All Sky Camera for Daytime Use

[Gina]

One possible advantage of the Fujinon zoom lens is that it has a (rather crude) aperture control.  The problem is controlling this.  Previously I've used a micro servo motor run from an Arduino Nano but these are notoriously unreliable and I've had lots of failures with them.  A stepper motor might be a possibility.

The ZWO cameras go down to 32 micro seconds exposure and this seems to cope with all but the very brightest of daytime skies.  The problem has been that INDI has only gone down to 1ms to date but there's a new version out with upgrades to the ZWO drivers so maybe they've fixed that - I shall be upgrading and testing that.  I do like to use the Raspberry Pi 3 with WiFi to reduce the cabling to just a power cable.

[ChrisLX200]

This GPCAM (MT034) is down to 10us (0.0010ms) and gain setting of '1' - if you can believe those settings are really valid. An auto-iris would be a big advantage but I never managed to get one to work other than wide-open (with 5v applied to one of the leads) or fully stopped down, intermediate settings were tricky.

[Gina]

Been doing more thinking and examining the Fujinon lens.  Tried to take it apart but didn't succeed   There's some dirt on one of the internal lenses that I wanted to get rid of.  Fortunately I don't think it shows at the setting I want.  It comes into focus at widest angle of view.  A zoom lens means that the FOV can be set as required.

For the controls I'm thinking of extending the levers and terminating in a spur gear segment.  Then a pair of stepper motors with matching pinions can control the aperture and focus.  I don't think the zoom lever needs remote operation.  The focus should only need setting once but with the problem of manually setting focus on the night-time ASC some sort of remote control would be good.

I still want to use a Raspberry Pi for the main control and image capture but I might add an Arduino Nano if I can't get everything working directly from the GPIO of the RPi.  I'm thinking the aperture could be controlled using the Astroberry Focuser INDI driver. 

The focus only wants an initial (or occasional) movement one way or the other quite slowly while the result is watched with the KStars FITS Viewer.  The control could be provided with the Astroberry Board INDI driver which provides 4 ON/OFF controls via the GPIO pins.  One line to move focus in and another focus out.

A possibility is to use the Astroberry Board driver to provide logic control to an Arduino Nano that would in turn drive the focus and aperture.  Once the firmware has been uploaded to the Nano, no further USB control would be needed (although this could be provided by the RPi in theory).   The four lines of the Astroberry Board could be assigned as follows :-

1. Line A - OFF = dew heater off - ON = dew heater on
2. Line B - OFF = aperture wide - ON = aperture narrow (daylight setting)
3. Line C - OFF = do nothing - ON = move focus in
4. Line D - OFF = do nothing - ON = move focus out

[Gina]

Camera list :-

1. ASI158MC - 7.3mm x 4.6mm  3.75µm
2. ASI178MM - 7.4mm x 5mm  2.4µm
3. ASI1600MM - 16Mega Pixels 4656×3520  3.8µm
4. QHY5L-II C - 4.83mm x 3.63mm  3.75um

I've included the ASI1600MM-Cool purely to see what I might want to use for planetary imaging as the alternative use for the cameras rather than as an option for the ASC (which it isn't). 

Best camera for planetary would be the ASI178MM with its small pixels (I'm told it's possible to use a mono camera for colour planetary imaging even Jupiter which rotates fairly quickly).  Using the ASI158MC which I originally bought for planetary imaging would need more magnification and it would seem that the QHY5L-II-C would be as good.

For ASC use the ASI178MM has a lot greater resolution than needed and in fact more resolution than I can get with the fish-eye lenses and I've changed to 2x2 binning with no noticeable loss of definition.  The QHY5L-II-C is rather small and is very noisy for night use though alright for daytime.

Of course, I shall continue to use the ASI178MM for my night-time cloud watching unless or until I get an ASC that covers both night and day.  I think for daytime the ASI158MC would be the best option used with the Fujinon zoom lens.  For use at night - and combining both night and day into one camera would be good - the larger pixels of the ASI158MC would partly compensate for the lower sensitivity of a colour camera as compared with the ASI178MM.  I think the resolution would be quite sufficient.

[ChrisLX200]

4 hours ago, Gina said:

Camera list :-

1. ASI158MC - 7.3mm x 4.6mm  3.75µm
2. ASI178MM - 7.4mm x 5mm  2.4µm
3. ASI1600MM - 16Mega Pixels 4656×3520  3.8µm
4. QHY5L-II C - 4.83mm x 3.63mm  3.75um

I've included the ASI1600MM-Cool purely to see what I might want to use for planetary imaging as the alternative use for the cameras rather than as an option for the ASC (which it isn't). 

Best camera for planetary would be the ASI178MM with its small pixels (I'm told it's possible to use a mono camera for colour planetary imaging even Jupiter which rotates fairly quickly).  Using the ASI158MC which I originally bought for planetary imaging would need more magnification and it would seem that the QHY5L-II-C would be as good.

For ASC use the ASI178MM has a lot greater resolution than needed and in fact more resolution than I can get with the fish-eye lenses and I've changed to 2x2 binning with no noticeable loss of definition.  The QHY5L-II-C is rather small and is very noisy for night use though alright for daytime.

Of course, I shall continue to use the ASI178MM for my night-time cloud watching unless or until I get an ASC that covers both night and day.  I think for daytime the ASI158MC would be the best option used with the Fujinon zoom lens.  For use at night - and combining both night and day into one camera would be good - the larger pixels of the ASI158MC would partly compensate for the lower sensitivity of a colour camera as compared with the ASI178MM.  I think the resolution would be quite sufficient.

You're getting as bad as me for collecting these small cameras Gina   I have a QHYIII 178M arriving soon, this will be for my main ASC - either with the recently aquired 1.55mm lens from Modern Astronomy or the large fisheye I mentioned earlier. The ASI178 I'm currently using in that role I actually bought for planetary imaging and I want it back for when Jupiter is in a better position. I'm wondering if I can attach my Atik EFW2 to it for RGB planetary stuff - I don't really want to have to buy another wheel. I do have a colour GPCAM (early version) but I think I'll get better resolution with mono. The QHYIII178 is physically smaller than the ASI so it will fit in the 3D printed case I have, the metal case currently holding a QHY5L-II I will keep for 24/7 usage (it's attached to the side of the Obs). The old QHY5L-II is very noisy compared to - well, anything else I have really Cameras have come a long way in such a short time.

[ChrisLX200]

Just posting an image using my new QHY5III178M which shows the FOV witht the 1.55mm lens I metioned earlier. Using SharpCap (or FireCapture for that matter) I can select the capture frame to just include the circular FOV - in this case 2048x2048 instead of 3056x2048. That crops off the unused sides of the sensor and reduces file sizes somewhat. It's cloudy outside with fine drizzle so this is an image with the camera setup in my Obs. Not much to see but I think the lens provides a sharp image edge-edge.

 

[Gina]

Yes, that looks good   I select the pixel range in KStars to select just the rectangle to cover the image on my ASI178MM. 

Looks like you have found a good matching camera and lens   My only success in that sense is with the zoom lens.  The QHY5III178M has a bigger sensor than the ASI178MM so that lens would give too large an image circle by the looks of it.  Also, I think I should use what I have rather than spending more money on another lens.  I have a Rayburn repair to pay for soon so I'd better curtail my astro spending for a while until I see what my finances will be like

[ChrisLX200]

8 minutes ago, Gina said:

Yes, that looks good   I select the pixel range in KStars to select just the rectangle to cover the image on my ASI178MM. 

Looks like you have found a good matching camera and lens   My only success in that sense if with the zoom lens.  The QHY5III178M has a bigger sensor than the ASI178MM so that lens would give too large an image circle by the looks of it.  Also, I think I should use what I have rather than spending more money on another lens.  I have a Rayburn repair to pay for soon so I'd better curtail my astro spending for a while until I see what my finances will be like

Well it's actually the same sensor used in both cameras (Sony EXMOR IMX178), and from what I can see there's better noise control in the ASI version - not that the QHY is particularly bad, but the ZWO ASI178 is a little cleaner with less hot pixels visible. On the plus side the QHY has excellent control over amp glow - there is none. Darks remove the few hot pixels perfectly though. My image above was using the smaller f/2 lens I got off Bern @ Modern Astronomy (in case I wasn't clear) not the larger f/1.8 Fujinon lens I got off Ebay. But I've decided to use this one from Bern I think because it's easier to house - at least, I don't believe I could lever any other advantage to using the Fujinon (apart from the fact the Fujinon is faster @ f/1.8 instead of f/2). I have the other Fujinon attached to a GPCAM2-M and I may move that over to a colour camera for some meteor work. I had no real need to order that extra Fujinon off ebay but it had been so difficult to find a lens like this over the past year and it was just such a bargain that I simply couldn't resist! However, if you wanted to buy that second one off me for your own ASC (at cost £26.50 + the extra postage to you) you can have it - just PM me. There's no urgency in this and I'll be keeping it safe rather than trying to sell it elsewhere. What I'll do later is try the Fujinon on the QHY5III178 just to check what the coverage looks like - I cannot check with the ASI178 because I don't have a suitable focus mount but the sensors are exactly the same so coverage will also be the same. That was another advatange of the QHY5III178 - the 1-1/4" body is the same as all the other eyepiece cameras out there so it's more compact than the ASI. I was hoping the QHY5III178 would fit straight into my 3D printed case without modification but sadly it won't - it's too long! I guess I can print a new modified case so it's deeper, the top part and dome can reamin the same.

[ChrisLX200]

I said I'd post the result with the Fujinon attached to the QHY 178 sensor camera, this is it   So this is a f/1.8, 1.4mm focal length, C-Mount lens. The other lens from Bern is an f/2, 1.55mm focal length, CS-Mount lens.  I know the 1.55mm lens is 1/2" format (it says so on the side!) but I have no such info for the Fujinon but I assume it's also nominally 1/2" format. Being a little shorter in focal length the Fujinon gives a slightly wider real FOV (i.e, included angle) and it also offers a slightly larger image circle so when cropped to 2048x2048 it just barely fits the entire field onto the sensor. If the Fujinon was exactly the same format (assumed 1/2") then the image circle should have been the same size and covered the same number of pixels. It's a minor difference though, and what it provides is exactly what you want I think as it makes ideal use of the available pixel area.

Having played around with just screwing the lens into the camera without the additional support provided by the adapter I made (I was being lazy and just wanted to take an image without the bother of swapping that adapter over) it's clear to me just how absolutely crucial it is to get that lens perfectly on-axis to achieve good focus all over the FOV. The slightest amount of wobble and you get blurring at one side or the other. My adapter ensures perfect alignment and the lens then performs as it should. Just something to bear in mind.

Chris

 

[Gina]

Thank you Chris   Very interesting - I'll have to have a good think   A lot depends on whether I can get one ASC working for both day and night.

[Gina]

Every time I run my ASC I don't like the view it gives.  Insufficient sky coverage and impossible to get decent focus.  The more I use it the less I like it!!  I'm going to have to do something about it before I loose my temper and hurl it into the middle of next week!!  But I'm just not happy at trying to use the Fujinon zoom lens - it's just too complicated.  I might have another go at it later but ATM I just don't fancy it.  So... your 1.4mm f1.8 lens is looking ever more interesting.

[ChrisLX200]

I will see if I can make a supporting bracket that fits the ZWO178 camera (well, two of them, I want one) that facilitates focussing. Lens is no use without that unless you want to try to make a spacer exactly the right size so when it's screwed all the way in it's in focus.

 

[Gina]

Thank you Chris - that's great   I'll PM you shortly and we can arrange things - I would like to buy your lens  

[ChrisLX200]

I've only just started to look at this Gina, I've been down with that norovirus all week (or whatever it's called) and it's not gone yet. Anyway, I just checked the focal length with the ASI178 and surprise - the focus distance is set for CS-Mount lenses by default not C-mount. Well that might offer more choice but it also means you need to use the little 5mm spacer which converts CS to C mount (see photo - that is in correct focus position). The adapter I have in mind will fit over the lip of the red anodised case, held in place there by some grubscrews. It's bore will be lined with acetal and a close fit on the barrel of the lens - that will hold it on axis. You can see the size of this lens, it's almost as big as the camera (the standard supplied lens is on the left for comparison) You will need that 5mm spacer though, it used to be given away as accessory with QHY cameras so perhaps you have one lying around?

The FOV is as expected - similar to the QHY5III178, the circle just fits on the chip and is perfect for making best use of the sensor size. Image quality is not a great example because the lens is as yet unsupported so not held in line...

 

ChrisH

[Gina]

Oh dear Chris, that bug sounds nasty - hope you get better soon   Just take things easy.  Lens looks good - I don't have C to CS adapter but probably easy enough to get.

[ChrisLX200]

The adapter looks like this, sans clamp screws at the moment, but it still works to hold the lens correctly.

 

 

Edit: Done now

 

I also needed to make a lens cap for this one as came without (unlike the first which came with a nice plastic cover..)

 

Edit: BTW, after re-reading my post I hope it doesn't sound like I'm pushing my adapter on you - you may well have your own plans (perhaps a 3D printed thing?) so just take the lens if you wish. I made these adapters for my own use really

 

[Gina]

That's a very fancy looking adapter Chris   When you said you were making an adapter I was thinking it was a 3D printed one so I was surprised to see a nice shiny aluminium one

I think, in fact, a 3D printed one should be better is a couple of ways.  Firstly, I'm cooling my camera and an aluminium adapter would conduct the cooling to the lens with the possibility of condensation unless I dry the contained air - and secondly, the cooling is going to be less effective.  OTOH would a 3D printed adapter be too flexible, I'm wondering.

[ChrisLX200]

A 3D printed one would be fine - provided you can get the sizes right! You want no slop in the bore holding the lens vertical, and a good fit over the camera. I was surprised at just how sensitive the arrangement is to the lens tilting, it quickly goes out of focus on one side or the other if its fractionally off vertical. Perhaps it's because of the type of lens and the acute angles involved where the light cone meets the sensor face - or maybe I'm just too fussy about getting focus and I hate blurry edges

ChrisH

[Gina]

I can get within 0.2mm with 3D printing.  For accurate fit I sometimes need a second print with slight adjustment of the size(s).  I've made accurate parts several times now

[ChrisLX200]

This is a short (35sec) clip, using my QHY5III178 this time. Same sensor as the ZWO ASI178 though. Gives you some sense of the quality available if you watch in HD (1440p is good).

https://youtu.be/17NWljUf1lY

[Gina]

Looks great - monitor is 1080p full HD   Far far superior to what I'm getting ATM for the "chuck it in for free" ZWO lens

[Gina]

Decided to stick with separate day and night ASC for now - the requirements are not really compatible.  A colour sensor is not really sensitive enough for night sky and I do want colour for daytime to see the difference between dark grey clouds and blue sky.  Also, I would like to see fairly sharp stars in a night sky whereas in daytime, clouds just don't need high resolution.

[michaelmorris]

My main concern about using a highly sensitive astronomical camera for daylight imaging would be the risk of damage to the sensor caused by prolonged exposure to direct sunlight.  Personally, I would only consider this option if I were using a CCTV lens with an auto iris function.

[Gina]

These cameras have ASC as one of their specified uses with a fixed aperture fisheye lens with which they come supplied for this purpose.  I'm not talking about the ASI1600MM camera in this instance but the smaller ones intended for lunar, planetary or ASC use.  I haven't decided which camera I shall use for daylight ASC nor even which fisheye lens but at least the ZWO cameras are designed to cope with direct sunlight, I'm far from sure others are.  I do have the Fujinon zoom lens which has a manual aperture control.

[Gina]

While testing an RPi board to use for my main imaging rig in the observatory, I have been using the ASI185MC and Fujinon zoom lens.  In daytime the aperture has needed setting quite small.  The focus was out of range when the lens zoom was adjusted to fit the round image onto the sensor so I've inserted some layers of card between the T2-CS adapter and camera to add to the back focus and can now reach focus.  Here an image roughly focused with the camera just sitting on the table near the window.