To cap or not to cap?

[Mike Dodd]

I'm looking for some experienced advice about capping the telescope between imaging sessions.

I have a 5" f/7 APO in a roll-off roof observatory. At my former home, the observatory was 50 feet from the house, and did not have a motorized roof, so I walked out in the evening to uncap the OTA and roll the roof open. In the morning, I closed-up everything.

The new observatory is 300 feet away, and I have a motorized roof opener, so I can do everything from inside the house -- except cap the telescope. I can think of three options:

1. Build a motorized lens cap controlled by an Arduino single-board computer, and operated remotely via Ethernet. (Or perhaps I could control the lens cap with an auxiliary relay contact on my Foster ROR controller.)
2. Walk to the observatory to uncap/cap the OTA before/after every session.
3. Leave the OTA uncapped most of the time, capping it only when several nights of clouds are forecast.

The observatory is not sealed, so dust can infiltrate around the roof and through the screened floor gap around the pier. I don't think there's a lot of dust in fall/winter, but pollen and dust are present in spring/summer. In those seasons, I think the OTA should be capped whenever it's not actually imaging.

What is the common wisdom about capping or not capping the telescope in a remote observatory? Any recommendations on what I should do?

Thanks.

--- Mike
http://astronomy.mdodd.com

[Colin Haig]

You might check out the Flip Flat.

https://optecinc.com/astronomy/catal...k/flipflat.htm
It's not exactly what you want, but may serve 2 purposes.
(I don't have one, but know a couple folks do).

My RASA gets manually capped the morning after a run if the WX looks like it will be bad for a few days. Yes, I have forgotten a couple times.

[Mike Dodd]

I considered Flip-Flat, but don't want to spend the big money. For flats, I'll use either sky flats or an LED light box that's fairly flat. I can make a motorized lens cap, but I was asking for common wisdom before I undertake that project.

--- Mike