Thermal Management--RH305


willsonjared
 

Hello, Group!

I recently relocated my Riccardi-Honders to a remote site in New Mexico, and that has the potential to create new issues. I wanted to get some advice from fellow users of AP telescopes (Honders or Maks)...

The temperature gradients in the high desert of New Mexico are dramatically worse than those here at home in the Bay Area of California. Have any of you tired Reflectix or equivalent? Is it an improvement over the layer of neoprene that came with the Honders? I do not have the ability to actively (or really even passively) cool my Honders in NM. The blanking panels in back must stay on to prevent bugs and rodents from making a home in the telescope, so reaching equilibration seems unlikely. Plus, the temps just keep falling with little water vapor to hold the heat in. I don't know whether I would be better off swapping the neoprene for Reflectix or leaving things as they are. Since it's a remote site, it's not easy for me to test different scenarios, so I'd love any advice the group may have to offer.

The second related issue is dew prevention. I bought a Kendrick Dew Strap for the scope, but I have absolutely no idea what a good starting setting would be for both temperature delta the heater is supposed to maintain or for power. It's a big scope, so I assume a fair amount of power is required. Again, I have limited ability to test, so if anyone has experience with a good starting point I'd love to hear from you. Otherwise, I'm at the mercy of the on-site people to make changes for me that I can try over a night or two, and I don't want to be too much of a pest.

Thanks for any advice you all can offer! 

- Jared


weems@...
 

I don’t have an RH, so I can’t answer the question about the neoprene. But I’ve put reflectix on my C14, which has to deal with New England temperature swings. Covering the tube was only marginally helpful. The benefits only appeared after I also covered the rear cell and the lens cap.  It seems that it is equally important to reduce thermal gain during the day as to slow the rate of loss at night. Although I only do visual observing, I can start using the scope as soon as I open it. Before the reflectix it took at least an hour for the tube currents to settle. Sometimes much longer 

Chip


John Jennings
 
Edited

Hi Jared,

I had a remote observatory at Granite Gap (30 miles from Douglas)  in NM for 6 years before the site closed. (1000 miles away from my home.) Totally unattended and no one to ask for help if something went wrong.  I imaged 4 years daily with a 14 inch HyperStar. The things I fought the most were:

1. Dust. It will get on everything. I sealed the roll-off section with multiple overlapping rubber seals and calked every crack to prevent dust from entering during dust storms. I recorded some wind storms as high as 70 mph. I listened in with my surveillance camera's audio and it was almost frightening. My observatory was pitch black inside during the day with no light leaks. Place filters or fine cloths over any fans you use to cool the telescope and don't use them if it's windy. That's where I learned you really can image with dirty optics...

2. Dew. You will need high power dew heaters. I placed them on the front and rear cells of the scope. Dew during many of the best imaging nights caused the scope to become drenched in water. I could actually see water dripping off the scope through the cameras in the morning sun. I sealed most of the USB or electrical connections with a small bead of silicone rubber along the outside. After a couple of years I had some that quit working due to repeated moisture until I started the seal regime. I also placed some dielectric paste on connections as well.

3. Rats & mice. Not many good answers there. You will have them for sure. While visiting the observatory I had one climb down a cat 5 cable one night right in front of my monitor. He stopped and looked at me in the red light and immediately ran back up the cable. I visited the local (50 miles away) grocery store the next day and purchased a bunch of country sized traps and peanut butter. Placed them in the observatory at 5pm and at went to dinner. (40 miles away)  Went back in at 7.00pm and I had a massacre on my hands.

4. Spiders & scorpions.  I ended up paying a professional exterminator to come out and spray around the inside and outside once a month. It was the only way to prevent a build up. Since they do it regularly, they use environmentally friendly low toxicity stuff. 

5. Temperature swings are just a fact of life there. I did modify my scope with a number of fans to cool the inside. It helped for sure. But see my comment about the filter.......

Overall, these issues ended up being a nothing burger.

Most fun I've had with astronomy ever!  I miss my observatory!

John


Greg Bradley
 

Hi Jared,

I have only used the thermal blanket supplied with the scope.
I use a FLI Atlas focuser and have been using a QHY6000M camera.

I would take the back covers off before an imaging run. I find that helps a lot in achieving fine focus and tighter stars.

But the temperature swings are hard on that system. I use temperature compensation with the Atlas focuser. It works better with the 
FLI Proline 16803 with its 9 micron pixels. The QHY600m with its 3.76 micron pixels is harder on any scope's optics and it shows up
weak focus that the Proline would not show.

Additionally the temperature shifts are not straight line relationships but more of a curve. The initial drop in temp seems to affect focus the most.

So I would usually cool the scope as early as possible. Then focus and take some images then refocus after about an hour where it would tighten up coinsiderably.

Then set temp compensation to around 350 steps per degree C.

Ideally you would set up autofocus meaning Focus Max every 1-2C shift or some other focusing software. I asked about what is the best autofocus software and a lot 
said Nina.

I don't like the idea of Focusmax slewing to another star, refocusing then plate solving back. I find plate solving to be unreliable at times and a bit quirky. Great when it works if it works.

Greg.