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View Full Version : Guiding - bit geekie - got it working.



Skywatcher
21-12-2008, 01:44 PM
As I posted a few days ago I have bought another small cheap telescope that now sits onto of my imaging telescope thus
I take pictures through the gold one, the job of the blue one is to focus on a star using a ccd camera and to keep that star dead centre by sending signals to the telescope mount - as you can imagine this takes a LOT of wires and a lot of very very careful calibration as we are talking about adjustments that are 1/4 of a pixel !! - anyway setting that all up took most of yesterday, and as luck would have it at about 11 o clock we had about 1.5 hours of clear skies - it took me an hour to set up but I have managed to get it working . Here is a demonstration

This is a 90second shot I took of the very feint Rosette Nebula in November - even at 90 seconds on a high ISO (very sensitive but lots of noise) you can see stars beginning to trail (not round) and no sign of any nebulosity - the red to the right is sensor noise from the camera getting hot

http://i204.photobucket.com/albums/bb84/sidleydoc/rosetteguiding1.jpg

Usually to combat this I stack 20 or 30 pictures to help with the signal to noise ratio to at least get some picture and then try and increase the various brightness and colour channels to ease out a picture but this nebula is far too feint and all I got was this

Yuk! - If you squint some red fug in the middle

http://i204.photobucket.com/albums/bb84/sidleydoc/rosetteguiding2.jpg

Last Night however with the setup I was able to get a rather impressive 10 minute exposure!! at ISO800 - normally at this sensitivity I would see absolutely nothing but as the exposure time is much longer you get - this straight out of the camera - the squashed stars top right are due to my lens not star trail

http://i204.photobucket.com/albums/bb84/sidleydoc/rosetteguiding3.jpg

I think you will agree that is much better not only shape but even dust lanes in the middle of the Rosette - a little tweak in PS and it gives you

http://i204.photobucket.com/albums/bb84/sidleydoc/rosetteguiding4.jpg

Now this is just one picture I would usually still get 20-30 at least and clean them up and remove the noise but the clouds rolled in. - So hopefully there should be some much better pics soon.

Chris x

keith
21-12-2008, 01:48 PM
That's unbelievably cool Chris!!!!

To be honest, I hadn't quite understood that you werent tracking with the movement already given your photos were so great! So I'm really excited to see what you get now with the guidescope, I can definitely see the benefit in the pics below :yes:

ukwdwnut
21-12-2008, 01:51 PM
wow great photos chris especially the last one thanks for sharing :)

Skywatcher
21-12-2008, 02:06 PM
That's unbelievably cool Chris!!!!

To be honest, I hadn't quite understood that you werent tracking with the movement already given your photos were so great! So I'm really excited to see what you get now with the guidescope, I can definitely see the benefit in the pics below :yes:

I was tracking Keith, with a highly acurate mount that has to be carefully aligned with the stars - but even with that I was still only managing about 2-3 minute exposures under excellent conditions - the only way to get longer is computer assisted - this s only the raw data - I really need another 3-4 hours worth to get a truely good picture

keith
21-12-2008, 02:18 PM
I was tracking Keith, with a highly acurate mount that has to be carefully aligned with the stars - but even with that I was still only managing about 2-3 minute exposures under excellent conditions - the only way to get longer is computer assisted

Right! that explains it


- this s only the raw data - I really need another 3-4 hours worth to get a truely good picture

it already looks like a truly good picture to me but I understand what you're saying :) Cant wait to see more

Skywatcher
21-12-2008, 02:39 PM
Bit bored so had a fiddle with what i have.

Not happy until I get more data though

http://i204.photobucket.com/albums/bb84/sidleydoc/softrose.jpg

josh.p.
21-12-2008, 04:13 PM
Wow, stunning pictures :D