Changing ZWO1600MM-Cool Desiccant

[groberts]

I acquired my ZWO1600MM-Cool camera at the end of 2016 and therefore think it's second generation?

I'm not aware of any condensation issues but have been having some problems with smudges / fairy rings:

Amongst other things I'm looking at I'm thinking that it might be worth changing the desiccant, as it's never been done before and after looking at the ZWO intructions, as usual I am confused.  Is this a good idea?

Am I correct in thinking that you take off the silver screw (see image below) and attach the ZWO desiccant tube + new tablets and either: 

1. It stays on thereafter / until renewing the dsseicant tablets again at a later date? 
2.  Or after leaving the tube + desiccant on for 24-hours, it is removed and the silver screw is replaced?  

The manual seems somewhat ambiguous or I'm just stupid!

Graham

 

   

 

 

 

[Kev M]

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

 

 

[Dr_Ju_ju]

just zap them in the microwave oven, for 2\3 5min bursts ....

Note that what you've identified above is for a secondary desiccant bolt-on device & not the default tabs, which are inside the camera (around the imaging chip). So to dry these out, you have to remove the front plate of the camera....

Also note the 2 types of desiccant tablet are DIFFERENT sizes, & putting the larger (additional side bolt on) into the main body WILL result in a broken tablet & 'crumbs' distributed inside the main body & can end up on the sensor....

Edited May 12, 2020 by Dr_Ju_ju

[symmetal]

2 hours ago, groberts said:

I acquired my ZWO1600MM-Cool camera at the end of 2016 and therefore think it's second generation?

I'm not aware of any condensation issues but have been having some problems with smudges / fairy rings:

Amongst other things I'm looking at I'm thinking that it might be worth changing the desiccant, as it's never been done before and after looking at the ZWO intructions, as usual I am confused.  Is this a good idea?

Am I correct in thinking that you take off the silver screw (see image below) and attach the ZWO desiccant tube + new tablets and either: 

1. It stays on thereafter / until renewing the dsseicant tablets again at a later date? 
2.  Or after leaving the tube + desiccant on for 24-hours, it is removed and the silver screw is replaced?  

The manual seems somewhat ambiguous or I'm just stupid!

Graham  

The manual originally stated to leave the tube screwed in the side for 24 hours and then remove and replace the screw but posts on CN and elsewhere recommend leaving the tube in place permanently once you first use it as the 24 hour cycle has little effect.

There are 4 desiccant tablets inside the camera surrounding the sensor so if they are 'saturated' then plugging 2 tablets in the side won't have a great deal of effect as all they can do is absorb some moisture until all six tablets have the same water content. It would take longer than 24 hours for this to happen I would think as the hole in the tube is quite small and so the moisture exchange would be slow. You could keep repeating this procedure drying the two tube tablets in the microwave or oven each time but this would take quite a time.

As you seem to have dust bunnies present it's worth removing the camera front plate as described in the post above and drying out the 4 internal tablets in the microwave or oven. You can then clean the sensor and protective glass plate and reassemble with the newly dried out tablets. If you wish, you could at this point keep the tube attached to the side with 2 more tablets and every month or so dry these 2 tube tablets out and replace. This should stop the internal tablets getting too saturated to the point where they stop working. It depends on how well sealed the camera sensor chamber is. Some cameras go for years without problems while others have moisture problems every few months.

Later cameras like the ASI071 still have the screw hole in the side but don't include the desiccant tube anymore and you can't buy it separately so I think they realised it has little benefit.

Alan

Edited May 12, 2020 by symmetal

[groberts]

Thanks to everone, all very helpfull.  As you may have gathered, this is the sort of job I like to put off but after +3-years reckon a spring clean is a good idea.

Kev - couldn't open the link but have managed to locate the file elsewhere + looks very helpful. 

Julian - that's good advice and will beed to check - I've already bought repalcements form FLO so hope they're the right size https://www.firstlightoptics.com/zwo-accessories/zwo-desiccant-tablets-for-cooled-cameras.html 

Alan - so it seems the desiccant tube is really for use in the event of a condensation 'incident' and for routine replacement it's still best to remove the front plate, as instructed in the manual for the first generation camera. 

I'm not aware of any condensation issues but thought after more than three years replacement might be a good idea.

Graham

PS obviously I need a new set of flats after cleaning etc. but are new darks and bias subs also required?  

 

Edited May 13, 2020 by groberts

[symmetal]

Graham,

Generally the first sign of excessive moisture is ice forming on the sensor when you cool it below zero. This may not show up too much on the lights with just a slight patterning visible on the sky background but flats show it very well. At least that's how it was with my 071 camera. My 1600 is first generation and I've had no moisture or icing issues with it at all and it has never been opened or had the desiccant tube fitted.

Only new flats are needed after cleaning. Bias is not normally used with CMOS cameras as darks and flat darks are preferred.

Alan

[groberts]

OK thanks again Alan, now I'm begining to think I should leave well alone and just take a look at the sensor window and filters?  Like you, I'm not aware of any icing or condensation problems but just thought it was good proactice to keep these things up-to-date. 

I did not know that bias was not used with CMOS sensors though you seem to indicate they might be sometimes-  when would that be? 

Excuse my ignorance, what are dark flats + / how do they differ from darks which I've been using hitherto?

Graham

[symmetal]

 

1 hour ago, groberts said:

OK thanks again Alan, now I'm begining to think I should leave well alone and just take a look at the sensor window and filters?  Like you, I'm not aware of any icing or condensation problems but just thought it was good proactice to keep these things up-to-date. 

I did not know that bias was not used with CMOS sensors though you seem to indicate they might be sometimes-  when would that be? 

Excuse my ignorance, what are dark flats + / how do they differ from darks which I've been using hitherto?

Graham

If your camera hasn't been opened then hopefully any dust is just on the front of the protect window so cleaning that should suffice. The 1600 doesn't have a heated protect window, (at least the early ones didn't) so there is a chance of condensation forming on the exposed front of the protect glass, though I admit have never had any issues with this and I cool my 1600 down to -30C in the winter. You can buy heater strips from Zwo to fit around the protect window if you want.

Short exposures (around less than a second) on CMOS cameras operate in a different mode to long exposures as discussed here and in more detail here. In order for the flats to match the lights you should take longer flat exposures of around 2 seconds or more, and corresponing darks (called flat darks), matching the length of the flat exposure to calibrate the flats and not just use bias instead. You can use bias if you wish with short exposure flats and some people report no issues but it seems to be recommended not to use bias with CMOS cameras. It's fine to use bias with CCD cameras though.

Alan

[groberts]

OK I'll read that tomorrow Alan - sounds like I might need to change my calibration techniques. 

Hitherto I've been doing conventional darks, bias & flats and the results seem to have been fine, except for the 'fairy rings' mentioned elsewhere, which are more likely to be down to dust etc? 

Many thanks.

Graham 

 

[Adam J]

On 12/05/2020 at 16:40, groberts said:

I acquired my ZWO1600MM-Cool camera at the end of 2016 and therefore think it's second generation?

I'm not aware of any condensation issues but have been having some problems with smudges / fairy rings:

Amongst other things I'm looking at I'm thinking that it might be worth changing the desiccant, as it's never been done before and after looking at the ZWO intructions, as usual I am confused.  Is this a good idea?

Am I correct in thinking that you take off the silver screw (see image below) and attach the ZWO desiccant tube + new tablets and either: 

1. It stays on thereafter / until renewing the dsseicant tablets again at a later date? 
2.  Or after leaving the tube + desiccant on for 24-hours, it is removed and the silver screw is replaced?  

The manual seems somewhat ambiguous or I'm just stupid!

Graham

 

   

 

 

 

That is a very odd imaging train you have, looks like you are going from the reducer to a t-adaptor to a camera lens adaptor to the filter wheel to the camera. That is extreamly sub optimal. Why not just just t-2 extenders to make up the correct back focus as that camera adaptor is a potential source of tilt.

Adam

[groberts]

I have used this for +3 years OK but I take your point, do you know what size it would need?

[Adam J]

On 14/05/2020 at 15:12, groberts said:

I have used this for +3 years OK but I take your point, do you know what size it would need?

You should have gotten the correct T2 spacers in with the camera. 

[groberts]

Many thanks Adam but no. 

See this separate thread I subsequently started as a result of this issue and have now purchased a Baader Varilock extender - see this thread for more info:

 

 

 

[Adam J]

Cool looks like you are sorted then.

Adam

[groberts]

🤞