22 replies to this topic

[Desertanimal]

Tl/dr version: Pics used to be good, now they suck. Dust moves. I’m lazy. How do you do it?

 

 

Some of this is specific to Astro Pixel Processor, other parts are generic questions. My setup consists of a Losmandy G11, Zenithstar 73, Focus cube, QHY533c, on mount Mele q3 mini computer. It’s all essentially permanent and I operate it remotely from indoors using Nina.

What I used to do used to work for multi night imaging, I’m talking within the last few months. I would pic a target, shoot a bunch of light frames for a couple or a few nights, collecting on average 12 ish hours of data we’ll say. During, before of after one of those nights I will shoot Darks and Bias frames. Likewise, one of those nights, maybe the same night, maybe not, I will shoot Flat frames. These are done with a tracing tablet and the Flat wizard in Nina. Usually goes very smoothly and quickly.  Now I have a bunch of light frames and all my calibration frames. I’d load those into APP, I would uncheck multi night box, and I’m off to the races, at least on to post processing. Picture would be as expected and I’d save it for photoshop later. 

 

NOW…..

The last couple of sessions of the same work flow I get horrible “dust mote” looking circles in the completed stack out of APP. Like I didn’t use any flats. Keep in mind I’m in Tucson so dew isn’t a thing. Well, wasn’t. Lately however, it’s been quite cold and wet. Am I seeing dew/frost, dust in a new spot because of dew etc? What it is isn’t that important I don’t think, what is important is the fact that the flats I took maybe two nights ago are not correcting for the “stuff” and it’s new position tonight. Does that make sense? Also I’ll point out during one of these multi night sessions nothing in the image train is moved except for focus changes.

 

To rule out anything really odd, the other night I shot my Lights, and all calibrations in one evening. Into APP and out comes a good picture. So I’m thinking my thoughts above are correct. 

 

So what is your work flow for multi night sessions? Do you take flat frames every night? If so, when do you do them, before, during, after the session? My flats are not automated so I don’t want to go out in the middle of the night to do them, yeah I’m lazy. 

Also for you peeps using Astro Pixel Processor, how do you load the multi night subs into the software? It’s not super easy finding a lot of instructions for APP.

 

Sorry this is long winded, but I certainly appreciate all the help I receive from all of you.

 

Chris

[pedxing]

I take flats for each session, either immediately before tearing down or if I'm staying set up, in the morning. Flats are quick and easy enough that I haven't considered not taking new ones for each session.

I re-use a library of master darks and biases for about 6-9 months.

[Desertanimal]

I’m thinking I might try to go the morning route and see how that works with my schedule.

[choward94002]

IMHO flats should be taken at the end of the session, not before ... why?  There are two types of dust that you're dealing with, the first is the "sticky" kind that won't move when the scope changes orientation; that kind the flat time doesn't matter.  The other kind is the airborne "floating" dust that when your telescope moves around will also move around, like a snow globe.  During the day that dust will settle, so a flat taken in the evening won't show those floaters ... but during imaging those floaters will wander around.  By taking your flat at the end of the session you have a better chance of catching those floaters ...

[don314]

I’m in New Jersey, use a 100mm refactor, OAG, FW, ASI2600.  I never take the camera off the OTA.  I set up and tear down each night.  I shoot flats perhaps once every few months (mainly if I rotate the camera), I don’t have any problems with them.  I use a dew shield and dew heater, so never have dew problems with the lens.  Have had dew/frost on the outside of the OTA and on the mount.  I shoot darks and flat darks about every 6 months (the camera dark current does not change radically, so most people only shoot darks, flat dark, bias once or twice a year).  I use SGP and Pixinsight for everything.   When I assembled the camera, FW, OAG, I was super careful to be sure there were no loose dust particles in the assembly or on the sensor or filters.  My flats basically only show vignetting with no dust spots.  Not sure why you’re having problems.  If you’re not using a dew heater, consider getting one.

[Psychlist1972]

You have a cooled camera. Instead of taking imaging time taking darks and biases, build a dark library. These can be used for a full season, if not a full year. Just take at your usual temperature and the variety of exposures you normally take. 

 

This is assuming you keep temperature/gain/offset relatively stable over time.

 

Pete

[don314]

I might add that after each night of imaging, I make calibrated and cosmetically corrected (_c_cc) files, blink them, then save them.  After I have enough hours on a target I SFS the _c_cc files, the integrate them.  This way if I have a problem I know right away.

[Psychlist1972]

Oh, and I group flats and lights by "session". I've built a NINA plugin to make that easier, but it's also easy enough to just use the "date -12 hours" value as a group.

 

Then, I bring those into PixInsight and group flats and lights on that same value (and also by filter).

 

Pete

[mehresman2]

Have you tried cleaning your optics?

[arbit]

Oh, and I group flats and lights by "session". I've built a NINA plugin to make that easier, but it's also easy enough to just use the "date -12 hours" value as a group.

Then, I bring those into PixInsight and group flats and lights on that same value (and also by filter).

Pete

Hi, I know OT, but which plugin is it? Couldn't seem to find it in NINA.

Also, how is the "date-12hours" implemented? Couldn't seem to do that in WBPP (if that's what you were referring to).

Thanks in advance

Sent from my SM-S908E using Tapatalk

Edited by arbit, 26 January 2023 - 10:47 PM.

[Desertanimal]

You have a cooled camera. Instead of taking imaging time taking darks and biases, build a dark library. These can be used for a full season, if not a full year. Just take at your usual temperature and the variety of exposures you normally take. 

 

This is assuming you keep temperature/gain/offset relatively stable over time.

 

Pete

I will keep the darks and bias sometimes, if I’ve done a recent run with that exposure. I’ve been playing with a new L-extreme filter so it has mixed up my times some. But yes, I do save them for a bit, not 6 months thouogh.

 

Have you tried cleaning your optics?

Other than an air blower, no.

[dswtan]

I'm similar to OP but don't have the problems. In fact, I'm even lazier -- with good (for me) results. Sorry!

 

- Effectively permanently mounted, only cables to connect each night.

- I took darks, um, maybe a year ago.

- My cameras require flat darks not biases.

- Every few weeks, ideally only forced by an optical train change, I will take flats and flat-darks, when cloudy if possible. Amazon $40 flat panel. T-shirt.

- I collect subs on a target or set of targets for a week, or sometimes a few weeks. I process per target, with the most recent set of flats/flat darks, per the optical train used.

- I dump everything into WBPP in PixInsight. I generally Blink first for anything really gross or to spot equipment issues.

 

That's it.

[Desertanimal]

I'm similar to OP but don't have the problems. In fact, I'm even lazier -- with good (for me) results. Sorry!

 

- Effectively permanently mounted, only cables to connect each night.

- I took darks, um, maybe a year ago.

- My cameras require flat darks not biases.

- Every few weeks, ideally only forced by an optical train change, I will take flats and flat-darks, when cloudy if possible. Amazon $40 flat panel. T-shirt.

- I collect subs on a target or set of targets for a week, or sometimes a few weeks. I process per target, with the most recent set of flats/flat darks, per the optical train used.

- I dump everything into WBPP in PixInsight. I generally Blink first for anything really gross or to spot equipment issues.

 

That's it.

Do you deal with dew? That worked before, now no.

[Psychlist1972]

Hi, I know OT, but which plugin is it? Couldn't seem to find it in NINA.

Also, how is the "date-12hours" implemented? Couldn't seem to do that in WBPP (if that's what you were referring to).

Thanks in advance

Sent from my SM-S908E using Tapatalk

The plugin is for NINA 3.0. So I'm using it myself a bit to test to make sure it's good before foisting it on others. NINA 3.0 is still in preview. It adds some file naming patterns, but also sets the FITS OBS_ID keyword.

 

Date-12: in NINA today, in your file naming pattern, add either a folder named Session_$$DATEMINUS12$$ or add that to the file name itself. Both work. The word "Session" here is the grouping keyword. PixInsight looks for Keyword_Value pairs in directory or file names, and makes them available for grouping just as through they were FITS keywords. Then, on the right in WBPP, you add "Session" to the grouping keywords (You have to check the "Grouping Keywords" checkbox above it first.

If you do that, you'll see it reflected in the treeviews for your Flats and Lights, and in the calibration tab, you'll be able to see which lights are calibrating with which flats.

 

Pete

[Psychlist1972]

Have you tried cleaning your optics?

Unless you dropped the scope in the mud, this often makes things worse, within reason. Most of the dust you see is on the camera sensor, the filters, and if used, the flattener. Futher up the OTA, they tend to be super blurry and nearly invisible. Sometimes you can still see them, but that would be like when a bird drops a fat one right on the objective.

Pete

[arbit]

I'm semi permanent, in the sense that the imaging trains stay asis on the scope for a long time.

Dark libraries are obviously a tine saver.

Flats vary. They can last for weeks, except when you get dust in. This imaging season I have had problems with dust due to nearby construction, so am taking flats daily.

Routine is take them the next morning after the imaging run, sky flats with a perspex sheet as diffuser.

Use Sharpcap Capture Flats, which makes a master flat automatically with either dark flats (either manual or with a dark filter) or bias (automatic 1 ms exposures) as desired. You can also save individual flat files if you want. Takes just a couple of minutes.

Sent from my SM-S908E using Tapatalk

Edited by arbit, 27 January 2023 - 12:56 AM.

[arbit]

The plugin is for NINA 3.0. So I'm using it myself a bit to test to make sure it's good before foisting it on others. NINA 3.0 is still in preview. It adds some file naming patterns, but also sets the FITS OBS_ID keyword.

Date-12: in NINA today, in your file naming pattern, add either a folder named Session_$$DATEMINUS12$$ or add that to the file name itself. Both work. The word "Session" here is the grouping keyword. PixInsight looks for Keyword_Value pairs in directory or file names, and makes them available for grouping just as through they were FITS keywords. Then, on the right in WBPP, you add "Session" to the grouping keywords (You have to check the "Grouping Keywords" checkbox above it first.

If you do that, you'll see it reflected in the treeviews for your Flats and Lights, and in the calibration tab, you'll be able to see which lights are calibrating with which flats.

Pete

Hi,

Okay, the NINA 3 part explains it.

Thanks for the details on the filename in NINA. I currently do a batch rename of the image files with PowerRename (Win powertoys), to add the session number and get it ready for WBPP, but this is so much better.

Thanks a lot.

Sent from my SM-S908E using Tapatalk

[Psychlist1972]

Hi,

Okay, the NINA 3 part explains it.

Thanks for the details on the filename in NINA. I currently do a batch rename of the image files with PowerRename (Win powertoys), to add the session number and get it ready for WBPP, but this is so much better.

Thanks a lot.

Sent from my SM-S908E using Tapatalk

I'll tell Clint (the dev who created Powertoys) that Powertoys has another fun use

Pete

[dswtan]

Do you deal with dew? That worked before, now no.

Northern California winters can get dewy, though the summers are admittedly essentially dew-free.

 

On my EdgeHD 8 I have the Celestron heater ring and (somewhat) integrated dew shield. No issues. On my refractors I use one of those cheap Amazon 5V USB velcro straps with no issues and their integrated shields.

Coincidentally I have recently run into a strange growing HFR issue, but it's different to your symptoms. I'll mention it in case it inspires...

 

My current theory is the camera desiccant tablets need refreshing/cooking. I think one of my ASI294MMs is frosting up. My normal HFR on the EdgeHD 8 in my skies is 3-something. I've seen it creep up at strange times, and then increasingly often -- I was getting 6-8, WTH!

 

I thought it was a focus issue at first, and tightened up the autofocus. Happened before. Didn't cure it this time. Realized today I could diagnose next by swapping out the camera since I run two ASI294MM rigs normally, but currently one is resting while I'm taking the comet with an OSC. So I just did that tonight, using the second ASI294MM. Bingo! I'm back to my 3-something HFRs. Time to cook the desiccant tablets on the original cam! Will do the other one too while I'm at it.

[Desertanimal]

That inspires, I hadn’t thought About the desiccant. I’ll check that out.

[AnotherMoneyPit]

IMHO flats should be taken at the end of the session, not before ... why?  There are two types of dust that you're dealing with, the first is the "sticky" kind that won't move when the scope changes orientation; that kind the flat time doesn't matter.  The other kind is the airborne "floating" dust that when your telescope moves around will also move around, like a snow globe.  During the day that dust will settle, so a flat taken in the evening won't show those floaters ... but during imaging those floaters will wander around.  By taking your flat at the end of the session you have a better chance of catching those floaters ...

If they're floating, doesn't that imply that at any point in time that you take your flats, you won't be accurately capturing the state of your optics? If there was dust not yet settled during your imaging, and you correct for it once it has, doesn't your correction become an anomoly? And if the dust is so light that it behaves in the manner you suggest, isn't it also light enough to dramatically change in amount and / or distribution from virtually any input? 

[Psychlist1972]

IMO, the main reason to prefer flats at the end of the session instead of beginning, is you are likely closer to the average focus you had during imaging. This is especially true if you tear down equipment between sessions.

 

Pete

[choward94002]

If they're floating, doesn't that imply that at any point in time that you take your flats, you won't be accurately capturing the state of your optics? If there was dust not yet settled during your imaging, and you correct for it once it has, doesn't your correction become an anomoly? And if the dust is so light that it behaves in the manner you suggest, isn't it also light enough to dramatically change in amount and / or distribution from virtually any input? 

No; dust motes only become an issue when they are very close to the imaging focal point, otherwise they are microscopic ... while they are floating they are essentially harmless

 

As you surmise, the decision on when to take the flats depends on how the equipment is used ... in my situation the "home" position for my scopes is nose down to the ground, tail vertical and so they sit for most of the day.  That means that any floaters will be settling on the inside of the corrector plate.  When I image it's in an arc within 45deg of zenith, so now the scope is essentially upended and the floaters migrate down the the optics through the night

 

When I take my flats the scopes (slowly) move to a horizontal orientation to aim at a flat screen mounted a few dozen yards away, which likely dislodges some motes and again cause artifacts

 

If I were to take my flats at the beginning of the session, the floaters are just beginning the journey from corrector plate to imaging optics and are harmless ... so the flats will be clear, but as the imaging session continues those floaters will settle and I'll get artifacts

 

If I take the flats at the end of the imaging session, after the floaters have settled then the flats will have all of those ... but images taken at the beginning of the session won't have those motes, so the flats will be incorrect and I'll get artifacts

 

The situation would be made worse, of course, if I did meridian flips where the scope would act like a shaken snowglobe and flats taken at any time would be flawed

 

In my processing I've found that I get less artifacts with flats taken at the end of the session rather than at the beginning ...