When to shoot; and when not to!? [Deep Sky] Acquisition techniques · schmaks · ... · 26 · 1135 · 1

schmaks 0.00
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Greetings,

I am sure I am not the only one out there waiting for the clouds to pass and stars to come out.

That said, it has me wondering:
  • If it's not fully overcast but just some scatted clouds, do you still shoot and the cull through to get rid of unusable shots; or flex your patience and await cloudless nights?
  • When it comes to transparency and seeing (I use the iCSC app), what is the point wherein you do/don't shoot?

I understand that it's all relative but am curious to know your personal preferences.

A bit further down the rabbit hole... for anyone with a fully (or nearly) automated system, I'd love some insight into your observatory's setup and how your automation is set regarding the sky's conditions.

Clear Skies!
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Chris-PA 3.31
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I try to get data whenever possible. Sometimes (especially lately), the data don't end up being usable due to poor transparency, but these 'lab nights' keep you from becoming rusty in your acquisition skills, so when conditions do end up being good you end up making fewer mistakes. Also, if you're shooting narrowband with a monochrome camera, you can often get usable RGB stars under pretty terrible conditions.
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ODRedwine 1.51
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Just shoot, the photos are essentially free anyway.  Culling really doesn't take that much time if you something like Pixinsight Blink.

The only real problem is that clouds can cause your guidance system to lose the guide star.  On a few nights I've shot unguided with short exposure time to avoid that problem.
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schmaks 0.00
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Thanks!

Might get some decent skies tonight! Definitely looking forward to narrowband SHO filter wheel upgrade one day.
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rveregin 6.27
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Unless you get perfect skies regularly, I would suggest you snatch whatever time you can. And practice does make perfect, there are so many ways to go wrong, that it is easy to do if you wait weeks between getting out. I try to focus on one or two targets at a time, to get to know them. Only with some bad nights on a target do you realize what is good. I stack with DSS and generally find sky background, FWHM, number of stars detected are relatively consistent from night to night, if you get rid of the bad images, which is very easy to do once you know what is good and what is bad for that target. Remember that seeing is a function of aperture, so for smaller apertures seeing is better than what might be posted. And on cloudy covered nights, the sky between the clouds can still be excellent, you just need to be picky with your images.
"Clear-ish" skies!
Rick
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shomstead 0.90
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I shoot when ever I get the chance.  Too few clear skies this summer not to be out having
fun and keeping my hand in the game.  Being an amateurs' amateur it  allows me the opportunity
to work with questionable data and squeeze as much out of it as I can to practice and learn.
My issue is more "when to post and when not to post" ;)
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schmaks 0.00
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Scott Homstead:
My issue is more "when to post and when not to post"


haha—this IS the real question!
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sink45ny 0.00
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If PHD2 can keep the guide star I will probably try to image, especially near the Meridian. The Moon stops me from imaging if it's within 60 degrees of my NB target.
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astropical
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When in a cloudless night a bull elk is running towards your scope, then you shoot. 😎
Since I do not own any filters, I gave up imaging when the sky is sad sparing myself a few disappointments.
Cheers, Robert

For instance, this is NG.

japan-south-large.jpg
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jzholloway 2.97
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I shoot whenever one of the million apps say it is going to be clear - or at least I setup the rig.

I do periodically check when my imaging is running to see if it becomes real cloudy and I will pause my run until it clear up - but that is only if I notice.
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BradleyWatson 7.33
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Yep, I pretty much shoot when I can, getting rid of any bad subs. I recently built my observatory which has made imaging in sporadic weather much easier, literally roll the roof on if necessary and resume when possible in the night (no more tearing the gear down and putting it up and PA etc etc. It makes a hell of a difference).

I will look into automation in the summer using cloud cover as a metric for controlling the roof, but until then - I am as I believe we all are an opportunist. I am literally working on 3 projects and they each have several nights data already.

CS
Brad
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limeyx 1.20
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We have had ONE clear night in my area in 2021 and that with a 50% plus moon. I shoot whenever possible but if its only clear for an hour or two, it feels silly to setup since it takes me a long time to get shooting (hopefully this will improve)
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DavidNI 0.90
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I also shoot whenever possible! Cloudless nights are very rare in Northern Ireland. Sometimes even if it is cloudy but the moon is still somewhat visible I will just leave the scope tracking on the moon and keep an eye on the laptop to see if the clouds clear at all. If they do I will have a go at imaging something at least. As others have said already, it is good practice and helps to iron out problems that could crop up at a more critical time when the skies are at their best. I find my big long lynxastro usb cable handy for this so I can monitor the skies "remotely" from indoors.

As for discarding unusable subs I generally just make the thumbnails large on windows explorer and delete all the obviously bad ones. Then I find that the deep sky stacker score works well enough in helping me to sift out the ones that i didn't notice. I just click the check all above threshold box on deep sky stacker and then put in a minimum score that seems to be reasonable whilst still making the most of the data.

I am relatively new to this hobby and I am constantly trying to improve my pictures so maybe some day I will become a bit more meticulous with my work flow in this area :-) Sometimes I consider whether I should be discarding more subs. Does anyone know what is best practice when it comes to this? Would you prefer to use more "average" quality subs or less "good" quality subs?
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Doc248 0.00
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Cloudless nights are rare in Southern Ireland also; so the time is precious. If my system will guide then it's rare not to get something and If it clouds over I can shoot darks or flats and dark flats and watch for clearing on my guide camera.

Because we get so few really good nights, I run two rigs, a side-by-side wide field setup and an RC with reducer. Being retired is the key to doing this; I can spend an hour setting up in the afternoon.

The extra wasted subs really don't matter to me, I cull the lights pretty carefully anyway and there are lots of causes of bad subs.
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rveregin 6.27
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Just to David's comment on using DSS stacker low scores to eliminate subs, I would not recommend depending on it. If everything else is constant (seeing, tracking, wind, focus) scores actually decrease when the sky gets darker (or if you target is higher in the sky). I think the brighter sky brings fainter stars above whatever star threshold you set. If seeing is worse or focus goes off a little, then FWHM increases which does decrease score. But if your stars are really dancing around due to poor seeing, or your focus is really bad (donuts), or you have wind vibrations or poor tracking in one direction then FWHM can actually go down, which increases the score. So if it is getting darker and my target is going up in the sky, I expect scores to trend down. On that trend line I look for scores that are off that trend line, or FWHM that are off the line, up or down, or number of stars suddenly goes down (dew or clouds). I inspect those in DSS with the magnifier to quickly confirm the problem prior to deleting. Of course, if you are seeing scores like 500 consistently, obviously if you suddenly see 0 or 100 you can delete without further thought.

In my workflow, I typically register all my images, click on the data line for any one of the subs in that tab,  then use the copy to clipboard, which copies all the information for all the subs in that tab. Images on different tabs need to be copied separately. I copy directly into an excel template I created, which then graphs for me FWHM, stars, background, score (and also x and y values to see what my tracking is doing), makes it easy to see the outliers that need to be inspected and potentially deleted. A real time saver if you have lots of subs.

In theory one can also see everything plotted as you make your subs using DSS live. However, on my laptop, when I am running acquisitions it tends to crash. So I prefer to use the full version later as I am working up my data.

Hope my experience (throwing out good data), helps others to not throw out good data with the bad.
Clear skies all!
Rick
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profbriannz 16.10
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Hi Schamks

Great question!

I have two rules of AP.

1) Always shoot first [and ask questions later].

2) Post all images.

As other folks in this post have correctly observed, gaining experience is vital.  And you never know what might turn up.

I always post to Astrobin. For me. it serves as a record of my attempts - and may also help others learn what is possible (and not) in less than ideal conditions.  For me, some of the most inspiring images posted on Astrobin by others , are those where the conditions were less than ideal.   It inspires me to "have a go" - and that it what this hobby is all about.

[But that is just me.  I have never liked "greatest hits" albums.  I have always wanted to hear/see all work - warts and all.  In that lies great beauty and significant learning]
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limeyx 1.20
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I have had ONE clear night in 2021, so right now I will take what I can get. However, I have to babysit my gear as it sits by the sidewalk and will get stolen if I leave it - I do have alarms on it but ... I am not going to get there in time to do much

Given this, I do try to pick the best day if I have 2-3 predicted clear days in a row. If it's a single good day and not too many meetings, I try to go for it

Without a GOTO mount, multi-night projects are tough, so I try to capture 4-6 hours in a single session if possible
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paolostivanin 0.00
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We don't have tons of clear nights during winter, but still what I do is:
  • are clouds still there at 21:30? If yes, then no imaging. I know that in my Bortle 7 zone with a stock DSLR I've gotta take tons of data. And I also know that I have to work the day after, so I usually don't stay up after 02:30 I'm working on automating the whole thing, but it will take time
  • transparency: I can estimate how good it is in my area, because I've watched how the constellations "disappear" with moon and/or light pollution. Also, I own a SQM reader now, so it's easier!
  • seeing: that's though to estimate for me. If I see that bright stars are twinkling near the zenith, then I setup everything do PA and hope for the better. If I see that stars close to where I'm shooting are twinkling, then I do PA and wait for the object to rise.
  • I post everything. I'm a newbie and I need all the feedback I can get
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wsg 11.24
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I think everyone should "automate"as much as they possibly can in order to save set up time.  Some have full rigs on rollers, others have tripods permanently placed, some have complete set ups ready to go in a garage.
I have 2 telescopes that are each out fitted permanently with dew heaters, cables and reducer/flatteners, so I don't have to put them together every clear night.
I now have the luxury of living out of town with a fenced yard so I have a pier and rig permanently mounted and covered 24/7, but I used to have just a tripod set up on cement pads that never moved.
I am now polar aligned and ready to shoot in around 5 minutes mostly because I still manually focus with a Bahtinov mask.
I shoot all the time.  I shoot in between rain storms.  I shoot during the full moon.  I Polar Align through clouds just to practice.  My images are not always good, but I don't want to miss an unpredicted clearing.  Chris Sullivan is correct

scott
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churmey 1.51
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I think it depends on if your having to manually set up every time, and the size of your equipment. For instance, if i'm shooting with a 100mm or smaller refractor on a light weight mount, i'd be inclined to set up and acquire data even if the clear window is only a few hours. One thing to note : Don't go by the ICSC data alone....it can be wrong. Compare what you see in ICSC against the cloud radar feature at weather.com within your local area. On more occasions than i can remember, one of the two can be wrong or not accurate. I've learned the cloud radar on weather.com (run the future model) is more accurate than ICSC.  My rule of thumb is, if both systems show clear, it's an all systems go.  If, on the other hand, I'm having to set up my RASA 11 on a CEM60, I want the majority of the night to be clear.  I tend to stay away from nights that have thin clouds showing consistently throughout the night as the data isn't that great and it tends to produce unusable data due to guiding issues.  Lastly, if all your wanting to do is gain practice, get out there every chance you can get and have fun.
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andreatax 7.22
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I image every single time there is a chance, even through thin clouds (that's UK for you). As I have everything set-up in the back garden that is relatively easy (still around half-hour wastage). And I have two rigs so I can pick and chose or run them concurrently.
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barnold84
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Due to the recent scarcity of clear skies (with that I mean even clear sky patches) in the recent months, I'll try to catch all the nights possible. 

Nevertheless, to me it's a hobby and I'm not doing it for winning prizes or competition but for enjoying the process of setting up the equipment, working with it and getting some photos out of it. So if there's a night when I feel that I just don't like getting out because it's too cold or whatever, I'll let this night pass.

In summary: shoot whenever you like, you shouldn't feel under pressure to get out. You'll know quickly by yourself when the weather isn't worth the effort to invest half an hour to 45 minutes to set everything up. If you see that the weather doesn't allow you to collect a lot of images, change to visual observation (the setup will be even quicker then).
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horrifiedonlooker 0.00
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I also shoot whenever I can. Living near Chicago we can go months without clear nights and the "good" nights often have poor seeing or transparency.
I usually set up my gear and watch it for a while then eventually go to sleep.  I use Sequence Generator Pro for imaging and with broken clouds it can end your session with a terminal error if you don't have your settings right.  I found this out the hard way, but you can tell it to "retry" repeatedly and it will recover the sequence when the sky is clear again. With it set up correctly, I've been able to sleep through partly cloudy nights and wake up to a directory full of images. Culling through them I can see the clouds approaching, overtaking then clearing out again. There's definite down-time when the clouds are around but at least it's been able to get some decent images and recover my imaging session most of the time, nothing’s 100%. 

Like others have also said, even on poor nights, it's good to keep your skills up to date, especially if clear nights are rare. It's easy to forget a lot of details when you haven't set up for months then you waste precious time reacquainting yourself during a genuinely good opportunity. On the marginal nights I’m on the fence though and I learned to tamp down my expectations, especially those nights with a thin layer of clouds where the sky looks clear but images don’t pick up fine details and guiding isn’t very good.
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FiZzZ 2.11
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I shoot whenever I can... dodging clouds, holding the wind, cracking cables for the cold and so on...
I am a total beginner so I consider my first equipment a bit “expendable” due the very probable mistakes I will do...
The rig is permanently installed on my balcony facing east, protected with a 365dd cover... this saves really a huge time setting up.
I generally start an imaging session if at the time of the dark hours the sky is clean or with just some little clouds.
then I leave everything unattended and sleep till the meridian flip
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rishigarrod 0.00
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I shoot with an OSC. I notice that if I try to wait for clear nights with no moon I can hardly do any imaging so a use a dual narrowband band filter which i use when there is a lot of moonlight.
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