Quote from: mark100 on September 10, 2014, 03:05:06 PMIts not as if, one day Mike is going to look through his scope and see a housing estate and ASDA up there.

Maybe not one day soon
Although, give Sir R. Branson half a chance and who knows , , ,

Quote(visions of the secondary mirror dropping down the tube )

Perish the thought !
Arnt you supposed to do it one screw at a time ! ?
(says me trying to be clever, never having done it !! )
Bobs Knobs, or gp machine knurled?

Fascinating that there are so many amateur astronomers on this forum. There's not an obvious link between model railways and the great Out There. Perhaps those of us in both camps should be dubbed "supernerds"... Sorry...

Quote from: MikeDunn on September 09, 2014, 08:21:04 PM
Sorry, but the "SuperMoon" is mainly hype ...

Yes, it's closer than usual - but that happens quite a bit.  The Moon is at perigee ... the term "supermoon" is something an astrologer slapped on to make it sound 'cool', very few astronomers use the term.  The average distance the Moon is from us is 238,000 miles away; tonight it's a bit less than 223,700 miles.  Conversely it can be further away; over about 248,500 miles is a "micromoon" (apogee).  As the orbit is elliptical ...

There is actually quite a difference between a "supermoon" and a "micromoon". Monday's Astronomy Picture of the Day puts them side by side: http://apod.nasa.gov/apod/ap140908.html . Whether you'd notice if they weren't side by side, I'm not sure.

Quote from: MikeDunn on September 09, 2014, 08:21:04 PM
Why does it look bigger when the distance isn't that much closer ?  Refraction ... an object closer to the horizon goes through more atmosphere, which magnifies it.  In a few hours, you'll think it a lot smaller than now - and it will be about the same distance away ...

I've got to disagree with you there, I'm afraid, Mike. The difference between a "supermoon" and a "micromoon" is a real difference in the angular diameter of the Moon as viewed from the Earth, due purely to the difference in distance arising from one being near perigee and the other near apogee. You could see it from orbit, if you were lucky enough to get there!

However, irrespective of whether the Moon is "super", "micro" or just plain ordinary, some people, but not all, perceive the Moon as being much larger when it's close to the horizon, a phenomenon known since antiquity, and dubbed "The Moon Illusion". Although it is sometimes attributed to refraction, this is one of the proposed explanations that definitely isn't correct. Atmospheric refraction actually makes the Moon appear smaller, most notably in the vertical axis, although I believe that there is a slight horizontal effect. In addition, the Moon is slightly further away when nearer the horizon than when high in the sky, to the tune of approximately one Earth radius - because as the Earth turns we move more directly under the Moon as it rises higher. So, since both these effects (refraction and the change in distance) are in the same direction, when measured with instruments the angular diameter of the Moon is really smaller nearer the horizon than high in the sky - although the effects are only a few percent and aren't immediately obvious even in time lapse shots.

The large apparent diameter of the Moon (and Sun) near the horizon is an optical/cognitive illusion, and unless there's been a breakthrough recently, there is no single fully agreed explanation. If anyone is interested, and fed up of modelling for the evening (heresy, I know  ), there's quite a good exposition of the various issues and possible explanations on this website: http://www.lhup.edu/~dsimanek/3d/moonillu.htm

Quote from: MalcolmAL on September 10, 2014, 03:48:55 PM
Bobs Knobs, or gp machine knurled?

Bobs Knobs knock-off, Astro Engineering version.  Yes, one at a time ... you just need to make sure you have the one you put in right 

Quote"supernerds"

 

It is amazing just how big ones picture folder can become in such a short time, ever since Mark raised the topic I have been looking for 'one I made earlier' and wot got buried !

So, a montage of some apo- and peri- gee moons from 2011
fingers xxed and a drum-roll please :-



These were taken with my humble little bridge camera, a Panasonic FZ18.

My contribution to this thread is to say I got up before dawn so I could run with the Supermoon. It was beautiful and bright, although I must admit that without knowing, I'd probably not notice a difference in size. In fact, my wife and I joked that we'd probably just say "the moon looks bright tonight."

Megga supergeek warning ! Look away now if of a nervous disposition !
:-----

Quote from: MikeDunn on September 10, 2014, 12:57:38 PM
If you want to do imagery, forget the Dob though.

Dont dismiss Dobs and Alt-Az too much.
Depending on your choce of region of the sky you can do exposures typically (but depending on all sorts !) between 10 and  40or more seconds.
Then you de-rotate and stack in DSS.
Lots of DSOs within reach,
great pics somewhere on the web of the recent superniova in M82 by poster "smerral" in Scotland with an alt-az 8se,
and of course (as you have shown so well) the moon and planets dont need eq.

This is an interesting read :
http://autostarsuite.net/forums/storage/19/4981/field%20rotation%20v3.pdf
handy diagrams for the best sky regions for the longest exposures before field rotation effects take over.

You might like to have an experiment before you dangle your pride&joy off a wedge !
Oh PS - it needs tracking in alt-az/GOTO ? !

(/geek)

Quote from: scottmitchell74 on September 10, 2014, 10:19:03 PM
My contribution to this thread is to say I got up before dawn so I could run with the Supermoon. It was beautiful and bright, although I must admit that without knowing, I'd probably not notice a difference in size. In fact, my wife and I joked that we'd probably just say "the moon looks bright tonight."

Spot on. A "supermoon" is brighter than normal. From memory, about 30% brighter, but I think that mightbe as compared to a "micromoon". I forget. But almost certainly more noticeable than the size issue.

Quote from: MalcolmAL on September 11, 2014, 01:44:13 PM
You might like to have an experiment before you dangle your pride&joy off a wedge !
Oh PS - it needs tracking in alt-az/GOTO ? !

I'd never dangle my pride and joy off a wedge... My telescope, possibly....  (Actually it's hanging off a Vixen Equatorial...)

Quote from: MalcolmAL on September 11, 2014, 01:44:13 PM
Depending on your choce of region of the sky you can do exposures typically (but depending on all sorts !) between 10 and  40or more seconds.

Oh PS - it needs tracking in alt-az/GOTO ? !

40 secs ?  I want to be able to take 5-minute subs, or longer

And yes, the LX200 has full tracking & GOTO capabilities 

no prob, 8x40=5.3min
plus a few more for luck and to supress a bit of the extra wee noise 

But yes, I know what you mean, dont we all
but you said "If you want to do imagery, forget the Dob"
Just thort I'd stick my oar in in case others were interested and took you literally 
I can see that I'll have to track down some pretty pics for you from 'smerral' and 'rutigsmeg' (12" Dob)

Quote from: Nick on September 11, 2014, 02:15:51 PMFrom memory, about 30% brighter, but I think that mightbe as compared to a "micromoon"

I think you are on the right track, I found a wikip page saying "20% brighter" than ordinary.

Quote from: MikeDunn on September 11, 2014, 03:18:22 PM
40 secs ?  I want to be able to take 5-minute subs, or longer

Here you go, 10mins of M82+supernova :

My little thumbnail, to 'fair-use' illustrate this post, of ('smerral') Brian Ritchie's original (see below)
copyright etc remains with Brian etc

60x10sec (must have been near zenith ? ) with alt-az 8se + 0.5x focal reducer.
The supernova was unrecognised for several days (6 was it?) and that setup of Brian's would have been good enough for a Discovery credit !
Isnt that good then !

Brian's original can be seen in all its glory here :-
http://cdn.astrobin.com/images/thumbs/6f69d70fc4785431806aff730ed0b681.1824x0_q100_watermark.jpg

More of his amazing stuff here :
http://www.astrobin.com/users/smerral/?active=DEEP&public=&sub=subject

Quote from: MalcolmAL on September 11, 2014, 03:38:24 PM
no prob, 8x40=5.3min
plus a few more for luck and to supress a bit of the extra wee noise 

[techie bit again]
Yeah - but 40s isn't really long enough to get the faint detail ...  for that, you do need to be able to have long exposures & capture the "rarer" photons as well as the "common" ones ...  I'll be looking at producing DSOs with something like 12x300s as a starting point (+ bias + darks etc).  That photo is OK - but where's the detail ?

Using a Dob for imagery is do-able - but you get damn few people putting all the effort in because of the limited results.  Hence 'fracs and SCTs being used by serious imagers (more the former than the latter), and Dobs mainly for visual (95+% ?).
[/techie bit]

Quote from: MikeDunn on September 11, 2014, 04:36:49 PM
  That photo is OK - but where's the detail ?

Yep, I know all that but
(a) just "ok" !!OK!! when did you last discover a supernova !? a supernova discovery would be quite enough detail for me !!! Shame about the folks living near to it though 
(b )  "serious imagers", yep I know all that, but (pedant mode = on) you didnt say that back up there ^^ 

Oh, EDIT PS (3)
You can spend a fortune chasing Damien Peach but it still wont have all the detain of Hubble 'scope ?

mahatmacoat