SCT scope temperature and seeing

[Mai Ai Bing]

Newbie question here. I understand the need to ensure relative equal temperature within the SCT and the ambient temperature. However, I always leave my photo gear outside in a sealed bag for a few hours before shooting in extreme humid, hot or cold weather, sometimes with some added Scilica gels bags. Any reason not to do the same with the scope and be rid of any problems with unwanted air flow.

[Alkaid]

Absolutely, it is a necessity.  I put my SCT into a large plastic storage box and then cover it over with a waterproof bike cover (in case of any unforseen rain showers).  I leave it outside for a few hours before observing. Works well.

[Mai Ai Bing]

13 hours ago, Alkaid said:

Absolutely, it is a necessity.  I put my SCT into a large plastic storage box and then cover it over with a waterproof bike cover (in case of any unforseen rain showers).  I leave it outside for a few hours before observing. Works well.

Thanks! I thought so.  Just wondered when reading so many "complain" about bad seeing because of scope airflow, preferring using closed scopes etc.

[Deadlake]

It's the temperature gradient. Leaving an SCT outside before you view may not help as the SCT might not acclimate. Another approach is to use a fan to pump in air into the tube.

[Alkaid]

Can confirm that trying to use a warm SCT on a cold night (or any scope tbh) is like viewing through running water. I’ve heard that Mak’s are the worst due to the much thicker glass (but excellent once acclimatised).

[Gfamily]

An alternative approach is to insulate the OTA, as that also reduces the air currents. 

[dweller25]

Hello @Mai Ai Bing

I see you live in Abu Dhabi so make sure not to use your scope on hot surfaces - grass is best.

Also avoid looking over hot buildings which give off heat.

[m.tweedy]

This article is a few years old but still as valid today as the day it was written

https://www.skyatnightmagazine.com/advice/thermally-optimise-your-telescope/

[JamesF]

37 minutes ago, Gfamily said:

An alternative approach is to insulate the OTA, as that also reduces the air currents. 

Indeed.  That's on my list of things to do with my C9.25 as soon as a get a bit of free time.  If I'm feeing very enthusiastic I might even do the 127 Mak.

James

[Mai Ai Bing]

Thanks for all the suggestions! I understand about the gradient. But that's mostly a management problem here. Did see a couple of pictures of isolated scopes  - its an option that I'll keep in mind if need be. Happy seeing!

[AKB]

2 hours ago, JamesF said:

That's on my list of things to do with my C9.25 as soon as a get a bit of free time.

Just recently done that myself.  Seems to help...