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Tempest Fan Results and JMI Motofocus

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#1 aeroman4907

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Posted Yesterday, 10:12 AM

I am just beginning to process a whole lunar mosaic imaged from last night in decent seeing.  I installed my Tempest fans and my JMI motofocus to my 8" EdgeHD.  The tempest fans did seem to make a difference, and I really liked the hands-off focusing with the JMI, even if it was still just focusing with the primary mirror.

 

I did a cropped test of Copernicus.  I should have chosen another crop where I remember craters that are hard to resolve, say around Rima Hadley, but here is my offering for Copernicus.  Pickering was variable from 4 to 5 while collimating.  Unfortunately I don't know the Copernicus region as well and some of my other images of the area are in significantly different lighting.  I think it is an improvement, but I can't yet tell how much closer to the limit of my 8" EdgeHD I am at.  Presented at 0.23"/px.

 

Copernicus.jpg


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#2 RedLionNJ

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Posted Yesterday, 11:11 AM

This looks really promising, although I'm not sure what one (or more) criteria should be changed to get to that point of maximum resolution.

 

The extended Copernicus region is one of the tougher areas to align/stack really, really well - such a variation in brightness, with some dark areas being almost devoid of detail as well as some lighter areas. As you already knew, sun angle can make quite a bit of difference, too.

 

I'm totally with you on the Hadley Rille area as being a good, very well-known test (and also quite pleasing to look at), or maybe the Burg region or the Straight Wall area. During a better libration, Clavius is also a very popular test.

 

For any extended period of imaging with a SCT, I still prefer a focusing mechanism which doesn't move the primary mirror, as then you're never 100% sure it's fully "settled" for the subsequent few minutes. This probably more of an issue when pointing close to vertical, though.

 

And, of course, 90% or more of any hi-res challenge is always the external-to-the-scope seeing. Can't do too much about that except wait. Just at dusk or just before dawn seems to be generally the best chance for me, this time of year.

 

Keep posting!


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#3 DesertRat

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Posted Yesterday, 12:06 PM

Very nice image of Copernicus!

 

Some of the smallest craters appear only a 4-6 pixels across, well differentiated with both brighter and darker sections.  If this image is 0.23"/pix then it appears you are close to the Rayleigh figure of 0.68" for this aperture.

 

However for a highly contrasted target one can do a little better than Rayleigh if the sampling rate is sufficient, seeing very good, focus essentially perfect, etc.  So bottom line is I think your closing in on the limit, which is pretty good.

 

I have not studied the moon in ages, so not sure what the actual size of some of those craters are, which would be an interesting confirmation.

 

Glenn


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#4 Lacaille

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Posted Yesterday, 01:07 PM

Good capture and nice processing!

To clarify, did you run the fans while imaging, or before? Did you get any internal/external temperature data? (My own method, with a C11, is to use a standing fan directed at the OTA for a couple of hours before the session, and proceed when the internal temperature is within 1 deg of external).

Regards

Mark
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#5 aeroman4907

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Posted Yesterday, 01:59 PM

Thanks for the compliments and likes everyone.

 

This looks really promising, although I'm not sure what one (or more) criteria should be changed to get to that point of maximum resolution.

 

The extended Copernicus region is one of the tougher areas to align/stack really, really well - such a variation in brightness, with some dark areas being almost devoid of detail as well as some lighter areas. As you already knew, sun angle can make quite a bit of difference, too.

 

I'm totally with you on the Hadley Rille area as being a good, very well-known test (and also quite pleasing to look at), or maybe the Burg region or the Straight Wall area. During a better libration, Clavius is also a very popular test.

 

For any extended period of imaging with a SCT, I still prefer a focusing mechanism which doesn't move the primary mirror, as then you're never 100% sure it's fully "settled" for the subsequent few minutes. This probably more of an issue when pointing close to vertical, though.

 

And, of course, 90% or more of any hi-res challenge is always the external-to-the-scope seeing. Can't do too much about that except wait. Just at dusk or just before dawn seems to be generally the best chance for me, this time of year.

 

Keep posting!

I think my processing for the whole panel is slightly better, inclusive of the Copernicus.  Rima Hadley has a bit more detail than my other captures, although lighting is not great for it.  My computer is currently processing a panel including Clavius that looks really promising.  AS!3 had perhaps one of the best quality graphs I have ever seen from one of my captures.  While never a guarantee of absolute quality, it is definitely a good hint of it.  The 75% quality line is for 25% of the images (the quantity I am stacking is therefore 1,250 frames out of 5,000), and the drop below 50% quality doesn't occur until about 93% of the frames.

 

Regarding focus, you are correct.  The moon was quite high last night and I did have to adjust focus a few times to try and maintain critical focus during my hour of imaging.  It makes me really nervous to touch focus after initial set, but I hope to be okay.  The bad thing is I won't know the results until I process all of the panels, which won't occur right away because each takes hours to complete due to the IMX 183C sensor size.  We also have vacation during our girls' spring brake away from home, so I'll have to wait until another week before I'll know how the whole mosaic comes out.

 

Very nice image of Copernicus!

 

Some of the smallest craters appear only a 4-6 pixels across, well differentiated with both brighter and darker sections.  If this image is 0.23"/pix then it appears you are close to the Rayleigh figure of 0.68" for this aperture.

 

However for a highly contrasted target one can do a little better than Rayleigh if the sampling rate is sufficient, seeing very good, focus essentially perfect, etc.  So bottom line is I think your closing in on the limit, which is pretty good.

 

I have not studied the moon in ages, so not sure what the actual size of some of those craters are, which would be an interesting confirmation.

 

Glenn

I have found my best crater resolves around 1.1km.  The moon was fairly close last night though at 1963 arcseconds in diameter.  I am running around 85% to perhaps 90% of max resolution, not bad considering the seeing was fairly good but not excellent by any stretch of the imagination.

 

Good capture and nice processing!

To clarify, did you run the fans while imaging, or before? Did you get any internal/external temperature data? (My own method, with a C11, is to use a standing fan directed at the OTA for a couple of hours before the session, and proceed when the internal temperature is within 1 deg of external).

Regards

Mark

Mark, I did run the fans during imaging.  I guess while the title talks about 'results', I don't have anything more scientific than getting better results than normal.  I don't have any temperature probes to test internal and ambient temperatures.  I only had so much time to image, and trying a 'test' run with and without fans would have been useless anyway as the seeing can change.  I can say I had my scope at ambient temperature about 4 hours prior to imaging, which is normal for me.  The fans did seem to make a difference though still with internal thermals and perhaps creating a laminar flow over the primary.  It helped with collimation, which I think was my best ever as well as getting a pretty good focus.  These are all key to maxing out the potential for imaging, excluding the one thing I can't control which is seeing.


Edited by aeroman4907, Yesterday, 02:03 PM.

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#6 aeroman4907

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Posted Yesterday, 02:11 PM

Here is a 200% enlargement around Plato.

 

Plato2.jpg


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#7 Lacaille

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Posted Yesterday, 03:59 PM

Thanks for the detailed reply - my close questioning is because I am trying to work out the possible benefits of cutting holes in the back of my C11!
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#8 aeroman4907

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Posted Yesterday, 05:30 PM

Speaking of the Straight Wall, here is a presentation at 120% of original capture, which would equate to the same size if I did a critical sampling at 5x my 2.4um pixel size.

 

Straight-Wall.jpg


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