Heater band for a coma corrector?

[almcl]

Got to use my homemade dew heater the other evening, on the guidescope. Worked a treat! It's nothing sophisticated, just a resistor ladder cobbled together from bits left over in the spares box from 30 years ago, running off a car battery. Without noticeably raising the temperature (2°C max) it kept the dew at bay when the scope and finder were positively running water off.

The guider's objective stayed clear, however, something in the imaging train didn't and the last few subs are very poor. Now, I am not absolutely sure about this, but it seems as if this might be down to dew on the coma corrector. This looked distinctly misty as I was putting it away in its box and while I didn't check it, or the secondary, in situ, it seems likely that one or both were to blame.

I know how to deal with the secondary problem, but how to attach a dew band, in a way that will be effective, to the coma corrector that is buried in the eyepiece holder and only a few cms from a sensor that the exif data claims is already at 30°C+ ?

[Jonk]

Did you notice the dew on the coma corrector indoors? It would only take a few seconds to mist up once in from the cold.

[Tinker1947]

The Coma Corrector has one end covered by the connector to the sensor, the other end is in the focus tube, high unlikely to get any dew in there, the stuff you see on it will appear as soon as you go indoors........

[almcl]

Thanks both!

I was putting it away in the unheated garage which is pretty much at ambient, but its plastic cover was damp (actually a bit more than 'damp') so that may have contributed.

I'll press ahead with the secondary heater and see if the prob goes away.

[laser_jock99]

Secondary mirror will probably dew up before the coma corrector- best checcked by shining a torch down the main tube. On really bad nights though I have seen the coma corrector succumb quickly as well though.

On these occasions it seems you are fighting a losing battle and it's better for your sanity to just pack away!