Shooting images through window pane glass

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Discussion Overview

The discussion revolves around the transparency and optical qualities of pane glass used in a domed observatory, particularly in relation to the use of a wind screen for air stability during astronomical observations. Participants explore the implications of glass quality on imaging and the potential need for alternative materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the transparency of pane glass, suggesting it may be around 70-80%, and raises concerns about its impact on CCD camera performance for astrometry.
  • Another participant notes that the optical qualities of window panes, such as flatness and coatings, may introduce color errors, which could be more significant than transparency issues.
  • A historical example is provided where an observatory used a removable Mylar window to maintain optical quality in extreme temperatures, suggesting that alternatives to standard glass may be beneficial.
  • A later reply indicates that the original question about glass transparency is no longer relevant due to limitations with the shutter control circuit card.

Areas of Agreement / Disagreement

Participants express differing views on the importance of transparency versus other optical qualities of glass. There is no consensus on the best approach to take regarding the use of the wind screen or the type of glass for optimal imaging.

Contextual Notes

Limitations include the lack of specific measurements for glass transparency and the potential effects of temperature differences and dirt on imaging quality, which remain unresolved.

solarblast
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For a simple starter, I'm curious what the transparency of pane glass is.

Moreover, we have a domed observatory and one of the two shutters (lower) has a common window pane about 3' on a side. In fact, there are three elements of the shutter area; upper, lower, and a wind screen (below the lower shutter). Typically, we do not use the wind screen. When used it can be attached to the lower shutter, and drawn up from a spool on which the screen is wound. In this format, it has the advantage of keeping air from circulating into the dome, and providing air stability.

It recently was brought to my attention that maybe the wind screen should be in use because of the stability just mentioned. However, that may not be good if the window transparency is say 70-80%. The CCD camera on the telescope is use for astrometry, so b/w is fine. No need for color photography. However, it may be that the glass might flex when the inside and outside temps are different. Possibly dirt on the window may be a factor. I have do idea yet if this would cause trouble.

Comments are welcome any of this?
 
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Hi, I don't have any input to your questions but I was curious to see an image of your observatory with the wind screen from the description.
 
The problem with window panes are other optical qualities (the big problem is not transparency but that they aren't flat, not coated, introduce color errors etc.) compared with optics. One could use optical quality glass but that would be very expensive.

Many years ago a guy in Kalix in northern Sweden built an observatory with a removable Mylar "window" so that he could observe when the temperature outside is -40 degrees C or colder. Mylar can have quite decent optical quality (see http://www.jstor.org/discover/10.2307/40680382?uid=3738984&uid=2&uid=4&sid=21102282123167 ).
 
Thanks. Yes, I recall the mylar approach.

As it turns out, my question is defunct. A circuit card that controls the shutter is more limited than I thought.

I have no photo of the wind screen in the proper position. I am providing one when it was out of the box that contained it.
 

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  • LanphierWindScreen 005.jpg
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