Gina's All Sky Camera Mark 6 with Fujinon 1.4mm Fisheye Lens

[mhard26339]

24 minutes ago, Gina said:

Good luck with you ASC Mike

It does me very well Gina, as you know I operate remotely often 1200 miles away and cannot just stick my head out of the door, it and my cloud sensor are invaluable, in fact essential before I open the shutter on the dome but I envy the speed of your camera, I need 1 to 2 minute exposures but they are always spot on. Having read this blog when I am next home instead of selling the ZWO, lens and housing I may put it together for a play, just need to sort out the heaters; there is a picture of the Ocullus on my build thread.

Regards

Mike

[gentlebear76]

Hi :-)

Gina, what lens is that? Do you perhaps have a link to a seller? I would love to get a better coverage of the sensor as well :-)

/Michael

[Gina]

It's a Fujinon fisheye 1.4mm f1.8.  I bought it from another member who bought it from ebay but since discontinued, I'm afraid.

[Gina]

Seems a dew heater is a must.  Ran the ASC last night in very damp conditions and the inside of the dome was fogged up in addition to a few rain drops on the outside from earlier rain.  I've brought it indoors to re-connect the dew heaters and check that they are still working.  Two sets of resistors provide 3 levels of heating plus off controlled from KStars using the Astroberry Board INDI driver.

[Horwig]

Mike's point of sensitivity is interesting, I was amazed at the lack of noise, but the detail is also amazing compared to my Fuji zoom lens on the QHY. Am I right that you used to use the same zoom as me on a previous incarnation of ASC?

How much of the difference in light gathering is down to light loss in the optics I wonder?

[Gina]

Yes, I used the Fujinon zoom in an earlier ASC.  I'm thinking of using it for a daylight ASC with colour camera ASI185MC.  I shall make use of the aperture control to reduce the sensitivity   There's a possibility that I may use a different camera later if I get into planetary imaging and want the ASI185MC for that.

The new big Fujinon fisheye lens has amazed me.  It seems that the amount of light transmitted has little to do with the quoted focal ratio.  The new lens is quoted as f1.8 yet it's very much brighter than the ZWO lens quoted as f1.2.  It's very much brighter than the zoom lens too.  Last night with a bright moon I was using 5s exposures yet still seeing stars between the clouds.  I needed 30-60s with the other lenses.  On a dark night I get good results with 10s exposure.

[Horwig]

56 minutes ago, Gina said:

It seems that the amount of light transmitted has little to do with the quoted focal ratio.

That was why T numbers were used instead of F numbers by some people in the film industry, it measured the lens transmission, not theoretical geometry, I assume the Fuji zoom if very lossy compared to the prime fisheye

[Gina]

From it's size and the width of glass in it I would expect the prime lens to be a lot better than the zoom and prime lenses are bound to transmit more light, other things being equal, due to the number of air-glass interfaces.

[Horwig]

Oh, bother, twitchy wallet finger AGAIN!!!!!!!

[Gina]

Found the problem with the dew heaters - wire broken off.  Now fixed.

[Xplode]

I got a 120MC-S, would the Fujinon lens work with that if i used a 5mm extension or would i need a homemade adapter like you have?

[Gina]

Latest image.  First since reinstalling everything on Linux Mint desktop.  Screenshot from KStars FITS Viewer.  Exposure 0.001s (1ms), gain 0 (zero = 1:1),  Gamma 60,  Brightness 0 (zero).

[Gina]

Clouds in abundance.  Moon has just risen.  Venus shining through the clouds.

 

[Gina]

Snowing here so I thought it might be a good test for my "raindrop drier" high power dew heater.  Let's see how it copes with this lot.  Melted the snow already

[Gina]

It's asking a lot when there is actual precipitation landing on the dome.

[Gina]

Think I'll have to look at the source code for the INDI driver for the camera and see if I can reduce the exposure.  This driver will only go down to 0.001s = 1ms whereas the camera goes down to 32µs = 0.000032s. 

The above images were captured with all the camera controls at minimum - gain=0, brightness=0.  Changing gamma doesn't help.  There is no aperture control on the lens.  Of course, this ASC is really only intended for night viewing but until I can get a daytime ASC done, this is all I have for daytime.

Edited February 11, 2017 by Gina

[Gina]

Heater working - the drops have dried off the leeward side of the dome (the side sheltered from the wind). 

This lens gives a FOV of 185° and goes just below horizontal.  Round the edge to the south (from E round to W) is the next door fields, E-NE is the snow covered apex roof of my observatory, NW is my bungalow, SW next door house.  And the mast to the NE carries the wind instruments for my weather station.

Edited February 11, 2017 by Gina

[Gina]

The snow has stopped and there's just cloud.  The droplets have disappeared from the dome

[Gina]

Very light rain, moon just rising, oooooodles of cloud...

[Gina]

Lots of rain earlier and raindrops on the dome plus lots of dew on the inside.  The heaters have been on for nearly an hour but there's still droplets on the outside and dew on the inside so I think I need to increase the power to the raindrop drier heater.

Edited February 15, 2017 by Gina

[Star101]

Hi Gina, what spacer is needed for focus? 

I ask because I have a couple of old camera's that I no longer use, NexImage 5 and a Opticstar 131C. Both cameras work with this lens if I hold the lens above the CCD. I am not sure what the spacing is...maybe 3mm upwards to 7mm. Just wondered if you could eliminate the guesswork ?  

The lens will screw into either cam but will not focus. Therefore I assume I need a C-Male to C-Female extender!

[Gina]

A C-CS adapter ring - available from several places - 5mm.  Plus a few tenths of a mm to get exact focus - I cut some cardboard to make a spacer which I inserted between the adapter and the camera.

[Gina]

Been doing some thinking as a result of another project.  Considering the extra light throughput of the new lens, I think I might get away with the colour version of the ASI178 in spite of the light loss due to the Bayer matrix.  This would convert this ASC from just nighttime to both nighttime and daytime by showing the difference between blue sky and dark cloud.  I think the resolution on the stars would still be satisfactory.  The upshot would be a combined ASC rather than wanting two separate ones, with a slight reduction in nighttime performance.

Anyway, food tor thought...

[Chriske]

Nice work..!!

[Horwig]

Hi Gina, is this the type of lens you are using?

http://www.ebay.co.uk/itm/Fujinon-DF1-4HB-L1-Fish-Eye-C-Mount-Lens-Complete-with-Mount-Adapter-New-/252289716694?hash=item3abda391d6:g:rAYAAOSwQYZWw4h1

 

Huw