Allan's Deepsky

Mons Piton

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Mons Piton
Captured using Toucam webcam and Lx200 at Brough. The mountain in the centre of the picture is 6625ft. high.
Posted by Allan on April 23, 2010 Full Size|

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6 Comments

Reply Doug
2:58 PM on April 29, 2010 
Flamencopaul says...
Hi Doug,

I just read the details of your scope a bit more closely - I hadn't realised that you were using a mak-newt...the diagonal inside the tube inverts the image.

In respect of image quality, using the webcam at 15 fps and using 30sec recordings gives us 450 frames to play with...selecting only the best 20 or so frames to stack means we get the best of the seeing within a 30 sec time period. That said, even over the small image scale of the webcam, some of the frames would be sharp in one area, and blurred in another.

With regards good seeing conditions - that's a bit more complicated. In general bad seeing is caused by temperature inversions, turbulance and moisture/particles carried in the air. For example, a warm wet airstream above a cooler dryer ground level airstream would produce generally bad seeing. Locally, seeing can be affected by a number of things...at BLAS, if we are looking east a thermal of warm air from the housing estate roofs produces locally bad seeing in that direction.

Seeing is also affected by the thickness of atmosphere, so it is good general practice to image an object when it is highest above the horizon.

Taking the above into consideration, good seeing conditions occur when the air is dry, stable, and has a smooth temperature gradient to high altitudes.

Getting these conditions in the UK is rare because of the nature of the weather we receive.

Paul.

Paul,

Thanks for the detailed response. Of course the diagonal is in the scope - penny drops; it's one of those things that is obvious when it's pointed out but not so obvious while you're in the mindset of an attachment rather than an intrinsic (hidden) design artefact.

As for seeing conditions I take your point and accept that the UK is not good from that point of view, and that planetary detail is degraded as a result. Although I have not got a webcam I do have a CCD colour security camera (well 2 actually with differing sensor sizes (1/4"-ish) - one is a Swann and the other a copy with smaller sensor) and a 1.25" nosepiece which I have yet to try out. That'd be something worthwhile experimenting with as I have a USB based video capture device with hardware MPEG decoding which works with my laptop. With a 2xBarlow on my 127MakC that would give a focal length of 3000mm. I'll have to work out the pixel size and see how that compares with the Canon.

Doug
Reply Flamencopaul
6:56 AM on April 29, 2010 
Hi Doug,

I just read the details of your scope a bit more closely - I hadn't realised that you were using a mak-newt...the diagonal inside the tube inverts the image.

In respect of image quality, using the webcam at 15 fps and using 30sec recordings gives us 450 frames to play with...selecting only the best 20 or so frames to stack means we get the best of the seeing within a 30 sec time period. That said, even over the small image scale of the webcam, some of the frames would be sharp in one area, and blurred in another.

With regards good seeing conditions - that's a bit more complicated. In general bad seeing is caused by temperature inversions, turbulance and moisture/particles carried in the air. For example, a warm wet airstream above a cooler dryer ground level airstream would produce generally bad seeing. Locally, seeing can be affected by a number of things...at BLAS, if we are looking east a thermal of warm air from the housing estate roofs produces locally bad seeing in that direction.

Seeing is also affected by the thickness of atmosphere, so it is good general practice to image an object when it is highest above the horizon.

Taking the above into consideration, good seeing conditions occur when the air is dry, stable, and has a smooth temperature gradient to high altitudes.

Getting these conditions in the UK is rare because of the nature of the weather we receive.

Paul.
Reply Doug
6:16 PM on April 27, 2010 
Flamencopaul says...
Hi Doug,

The shadows are the same, it's the orientation of the images that is different. Our's are oriented 'as real', i.e. as you would see it with the naked eye - your image is flipped N/S so I'm guessing you had a 45 degree diagonal in the image train?

Cheers,

Paul.

Paul,

I am trying to recollect the configuration that I was using. I am pretty sure the camera was straight into the focusser as image projection cannot be realised with an extended optical path, e.g. through a diagonal. The one thing I cannot remember is what I did in Paintshop.

It doesn't alter the fact that the images you and Allan took are pretty impressive. I guess that the conditions that night were approaching ideal as the images that I got are far better than the ones I have taken since in terms of sharpness (the heat haze effect is very evident in live-view on the camera at the x10 setting). I do appreciate that the casting of shadows enhances the contrast and these are diminishing as the moon becomes full.

As a matter of interest how often do we get good viewing conditions, particularly important I guess for planetary imaging. I don't think that I'll be allowed to go to the West Indies for three weeks like the chaps who are featured in May's Sky at Night (or Astronomy Now?).

Doug
Reply Flamencopaul
6:55 AM on April 27, 2010 
Hi Doug,

The shadows are the same, it's the orientation of the images that is different. Our's are oriented 'as real', i.e. as you would see it with the naked eye - your image is flipped N/S so I'm guessing you had a 45 degree diagonal in the image train?

Cheers,

Paul.
Reply Allan
9:03 PM on April 25, 2010 
Doug,
Took the avi's about 22:00 to 23:00 when the moon was high.

Regards Alllan
Reply Doug
1:02 PM on April 25, 2010 
Allan, that's pretty impressive. I had a look at mine that I took on the 21st (I've added it today to DJS 1st pics album) and I can make out the major features, but the detail on yours is quite stunning. You must have taken yours at a different time (mine was about 21:30 GMT) as the shadows are cast differently.

I notice that it also covers the area that Paul captured.

Regards,
Doug