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EAA Best Practices

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#1 bigbangbaby

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Posted 29 May 2024 - 09:59 AM

Needless to say, light pollution is a big discriminator, and those blessed with darker skies have an easier go. But I have to wonder how much of what we perceive as limitations to EAA are partly the result of poor (lazy) technique. I'm certain most who do EAA know all of this, but practicing it is another thing.

 

Some controllable factors that contribute to good (or bad) EAA results:

 

1) Excellent polar alignment. Sharpcap and NINA make it simple and fast.

2) Excellent focus. Use a Bahtinov mask or auto-focus tools in NINA or Sharpcap.

3) Proper backspacing. All information and required spacers are available online.

4) For those with mirrored scopes, excellent collimation. Not necessarily easy, but essential to good images.

5) Image tilt. ASTAP or NINA tools can quantify it and tilt plates can fix it.

6) Proper calibration frames. Not easy, but with deliberate persistence, doable. They can make an outsized improvement to image quality.

7) Appropriate combinations of camera gain, offset and exposure duration. Lots of discussion about this online, including an excellent Youtube video from Sharpcap's creator.

8) Image targets when optimally placed (near meridian, if possible). Obvious, I know.

9) Guiding optimization. Do you simply use the default settings?

10) Appropriate capacity mount for payload.

11) Optimal image scale; choice of pixel size and focal length

12) Check for wildfire smoke. It is the number two killer of successful EAA, second only to clouds! Astropheric is an excellent tool.

 

I certainly don't follow all of these all the time. And I may have missed a few too. By all means, add to the list.


Edited by bigbangbaby, 29 May 2024 - 10:43 AM.

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#2 steveincolo

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Posted 29 May 2024 - 11:07 AM

13) Giotto Rocket Blower

14) Minimizing set-up time.  For me, that's a Telegizmos 365 cover.  For you, that's your super cool Scopebuggy setup.  There's also repeatability (for example, marking the position of your tripod on the ground).


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#3 bigbangbaby

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Posted 29 May 2024 - 12:02 PM

Thanks, Steve. Good suggestions.

 

Re: 14) I use a phone compass to align the mount to within a degree or so of true north then fine tune during PA. A physical alignment spot would further simplify things.


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#4 Clouzot

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Posted 29 May 2024 - 04:36 PM

I'll add the usual suspects:

  • especially for those using *-Cassegrain scopes (SCT, Maks...), take the time to acclimate the tube, or wrap it into Reflectix-like material (if you're a believer). Collimation is worthless if the OTA out of thermal equilibrium.
  • unless you have a carbon fiber tube, refocus frequently, and then some (at least hourly, or when temperature is dropping by 1°C or more - monitor it with a weather station, for example)
  • chase all sources of stray light: use a dew shield, make sure the imaging chain is light-tight, lower the brightness of your laptop (or use a tarp to shield it) if you're observing outside, tape the red LED on the camera, slingshot your neighbor's lights out...

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#5 MunichAtNight

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Posted 30 May 2024 - 03:02 AM

Hello!
In some cases, however, I only agree with the above list in very few points.

What strikes me in this list is that, in my opinion, many of the points listed are only necessary if you want to work in the direction of astrophotography. Since I only act as an EAA observer, my main focus is on getting as much done as possible and as simply as possible, automated, using software. I also want to be ready for action with the shortest possible preparation time. This is particularly important to me because I carry my equipment into the garden and back into the house every night.

 

1) Excellent polar alignment. Sharpcap and NINA make it simple and fast.

The most important distinguishing feature between EAA and astrophotography is already made in the first point. EAA does not require long (minutes) individual exposure times like astrophotography. That's why an EQ-guided mount is neither necessary nor required at all.

My Skywatcher AZ-EQ5 works exclusively in AltAZ mode and, thanks to the Celestron Starsense autoalignment module, carries out a complete and fully automatic alignment within about two minutes. One push of a button and in two minutes I have a perfectly aligned and sufficiently accurate tracking mount that hits every DSO point approached via GOTO exactly and the camera sensor in the middle.I don't need any special preparation for the mount itself. Neither a north orientation nor a horizontal alignment of the mount needs to be taken into account when setting it up.
 

 

2) Excellent focus. Use a Bahtinov mask or auto-focus tools in NINA or Sharpcap.

Perfect focus is the most important thing of all. You will never achieve perfect focus with Bahtinov mask and fiddling around, manual handling and, worst of all, manual handling that cannot be carried out remotely. Therefore, attach the ASI EAF to the OAZ and a perfect focus point is ensured within about two minutes. Reproducible and stress-free. No cold fingers, no sweat on your forehead and no mosquitoes to annoy and irritate you when performing difficult manual tasks that also require a lot of concentration.

 

3) Proper backspacing. All information and required spacers are available online.

5) Image tilt. ASTAP or NINA tools can quantify it and tilt plates can fix it.

10) Appropriate capacity mount for payload.

11) Optimal image scale; choice of pixel size and focal length

That's right points. But once you have installed all the required optical components on the telescope in a fixed and unchangeable manner, you can optimize everything in advance and then “on-site” for a few nights. But once you have reached a perfect state, nothing changes. In my screwed optical train I can still easily switch between different astro cameras. All that is required is that all of the astro cameras I use always have the same distance between the camera thread and the sensor. In my case this is 6.5 mm. Point and done.


 

4) For those with mirrored scopes, excellent collimation. Not necessarily easy, but essential to good images.

There is always a lot of fuss and tragedy being made, told and claimed here. I use two different Newtons for EAA. 1000mm | f/5 and 504mm | f3.4 - both instruments retain collimation for many, many months. Normally, in the worst case scenario, I collimate my instruments once a year. And I don't have Takahasi Newtons that cost thousands of dollars and have been proven to only have to be collimated once in lifetime, but cheap Skywatcher mirrors that cost a few hundred dollars.



 

6) Proper calibration frames. Not easy, but with deliberate persistence, doable. They can make an outsized improvement to image quality.

This point has also been resolved for me a long time ago. I don't do darks or flats but rely exclusively on Sharpcap's capabilities with "hot pixel removal" and "gradient removal". Sometimes difficult light/moon situations require some reworking of the final stacks with Photoshop. However, the time required for this is not worth mentioning compared to the tens of minutes, or what feels like hours, to create new flats and occasionally new darks each time. And again I have to emphasize that I make EAA observations with the opportunity to keep the stacked images I gained as a souvenir of the night and for "long-term documentation purposes". I don't do astrophotography.
 
to be continued ...

Edited by MunichAtNight, 30 May 2024 - 03:07 AM.

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#6 MunichAtNight

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Posted 30 May 2024 - 03:03 AM

7) Appropriate combinations of camera gain, offset and exposure duration. Lots of discussion about this online, including an excellent Youtube video from Sharpcap's creator.

In my opinion, there is too much fuss being made here. I start with a standard setting for my three different ZWO cameras, ASI294MC, ASI183MC, ASI533MC with gain 300 and 4 seconds exposure time. However, depending on the DSO observed, I try to work with the lowest possible gain and short exposure times. After a short time and looking at how the respective stack develops visually, I correct the values ​​accordingly, halving / doubling the exposure time, 1s, 2s, 4s, 8s and gain in steps of 50. After an adjustment/observation/test phase, I then restart the stack and then no longer change the set values ​​for this object that night, even for a period of one, two or three hours. However, I admit that my years of experience in electronic image processing due to my professional activity help me a lot. But even with little experience in this area, with a little training you can still achieve good, even very good, results. Just do it, observe critically, adjust and again, we don't really do astrophotography.
 
 

8) Image targets when optimally placed (near meridian, if possible). Obvious, I know.

Since in my garden I only have a view to the south, somewhat west and northwest or very high above the horizon somewhat toward the northeast and at the same time I am obstructed by nearby trees, neighboring houses and bushes or trees in the neighbor's garden, I have to I select the observable objects very carefully in advance. I also have to take into account that the object does not disappear or become hidden behind optical obstacles after a short time.

 

9) Guiding optimization. Do you simply use the default settings?

For me, this is more a matter of setting and the difference between EAA with exposure times of seconds, 1s, 2s, 4s, 8s and astrophotography with exposure times in the range of a few or even many minutes. My AltAZ mount, which was set up automatically, simply and effectively at the beginning of the night, works sufficiently well with very good alignment that no guiding is required.
In addition, a Sharpcap allows you to pause stacking at any time, reposition the object perfectly in the center via platesolving and then continue stacking. I can definitely achieve that, for example, a stack of the Andromeda Galaxy, M31, which only finds enough space diagonally in the image field of my ASI294MC witn 504 mm | f3.4, hardly shows any black image areas even during a stacking of almost three hours. However, to avoid AltAZ-based field rotation, I use a motorized Pegasus Falcon camera rotator that has an automated, software-controlled derotation function. Another piece of equipment that I recommend and that I never wanted to do without.

 

12) Check for wildfire smoke. It is the number two killer of successful EAA, second only to clouds! Astropheric is an excellent tool.


Fortunately, we in Munich, in the south of Germany, Europe have not been affected by wildfire smoke so far. But recently we have sometimes had a continuous stream of dust and sand from the Sahara for several days and even for over a week, which, although or probably because of this, remains at higher altitudes in the atmosphere and has a negative impact on astronomical observations, not least through yellowish light.

 

I feel more affected by the bright moon phases, which sometimes have a very strong and detrimental effect on the results that can be achieved.

Servus - MunichAtNight - Ewald


Edited by MunichAtNight, 30 May 2024 - 03:15 AM.

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#7 jml79

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Posted 30 May 2024 - 09:33 AM

Hello!


6) Proper calibration frames. Not easy, but with deliberate persistence, doable. They can make an outsized improvement to image quality.

 
This point has also been resolved for me a long time ago. I don't do darks or flats but rely exclusively on Sharpcap's capabilities with "hot pixel removal" and "gradient removal". Sometimes difficult light/moon situations require some reworking of the final stacks with Photoshop. However, the time required for this is not worth mentioning compared to the tens of minutes, or what feels like hours, to create new flats and occasionally new darks each time. And again I have to emphasize that I make EAA observations with the opportunity to keep the stacked images I gained as a souvenir of the night and for "long-term documentation purposes". I don't do astrophotography.
 
to be continued ...

SharpCap's Hot Pixel removal has failed me many times and with a high amp glow camera (294M) Darks can really help. I have lots of images with dithered hot pixels. But I really only need 1 dark frame to eliminate hot pixels and reduce amp glow. 5-10 Darks and it's perfect. I can and do shoot the darks "offline" meaning not during imaging time. For my cooled cameras it is really easy to have a dark ready for my common exposure times (8s, 15s, 30s, 60s) and for my uncooled camera I use fridge darks (3*C ish), basement darks (18*C ish) and somewhere in between (10-12*C) taken on a cloudy night. Darks can last for many many months. It's a bit of prep work but once it's done I have the library and I might update it every 6 months or so. My OSC IMX585 camera seems to work pretty good without darks using SC's Hot Pixel Removal but my Mono 294M's have terrible dithered hot pixels. When I Stack in Siril I need darks because it doesn't have hot pixel removal.

 

As for flats, I rely on the smaller sensor not having to much vignette and careful cleaning and handling. If I have a flat stack from a recent AP project, I might use that but for EAA I generally don't take the time to do flats even though it's only an extra 5 minutes or less. If I get the kids to bed and I'm out at the scope early then I will take a flat, maybe.



#8 MartinMeredith

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Posted 30 May 2024 - 09:57 AM

Fascinating to hear about the mono/OSC differences for hotpix removal. I have the opposite issue: I'm finding that the simple but apparently robust algorithm (*) I developed for mono in Jocular doesn't work quite so well for OSC.... the presence of the Bayer matrix appears to demand a different approach. Maybe I can do an algorithm swap with SC ;-)

 

cheers

 

Martin

 

(*) For anyone interested it goes like this: 1. normalise image by subtracting minimum intensity; 2. divide normalised image by a 3x3 Gaussian smoothed version of the normalised image. 3. define hotpix as any values more than N standard devs from mean (above or below) of the image in step 2 (N=5 works well). Finally 4. replace outlier candidates with the median computed in a 3x3 window.


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#9 Meies

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Posted 30 May 2024 - 11:31 AM

A handy tip for swapping cameras. Use spacers to make them parfocal to one another. The ASI2600MC, for example, has 17.5 mm from the front to the sensor. My un-cooled planetary cameras have 12.5mm, so I put 5mm spacers on all of my planetary cameras. I can swap out any camera for any other camera and be close to the same focus. Yes, I still use an autofocus routine with SharpCap or the AA+, but I am starting from close, rather than 5mm off.


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#10 MarMax

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Posted 30 May 2024 - 04:47 PM

Nice list Larry. I have a few additions.

 

- blue painters tape markers for kit components

- check (occasionally) for software updates, especially SharpCap

- check (occasionally) your mount fasteners and tripod

- a paper notepad for things like EAF steps, SQM-L or other pertinent information

 

I mark the backfocus for each imaging train with blue tape. I also put caps on everything when not in use with a blue tape marker with either backfocus or kit information. I also use a filter drawer so each drawer is marked with blue tape to ID the filter.



#11 bigbangbaby

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Posted 30 May 2024 - 07:24 PM

A handy tip for swapping cameras. Use spacers to make them parfocal to one another. The ASI2600MC, for example, has 17.5 mm from the front to the sensor. My un-cooled planetary cameras have 12.5mm, so I put 5mm spacers on all of my planetary cameras. I can swap out any camera for any other camera and be close to the same focus. Yes, I still use an autofocus routine with SharpCap or the AA+, but I am starting from close, rather than 5mm off.

 

 

Nice list Larry. I have a few additions.

 

- blue painters tape markers for kit components

- check (occasionally) for software updates, especially SharpCap

- check (occasionally) your mount fasteners and tripod

- a paper notepad for things like EAF steps, SQM-L or other pertinent information

 

I mark the backfocus for each imaging train with blue tape. I also put caps on everything when not in use with a blue tape marker with either backfocus or kit information. I also use a filter drawer so each drawer is marked with blue tape to ID the filter.

Great suggestions that underscore the benefits of being organized. I'm taking notes. 



#12 Udi

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Posted 01 June 2024 - 05:41 AM

Very important per my experience with Sharpcap: Use FHWM to filter out 'noisy' images.



#13 alphatripleplus

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Posted 01 June 2024 - 06:50 AM

A couple of obvious tips that I have learned the hard way:

 

1) If it's too windy, don't bother with longer focal length EAA unless you know for sure that your set-up can handle wind, e.g. it is shielded in an observatory and/or it's on a rock solid pier. You can try shorter subs, but even at 5s subs, the wind can be a killer.

 

2) If you are operating remotely from inside, don't forget to check that you turned off the porch lights before you start doing EAA. (Happens to me more than I want to admit.lol.gif )


Edited by alphatripleplus, 01 June 2024 - 01:21 PM.

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#14 PeterC65

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Posted 01 June 2024 - 09:26 AM

1) If its too windy, don't bother with longer focal length EAA unless you know for sure that your set-up can handle wind, e.g. it is shielded in an observatory and/or it's on a rock solid pier. You can try shorter subs, but even at 5s subs, the wind can be a killer.

I've found the SharpCap FWHM filter helps when it's windy and I'm using a scope that is liable to wobble during the gusts.



#15 MarMax

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Posted 01 June 2024 - 10:30 AM

In addition to the FWHM filter you should also use the Brightness filter. My area gets the marine layer that can roll in within minutes. I usually set it to 70%. It's not so much to eliminate bad frames but to tell you when you are clouded up.

 

Even though I'm sitting in the garage looking out at the rig, I'm not always looking up and don't notice clouds without the Brightness filter.


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#16 RodgerDodger008

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Posted 04 June 2024 - 04:09 AM

See you and raise you, find that the FWHM filter does not always see a wind affected frame but strangely the brightness filter cam sometimes help with wind even if no cloud. Just set the brightness filter to 95% on windy days and watch how helps.

But agree, I have to be desperate to use long focal lenght if really windy.
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#17 alphatripleplus

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Posted 04 June 2024 - 06:33 AM

Yeah, unfortunately the FWHM filter does not always work to cull wind affected subs. 

 

One best practice that I would really love SharpCap to include is to give the user the ability to manually reject the last sub in a live stack... for any reason. I've asked about adding this feature to SharpCap in the past, but it just  hasn't happened.frown.gif  My all time favourite EAA software (Starlight Live, only runs Starlight Xpress cameras) has that feature, as  does ASILive for ZWO cameras, so it is definitely a feature that can be implemented in EAA software.  Some of us actually try to watch every sub come in and would use the feature in any EAA software that it is available in. Forgot to mention that Jocular has it too.


Edited by alphatripleplus, 04 June 2024 - 07:53 AM.

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#18 steveincolo

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Posted 04 June 2024 - 12:42 PM

Martin’s software has a bit more feature wise.  You can go back through the stack, look at the subs, and remove any of them.  Wind gusts, clouds, satellites.  So you don’t have to be quite on top of things as much. 




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