Gina's DIY All Sky Camera - Mark 4 - with ZWO ASI185MC

[Gina]

42 minutes ago, ChrisLX200 said:

Yes I have, but the 178 is my Solar/Lunar camera so I've never tried it with the supplied 2.5mm lens. I had to search out the box with the C/CS adapter in it to try on the 174, and that's when I found the lens   The supplied lens itself is a bit odd as it screws onto the end of the camera without needing to use the adapter plate (i.e., it has the same diameter thread as the adapter plate itself) so it cannot be attached to any other camera like the QHY or GPCAM which all use a C/CS thread. It will screw onto the 174 of course as it is the same basic camera body but because it's basically a CS lens it cannot reach focus with it. Only a C-mount lens will reach focus on the 174. Complicated isn't it?

If we ever get a clear sky again here I'll take a couple of images using the 178 with the supplied lens.

ChrisH

Thank you Chris

[Gina]

I thought the ASI178 had the same arrangement as the 185 as shown below.

 

[Gina]

I've designed and printed a device to turn the lens for focussing.  This is a spider that clamps onto the lens and the legs press on the inside of the part that holds the dome.  This is a loose fit on the camera casing and can now be turned by hand to focus the lens with the dome in place so that the change in focus due to the dome is corrected.

[Gina]

Here's an image capture - I focussed the lens on my weather station mast on the right of the image.  Not at infinity but may be near enough (or should that be far enough ).  I might make a new casing with mechanism to turn the dome and hence the focus but this is an interim step.

[Gina]

Beginning to get dark now and no moon yet but now have a lot of cloud.  Some stars showing in a cloud gap.  Focus looks better.  Dome is in place.

[Gina]

A gap in the cloud and reasonable darkness - exposure on automatic has nearly reached a minute.

[Gina]

Dratted cloud   but now the moon is about to rise - it's already lighting up the clouds - no sign visually yet though.  There's hot pixels showing now - it's a warm night and reduced cooling with the dome on and bottom covered in plastic.  Keeping dew at bay though.  I might arrange an aluminium plate to the camera base rather than using printed ABS to improve cooling.  Milky Way showing again now

[ChrisLX200]

Looking sharper Gina! Still a thin covering of cloud here but I'll give it another hour to see if it clears.

ChrisH

[Gina]

Yes, I think it's sharper.  The cloud is coming and going here.  The moon has just popped up over the eastern horizon.

[ChrisLX200]

I just noticed that the CS-mount 2.5mm f/l lens supplied with the 178MM is only a 1/4" format - which explains the horrendous edge of field image quality I was seeing last night. I didn't get chance to try any other lens on the 178 but it's clear that I really need a C-mount lens of 2-3mm focal length and at least 1/2" format. So far I've failed to find such a lens anywhere, the closest I could find was a varifocal 4-10mm 1/2" format but that won't really give me an all-sky view. The 6mm lens I tried on the 174 only offers about 90deg section of the sky.

ChrisH

[Gina]

That's strange.  The 2.5mm lens I got with my 185MC performs very well right to the edge of the image on the 185 camera as you can see from my images.  And I'm sure mine is 1/3" format - I'll check...  It's better than that - 1/2.5".  I wonder why yours is different - have you had it a long time?  Wondering if ZWO have upgraded their lenses.

I won't be buying a 178MM just yet - I need another infusion of funds first and I can't see that being before next month as things are going.  Anyway, it's possible that the 185MC may be adequate.  For a short while last night before the moon swamped everything there was a clear area of sky showing the Milky Way quite well.  I don't think I've exhausted the possibilities of the 185 just yet - simply not had the conditions to try it to its limits.

[Gina]

Here's a screenshot from the video I took last night - there was just one frame where there was a gap in the clouds showing the Milky Way.  Gamma was set to 2 and the maximum auto exposure set to 1m with max gain set to the standard 240.

[Gina]

Using Windows Movie Maker, I've found a better frame.  There are actually three frames showing the Milky Way.  I think this frame must be a full minute of exposure.  The Snipping Tool screen capture has lost some detail so I'll see if I can separate out this individual frame and save it.

[Gina]

Here is a snapshot from the video.  Capture format was AVI and therefore only 8bit.  Also, it has lost resolution.

[Gina]

This is the next frame snipped from the video - catching an individual frame as the video is running is pretty difficult.  WMM seems to be seriously lacking in its snapshot capability - unless there's something that needs tweaking.  On screen I can see a much sharper image with individual RGB hot pixels well in evidence by the dozen.

[Gina]

Could be promising.

[Gina]

Gradually getting darker and exposure up to 11s.

[Gina]

Auto exposure now up to 1m.  Moon starting to rise.

[Gina]

After a lot of thick dark cloud, the sky seems to be clearing a bit so there's a reasonable chance of seeing the sky and Milky Way before moonrise.

[Gina]

Hmmm... May have spoken too soon - more black clouds gathering from the SW.

[Gina]

The clouds are coming and going so who knows...

[Gina]

I think I see a hint of the Milky Way.

[Gina]

Screenshot from last night's video.

[Gina]

And histogram stretched in PS.

[Gina]

No chance of any imaging tonight - a mixture of thick cloud and rain