Dust Motes on Flats - Forums

Topic starter

Jul 19, 2024

When I take flats at home they have 0 to maybe 2 dust motes. I keep my camera sensor and filters very clean and when I do clean them I am very careful and the results are good.

My new remote setup has flats that are showing 10-12 dust motes. Obviously I can't clean the sensor/filters as I am nearly 1000 miles away.

My question is how many dust motes are too many? In other words when will calibrated flats fail to even-out the sky background even if in other respects (exposure, temperature) the flats are OK?

Thanks!
Jerry

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John Hayes

Frequent contributor

Jul 19, 2024

In optical terms, you can’t have too many dust motes—at least up until more than about 40% of the total light is being blocked. If you’ve got a good filter wheel, flats will correct whatever motes you have in your system and they shouldn’t affect the quality of your images.

Operationally, it’s good to minimize dust. As you’ll discover, dirt gets EVERYWHERE in a remote installation so it is very important to seal everything as much as possible. Even the tiniest opening will eventually fill with dust. The related problem is that things at remote observatories are generally so dirty that it is very difficult to clean things in the field. Just taking something apart and exposing it to the air for a minute or two is enough to gather dust—almost no mater how careful you are to blow things clean before putting it all back together. The worst situation is when there’s a small opening that lets dust into your filter wheel (or camera) so that the dust motes change over time. Whenever possible, I use a high quality 3M, wide temperature range vinyl tape to seal the interface between components and that has worked really well to keep dust out. And I use a lot of it! To a casual observer walking through the observatory, my scopes look like they are simply taped together. The upshot is that my systems are completely dust tight and my flats last a REALLY long time—like for years.

Good luck with it Jerry!

John

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Jerry Gerber

Topic starter

Jul 19, 2024

John Hayes:
In optical terms, you can’t have too many dust motes—at least up until more than about 40% of the total light is being blocked. If you’ve got a good filter wheel, flats will correct whatever motes you have in your system and they shouldn’t affect the quality of your images.

Operationally, it’s good to minimize dust. As you’ll discover, dirt gets EVERYWHERE in a remote installation so it is very important to seal everything as much as possible. Even the tiniest opening will eventually fill with dust. The related problem is that things at remote observatories are generally so dirty that it is very difficult to clean things in the field. Just taking something apart and exposing it to the air for a minute or two is enough to gather dust—almost no mater how careful you are to blow things clean before putting it all back together. The worst situation is when there’s a small opening that lets dust into your filter wheel (or camera) so that the dust motes change over time. Whenever possible, I use a high quality 3M, wide temperature range vinyl tape to seal the interface between components and that has worked really well to keep dust out. And I use a lot of it! To a casual observer walking through the observatory, my scopes look like they are simply taped together. The upshot is that my systems are completely dust tight and my flats last a REALLY long time—like for years.

Good luck with it Jerry!

John

Hi John,

That makes sense, removing the camera to clean the sensor and filter wheel is going to inevitably introduce new dust because the environment itself is so dusty.
I'll ask the tech at Deep Space Remote to use the right tape to start sealing stuff off.

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Christian Bennich

Jul 19, 2024

John Hayes:
In optical terms, you can’t have too many dust motes—at least up until more than about 40% of the total light is being blocked. If you’ve got a good filter wheel, flats will correct whatever motes you have in your system and they shouldn’t affect the quality of your images.

Operationally, it’s good to minimize dust. As you’ll discover, dirt gets EVERYWHERE in a remote installation so it is very important to seal everything as much as possible. Even the tiniest opening will eventually fill with dust. The related problem is that things at remote observatories are generally so dirty that it is very difficult to clean things in the field. Just taking something apart and exposing it to the air for a minute or two is enough to gather dust—almost no mater how careful you are to blow things clean before putting it all back together. The worst situation is when there’s a small opening that lets dust into your filter wheel (or camera) so that the dust motes change over time. Whenever possible, I use a high quality 3M, wide temperature range vinyl tape to seal the interface between components and that has worked really well to keep dust out. And I use a lot of it! To a casual observer walking through the observatory, my scopes look like they are simply taped together. The upshot is that my systems are completely dust tight and my flats last a REALLY long time—like for years.

Good luck with it Jerry!

John

@John Hayes - do you simply "tape up" the connections?? Also the threaded ones?
I would really like to see a picture of it. It does seem like a simple and easy way to solve such a problem.

John Hayes

Frequent contributor

Jul 20, 2024

Here's a quick download of a couple of phone shots. The tape is only required on non-dust tight interfaces. It's hard to tell in the photos but there are multiple layers of tape to insure that everything is completely air tight.

John

Christian Bennich

Jul 20, 2024

John Hayes:
Here's a quick download of a couple of phone shots. The tape is only required on non-dust tight interfaces. It's hard to tell in the photos but there are multiple layers of tape to insure that everything is completely air tight.

John

thx, that does give a good impression of the solution 👍