Lagoon and Trifid 3nm HA

[avandonk]

Did not have a lot of time as I wanted to align the mount far better. The weather in Melbourne has not been clear.

I managed to get a bit of data on something bright.

Low contrast image 1.8MB

http://d1355990.i49.quadrahosting.co...2_04/LT_4k.jpg

Enhanced version 4MB

http://d1355990.i49.quadrahosting.co..._04/LTe_4k.jpg

Bert

[jjjnettie (Jeanette)]

Love the high contrast version. All that swirly stuff.

[alpal]

Looks like you're getting it sorted now - great image.

[tilbrook@rbe.ne (Justin Tilbrook)]

Hi Bert,

What a beast you have, so much fine detail in the nebulosity, can't wait to see colour from this setup.

Cheers,

Justin.

[DavidU (Dave)]

Wow ! Bert is going to have a lot of fun with the new rig !

[acropolite (Phil)]

Lovely stuff Bert, look forward to seeing some colour.

[Peter Ward]

The corner stars look a little weird, some are eggy or not quite registered, ....hence you might want to look at your frame stack alignment.

The data also looks a little compressed to me, playing with gamma levels can often reveal shadow and highlight details otherwise hidden in good data.

Nice wide field for sure. Stick with it

[gregbradley]

A big jump forward Bert.

Looking pretty good. You've got either some tilt or some flex where the left side is at a different plane to the right in the image (not sure if that means the reverse on your actual scope -I think so - right?).

I went through exactly the same thing with my TEC110 as the focuser was having trouble with the heavy Proline.

Its a trial and error thing. If you have that adjusting plate you should be able to nail it after an hour or so.

Something is happening with the processing where you are black clipping the data so the dim areas are being clipped and instead of being smooth like the first they go splotchy.

What software are you using to enhance the image?

I use CCDstack and also the plugin aligning software that does an incredible job.

Greg.

[avandonk]

Thanks for the comments folks. It will take some time to get on top of everything I need to know to get the best out of this system.

You are correct Peter I was just trying to see what this system would do.

Greg you have nailed it the left side of the image plane is closer than the right side of the image plane to the incident light. This of course means the detector is physically the reverse as the image is inverted to the object.

When I get a chance I will do a series of exposures and change the focus by a set amount between them. I have already seen the effect of moving focus out. The LHS corners are eggy and the RHS is fine. By moving out by 800 steps of the Atlas focuser the LHS is then good and the RHS takes on the appearance of the LHS previously. This is about 80 micron! This gives me a ball park figure for adjusting the rear plate of the RH200.

Below are a couple of way out of focus images 20k steps apart of the Atlas focuser. You can see how a slightly out of focus star can produce an ellipse due to the inherent vignetting that is inevitably present in any wide field optic.

I do not want to start adjusting the optic until I am sure of all the facts.

The images so far though indicate that this large sensor will work satisfactorily with the RH200 for widefields and mosaics. The corners will never be as good as the centre but what optic is at F3. When we can make a concave spherical CCD we can then ignore field curvature! Remember curved film in Schmidt cameras.

Thanks for any advice again as it is good to get confirmation or otherwise on my ideas. The weather is the main thing stopping progress but it gives me more time to think things through thoroughly.

At position zero 4MB

http://d1355990.i49.quadrahosting.com.au/2012_04/0k.jpg


20k steps further back 4MB

http://d1355990.i49.quadrahosting.co...012_04/20k.jpg

From the shape of the out of focus stars you can get a visual idea of the amount of vignetting. The factory set collimation also looks OK.

Bert

[gregbradley]

A fast way to correct it Bert would be to set the scope on a large starfield so the image is full of stars then do continuous 5-10 second focus images and adjust the plate as you go to get the stars as evenly round in 4 corners as possible.

Of course if you have to remove the camera to get access to the adjustiing screws that won't work.

A short focus image though is all that is needed to verify the change you just did. It may only take half an hour (yeah right, famous last words!).

Greg.

[avandonk]

With all the cloudy weather I set up two sheets of thick white paper over the RH200 and used the overcast sky as a light source to get some decent flats. Even then I had to limit the opening in the roof as the system is so fast.

The RGB exposures were 0.05 seconds and NB were 3 seconds. Luminance was overexposed.

I think I need one of those lightbox thingies as twilight is not long enough and too variable to get decent flats for all nine filters.

This data was taken with the old autoguiding setup. I have since got the Lodestar working with MaximDL and this is far better.

This is the same data as below except correcting with a much better flat.

It is only eight frames of four minutes each. 32 minutes!

Full resolution image at maximum quality 10MB

http://d1355990.i49.quadrahosting.co...5/LT_fr_NF.jpg


The weather forcast is for a chance of clear skies tomorrow. We can only hope.

Bert

[naskies (Dave)]

Great images, Bert.

[dvj (John)]

It is extremely difficult to understand what is going on with the star shapes from the image processing. Perhaps post some unedited files with just a curves and levels stretch ?

These look like a DDP non-linear processing has been applied. Only an assessment of raw files will yield valuable collimation information. From what I can see, it looks like the center of the field is slightly out of collimation.

It would be good to use an autocollimator, but I think you would have to apply a central spot to the secondary to align the "hall of mirrors". Autoguiding isn't even necessary as all adjustments could be made with very short exposures. Of the 3 point adjustments on the back of the mirror cell, only 1 or 2 of the axis probably need a minor tweek.

good luck