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What's the effect of imaging through jet stream?

Cheng-Yang Tan
 

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

IMG_0272.png

IMG_0272.png

Mike Shade
 

Consistent problems suggest hardware problems, polar alignment, PEC curve issues, flexure, poor guiding parameters, this sort of thing in that they impact everything consistently.  Unusual or rare problems like you are sharing suggest transient issues the most likely being seeing.  I work with a 17" telescope at .63"/pixel, I know how seeing can ruin things.  If the system returns consistent results and then all of a sudden doesn't, first thought is seeing.  The fact that your stars were not messed up in one consistent direction is a clue.  I did have a time where my images were horrible all of a sudden and then get good.  Finally went out and found a rather large owl sitting on the edge of the telescope upper ring.  Luckily there was no deposit on the primary mirror.

 

There are numerous reference on the impact of seeing and how professionals monitor and search for sites with good seeing.

 

Mike J. Shade

Mike J. Shade Photography:

mshadephotography.com

 

In War: Resolution

In Defeat: Defiance

In Victory: Magnanimity

In Peace: Goodwill

Sir Winston Churchill

Already, in the gathering dusk, a few of the stars are turning on their lights.

Vega, the brightest one, is now dropping towards the west.  Can it be half

a year since I watched her April rising in the east?  Low in the southwest

Antares blinks a sad farwell to fall...

Leslie Peltier, Starlight Nights

 

International Dark Sky Association: www.darksky.org

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Cheng-Yang Tan via groups.io
Sent: Saturday, May 30, 2020 10:53 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] What's the effect of imaging through jet stream?

 

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Leon Fasano
 

Sorry to lunch on here, but, was wondering if anyone could tell me on phd2 how agressive should the setting be when using an AP1100? I noticed My settings are around 65 and55. Is there a recommendation for that for the 1100?  Thanks


On May 30, 2020, at 1:08 PM, Mike Shade <mshade@q.com> wrote:



Consistent problems suggest hardware problems, polar alignment, PEC curve issues, flexure, poor guiding parameters, this sort of thing in that they impact everything consistently.  Unusual or rare problems like you are sharing suggest transient issues the most likely being seeing.  I work with a 17" telescope at .63"/pixel, I know how seeing can ruin things.  If the system returns consistent results and then all of a sudden doesn't, first thought is seeing.  The fact that your stars were not messed up in one consistent direction is a clue.  I did have a time where my images were horrible all of a sudden and then get good.  Finally went out and found a rather large owl sitting on the edge of the telescope upper ring.  Luckily there was no deposit on the primary mirror.

 

There are numerous reference on the impact of seeing and how professionals monitor and search for sites with good seeing.

 

Mike J. Shade

Mike J. Shade Photography:

mshadephotography.com

 

In War: Resolution

In Defeat: Defiance

In Victory: Magnanimity

In Peace: Goodwill

Sir Winston Churchill

Already, in the gathering dusk, a few of the stars are turning on their lights.

Vega, the brightest one, is now dropping towards the west.  Can it be half

a year since I watched her April rising in the east?  Low in the southwest

Antares blinks a sad farwell to fall...

Leslie Peltier, Starlight Nights

 

International Dark Sky Association: www.darksky.org

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Cheng-Yang Tan via groups.io
Sent: Saturday, May 30, 2020 10:53 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] What's the effect of imaging through jet stream?

 

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Roland Christen
 

Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Cheng-Yang Tan
 

Hi Rolando,
   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

cytan

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.


On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Leon Fasano
 

Stellarvue 80mm with star shoot guide camera sitting on a tmb6” refractor and asi071 camera


On May 30, 2020, at 2:32 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Roland Christen
 

My first and only guess would be that the main scope is flexing with respect to the guidescope. Especially if the guidescope is mounted on the rings of the main scope. That's a guarantee of flexure and poor images. Jet stream - not an issue.

Rolando



-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, May 30, 2020 2:41 pm
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

Hi Rolando,
   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

cytan

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.


On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Cheng-Yang Tan
 

Thanks! Hopefully I’ll never see this problem again after I install the OAG. So, Rolando, the jet stream has never been a problem for you when you image?

On Saturday, May 30, 2020, 5:14 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

My first and only guess would be that the main scope is flexing with respect to the guidescope. Especially if the guidescope is mounted on the rings of the main scope. That's a guarantee of flexure and poor images. Jet stream - not an issue.

Rolando



-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, May 30, 2020 2:41 pm
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

Hi Rolando,
   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

cytan

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.


On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Worsel
 

CY

Jerry Lodriguss' take on the jet stream and seeing

http://www.astropix.com/html/i_astrop/Planetary_Imaging.html

Bryan
Joseph Beyer
 

Cytan,

I was having the same problem with my FSQ mounted on my Mach1. I purchased the Baader guide scope and mount combination A-P sells and moved the guider off the rings. That helped quite a bit. The biggest improvement was made by purchasing APCC Pro and running a model with APPM and turning off the guider.  I ran the guider for several nights with the tracking model running and it added little to nothing.  The star morphology has not been better. 

Of course your situation may be different.  The seeing changes quite frequently where I live along the west coast.  At times it seems the guider just makes things worse. 

Joe



On May 30, 2020, at 4:24 PM, Worsel via groups.io <bryancashion@...> wrote:

CY

Jerry Lodriguss' take on the jet stream and seeing

http://www.astropix.com/html/i_astrop/Planetary_Imaging.html

Bryan

Cheng-Yang Tan
 

Thanks for the info. Hopefully, the upgrade to an OAG this coming week will remove all doubt that it is flexure that's the underlying problem.

And I'm looking forward to the new firmware on the keypad and CP4. Thing can only better.

cytan

On Saturday, May 30, 2020, 06:47:58 PM CDT, Joseph Beyer <jcbeyer2001@...> wrote:


Cytan,

I was having the same problem with my FSQ mounted on my Mach1. I purchased the Baader guide scope and mount combination A-P sells and moved the guider off the rings. That helped quite a bit. The biggest improvement was made by purchasing APCC Pro and running a model with APPM and turning off the guider.  I ran the guider for several nights with the tracking model running and it added little to nothing.  The star morphology has not been better. 

Of course your situation may be different.  The seeing changes quite frequently where I live along the west coast.  At times it seems the guider just makes things worse. 

Joe



On May 30, 2020, at 4:24 PM, Worsel via groups.io <bryancashion@...> wrote:

CY

Jerry Lodriguss' take on the jet stream and seeing

http://www.astropix.com/html/i_astrop/Planetary_Imaging.html

Bryan

Cheng-Yang Tan
 

That's an interesting link. The star looks like it's boiling!


On Saturday, May 30, 2020, 06:24:31 PM CDT, Worsel via groups.io <bryancashion@...> wrote:


CY

Jerry Lodriguss' take on the jet stream and seeing

http://www.astropix.com/html/i_astrop/Planetary_Imaging.html

Bryan

Roland Christen
 

The jet stream produces fatter stars with lower resolution.

Rolando



-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 5:24 pm
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

Thanks! Hopefully I’ll never see this problem again after I install the OAG. So, Rolando, the jet stream has never been a problem for you when you image?

cytan 


Sent from Yahoo Mail for iPad

On Saturday, May 30, 2020, 5:14 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:
My first and only guess would be that the main scope is flexing with respect to the guidescope. Especially if the guidescope is mounted on the rings of the main scope. That's a guarantee of flexure and poor images. Jet stream - not an issue.

Rolando



-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, May 30, 2020 2:41 pm
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

Hi Rolando,
   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

cytan

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.


On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Mike Shade
 

What do the stars look like when you take the system out of focus like for a focus run?  Are they nice concentric circles or do they go from round to oval to any one of a number of shapes?  This can be a rough look at seeing.  The type of seeing can do different things (high seeing like from the jet stream to local seeing from heat rising off of a building).  If you are imaging through a river of moving air, you are likely to see this in your images.  If your system has returned round stars consistently, and all of a sudden it doesn't then something has changed.  If you haven't moved, adjusted, screwed with the imaging train or instrument, changed software settings, anything like that then seeing can be a potential culprit.  If the system has struggled to return round stars and the issues you described are not new, then there is another issue and differential flexure is a likely suspect.  If the jet stream is overhead with that river of fast moving air, seeing will likely be poor.

 

Mike J. Shade

Mike J. Shade Photography:

mshadephotography.com

 

In War: Resolution

In Defeat: Defiance

In Victory: Magnanimity

In Peace: Goodwill

Sir Winston Churchill

Already, in the gathering dusk, a few of the stars are turning on their lights.

Vega, the brightest one, is now dropping towards the west.  Can it be half

a year since I watched her April rising in the east?  Low in the southwest

Antares blinks a sad farwell to fall...

Leslie Peltier, Starlight Nights

 

International Dark Sky Association: www.darksky.org

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Cheng-Yang Tan via groups.io
Sent: Saturday, May 30, 2020 12:42 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

 

Hi Rolando,

   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

 

cytan

 

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.

 

 

On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

 

 

Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

 

Rolando

 

 

 

 

 

-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Cheng-Yang Tan
 

Well, I set up my scope tonight and all subframes were good. The rms error was a little bigger 0.6 to 0.7 arcsec rms compared to 0.5 arcsec rms, but I think this is because it was windier tonight than last.  Who knows what went wrong last night. I was imaging M101 again and so the scope was pointing at about the same altitude as last night. That's the problem with portable setups, each one is just slightly different ... 

cytan

On Saturday, May 30, 2020, 05:24:47 PM CDT, Cheng-Yang Tan via groups.io <cytan299@...> wrote:


Thanks! Hopefully I’ll never see this problem again after I install the OAG. So, Rolando, the jet stream has never been a problem for you when you image?

On Saturday, May 30, 2020, 5:14 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

My first and only guess would be that the main scope is flexing with respect to the guidescope. Especially if the guidescope is mounted on the rings of the main scope. That's a guarantee of flexure and poor images. Jet stream - not an issue.

Rolando



-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, May 30, 2020 2:41 pm
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

Hi Rolando,
   I used a guide scope that is 4.59 arcsec/pixel (focal length 168 mm). Scope is a FSQ106. I plan to image again tonight. Again, the jet stream seems to be quite bad: 45 m/s. So if there's anything else to check, I'm open to suggestions.

cytan

P.S. I will be upgrading to OAG next week after my SBIG Starchaser SC-2 arrives. This is in preparation for an Adaptive Optics AO-8A in the future.


On Saturday, May 30, 2020, 02:32:25 PM CDT, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:


Are you using an off-axis guider or separate guide scope? What is the main scope you are imaging with?

Rolando





-----Original Message-----
From: Cheng-Yang Tan via groups.io <cytan299@...>
To: main@ap-gto.groups.io
Sent: Sat, May 30, 2020 12:53 pm
Subject: [ap-gto] What's the effect of imaging through jet stream?

Hi guys,
   Hopefully my question is not off topic. But here goes:

   I imaged M101 last night (alt at 76 deg and close to the meridian) with my Mach1GTO and I had to throw away 1/2 my subframes. I examined the bad subframes and there's no consistent direction for the eggy stars from each subframe. Some subframe's eggy stars were in RA direction, some were in DEC direction and some were angled w.r.t. RA and DEC. I looked at the meteoblue seeing map (attached) and it says that the jet stream was at around 31 m/s last night. PHD2 guide graph was about 0.5 arcsec rms error for the entire night which wasn't too bad for the entire session because my image scale is 2.1 arcsec/pixel.

Is the above something that I'd expect imaging through the jet stream? Or I should be looking for something else to blame like flexure?

Thanks (before I start tearing everything apart :) )

cytan

Glenn D
 

cytan,

I generally have poor local seeing, but I am amazed at the variation that is possible. On good nights, guiding with my Mach1 (last generation) is around 0.3-0.4 arc seconds and the resulting HFD of the subframes is in the 2-3 range. On bad nights, particularly when the jet stream is a factor, guiding is 1.5 arc seconds or worse and the HFD is much higher. On the worst night in memory, my HFD was 10+! I thought there was something wrong with my optics—the stars looked like giant snowballs and refocusing did not improve them. But a couple of nights later, guiding and image quality had returned to normal. So in my experience the jet stream can significantly degrade both guiding and image quality. 

Regards,

Glenn
Cheng-Yang Tan
 

Hi Glenn,
  Good to know that my earlier problem was also observed by you. Unfortunately, l am not completely convinced because my setup is torn down and reinstalled each evening. Although I always set up close to the same spot on the sidewalk, and I try to be consistent setting up, I really cannot guarantee that each install, PA is identical.
   Everything went smoothly last night though despite the wind. Who knows what the real cause is if it’s not the jet stream the previous night.

On Sunday, May 31, 2020, 8:58 AM, Glenn <public@...> wrote:

cytan,

I generally have poor local seeing, but I am amazed at the variation that is possible. On good nights, guiding with my Mach1 (last generation) is around 0.3-0.4 arc seconds and the resulting HFD of the subframes is in the 2-3 range. On bad nights, particularly when the jet stream is a factor, guiding is 1.5 arc seconds or worse and the HFD is much higher. On the worst night in memory, my HFD was 10+! I thought there was something wrong with my optics—the stars looked like giant snowballs and refocusing did not improve them. But a couple of nights later, guiding and image quality had returned to normal. So in my experience the jet stream can significantly degrade both guiding and image quality. 

Regards,

Glenn

Mike Shade
 

I have seen about every geometric shape possible with out of focus stars during a FocusMax run with the 17", worse when the seeing is poor.  According to my seeing monitor, I tend to run around 2" on average, with some periods of significantly better, 1.5" or less and sometimes 3" plus, on the same night.  It can be reasonable right after sunset for about 30 minutes, and can be reasonable before dawn-sometimes.  I have done what is possible around and in the observatory to minimize heat effects (I am in SE AZ), but I can't control the upper atmosphere.  

 

Mike J. Shade

Mike J. Shade Photography:

mshadephotography.com

 

In War: Resolution

In Defeat: Defiance

In Victory: Magnanimity

In Peace: Goodwill

Sir Winston Churchill

Already, in the gathering dusk, a few of the stars are turning on their lights.

Vega, the brightest one, is now dropping towards the west.  Can it be half

a year since I watched her April rising in the east?  Low in the southwest

Antares blinks a sad farwell to fall...

Leslie Peltier, Starlight Nights

 

International Dark Sky Association: www.darksky.org

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Glenn
Sent: Sunday, May 31, 2020 6:59 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] What's the effect of imaging through jet stream?

 

cytan,

I generally have poor local seeing, but I am amazed at the variation that is possible. On good nights, guiding with my Mach1 (last generation) is around 0.3-0.4 arc seconds and the resulting HFD of the subframes is in the 2-3 range. On bad nights, particularly when the jet stream is a factor, guiding is 1.5 arc seconds or worse and the HFD is much higher. On the worst night in memory, my HFD was 10+! I thought there was something wrong with my optics—the stars looked like giant snowballs and refocusing did not improve them. But a couple of nights later, guiding and image quality had returned to normal. So in my experience the jet stream can significantly degrade both guiding and image quality. 

Regards,

Glenn

Robert Berta
 

I think you mentioned that you were setup on a sidewalk.....if so were you shooting over pavement, or perhaps over roofs of houses? Both of those conditions will destroy your image quality.
Cheng-Yang Tan
 

Yes, both conditions can destroy image quality. For the heat from the pavement, at least from my experience, there's enough cool down time for the pavement from installation to the first image that it really doesn't matter. Hot roofs on the other hand is a different story. I try not to image above the roofline which is south of me. I try to image as high in the sky as possible and that's works well. That's the travails of imaging in suburbia.

cytan

On Sunday, May 31, 2020, 05:59:58 PM CDT, Robert Berta <biker123@...> wrote:


I think you mentioned that you were setup on a sidewalk.....if so were you shooting over pavement, or perhaps over roofs of houses? Both of those conditions will destroy your image quality.

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