatively new, lurker here. So, a few months ago, I acquired this Obsession with a 3" thick, 30" f/5 Sitall primary (yes, it weighs a ton). While it...
20297
Shane LaPierre
ctastronomer
Oct 2, 2012 8:16 pm
The substrate is stable as temps change. It's that so-called "boundary layer" that would be problematic. So blowing that away would be ideal at least until...
20298
geodandrew@...
geodandrew
Oct 2, 2012 8:59 pm
Rob Teeter puts fans on the back of the mirror box on a lot of his scopes. George Verizon HTC Incredible II ... From: hustonfamily@... To:...
20299
Roger Greenwood
astrocrumb
Oct 3, 2012 1:59 am
Hello Jeff, I have always had temp issues living in New England. Temp moves all over the place. I have an 18" Obsession, so it isn't a direct comparison,...
20300
Richard Carner
rmcarner
Oct 4, 2012 7:45 pm
Roger, When you say that it 'works quite well' what do you mean? I'm really not trying to put you on the spot or anything. I'd just like to know if there is...
20301
Roger Greenwood
astrocrumb
Oct 4, 2012 10:00 pm
Dick, Mirror temp drops to ambient quicker, IMO. Eliminates the possibility of a boundary layer during cool down. That is more feeling than measurable. No...
20302
Richard Carner
rmcarner
Oct 4, 2012 11:09 pm
Understood. Then its more of a 'feeling' than anything quantifiable. I've never gotten to ambient with my 20". It is always a catch up sort of thing. I'm half...
20303
walter kennison
walterkennison
Oct 4, 2012 11:41 pm
I did write a bit about this earlier this year,,,,the cooling fans are terrific at removing the heat from the surface and creating a differential temperature,...
20304
Roger Greenwood
astrocrumb
Oct 5, 2012 1:22 am
That is why I replaced my 18" 2" thick with a 1.6" thick. That in combo with fans, I can keep it about a degree above ambient. Which is very good compared to 5...
20305
walter kennison
walterkennison
Oct 5, 2012 1:53 pm
Cool,,, I keep hoping to find the right person to work with to get the design down to 1/2 inch thick, there should be some heat flow software somewhere that...
20306
Richard Carner
rmcarner
Oct 5, 2012 2:26 pm
Thanks Walter, This has been my understanding for a number of years: that the center of the mass of the mirror has got to transfer its heat before ambient is...
20307
walter kennison
walterkennison
Oct 5, 2012 2:40 pm
My thoughts are to create a hexagon substructure. same thickness runners as the mirror. at the attachment point to the mirror surface glass the mold will...
20308
Robert Bunge
bungerob
Oct 5, 2012 3:40 pm
I've worked with both thin and crated, or structured mirrors. They can work just fine if properly designed and supported. However, be careful regarding the...
20309
walter kennison
walterkennison
Oct 6, 2012 11:44 am
great points,, might be just well enough as is.  thanks ________________________________ From: Robert Bunge <bbunge@...> To:...
