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First light- FLI CFW-5-7 Filter wheel

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#1 pyrasanth

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Posted 18 May 2021 - 02:40 AM

Normally we would expect to see first light associated with a new camera or optical tube.

 

However I have just changed from the Optec IFW3 filter wheel to the FLI CFW-5-7. The difference is unexpected and dramatic. My calibration frames are now quite superb- I'm not seeing a single trace of dist bunnies or field vignetting. This is probably about as good as it is going to get and the bonus is that as the wheel carries 7 filters I now have the full LRGB and narrow band filters loaded in the one wheel- the previous wheel could only carry 6 filters.

 

Last night I was able to focus the telescope & adjust the focus of the guide camera. I was really careful to get the back focus at 147 mm. This is 146 mm for the Edge optics and 1 mm for the filter effects. I had previous problems with the blue filter and suspected that it was a focus issue where because the back focus was out on the previous build the blue may have been shifted somehow. The issue appears to be resolved by getting the back focus very precise allthough we never know if 146 mm is going to be exact for all Celestron C11 and C14 OTA's.

 

Last night was very hazy so I choose M13 to do my test and only needed a short number of subs to test flat frame calibration. The image presented consists of 10 30 second RGB subs each and 15 30 second L subs.

 

I'm really pleased with the result of the calibration- it is so much better than my earlier filter wheel and I look forward to great results moving forward.

 

M13_LRGB3_CN.jpg


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#2 Mert

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Posted 18 May 2021 - 06:23 AM

Happy to read it works good now Mark!
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#3 pyrasanth

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Posted 18 May 2021 - 07:39 AM

Happy to read it works good now Mark!

Thanks Mert- it was a relief to find that pretty much everything is now so much better, and I hope, easier on the calibration front moving forward. There was nothing worse than taking 40 hours of data and finding not one of the flats was working correctly which happened on my last project- I need to redo an awful lot of data.



#4 SeymoreStars

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Posted 18 May 2021 - 07:50 AM

I have the same filter wheel Mark and it is rock solid. 


Edited by SeymoreStars, 18 May 2021 - 09:21 AM.

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#5 Mert

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Posted 18 May 2021 - 08:37 AM

Oh well, I don't have any filterwheel just a filter slider, but using

a OSC camera ...... :shrug:

Maybe in the future but will certainly look for a solid filterwheel if

or whenever I'm going to the dark side of mono imaging :-)

 

Stay well,

Mert


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#6 pyrasanth

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Posted 18 May 2021 - 10:24 AM

I have the same filter wheel Mark and it is rock solid. 

Hi Steve,

 

I'm impressed with the wheel. I've not seen calibration frames as good since I put the C14 in a few years back- yes that long. I suspect it is to do with the very high accuracy of the wheel. I especially like the way the chain grips the circumference of the wheel on those razor sharp spikes!



#7 gregbradley

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Posted 18 May 2021 - 07:44 PM

I use this filter wheel as well. I also have the CFW 4/5. Both are very reliable and work well. The only criticism is the adapters that screw into it have to have a very depth as there is very little thread to screw something in solidly before it hits the filters.

 

Greg.



#8 pyrasanth

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Posted 19 May 2021 - 04:31 AM

I use this filter wheel as well. I also have the CFW 4/5. Both are very reliable and work well. The only criticism is the adapters that screw into it have to have a very depth as there is very little thread to screw something in solidly before it hits the filters.

 

Greg.

I noticed this as well- there is not much thread depth. I got around this by using precise parts adaptors and whilst these are expensive the thread depths are exact so you don't get a threaded device diving under the fixing point.

 

I really like the feature to be able to rotate the camera- a lot of thought went into the design of this wheel.


Edited by pyrasanth, 19 May 2021 - 04:33 AM.


#9 gregbradley

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Posted 19 May 2021 - 05:53 AM

Yes thread depth is something you just need to be aware of and then its not a problem.

 

I tend not to rotate the camera in the filter wheel as I pack out the camera where it joins the filter wheel to adjust for tilt.

 

Greg.



#10 pyrasanth

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Posted 19 May 2021 - 03:19 PM

I'm trying a new test- it's good at F11. I've just added the reducer and am going to test at F8 to see if that is viable. I had previous issues with the reducer however that may have been something to do with the last wheel. The weather may hold so I can test tonight and let you know in the morning.


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#11 pyrasanth

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Posted 20 May 2021 - 02:49 AM

I tested the F8 setup on M13 last night. The image below is 108 30 second subs on a 3x3 bin on the ASI6200 giving about 0.8 arc secs per pixel. I had to use quite a high ADU of over 40K on the flats to remove some of the rings left by the reducer. There are still some traces in the image however conditions were not ideal with the brighter moon which of course makes calibration harder. I do not fear binning on the ASI6200- it is preferred otherwise over sampling is ever real at lower binning levels.

 

The spikes on the brighter stars is from the SMFS ethernet cable which currently is not optimally curved- I will work on that in the near future with the same system I used for the RASA.

 

I think F8 with the new filter wheel is workable and I expect better results in the next few months when we come back into the darker skies as we are in the twilight zone for the next few months.

 

The L frame is posted below- I also captured the RGB however I need to prepare the higher ADU flats or use the L which may not fully correct the dust bunnies.

 

M13_F8_L_CN.jpg


Edited by pyrasanth, 20 May 2021 - 02:51 AM.

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