first light moon and stars with diy mirror

[ponytale]

hi all , had my first proper look at a star with my diy mirror (uncoated)

there is some coma at the outer edges of fov, stars look like they have at least 2 rings although seeing was very turbulent and i had a lot of air currents across the mirror as the wind is up a bit and it was 10:30 pm not very dark, i did adjust collimation a little to centralise the secondary shadow to centre of the out of focus star. while out,the moon came into clear view and that was awesome, even in an uncoated mirror ,pin sharp focus across the field of view with clear uncolouredand sharp edge to the limb, great shadows and highlights at he penumbra ? and nice clear crater edges , i feel i can send the mirror of for coating next week and can't wait to get it back , the eyepieces are poor quality plossl 10mm and H20 ? from tasco so what will i see with descent ones say tv 10-15mm , maybe the coma is in the eyepieces ? sorry if i sound over -excited but i am well pleased with the mirror /glass , i will set up web cam for tommorow night weather permitting and get some pics of the moon, i am lucky that my garage door opens facing south west and the moon is very low at present so i can get it ready early tommorow , the local council has just upgraded the street lights to new more downward facing less orange type lamps, which is better for me, i am going back to australia in august so i hope to have glass back by then for aussie :Dspringtime skies.

[barkis]

Great stuff PT. The big thrills are to come, and the completed scope will become your best friend.

Perhaps any worries you have are premature, I'm sure you may have been eager to first light the mirror, and neglected the cooling period or something. I know you will give the mirror every opportunity to perform to it's full potential, and with a good eyepiece too.

It's no mean feat you have accomplished, so congratulations, and I'm sure John (Glasspusher) will be chuffed too, he was a great inspiration and help on this project.

Ron.

[ponytale]

ron thanks for great comment, the scope was out in my garage all day which is pretty much as cold as outside, the test was quite early and air temp was around 15 degrees C

but incoming cloud which was from south west which is usually quite warm air cut short the viewing and today looks like a no go .yes John is a great inspiration for me, he is due loads of credit for his help and advice/tutorials on line,thanks again John

[FraserClarke]

Good job Ponytail! Remember that coma is what you expect from a parabolic mirror -- it's not a sign of a problem with the mirror, just a consequence of that shape of mirror.

[Glasspusher]

Well done PT, looks like the mirror is going to give many happy hours of observing, what a thrill to observe with a mirror made with your own hands! Too many folk dismiss the possibility of making their own optics as being a task too difficult to undertake.....you have disproved this misconception, and I hope others will follow your example. Mirror making is a wonderfully fulfilling experience, one which has enriched my own life greatly!

John

[Tom How]

I keep telling myself I'll think about making a mirror one day, however, I'm terrified of another addictive source of projects taking over my life. The homemade mount was bad enough.

But if one did want to think about it, what is the best primer to read? Online and/or printed...

[earth titan]

Well done. Good to hear all has gone well.

I can't wait to get on with my mirror, but kitchen refit has taken priority.

[Glasspusher]

Tom, you could do worse than have a look at this....Stellafane ATM Main Page, and there is my humble offering here....http://stargazerslounge.com/diy-astronomer/113596-making-12-inch-mirror.html

Hope this helps.

John

[BAZ Senior]

You should be rightly proud of a job well done there, it's good to see that diy scope building is alive and well.

[Luke Inup]

This looks like the section for mirror and lens grinding then...

I think I will lurk awhile if that's okay!

Cheers.

JonJon

[rfdesigner]

and i had a lot of air currents across the mirror as the wind is up a bit

This is a good thing, not a bad thing

What kills a mirrors performance is a nice thick slowly rolling layer of air that is a good few degrees warmer than the rest of the air, especially just in front of the mirror where any change in refractive index is doubled due to the light traversing that layer twice.

High speed air that's all the same temperature is not going to bend the light as it's all the same refractive index, and will prevent a thick distorting rolling layer forming on the front surface.

Well done on getting to this stage.. now it's time to foul up the mirror with a poor tube design ;-)

Derek

[ponytale]

hi Derek,my scope is home made of this open adjustable length 4 strut design, see sketch attached, so far it holds collimation once set up, when i am happy with everything i may change poles for single 1"thick walled alloy poles and have two sets for my 2 different focal length mirrors rather than telescopic tubes, this may or may not be a good design but hey its diy and ongoing, especially with all these cloudy nights keeps me away from the tv.

truss dob2.doc

[rfdesigner]

hmmm... looks like a good tube design too then, excellent. You must be very proud of what you've done, you certianly deserve to be.

Can I just ask you not to get the mirror aluminised mid August.. we're on holiday then

Derek