ASI1600MM PRO Desiccant Change

[Adam J]

Hi all,

This is just a little commentary on my recent desiccant change on my ASI1600MM PRO. About three weeks back I started to notice a dark area in the centre of my images. Some experimentation showed that the size of this dark disk increased with deeper cooling and vanished with cooling turned off. 

I put this down to moisture in the sensor chamber. I did some research on changing the desiccant but was not able to readily find a link to the instructions on ZWOs main page. The camera instructions themselves are useless in this regard and barely mention maintenance at all. What is given talked about the original V1 version of the camera and describes the threaded front plate. I contacted FLO and they linked this document to me:

https://astronomy-imaging-camera.com/manuals/How_to_clean_ASI_camera_and_redry_the_desiccant.pdf

Note: That this still pictures the V1 camera and not the PRO. 

The main issue I have with this is that on the PRO there is a black plug on the side of the camera and under that plug there is a screw head, for all the world it looks like it might contain the desiccant as would be the case on a ATIK 400 series camera. IT DOES NOT! 

A reply on the ZWO forum is the only reference to this and it says that this is not designed to be removed by the user and that is why it has a black plug over it. SO DO NOT REMOVE IT. 

In fact the desiccant on the ASI1600MM Pro is actually accessed by removing the entire front of the camera exactly the same as with the V1 but by removing the four silver hex head screws as opposed to twisting it off. 

On removing the front of the camera you will find that the desiccant is not located next to the PCB / Sensor board as per the ZWO link above but instead on the reverse side of the camera front that you just removed, that confused me for a couple of seconds until i turned the front over in my hand. 

The problem with this system as opposed to the ATIK system is that in removing the front of the camera there is ample opportunity to introduce dust. I took three steps to minimise this possibility. 

1) While its cheapest to re-charge the desiccant in the microwave the camera is open while you are doing this. So to reduce the amount of time that the camera was unsealed I decided to purchase a second set from FLO: https://www.firstlightoptics.com/zwo-accessories/zwo-desiccant-tablets-for-cooled-cameras.html. this allowed me to rapidly change the desiccant over without having to wait for it to re-charge. It also means that I have a second set to perform this switch again in the future. 

2) I used latex gloves to prevent my finger accidentally touching the sensor or the inside of the sensor window during this process. 

3) I placed the open body of the camera within a plastic freezer bag while I was working on the lid with the desiccant attached. All four tablets just pull out and are held in place by friction only.  

Following the switch over of the desiccant I gave the inner surface of the sensor window a quick blow with a rocket blower and then I replaced the camera front making sure that the rubber seal was correctly seated and that the front was orientated in the same way as when I originally removed it. These two actions prevent damage to the seal and mitigate the effects of any imperfection in the seal caused by their initial mating. 

I then left it in its case for a couple of days to allow the new desiccant to work and fired it up. No more problems!

Hope this helps anyone who needs to perform the same task. 

Adam 

 

 

Edited December 13, 2019 by Adam J

[spillage]

I have the V11 version and this came with a screw in canister that takes two desiccant tablets. This screws into the side of the camera once you remove that screw behind the black bung.

Edited December 13, 2019 by spillage

[Adam J]

14 minutes ago, spillage said:

I have the V11 version and this came with a screw in canister that takes two desiccant tablets. This screws into the side of the camera once you remove that screw behind the black bung.

The later models don't come with that canister. The dropped it for V3 and Pro models. Its now sealed on the inside under the screw with a thin plastic film. I dont know why they did not just remove it. Probably kept it just in case or because they have huge stocks of that design and eventually they will remove it.   

[Tailspin45]

FWIW, 2-minutes in the microwave was enough to turn three of the tablets a very dark color. The color did not go away after they cooled enough to pick up.

I wonder if the oil on our hands has any affect on them?

 

[skybadger]

The silica gel I use recommends 10mins on defrost to regain their potency, proportional to weight. 

One good practise is to do this all at arms length due to all the dust you shed just living. Long hours in the clean air bench taught me that .

 

[The Admiral]

On 13/12/2019 at 16:09, Adam J said:

I used latex gloves to prevent my finger accidentally touching the sensor or the inside of the sensor window during this process. 

Just be aware that some (latex) gloves are powdered on the inside to aid getting on and off, if I understand correctly, so using this type risks introducing dust. Choose a powder free variety.

Ian