Thermal Equilibrium - Telescope Position / Caps

[Peter_D]

Hi,

I have a 114mm Newtonian and a 102mm Mak.

What position should they be in when they are left outside to achieve thermal equilibrium? Should they be mounted on their respective tripods?

Also, should the lens / dust caps be left on or off?

Should any attachments be removed from the back of the Mak?

Thanks for any photos, guidance or advice!

Peter

[John]

Removing the caps is always a good idea to let warm air escape from the tube easier.

Pointing the mak towards the ground will help ensure that warm air escapes through the rear port. A mirror diagonal can be left in place but a prism diagonal should be removed to aid warm air escape. I do this with refractors as well.

The newtonian should be pointed with the large aperture pointing towards the sky but not necessarily vertical to avoid the chances of anything dropping down the tube and onto the mirror.

 

[Peter_D]

Many thanks John for the prompt response and the great advice - just what I wanted!

[RT65CB-SWL]

Following on from @John comments; when packing your equipment away for the evening and back indoors; unpack everything again and leave it to dry overnight, (not near a heat source), or for a few hours while you get some rest/sleep. Then when you recover/wake up, your equipment should be dry, both inside and out, ready for repacking. Remember to remove the caps, and leave them out to dry.

If you can obtain any used 35mm film canisters; drill a few small holes in the base of them ---> insert a few sachets of Silica Gel/desiccant crystals ---> replace lid ---> place it in focusser. They are the correct size for 1.25" and will help removing any moisture within the OTA. When the crystals have changed colour, then you know they have absorbed the moisture and will need to be replaced or recharged, (i.e. on a baking tray in a conventional oven or non-metallic tray if using a microwave oven)... 

...alternatively you can buy this --->https://www.firstlightoptics.com/astronomy-optics-cleaning-protection/flo-125-2-inch-desiccant-cap.html 

 

Edited August 21, 2019 by Philip R