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The ASI6200MM - the Lord of Light (leaks)?

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#1 xthestreams

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Posted 12 October 2021 - 12:53 AM

Heya everyone - I've been fortunate enough own the ASI6200MM for a few months now and have been slowly completing and tuning my image train. I've noticed a few issues with teh ZWO solution and I am wondering if;

a). I'm the only one?

b). whether QHY users have had it just as bad?

c). is this just "the way it is" in general?

 

I started by adding ZWO's EFW 7x2"50mm filter wheel (which bolts onto the chassis of the camera) and the new ZWO OAG (which surprisingly comes with an M48 aperture, so quick trip to the astro store for the M54 port.

 

First light and I quickly realised that the ZWO 2" mounted filters have some crazy reflection artefacts and also discovered that the M54 OAG light path (through eh stalk to teh OAG camera) was too narrow to be truly useful.

 

Off to purchase some Antlia 50mm unmounted filters and the ZWO introduced OAG-L shortly afterwards - giving me the opportunity to spend money twice - love this hobby! (note: the new OAG only comes with the M54 plate, I had by that time decided to go with an M68 image train to avoid creating shadows with the larger OAG prism, so yup - more money.) 

 

Finally, a working image train - or IS it?

 

I had been trying to diagnose a calibration problem with my OIII filters (flats/vignetting) when it occurred to me that perhaps I was dealign with a light leak - so set about testing by covering up the "light sucking" end of the OTA and a series of long darks frames when I noticed that there was indeed not one but at least three light leaks;

1). around the edge of the tilter (the M68 version has no protective foam unlike the M54 and M48 versions - this has been published elsewhere) - so I taped that up

2). around the upper back of the filter/camera body interface

 

I was getting ready to pack up when I swapped filters from the Ha I had been testing on (it was the last filter I'd used) to Lum (in preparation for testing OIII, not sure why I just did) and I saw a sudden jump in my ADU counts - there was another light leak, which brings me to;

 

3).  near or around the stalk of the OAG assembly - by this stage I had decided I was going to smother the thing in black tape so I can't yet be specific enough

 

Which brings me to my question - what the heck are these guys doing?! :-)

 

It's not like I am taking a domestic camera and using it for AP, I would expect light leaks, Im using it outside of it's design parameters - but this is an AP image train manufactured by the one company (so no blaming "the other guy" for messing up).

 

Don't get me wrong, I really love the camera, the data it produces, etc - but this is bordering on being unfit for purpose - it's hardly surprising so many beginners find the hobby hard, when they spend their hard earned on an integrated solution that basically won't enable them to get the results they need without some considerable troubleshooting skills (again to be clear, the tinkering is half the fun for me, but I can imagine a lot of people thinking it's them and not their equipment and giving up the hobby not realising they were probably on the right path, but they were let down).

 

I've recently been looking at the Moravian version of their IMX455 camera wondering if they've managed to narrow down the source of light to just the open end of the OTA :-)

 

p.s. my OIII "vignetting" problem persists, about to try out some new 3D printed masks from local supplier Testar who've been super helpful in trying to work this out 



#2 RogeZ

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Posted 12 October 2021 - 11:41 AM

It seems you have chosen parts incorrectly a couple of times; the 6200 used the now discountinued M68 OAG and nowadays the OAG-L.

The OAG-L comes with a “free” M48 plate but the 6200 includes the M54 plate.

I would recommend you read the camera’s manual.

#3 xthestreams

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Posted 12 October 2021 - 03:47 PM

Apologies Yiu are correct, I recall now that the reason I purchased the M54 plate was to use the OAG with my (now sold) ASI2600MC, which comes shipped with the M48. In that case it turns out you can’t attach the OAG directly to the camera body (even the OSC), you need an EFW.

 

thanks for the correction.



#4 RogeZ

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Posted 12 October 2021 - 05:46 PM

A FW or a FD, the M54 FD works really well.


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#5 xthestreams

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Posted 12 October 2021 - 06:19 PM

I wasn't sure if the M54 filter drawer would work - thanks for the tip!

 

So off the original topic, but related given you raised the need to RTFM - after finding out my M54 OAG wouldn't work with the ASI2600 I re-read all the ZWO manuals trying to determine how this might work, even going to the trouble of asking ZWO, who told me I needed to use an EFW - so I sold the colour camera and went back to mono and filter wheels! (this time with a 6200).

 

I'd love to hear other views, but for me ZWO's docs leave a lot to be desired.

 

Virtually none of the new products have any manuals and the web pages that describe them aren't completely clear (which is where I would normally turn to the manual) - as I write this;

- the EFW manual is for the old product

- the web page for the 2" EFWs fails to mention that they only mount to the newer 2600 & 6200 (2400?) cameras - there's some poor schmuck in teh Q&A section who found that out the hard way 

- there is no manual for the new OAG (at least that I could find) - again, it looks like a great product for someone looking to buy an OAG, but it's only going to work with ZWO cameras

- the ASI2600 manual states that you can use an OAG with the camera without a filter drawer, but it neglects to mention that it will only work with the OLD OAG (I guess this could be my fault for not considering that the term OAG is not being used generically here but specifically to refer to a model).

- as at current writing the OAG-L product description states that it comes with an M48 tilt panel when it in fact comes with an M54 (but not, for reasons that I don't completely understand, an M68 - which is what the old model used to be called, yet shipped with an M54 and you correctly pointed out).

 

Again, I love their cameras, I own a boat load of them - I just think a little more documentation wouldn't hurt

 

Back to the core topic - light leaks on the M54 filter drawer?



#6 RogeZ

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Posted 12 October 2021 - 06:51 PM

I think you need to read the “How to get 55mm of backfocus with ASI6200” page.

Also, you are incorrect in which adapter are included where. M68 came with no tilt plate, OAG-L comes with M48.
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#7 OldManSky

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Posted 12 October 2021 - 10:35 PM

As to the original topic...

I have to admit that I've never checked for light leaks in either of my ZWO camera setups (ASI183mm-pro with 8-pos EFW and ASI2600MC-Pro with ZWO 2" filter drawer).  I've never seen any in any of my images, though.

So it makes me wonder -- where is the light that is leaking in coming from?  I mean, it's dark outside when you're taking images, yes? 

Are these "testing in daytime" light leaks, and if so -- are they going to be a problem at night?  

In other words, do they actually matter?

 

Just wondering...



#8 xthestreams

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Posted 13 October 2021 - 01:58 AM

As to the original topic...

I have to admit that I've never checked for light leaks in either of my ZWO camera setups (ASI183mm-pro with 8-pos EFW and ASI2600MC-Pro with ZWO 2" filter drawer).  I've never seen any in any of my images, though.

So it makes me wonder -- where is the light that is leaking in coming from?  I mean, it's dark outside when you're taking images, yes? 

Are these "testing in daytime" light leaks, and if so -- are they going to be a problem at night?  

In other words, do they actually matter?

 

Just wondering...

GREAT question! I'm far from an expert on the topic, I used to read the posts by others on CN thinking "what kind of nutcase goes looking for light leaks, it's dark?!" - now I am that nutcase.

 

Like you I've owned both those image trains before and never really thought too much about it until I moved to the 6200 and the vendor suggested that the issue I was having with flat calibration (only of the OIII filter) might have been due to non-linear data (ie: a leak) during acquisition.

 

I needed to prove to them AND myself that the problem I was seeing had nothing to do with leaks - so I went for the most extreme option I could think of. 

 

1). So, yes, the testing for leaks was done during the day, mainly as I could not think of another way to test for leaks other than during the day (not without losing my mind)

 

2). Sooooo many places for light leaks during the night (not sure there are enough to matter, but I am trying to debug a problem so until it's eliminated as a variable, it's on the table)

a). my dome seems to be filled with loads of little LEDs that despite me thinking I've taped over them all, another appears (there's a whole CN thread containing my rant about Bisque putting 4 LEDs on their mounts! https://www.cloudyni...eds-everywhere/) - are they enough cause the problem, I dunno! (but I am seeing a pattern of me posting the occasional rant, seems i am a "letter to the editor" type and I didn't know it)

b). I live in a MPSAS 18.1/Bottle 8 zone - extraneous light is not something I am in short supply of - the Nexdome being white on teh inside allows incident light to bounce around

 

I would not imagine that these low levels of light pollution would be enough to create a serious problem, but i was also aware that my "dome" monitoring camera (being an ASI224MC) shows the inside of my dome as being near daylight with roughly 30 second frames - given the filter I was talking about is shooting for 600 seconds - any leak is likely to be amplified enormously (especially with the QE of the IMX455 being as good as it is)

 

So to follow up your question @OldManSky, are light leaks really that much of a problem that I need to be concerned about closing them off? 


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#9 OldManSky

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Posted 13 October 2021 - 08:39 AM

I didn't mean to imply you're a nutcase!  You might be, but I don't think that's relevant to the question... :)

 

I guess the answer to whether or not they're a problem depends on your 2. a) and 2. b) above.  Doesn't help having a white dome interior, I'm sure.  For me, despite having a few things in the observatory with LEDs, a light leak would only be a problem if I tried to take darks during the day with the roof open.  For you it may be different.  I was mostly just wondering...if the quest to find light leaks was to solve an actual problem or just academic...for you I say problem-solve away!

 

BTW I was watching a couple of observatory-building videos on YouTube the other day, and came across a gentleman from the UK, whose Rubbermaid-shed observatory was lined entirely with reflective-silver insulation panels...and I thought to myself, "geez, way to guarantee some spurious reflections and light leaks!"   So I do get it.

 

And good luck tracking 'em all down.


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#10 Rasfahan

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Posted 13 October 2021 - 04:02 PM

You‘re not alone (also not alone ranting about equipment… there‘s some long rants by me here somewhere, too).

 

The ZWO and QHY cameras and accessories really are the cheap end, it seems. I‘ve had light leaks that ruined O3 subs from the M68 OAG (past the guide cam, removed a window and pushed it further in), the M68 tilter plate (no rubber, attached a 3D printed shield from thingiverse), my 36mm filterwheel (past the filter holders, ordering 3D printed ones from buckeyestargazer fixed that) and from a missing part of my bought-used moonlite focuser (tape). The sensors of my 1600MM and ASI183MC were seriously tilted. But at least the ZWO cameras work. I’m on my 4th QHY294M, the whole sky time for them since last November is about 5 hours.

 

I‘m eyeing a Moravian, too, but waiting for reviews to come in.


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#11 rockstarbill

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Posted 14 October 2021 - 12:41 AM

I think you need to read the “How to get 55mm of backfocus with ASI6200” page.

Also, you are incorrect in which adapter are included where. M68 came with no tilt plate, OAG-L comes with M48.

Lol. Really helpful work here man.

Edited by rockstarbill, 14 October 2021 - 12:41 AM.

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#12 xthestreams

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Posted 14 October 2021 - 06:54 AM

Lol. Really helpful work here man.

 I know, but…. Anyways, I purchased the M68 guider, I cam tell you for certain it comes with an M48 tilt plate (why, oh why when it’s branded M68, but I guess that’s my point).

 

the M68 “large” comes with an M54, again, wha?!

 

manual, non existent 


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#13 ChrisWhite

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Posted 14 October 2021 - 07:35 AM

As long as you dont use the tilt plate I have found it to be a perfect light blocker whether you use the foam lined or the unlined plates.  I've never seen light leak around my prism stalk and I have not seen light leak in from between the FW and camera.  All three locations you are describing I have not had problems with.  Strange indeed if you are.  Did you retest flats after sealing up the areas you are suspicious of and see a resulting drop in ADU in a dark frame?

 

Best way to test for a light leak is to cap your OTA, and take dark frames.  30 seconds is enough.  Then shine a bright light at areas you are concerned about and take another dark frame for comparison.  This will be very obvious if you have a light leak problem. 


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#14 xthestreams

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Posted 14 October 2021 - 07:52 AM

Hey Chris, yup, tested for exactly that, a notable drop in ADU. I think it was 60,seconds though.

 

‘there’s an empty screw hole at the 12 o’clock position behind the filters that was certainly contributing, I am not sure where the other was, as mentioned I went bananas with black tape as it started to get really old really fast.

 

ive got some new masks to,replace the Buckeye versions, let’s see if they help, if not, I’ll do some more thorough research 


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#15 jerryyyyy

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Posted 29 October 2021 - 08:32 PM

Gentlemen,

 

Do you have some more room in your boat?

 

I got a ASI 6200M for my Stellarvue 130 a couple weeks ago and have been in light leak hell.... that trick with the darks led me to quickly tape my OAG/Tilt Plate.... but I have some terrible flats problems with my O-III Chroma.  The Chroma are unmounted with the "good" covers... may need better than good!

 

If it is still screwed up, I will post new images from tonight after the black tape extravaganza.

 

Does this look familiar!  Prior to taping:

 

2021-10-28 08_04_55-PixInsight.jpg


Edited by jerryyyyy, 29 October 2021 - 08:32 PM.


#16 Endymion

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Posted 30 October 2021 - 12:12 AM

jerryyyyy,

  It would help if you specified the type and order of items in your image train.   For reference, I have the following image train:

 

ASI6200MM -> 2" 7 Position ZWO FW -> M68 OAG -> M54 Tilt plate (pulled off the camera and moved here) -> M54 extenders -> ESATTO 2" Focuser -> C11 EDGEHD

 

I had a light leak at the M54 tilt plate.  This was due to both having the tilt plate not completely flat leaving gaps plus the way the tilt plate mates with the M68 OAG.   The foam gasket of the M54 tilt plate is not large enough in diameter to block the light in the M68 entrance to the OAG.   I fixed this by 3d printing an appropriate gasket that fits inside the M68 threads of the OAG and provides a surface for the M54 tilt plate foam gasket to contact.  I also flattened out my tilt plate since I didn't find I needed tilt correction.

 

The light leak was a problem when collecting my dark flats.   I take sky flats and get the darks right after the flats so the remaining sun light was an issue.

 

I haven't noticed any other light leaks.  I thought I had a leak on the OAG stem but after fixing the M54 tilt plate issue, I see no evidence of light leaks in my dark flats.

 

Hope this is helpful.

 

John



#17 jerryyyyy

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Posted 30 October 2021 - 11:03 AM

Thanks,

 

We seem to be in a similar boat (My flats from last night were not improved):

 

Please look at the image as it has the image train in detail... have been working on this for two weeks+ with Stellarvue and others.  It does not say but I have a Stellarvue 130T SVX.

 

The threading on the Stellarvue is unique in that it uses 69mm spacers and a field flattener but there is a 69mm adapter for the 68mm ZWO adapter.  The internal diameter is still 54mm.  Int interir ring was bright and was flocked to no avail. 

 

Everything up to the ZWO stuff worked flawlessly for years with an SBIG 8300M... but I wanted a new camera frown.gif

 

It sounds to me that the most likely suspect is some light leaks around the filters or elsewhere near the FW.  I have Chroma NB and Antilia LRGB (to save $).  But I get that same disk pretty much on all of them. Just the worst on the O-III, which has been flipped and rotated as suggested by the manufacturer.

 

Three senior astroimagers on Astrobin have taken pity on me... all have the camera... and they have it working on three different scopes... I will refer them here as maybe some communal brain can help.... Jon taped around his Tilt Plate and that definitely helped me.. but there is something else big going on. 

 

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  • 2021-10-30 08_45_13-Telescope Stellarvue ZWO Spacers 20211027.xlsx - Excel.jpg

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#18 hmaron

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Posted 30 October 2021 - 11:38 AM

External light leaks detection I found to be simple to do. It was a time consuming and labor intensive.  I use  3/4" 3M Super 88 black electrical tape. It leaves no residue and it comes off easily. It's "stretchy" so it really can wrap and seal contours well. The slightly thicker 88 grade tape is truly opaque but standard 3M tape would suffice, I feel. I have held the 88 up to the sun...it's opaque.

So.........I literally due a wrap on every "seam" in the train. FF to tube extender, extender to OAG, OAG to FW etc. etc. You can start higher in the train on the scope end or not (meaning focuser connection/juncture points...whatever you want) The most "difficult" wrap (which is easy) is where the adapter or device meets the FW or the FW meets the camera adapter because it's technically 90 degrees. But it seals.

 

I then take sequentially 60 sec darks during a sunny day with only one open "crack" at a time. It can be blatant when you see the dark. But even if it looks good I feel you have to compare them to a legitimate 60 second dark (taken at night and capped....or camera covered....whatever)  Look at them in PI stretched but take numeric readings randomly throughout the image.  I feel you need the 60 sec as a minimum......You're looking for leaks, right? So why not test with some sizable duration.

 

Oddly the only leak I had on my QHY600 train was where my Optec Sagitta OAG met my filter wheel. I found this odd because Optec uses a dovetail (which I love mechanically). But could it light leak? Surely possible, I thought But the telescope side of the Sagitta has the same dovetail and it showed no leak.  On the camera end of my OAG I use a Sagitta dovetail to 54mm threaded adapter to the QHY FW. So I have to conclude it was the threaded end. You wouldn't think a threaded adapter could leak.....but it did. So, I just keep a wrap of tape over that juncture always. Again, it comes off clean and in seconds and it takes seconds to wrap for those that take down their setup.

 

The amount of light we are talking about is negligible....but it's easy to find. it (BTW, I did this awhile ago and I can't even remember what the dark looked like but, if I think it had the appearance of a corner glow....but the numbers were higher in the field

 

All of this could be regarded as complete idiocy. I stand accused. But this method is rather easy if you want to waste an hour of a sunny day. You only do it once.

 

....and, yes, you can wrap the stalk areas of the OAG...whatever


Edited by hmaron, 30 October 2021 - 11:45 AM.

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#19 Endymion

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Posted 30 October 2021 - 11:57 AM

jerryyyyy,

  Your problem may not be light leaks (or only light leaks).  Your images look like what I see after a very wet night when I've forgotten to turn on the camera dew heater.   I get stuff like this for my flats.

 

2021 10 30 09 33 39 FlatWizard Ha  11.80 0.37s 0001
 
Are the images above the flats directly or the flats corrected by dark flats?  If the flats directly then I think you're seeing the dew issue.  What do the dark flats look like in the same environment you took the flats?  
 
John

Edited by Endymion, 30 October 2021 - 12:27 PM.


#20 Endymion

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Posted 30 October 2021 - 12:04 PM

jerryyyyy,

  Your image train is very close to mine.  You could be getting leaks through the interface between the plate of the tilt adapter and the OAG and then past the foam gasket as I mentioned above.  I suspect though that dew/moisture in the camera may be the biggest part of your flat problem.


Edited by Endymion, 30 October 2021 - 12:31 PM.


#21 jerryyyyy

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Posted 30 October 2021 - 03:30 PM

External light leaks detection I found to be simple to do. It was a time consuming and labor intensive.  I use  3/4" 3M Super 88 black electrical tape. It leaves no residue and it comes off easily. It's "stretchy" so it really can wrap and seal contours well. The slightly thicker 88 grade tape is truly opaque but standard 3M tape would suffice, I feel. I have held the 88 up to the sun...it's opaque.

So.........I literally due a wrap on every "seam" in the train. FF to tube extender, extender to OAG, OAG to FW etc. etc. You can start higher in the train on the scope end or not (meaning focuser connection/juncture points...whatever you want) The most "difficult" wrap (which is easy) is where the adapter or device meets the FW or the FW meets the camera adapter because it's technically 90 degrees. But it seals.

 

I then take sequentially 60 sec darks during a sunny day with only one open "crack" at a time. It can be blatant when you see the dark. But even if it looks good I feel you have to compare them to a legitimate 60 second dark (taken at night and capped....or camera covered....whatever)  Look at them in PI stretched but take numeric readings randomly throughout the image.  I feel you need the 60 sec as a minimum......You're looking for leaks, right? So why not test with some sizable duration.

 

Oddly the only leak I had on my QHY600 train was where my Optec Sagitta OAG met my filter wheel. I found this odd because Optec uses a dovetail (which I love mechanically). But could it light leak? Surely possible, I thought But the telescope side of the Sagitta has the same dovetail and it showed no leak.  On the camera end of my OAG I use a Sagitta dovetail to 54mm threaded adapter to the QHY FW. So I have to conclude it was the threaded end. You wouldn't think a threaded adapter could leak.....but it did. So, I just keep a wrap of tape over that juncture always. Again, it comes off clean and in seconds and it takes seconds to wrap for those that take down their setup.

 

The amount of light we are talking about is negligible....but it's easy to find. it (BTW, I did this awhile ago and I can't even remember what the dark looked like but, if I think it had the appearance of a corner glow....but the numbers were higher in the field

 

All of this could be regarded as complete idiocy. I stand accused. But this method is rather easy if you want to waste an hour of a sunny day. You only do it once.

 

....and, yes, you can wrap the stalk areas of the OAG...whatever

Thanks very much.  I will go back and do the 60s and have ordered that 3M tape... what I really need is a four leaf clover. 

 

I have the feeling this is in the filterwhel perhaps just the edges of the filters are not properly sealed.  There is a separate thread on this issue where some drastic measures were required:

 

https://www.cloudyni...ter/?p=10865578



#22 jerryyyyy

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Posted 30 October 2021 - 03:42 PM

 

jerryyyyy,

  Your problem may not be light leaks (or only light leaks).  Your images look like what I see after a very wet night when I've forgotten to turn on the camera dew heater.   I get stuff like this for my flats.

 

 
 
Are the images above the flats directly or the flats corrected by dark flats?  If the flats directly then I think you're seeing the dew issue.  What do the dark flats look like in the same environment you took the flats?  
 
John

 

Well, I am indeed in dew city near San Francisco but everything is very dry when I take the flats and the camera and OTA dew heaters are definitely on.  If you look at the O-III flat the edges of the artifact are crisp!

 

I thought it might be a reflection off the primary lens, which was pretty dirty, but after a stiff drink and a lot of hand holding from Stellarvue, I cleaned the lens... no help.  The insides of the parts are heavily flocked.... this journey has been going on for weeks. 

 

These are bias corrected flats... with the camera the dark noise is so low you get little (no) advantage to using darks... you add noise.... this is why I put up with this effort... the Chip really is great. The image is the Skull Nebula using the NB data unprocessed (cropped!).

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#23 jerryyyyy

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Posted 30 October 2021 - 03:51 PM

jerryyyyy,

  Your image train is very close to mine.  You could be getting leaks through the interface between the plate of the tilt adapter and the OAG and then past the foam gasket as I mentioned above.  I suspect though that dew/moisture in the camera may be the biggest part of your flat problem.

Yes, it is interesting that there are some little specs on the S-II center image, which I understand to be moisture which is there in the camera before the chip heater has time to kick in.  I recall there is some heater on the plate above the chip and the chip itself is cooled...  The S-II is the first flat done for dusk flats. 

 

As mentioned above that plate definitely had a light leak by the flashlight method of identification and it was taped for these images. 

 

After I get everyone's comments I will go back up and look at the system in more detail, especially the filters.  If there is a light leak around the edges of the filters I am screwed.  The Chroma NB filters look like little circular mirrors. 

 

Very complex all this... wish I had somebody who could make house calls.


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#24 Endymion

Endymion

    Mariner 2

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Posted 30 October 2021 - 04:00 PM

I use these filter masks https://agenaastro.c...ca_s_model=6435 to avoid light leaks around the filter edges.

 

John



#25 jerryyyyy

jerryyyyy

    Surveyor 1

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Posted 30 October 2021 - 08:20 PM

I use these filter masks https://agenaastro.c...ca_s_model=6435 to avoid light leaks around the filter edges.

 

John

Thanks,

 

These are exactly what I have on.  I was warned.  I am going tomorrow to check the screws on all of these.  Seemed to me that the 3mm filters were a good 1mm above the base of the filter wheel.  I hope the completely cover. I am going to try shining a flashlight into the filter (O-III) and see if there are light leaks around it.

 

The Stellarvue has on it a field flattener.  Others use it without problems with the ZWO, but I also have a focal reducer and I can switch that out.  Unfortunately I cannot remove everything from the image train because Stellarvue uses 69mm spacers....

 

Thanks again very much for the comments, every bit of information helps.

 

JY

 

PS  Despite all these problems the Chip in this camera is fantastic and the reason I put up with all this ??? engineering. Here is the Skull Nebula with the camera and the Stellarvue:

 

https://www.astrobin.com/m8oj8d/E/


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