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How Light Proof is your dome

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#1 hmaron

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Posted 10 June 2021 - 05:54 PM

Has anybody found a light proof dome? So, is complete darkness achievable during the day in any known manufacturer (assuming the installation is handled carefully). What about my question as it relates to a night sky. My motivation for asking this is from the standpoint of achieving suitable Darks with shutterless cameras when operating remotely. I suspect many are "dark enough" when closed at night particularly with a NB filter in place. But during daylight?
Just curious. I was particularly interested in Ashdome and my specifically ask them. Thx

#2 TOMDEY

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Posted 10 June 2021 - 06:29 PM

Interesting problem!

 

Completely dark rooms of any kind are rare unless you design for that right from the beginning. Even our aerospace optics labs at work. First thing we would do when moving into a new lab was to plug the light leaks, which we found all over the place. At first blush, turn off all the lights and things look acceptable. Then sit in the dark for fifteen minutes and leaks show up all over. Door cracks, even the dropped ceilings glowed in the dark. To the extent where I had a couple of techs pop all the panels, paint them black, and pop them back in. Rolls of black duct tape, covering any/all instrument lights etc. We finished up by hanging black velvet on all the walls before anyone could tell us not to.

 

Observatories would generally be far worse. A completely light-sealed dome... I'd say your chances are asymptotically close to zero. The only pragmatic approach is to buy what functions the best to keep out weather and open/close reliably. And then address the light leaks yourself.

 

Helpful also is a panel on the dome that is flat black. At least point your instruments at that for the darks.

 

External light traps are a big topic in coronagraphs. I did a lot of that back when I was doing (ironically) lighting design and development work for ITT and GE. A totally dark room is kinda Zen/transcendental/yin-yang --- the beauty of a complete lack of something --- in this case light!    Tom



#3 kathyastro

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Posted 10 June 2021 - 06:30 PM

I wouldn't try darks in my Exploradome in the daytime with a shutterless camera without an aperture cap in place.  There is quite a bit of light leakage under the rotation ring and at the edges of the shutters. 

 

I have most of the indicator lights on my equipment taped over, but not all of them.  So night-time darks would be better, but not perfect.


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#4 TeslaTrek

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Posted 10 June 2021 - 06:55 PM

My TI dome, made from fiberglass, was not opaque to sunlight let alone areas where the dome quadrants met.  In fact, I had set up an LED projector that received the night sky from Stellarium and bounced that image off a plastic convex mirror (the kind you may have seen in the corner of a drug store near the ceiling) and projected it onto the inside of the dome.   I could barely see the projected stars during the day due to the light, but at night it was great.



#5 hmaron

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Posted 10 June 2021 - 10:47 PM

I knew my question was hopefully naive. I actually just submitted the question directly to Ashdome for the 16 footer I am purchasing specifically wondering also about shutter preference in this regard. Though not a deal breaker i personally am disturbed by the increasing trend toward shutterless cameras. Call me old fashion. I own a QHY600 for example. Yet, to my knowledge Moravian is the only producer building a IMX455 camera with a shutter. The value to me strickly concerns darks. I have no belief otherwise that mechanical shutters are superior. All problems are solvable. None of this is insurmountable. I do really appreciate the responses.

Edited by hmaron, 10 June 2021 - 10:49 PM.


#6 TOMDEY

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Posted 11 June 2021 - 12:32 AM

Another approach is to introduce an up-stream shutter/cap reasonably close to the camera. Maybe something like an opaque plug in one filter wheel slot. So you go to that slot for your darks. Sure beats demanding that the entire observatory be completely dark.    Tom


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#7 hmaron

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Posted 11 June 2021 - 09:55 AM

Another approach is to introduce an up-stream shutter/cap reasonably close to the camera. Maybe something like an opaque plug in one filter wheel slot. So you go to that slot for your darks. Sure beats demanding that the entire observatory be completely dark.    Tom


Absolutely! Unfortunately, like most I "need" all 7 of my FW slots. (8 would be glorious). One solution is to never shoot WB in LRGB, rather RGB and permanently sacrifice the L slot to the dark on. (actually the LRGB vs RGB is and interesting debate with several important pros and cons). The other is a little super efficient technique I am working on that I hope I will be able to report favorably on soon.
Thanks.

When one builds something from the ground up, so to speak, I find I tend to "want" to go for everything in the ideal. Then there is reality. Given my age, this is my last and final shot at the perfect observatory. I wish there was such a thing.

I might start the dream observatory wish list thread.

#8 John Fitzgerald

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Posted 11 June 2021 - 10:36 AM

If a dome was made light tight, I doubt that the shutter and rotation would still function at all.



#9 Christopher Erickson

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Posted 11 June 2021 - 09:38 PM

I worry way more about observatories being rain-proof and bug-proof.

 

If your cam doesn't have a shutter for doing darks, investigate getting a robotic OTA shutter.

 

https://www.optecinc...nitak/index.htm

 

https://www.baader-p...d-shutters.html

 

https://optcorp.com/...copes-prishu600

 

Or bag your OTA for darks, if you can.

 

Or pick dark, moonless nights for darks.



#10 hmaron

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Posted 12 June 2021 - 09:35 AM

My scope does have such a shutter system. That is merely to protect the mirror. Note the baffle is open. BTW, the dark moonless nights "probably is adequate" particularly with an Ha filter in the slot. But I always wonder. I like occupying the night with lights too. So my automation is one that obtains Dawn Cals.....Darks. Believe it or not it is complex to do (but doable) in ACP (with Scheduler) because Scheduler is always ready to "go" and dispatch plans during any and all periods of darkness. This is when operating fully automated, of course. Everything is doable when you're there.

Edited by hmaron, 12 June 2021 - 09:46 AM.

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#11 xthestreams

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Posted 15 June 2021 - 07:41 AM

I am starting to prefer a Moravian for my 455 camera for this reason alone!



#12 hmaron

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Posted 15 June 2021 - 09:24 AM

I am starting to prefer a Moravian for my 455 camera for this reason alone!

I feel the same. I have the QHY600. After owning it, I mentioned on one thread that I feel disadvantaged with the lack of a shutter and regret not purchasing the Moravian. (I don't believe the Moravian was released at the time of my purchase ).  I was met with some odd responses like, "Just to take Darks???"  Yes, just to take darks!  To me that's a big deal particularly for those of us that operate automated or semi-such,

 

Moravian is a very European oriented company. Thus people in the US are hesitant. (Unlike QHY they don't have any service resources in the US....at least I'm told QHY does)  But I only hear nothing but accolades from customers.  The Moravian also has a cube profile which might be a negative to the RASA users. I think Moravian makes available the industrial grade IMX455, identical to the one QHY uses, rather than the consumer grade sensor used in the ASI/ZWO-6200.  That matters (to me). So.....I'd go Moravian in hindsight. Their website is very cool and informative.


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#13 xthestreams

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Posted 15 June 2021 - 11:59 PM

Yeah, if you’ve not run remote before it’s easy to underestimate the value of a shutter for darks (even for guiding). I’ve tried using a metal disc for blockout and it works well, provided your image train is light proof, but sadly most of the 2” filter wheels are 7 position only, leaving no room for NII or a blackout.

 

The positive seems to be that CMOS seems to suffer less from some of the defects that made refreshing darks a more frequent problem with CCD meaning you should be able to capture them prior to or during commissioning and annual services, assuming you don’t change your exposure times, dark scaling isn’t so good with CMOS in my experience, perhaps the QHY600 is better?



#14 hmaron

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Posted 16 June 2021 - 12:12 PM

My thought process exactly.  
Wish I had that 8th slot.



#15 xthestreams

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Posted 17 June 2021 - 01:21 AM

FLI Centerline is your friend!



#16 hmaron

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Posted 17 June 2021 - 10:29 AM

The Centerline is a brilliant and a colossal piece of equipment. I have to say 10 slots is overkill but that's what happens when you overlap 2 5-slot wheels as they have done. 

FLI puzzles me. They canceled production of their CFW 7-10 (which thankfully I already own). Why?  I think, though few in numbers, there will be  medium format shooters needing the 65mm square filters. 



#17 xthestreams

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Posted 17 June 2021 - 08:05 PM

That is a big filter!

 

I’m guessing that FLI are going down the same path as Apogee/Andor. Ultra high end, scientific. That would make the case for a 65mm or,larger more likely than not, so my guess could be wrong. 



#18 hmaron

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Posted 18 June 2021 - 10:41 AM

That is a big filter!

 

I’m guessing that FLI are going down the same path as Apogee/Andor. Ultra high end, scientific. That would make the case for a 65mm or,larger more likely than not, so my guess could be wrong. 

I'm not exactly following your point. Or are we agreeing? Why did they discontinue production now? It would seem that there will be more people, such as myself, moving toward medium format sensors. I am not saying these FW's will sell lot hotcakes. But they never did nor will there ever be a big market for sensors dependent on 65mm filters. But why discontinue it now? There used to be crazy size sensors like the GSense6060. But now you have QHY offering both the 411 and the 461 and more on the way.

Yes, the filters and the FW isn huge. I refer to my FLI CFW10-7 as the cocktail table.


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#19 xthestreams

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Posted 18 June 2021 - 05:07 PM

Agreeing, by a small detour of me disagreeing with myself! ;-) 

 

I haven’t checked with Andor recently, do they even do filter wheels any more? Perhaps in the high end imaging world (biosciences etc) it’s a different business model. 
 

I hope FLI continues to make cocktail tabes, it’s great to have a flagship provider out there.



#20 hmaron

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Posted Yesterday, 12:32 PM

Here's the irony. If you buy FLI you almost automatically get a shutter or option for one. I would stick with FLI as a company but their menu of sensors is more limited with respect to the sensors I am currently favoring. Where am I going with this? Well, assuming I acquire the IMX411 then it looks like it will be QHY by default. Thus I sure would have liked it if my so-called current cocktail table had that darn 8th slot for the "blank". Oh well. There's always a workaround.


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#21 xthestreams

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Posted Yesterday, 06:19 PM

Back to blacking out the dome sufficient for quality darks, safe to say, it’s not happening!




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