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Cooldown time c8 vs c9.25


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I recently got a c8 ota and quite enjoy it but of course there is always the nagging question how a bigger c9.25 would perform.

It seems cooldown time could be an issue with the c9.25 ota being nearly twice as big.

Could someone advise how the c9.25 and c8 would compare in this respect for the moderate climate here in the se of the uk. Scopes are stored indoors but the room is not heated (though still warmer then outside)

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I cannot give you any real idea but I will ask: Who actually bothers?

I mean in the sense of "I will not observe or use the scope as I am only 45 minutes into the 60 minute cool down."

Every scope like this I know of gets taken outside, the mount and scope is set up, all connections made, system checked and alignment performed, then it gets asked to goto something, people check immediatly to see if it really works, and observing in effect begins.

If you waited for the cool down then by rights the alignment comes after that, if you have done the alignmtnt then as said people very likely look through it at a "test" target - so you are observing.

Many will be in the position of squeezing in a 2 hour observing period, allow 60 minutes to cool, then 10 to align and that leaves 50 minutes, out of an intended 120 minutes, not a good return.

As said every scope I know of like this, and many bigger, the "cool down" is generally the time it takes to haul it outside and set it all up, say 30 minutes if not rushed. I have read of people "proud" o being able to set their scope up and get observing in 10 minutes not 30.

People may, having aligned and checked, go grab a observing list, coffee, food or whatever and throw in that cool down but I seriously doubt that many actually does a serious strict cool down. Standing around with a stop watch watching a scope is worse then watching paint dry. At least with paint there is a good chance of being in a room and having a seat  to use.

You must have seen the plus point people make of a big dobsonian over a goto - "I can take it outside and there is virtually no set up, I can get observing in minutes". Guess what is missing in that statement. No one say's I can take my dobsonian outside then stand looking at it for an hour.

So Yes allow an hour, but I bet you very likely never will.

Sceanrio: Clear sky, no moon, no star appers to be twinkling, Orion perfectly placed the nebula is calling to you, set up and alignment went smoothly and perfectly, 18 minutes has gone by, that Leica is in your hand. Are you going to walk away for the next 30 minutes to let the scope cool a bit more?

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Veiwing at high magnfications with a SCT or MCT that has not cooled suffiencly is a frustrating experience. I found my C8 needed 40-60 minutes to cool to the point where internal warm air currents had dispersed and were not affecting the view of double stars, planets etc.

For low power viewing, I could do that pretty much straight out of the house.

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In my situation it could make a difference. I find 2 hours now and then. Put my tripod with Giro down in 5 min and then I am good to go. If I would have to wait 2 hours before I could zoom in on the moon that would kind of make it impractical.

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This is where fans can help. Also of course where you store your scope and the temperature differential comes into play.

Ive been know to grab my newt tube and put it outside if its clear if i think i may have a chance of observing later.

Sent from my iPhone using Tapatalk

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If a c9.25 is simply a scaled up version of a c8 then the c9.25 would take approximately 15% longer to cool down. ( The amount of heat in a 9.25 is about 1.5 more than a c8, but the larger surface area of the 9.25 is better able to disperse the heat)

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  • 1 month later...

My C11 takes a while, so I do low power observing until it is ready... when it is ready...oh what great views , I love my c11...Best scope that I have ever had.  polar alignment scope ensures spot on go to each and every time,   and did I mention Spectacular Views !

Mark

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