SCT Cooler?

Matty P (Matt) · #1 28-05-2008, 02:38 PM

It can take up to a couple of hours for your SCT to reach ambient outdoor temperature. I was just wondering if anyone that owns a SCT would benifit with having one of these?

Lymax - CosmicOne SCT Cooler
http://www.optcorp.com/product.aspx?pid=105-766-6596

Lester · #2 28-05-2008, 03:15 PM

They are better than nothing.

matt · #3 28-05-2008, 03:27 PM

A lot of us have them...and have for a while

As Lester says, anything which helps with cooling an SCT is better than nothing.

It will get you close and help you cool a little faster...but...

Matty P (Matt) · #4 28-05-2008, 03:45 PM

Would I be better off just leaving my SCT out longer before an imaging session?

Robert_T · #5 28-05-2008, 03:48 PM

I have one, but don't often use it as I tend to setup well in advance (hours) and come to the scope well-cooled.

They help for when you setup at dark and want to be imaging within the hour. The benefit is probably felt more the larger your SCT. Small benefit for a C9.25, probably essential for a 14in SCT...

Matty P (Matt) · #6 28-05-2008, 03:54 PM

Quote:

Originally Posted by Robert_T

I have one, but don't often use it as I tend to setup well in advance (hours) and come to the scope well-cooled.

They help for when you setup at dark and want to be imaging within the hour. The benefit is probably felt more the larger your SCT. Small benefit for a C9.25, probably essential for a 14in SCT...

Thanks Rob,

Just what I wanted to know. I always put my SCT out a few hours prior to imaging so cooling to ambient temperature shouldn't a problem.

Thanks.

Dennis · #7 28-05-2008, 03:58 PM

I guess that if you image under conditions where the temperature drops rapidly and continues to do so without settling and becoming stable, then cooling is almost mandatory to optimise your results?

However, if your system cools down “naturally” and equalises without too much change in the outside temperature, maybe the contribution of these coolers is less important?

From what I have read, the top flight planetary imagers on Ice In Space tend to aim for a maximum 1 deg C delta betwixt optics and ambient.

Cheers

Dennis

iceman (Mike) · #8 28-05-2008, 04:26 PM

Ambient cooling (just leaving the scope out) will NOT be enough for high-resolution planetary imaging, especially since you live in Canberra where the temperatures drop very rapidly and the difference between daytime/nighttime temperatures can be harsh.

Anything which can help bring the temps down quicker is better than ambient alone.

Matty P (Matt) · #9 28-05-2008, 07:46 PM

Thanks for your replies.

I find that because I have a smaller SCT (8"). It cools to ambient temperature fairly quickly compared to its bigger brothers (12" & 14").

I don't have anyway of actually checking the temperature inside the OTA so I cannot be certain. If I leave the OTA outside for long before I start imaging it should allow the OTA to reach ambient temperature and stay close to it.

However, I am sure that being able to cool my SCT in minutes instead of hours would save me time I personally don't think I need it at the moment.

davidpretorius · #10 28-05-2008, 08:37 PM

You have the foremost temperature expert just up the road............Bird!!

Paul Haese has added peltiers to his c14 and it works a treat. As mike says, canberra sux (like tasmania) for constantly falling temps.

Basically, your mirrors never catch up.

THere are a few designs floating around where you can get the lymax blowing cold air inside........some guys will put the OTA in a fridge.

I have a feeling you will want to go peltier cooling

Matty P (Matt) · #11 28-05-2008, 08:44 PM

Hi Dave,

The only problem with the design of the Lymax cooler is that I can't have it running while I have the DMK connected. So I will have to keep removing the camera and attach the cooler constantly.

I don't like that idea.

I might just have to put my SCT in the freezer.

davidpretorius · #12 28-05-2008, 09:03 PM

The idea is to work within the +- .5 deg band.

I get my mirror about 1 degree under ambient, turn off the cooling, wait aprox 5 - 10 mins for the air to stop moving and the mirror to stop flexing......then i image until the ambient is .5 degrees under the mirror.

Moving air in the OTA will most certainly stuff the seeing.

If you get a c14, then peltiers will work a treat.... a c9.25, there is very little room behind the mirror and well for he c8... the fridge

OneOfOne (Trevor) · #13 29-05-2008, 07:44 AM

I found when I first got the C11 that I could not view anything for a couple of hours after setting up, at the moment I don't do any imaging. Using the Cat cooler I can get it cooled in less than 30 minutes. This is particularly useful because a lot of my "viewing" is done at public venues, I don't want to have to arrive 2 hours before viewing starts in order to setup and then stand around twiddling my fingers.

They are not cheap, but IMO I think they are worth every cent. A possible extension would be a cooler box to go around the intake with a couple of peltiers in it.

I read somewhere that with a C14, it is quite possible that it will never reach ambient temperature without some sort of thermal assistance...maybe they need to make an SCT with a flip top head to let all the hot air out!

Lester · #14 29-05-2008, 11:39 AM

I use ice water to cool my 14" LX200. I have coiled 12mm hose around the OTA, with cold water pumped through using a 12volt bilge pump in a large esky.

Have the esky half full of water and add 3 x 2 litre frozen containers, and can have the mirror to ambient in 1 hour.

I have got a temperature sensor mounted on the rear of the primary mirror. I can image planets while the pump is going. There is not any vibration as the pump is centrifugal with no pulses, but just a steady stream of water being pumped.

This setup doesn't require much power and is ideal for me where I don't have any mains electricity.