Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: Fay on Mar 06, 2011, 19:37:21

Title: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 06, 2011, 19:37:21
Well I have setup but still thick cloud. I have covered everything up in case sky clears too late as tomorrow night is supposed to be good.

Not wasting my time, have done 35 bias & now doing 35 dark 300s

Disappointed in the forecast, but I will be ready for tomorrow
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Carole on Mar 06, 2011, 20:01:07
I was just about to post something similar.  All the forecasts have said clear all night, even the IR satellites say there should be no cloud.

What's going on!!
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 06, 2011, 20:09:51
cracks me up! Why has no one got it right. It will probably clear in an hour or so
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mac on Mar 06, 2011, 21:21:21
Well its crystal clear down this way, but thats only because im off to work again.

Not too sure what way any clouds are going, so it might be going towards london.

Mac.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: MarkS on Mar 06, 2011, 22:00:31
Quote from: Carole
All the forecasts have said clear all night, even the IR satelittes say there should be no cloud.

The trouble with IR satellites is that when the cloud is the same temperature as the sky below, the clouds are invisible.

Mark
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 06, 2011, 22:05:53
About time they sussed out a reliable way to give us a proper forecast! :bug:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Ian on Mar 06, 2011, 22:07:57
going outside and looking up, it looks like the cloud might be breaking up.

Pity, I'm far to too tired to get any kit out. It was my son's birthday today and he's run us all ragged...
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 06, 2011, 22:11:12
Don't want you getting your kit out, this time of night Ian..............................too late        :parrot:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Carole on Mar 06, 2011, 22:23:43
Well it looked like it was clearing about 40 minutes ago, so I am aligned and on my target, so shall leave it there for the time being, so if the clouds do clear later I'm ready to go.  Meanwhile doing darks.

......and making myself a larger bahtinhov mask while I'm waiting.... fiddly bloomin job that is.

Carole

Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mac on Mar 06, 2011, 22:47:05
Quote......and making myself a larger bahtinhov mask while I'm waiting

as in bigger slats?
or physically larger?

Mac.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Carole on Mar 06, 2011, 22:52:08
Quoteas in bigger slats?
or physically larger?
Both.  

I've got a larger telescope so the existing Bahtinov is a bit small (currently got it suspended on bendy wires in the middle of the aperture as a temporary measure).  The larger one has slightly larger slats as well.  One reason why I didn't make one the first time around as they were so small. 

I've finished now just got to fix something to it to keep it on the scope and I'm done.  Worn a big blister on my finger doing it.



Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mac on Mar 07, 2011, 02:01:12
QuoteI've finished now just got to fix something to it to keep it on the scope and I'm done

Hammer and nail, or failing that, some glue. ;)
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Rocket Pooch on Mar 07, 2011, 07:44:34
was perfect here last night you should have done dsc at blacklands.....

shame i'm off to work in a min..
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Ian on Mar 07, 2011, 09:40:33
Quote from: Fay on Mar 06, 2011, 22:11:12
Don't want you getting your kit out, this time of night Ian..............................too late        :parrot:

I think it was too cold too. Anything relying on anything brass to hold it in place would have ended up on the floor last night...
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Tony G on Mar 07, 2011, 11:46:11
Quote from: Ian on Mar 06, 2011, 22:07:57
I'm far to too tired to get any kit out. It was my son's birthday today and he's run us all ragged...
Quote from: Fay on Mar 06, 2011, 22:11:12
Don't want you getting your kit out, this time of night Ian...........

The last time that happened, it produced the exact reason why he was run ragged the weekend.  ;)

Tony G
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Carole on Mar 07, 2011, 13:14:05
The skies cleared in Bromley at midnight, so stayed up all night.........really tired now, but my target had got too low by midnight (M1), so changed to something else.

Carole

Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 07, 2011, 16:31:45
Well I've just finished setting up and getting ready for the disasters - too many new procedures and fiddly bits.
Be a miracle if it all comes together but we shall see.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 07, 2011, 17:05:24
Well done Mick, you will be ok
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: RobertM on Mar 07, 2011, 21:58:46
Miracles do happen Mick  :lol: :lol:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 07, 2011, 22:16:53
Oh no they don't  :!

EQMod worked.......................................
That's all folks  :cry:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 07, 2011, 22:39:53
What you doing indoors Mick??

What went wrong?
  I must say I don't think the sky is all that
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: RobertM on Mar 07, 2011, 23:43:31
I'm sorry to hear that Mick, you'd better start another thread for your woes tonight !
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mike on Mar 08, 2011, 08:13:01
How can the EQMod working be a bad thing?
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 08, 2011, 08:16:25
I think Mick has gone underground... :(
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 09:02:20
EQMod was the only good thing.

Bad things - Couldn't get focus with eyepiece, finderscope out of alignment so couldn't do alignment, neighbours kitchen lights, Starry Night crashing

Managed to get the camera focused, but alignment still a problem - gave up when Starry Night crashed repeatedly.

I will be busy today investigating the problems - I did learn that a handset/joypad is essential with EQMod
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 08, 2011, 09:09:15
I think it is time for a beer!!!!!!!

Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 11:50:17
QuoteI think it is time for a beer!!!!!!!

Yes, Beer, Beer is my friend and the sun is over the horizon so it's not too early  :)

Overcome one "problem" - I can only bring an eyepiece to focus using the prism, camera is fine - Odd  :-?
Actually 2 problems - I can align the finder now I can see where the scope is pointing (that's something else added to my "things to remember" list)

Now where's that beer
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mike on Mar 08, 2011, 12:23:09
What is the length of the light path using both? Sounds like the focal point is quite far out.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Rocket Pooch on Mar 08, 2011, 12:47:34
Top tip with a DSLR Mick, get a ruller, if your focal length of the scope is 500mm you measure 500mm from the front element of the telescope to the film plane marker on the scope, you will probably need extention tubes.  This will give you approx focus for a refractor.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mac on Mar 08, 2011, 13:05:10
QuoteI think Mick has gone underground...

Na that was me. 8)
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 14:27:46
Top Tip is bang on my point of focus with the camera when imaging :)

I think I've added a bit randomness (yes it is a word) with my farting around.

The farthest thing I can see when sorting out the focusing is a roof about 150 metres away so I'm guessing everything is to cock.
The camera now focuses 20mm closer than on a star, or 580mm instead of 600mm as suggested in Top Tip.

Focuser has 80mm of travel
Light path of prism (measured from mating surface) 36mm
2 eyepieces I tried on the prism come to focus at 48mm and 62mm either of which added to the prism is greater than the 80mm of travel in the focuser.
But the difference identified in top tip for the ground target should give me an extra 20mm of travel - just enough.

I think last night was always going to be a failure once the first thing started going wrong.  In future, I'll do the alignment etc. using the prism with eyepieces before hooking up the camera - I'll also check out the eyepieces again without the prism if we ever get to see the sky again
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: MarkS on Mar 08, 2011, 15:03:19
Mick,

Instead of swapping eyepiece and camera for alignment, you could use a finderscope.  When the alignment star is visible in the finderscope it is easily bright enough to be visible in the camera viewfinder through the scope.

You can then make final adjustments using "frame and focus" in Nebulosity to get it exactly central in the camera field of view.

Mark
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 16:25:02
That's when it started going wrong - The alignment of my finderscope had moved so I couldn't figure out where I was pointing  :oops:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Ian on Mar 08, 2011, 16:43:02
Or you can use a long focal lenth eyepiece and sight along the telescope tube. Or if you're feeling very patient you could try an astrometry solve.

Are you sure you weren't just looking for a beer excuse?
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 16:51:20
I think I'd just popped round the pub when they were handing out the patience  ;)
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Carole on Mar 08, 2011, 17:01:19
After a whole night imaging Sunday and a late night last night I'm too Knac tired to get around to processing what I've done so far and looks like another clear start tonight even if it doesn't last.

I need to try my spare mount out tonight before I take it to Kelling in case there's a problem, so I'll be doing it the hard way tonight, i.e. sitting outside in the freezing cold!!! Might still see if I can network the laptops though.

Carole
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 08, 2011, 17:22:03
Mick, I do chuckle at your terms......................also what is a prism?
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 17:47:14
Oops, meant diagonal  :oops:
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Mac on Mar 08, 2011, 18:15:48
Quotealso what is a prism?
:o

Its an object designed to split light into its component wavelengths?
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: PhilB on Mar 08, 2011, 18:36:55
Quote from: Fay on Mar 08, 2011, 17:22:03
.......what is a prism?

It's also a device that, on a short focal length 'scope, puts a lovely greenish yellow ring round a full moon.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Ian on Mar 08, 2011, 19:16:13
a prism is a geometric shape constructed from a two dimensional polygon that is then extended along a third perpendicular axis.

The question is, is a cylinder a circular prism?
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: mickw on Mar 08, 2011, 19:20:14
QuoteThe question is, is a cylinder a circular prism?

Only if you don't read the instructions  8)
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Fay on Mar 08, 2011, 19:40:33
I just wondered where Mick was incorporating a prism in his setup
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: MarkS on Mar 08, 2011, 19:46:21
Quote from: Ian
The question is, is a cylinder a circular prism?

Mathematically it definitely is.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Tony G on Mar 08, 2011, 21:45:42
Quote from: Fay on Mar 08, 2011, 17:22:03
..also what is a prism?

It's a place where they keep comvicts. :)

Tony G
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: PhilB on Mar 09, 2011, 06:22:09
Quote from: Fay on Mar 08, 2011, 19:40:33
I just wondered where Mick was incorporating a prism in his setup

Back when refractors were routinely of long focal length, around f15 rather than the modern f6, it was common to use a glass prism instead of the modern first surface mirror, in the star diagonal. With the birth of modern 'scopes, the practice fell into disuse due to the high dispersion in such prisms giving rise to 'orrible colour casts in the image.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: Whitters on Mar 09, 2011, 13:48:00
QuoteBack when refractors were routinely of long focal length, around f15 rather than the modern f6, it was common to use a glass prism instead of the modern first surface mirror, in the star diagonal. With the birth of modern 'scopes, the practice fell into disuse due to the high dispersion in such prisms giving rise to 'orrible colour casts in the image.
My first scope had a glass prism... Thanks for making me feel sooooo old today.
Title: Re: Tonight, where have the clear skies at 6pm gone?
Post by: PhilB on Mar 09, 2011, 21:34:17
Old, but much, much wiser...