Dew heaters for 12" TT RC?

[DaveS]

Planning a new obsy rig, based around a GSO 12" Truss-Tube RC and was wondering what others do about dew control

Is it possible to fit dew heaters to the primary mirror? What about the secondary? I'm thinking that it should be possible to run a band around the baffle, then run the cable across one spider vane and down a truss.

How about a shroud? how important is it in a dome obsy? ATM I'm planning a dome on a square base.

[tomato]

I have seen a photo on this forum where thin copper strips have been run along one of the vanes to supply the current to secondary heater, but if the wires are run carefully along the top of the vane I cannot see them degrading the image to any extent. From what I have read, the shroud is worth having to exclude stray light and dust contamination, maybe less important if it is housed in a dome.  The shrouds are available commercially, but I'm told anybody with half decent sewing skills could knock one out for a fraction of the price of the commercial item.

Good luck with your setup, myself and Tomatobro were going to go the RC route but got cold feet over the maintenance concerns, so have gone with the big refractor approach instead. The TT RCs do look the business, mind.

[DaveS]

Thanks Tomato.

A 6" f/8 frac has been a possibility, but don't want to spend TEC / APM money. TS has an interesting 152mm f/8 triplet apo for 3.5k Euro, the same as the 12" RC, and I have considered it. I could get similar plate scales and resolution with a smaller-pixel camera, but from some other threads I've seen the 12" might get me more photons faster. I would pair it with a 16200 camera. Not sure which ATM though. Don't want any of the current CMOS due to amp glow, and cannot afford a FLI Merlin pro CMOS camera, by a long way.

[coatesg]

Amp glow should calibrate out with the correct darks (it does perfectly for my 163M).

The issue with CMOS cams on a long fl RC is that unless you bin, you're likely to be somewhat oversampled - the 6um pixels on the 16200 are better in that regard. You'll need a good quality mount to guide at 2400mm - I use a newt at 1580mm and that takes enough care.

 

For dew heaters, take a look at the Kendrick site - they offer round dew heaters that sit behind the secondary, with power going along copper strips on the vanes. 

I also have a set of shrouds by scopeshrouds - they are very good and should help enormously with stray light and dew prevention on primary.

[DaveS]

I don't have a mount for it yet, though based on experience I will be getting an ASA DDM85 Basic.

Amp glow on the ASI 1600 MMC does calibrate out *reasonably* well, but trying to get rid of it on my ASI 183 has been a nightmare, would rather solve the problem at source by going CCD.

 

Looking at the Kendrick site, I think their split-ring dew heater won't fit the design of the TT RC. Not sure yet about the behind-the-mirror design.