Ice and Clean

After the adventures in collimation of the night before, another clear night saw Jonathan and I again off to Kumeu (missing out on the AAS film night).  Jonathan was out there first and was quickly frustrated once again by frosting on the CCD sensor.  After a couple of "warm up" and "cool down" cycles still hadn't fixed it, it was clear this problem was going to start getting annoying rather fast.

Cleaning the corrector plate on the C14

After I arrived, we decided to leave the camera with the coolers off for a while and tackle another little job that's been on the list for far too long - the C14 corrector plate.  We haven't cleaned the corrector at all since we started (a long long time ago....) so you can imagine the quantity of dust, water spots, insect gunk and all manner of things on there. (Actually you don't need to imagine - we've got quite a few pics of the corrector on the blog!)

I'll get you....dust particles... 

Using the old faithful technique of a bulb blower,  soft white tissue and 30% alcohol solution in demineralised water, the outside surface of the corrector was slowly and carefully de-gunked  - which had the predictable effect of showing just how much gunk was on the inside of the corrector - this will have to be addressed in the short term.  A medium term project might also be to get the primary cleaned (I know people have had fantastic results using the novel cleaning kit from https://www.photoniccleaning.com/)  or potentially re-aluminized - as there is an appreciable quantity of dust and a small mould/fungal spot.

Dismantling the filter wheel on the SBIG ST10XME

We also checked out the filters, as we know the new RGB we were testing needed to be tightened up - but also noticed the L and the #12 Wratten filter were looking past their best too...  after pulling the flter wheel out it was clear that the L and #12 filters would definitely be causing issues with our images.  Even though we are planning to replace these filters, these too had a very careful cleaning and came out looking much better than they were originally.

Carefully cleaning the L filter

We reattached the camera and cooled it down, only to be instantly frustrated by frosting again almost immediately.  We are definitely going to "cook" the dessicant pack again, as it's clear there is obviously moisture in the system that's not being removed.  We jumped on the internet (via Steve's phone as we've not get this sorted yet still) and learned a couple of interesting things about this problem:

1. you can buy a replacement dessicant plug that takes disposable gel packs - this is fantastic as it would allow us to replace the dessicant quickly without the "cooking" process
2. A technique described on a forum for cooling down in stages to avoid the frost. 

We gave #2 a go and cooled the chip to zero for half an hour before taking it any colder - this seemed to do the trick (though it might have just been luck this time) as we managed to cool further without seeing any frosting.  We'll certainly add this to our process for the future to see if this will avoid this situation.  

One final challenge for the night is that the focal reducer we have is also in dire need of replacement/professional cleaning or removal - though at this point we noted that we don't have the original 2" nosepiece- something else for our shopping list.

After I left around 12:30, all Jonathan did  was try image for a while but soon got hit with more frosting issues so frustrated, packed down and cleaned up the observatory including removing a dead mouse from under the dome ( gross but at least we know the rat bait is effective ), Jonathan ended up taking the desiccant home and cooked it (it goes in the oven for 4 hours to dry out the dessicant material) the next day. He then took it back out to Kumeu and reinstalled into the CCD camera, hopefully that should resolve our frosting issues for a while.

Steve and Jonathan