CCD image issue

[rubecula]

I've just started this evenings session and got the first image down.  There's something odd (condensation, dirt???) showing in the bottom right corner of the image (see below).  I was imaging the same target last night and the blemish or whatever it is wasn't there.  It's not the top of trees or anything like that as the scope is pointing way above any obstruction at M51. 

Have you seen anything like it before?  Will it be safe to continue imaging.

Thanks

[rubecula]

Ah, it's gone!  Must be something to do with the cooling.  Which reminds me of a question I have been meaning to ask about cooling / warming rates.

With the Atik 383l+ I've been setting it to cool to -20C in five minutes and this evening the temp in the observatory is about +9C.

Last night I set it to warm up from -20C to +5C (about ambient) in 4 minutes.

Are these cooling rates too fast?

Thanks

[tooth_dr]

I have the same camera and I use APT to control the temp drop.  I have so far not seen this frosting issue, and am not aware of any option to control the speed of cooling or warming.  However I dont image immediately, since the cameras are cooling whilst I'm plate solving or focusing or setting up guiding.  

[rubecula]

Thanks Adam, SGP has this function to control cool down and warm up:

Like you I get the camera cooling first and then plate solve, etc. so It's probably more than 5 minutes until I take the first image.  On warming I try to get it back to the ambient temp.  I'll give it a little longer tonight.

[Uranium235]

Atik 383L+ says it all With that camera you have to bake the desiccant tablets roughly every 5 months to keep the moisture at bay.

Another thing I used to do was first, cool the camera to -10, let it stabilise for a bit (you could be doing your mount calibration or focusing while that is going on), then I drop it another 5c as my usual operating temperature was -15c (going down to -25 during colder months).

Great camera though, its one of the very few (in fact... i cant think of another!) that has a 1/4" photo screw hole - very, very handy if you are using lenses with it.

[rubecula]

Uranium235,

I only got the camera last November and baked the dessicant so I'll try your part cool method next time and see what happens,

Thanks