Cleaning an FLI Microline sensor

[LewisM]

My new-to-me FLI ML8300 turned up today - WHAT A CAMERA!!! Of course, first thing I did was fire it up in MaxIM tonight to do some testing.

The cover of the sensor is quite dirty - numerous motes showed. What is the way to open the shutter and clean the sensor face? Just set say a 10 minute exposure off telescope, start and clean whilst the shutter is open? Or is there a mechanical way to open the shutter to do this safely?

Appreciate the help.

I am absolutely DELIGHTED with this CCD! RAPID cool (went to -37.3° within 4 minutes, with an ambient today of 24°), VERY rapid image download (even for long exposures), not bulky and seems superbly built. Screwed straight onto both my Taks using the supplied adapter, NO flexure from compression rings etc. Just got to have my friend make a couple Tak extension tubes though

Definitely the best CCD I have used so far in terms of build quality, features etc. The SX SXVR-M25C was a delight, but I think this one will be better. Plus, it kind of looks like a Rolleiflex camera hanging off th back of your telescope

[LewisM]

FLI responded - just use the FLI Grab software and press Open Shuter... clean,close shutter

I never even knew the software installed that - it was automatically dropped to my start bar, NOT desktop.

[Paul Haese]

Why bother? That is what flats are for Lewis. I have never touched any of my sensors. Doing flats removes this problem.

[Paul Haese]

BTW, unless you bought the unit with a high speed shutter, you won't be impressed with the standard shutter. High speed shutter should be standard with these cameras but FLI don't seem to understand that. Everything else about the camera's is superb from what I have seen with my own two eyes.

[LewisM]

Problem is Paul, it is QUITE dirty - large motes and specks. Flats would work for the most part, agreed, but let's say I image M20 - unprocessed, there would be a LOT of artifcat in the bright nebulous area. Are flatrs going to remove that without dither? (academic, I always dither at least 3 pixels per every sub)

[RickS (Rick)]

Dithering by a few pixels will remove small artifacts like hot/cold pixels but it won't remove larger ones. Something like a dust bunny will just get smeared. The only way to remove these (apart from physically as you are doing) is by applying accurate flats.

Cheers,
Rick.

[LewisM]

After going through MaxIM looking for a shutter open/exposure delay setting, should not the Shutter Latency tool - that measures the latency of the shutter then adjusts integration accordingly - address this slow shutter issue?

FLI's software also permits you to open the shutter prematurely before integration begins too, and this same function is also present in the MaxIM FLI plugin.

Unless I am mistaken then, the slow shutter is not really a major issue now?

[LewisM]

Originally Posted by RickS

Dithering by a few pixels will remove small artifacts like hot/cold pixels but it won't remove larger ones. Something like a dust bunny will just get smeared. The only way to remove these (apart from physically as you are doing) is by applying accurate flats.

Cheers,
Rick.

Quite right - I did clean it just now. Clean as a whistle now.

I will build a flat library later today with the light box for each telescope. I intend running this camera at -35° constantly (which all accounts and users reports says it will all year round), so will build a -35° library for lights, darks and bias frames - thinking 100 frames per subframe type should tide me over.

Now to test if the shutter latency recording function works. Should help with time tagging the subs.

[LewisM]

Can't find my lens mount to run the shutter latency properly, so just set an arbitrary 2 second latency for now - should definitely take care of any issue. Tested it, and it worked as supposed to - no petal image at all even on a 0.01 sec exposure.

[Paul Haese]

Like Rick said accurate flats will remote any artefacts. Having a library of flats will not work for imaging at longer focal lengths too. You will need to do flats for every session. The short focal lengths this is not so bad if you don't take the camera off the lens or telescope. Once you do that you will introduce dust into the system and create errant motes. So there is no point in creating a library of different telescopes when it comes to flats.

[jase (Jason)]

haha, send it back to the factory for cleaning. I mean really? You've got a brand spanking new ccd camera and you are already complaining about dust on the sensor. You'll drive yourself crazy worrying about it. Perfection doesn't exist, even with a super clean sensor. As others have said, good flats will correct it. Dithering will only correct pixel/column defects, not dust donuts or uneven field illumination. Only flats will do the latter.

[LewisM]

I will do it for the fsq though. The f/6.3 102 can wait somewhat

[gregbradley]

I set my camera to a 2 minute or longer exposure so the shutter opens then blow it with a hurricane blower than wipe it with a camera lens microfibre cloth a few times. Then maybe a final blow with the blower to clean off anything residual. Then check with a new flat exposure then repeat if needed.

You can also clean the glass with Bintel lens cleaning solution, that works well. Use unscented white tissues and change them often.

That should clean it up nicely.

Same with filters. Then dust donuts tend to disappear and you are not depending on flats to remove them.

Cleanliness is far superior to relying on flats which if anything is slightly off start to not remove dust donuts. Or if you move the camera slightly etc etc.

Greg.

[LewisM]

Agree Greg - I would rather NOT rely on using pixel interpolation when I can clean the offending motes in the first place, leading to a generally better image overall.

It's like relying on Photoshop's Healing Brush to fix errors.

To each their own - I would rather clean the chamber cover glass than not. Same with objectives - I clean instead of letting crud and dust accumulate.